increased test coverage and splitted some utility functions by OS

Also made a litle change to scanner function moveOn(): now it moves on
the last char passed and only if there are more than one chars.

README.adoc

@@ -144,4 +144,4 @@ Variables and functions can be added to a context both programmatically and ad a
 
 == Expressions syntax
 
-See #TODO link to doc/Expr.html#
+See https://cdn.paas.portale-stac.it/howto/go-pkg/expr/doc/Expr.html[Expr documentation] for a complete reference of the expression syntax and available functions.

ast.go

@@ -8,12 +8,6 @@ import (
 	"strings"
 )
 
-type Expr interface {
-	Eval(ctx ExprContext) (result any, err error)
-	eval(ctx ExprContext, preset bool) (result any, err error)
-	String() string
-}
-
 //-------- ast
 
 type ast struct {
@@ -25,65 +19,69 @@ func NewAst() *ast {
 	return &ast{}
 }
 
-func (self *ast) ToForest() {
-	if self.root != nil {
-		if self.forest == nil {
-			self.forest = make([]*term, 0)
+func (expr *ast) TypeName() string {
+	return "Expression"
+}
+
+func (expr *ast) ToForest() {
+	if expr.root != nil {
+		if expr.forest == nil {
+			expr.forest = make([]*term, 0)
 		}
-		self.forest = append(self.forest, self.root)
-		self.root = nil
+		expr.forest = append(expr.forest, expr.root)
+		expr.root = nil
 	}
 }
 
-func (self *ast) String() string {
+func (expr *ast) String() string {
 	var sb strings.Builder
-	if self.root == nil {
+	if expr.root == nil {
 		sb.WriteString("(nil)")
 	} else {
-		self.root.toString(&sb)
+		expr.root.toString(&sb)
 	}
 	return sb.String()
 }
 
-func (self *ast) addTokens(tokens ...*Token) (err error) {
+func (expr *ast) addTokens(tokens ...*Token) (err error) {
 	for _, tk := range tokens {
-		if err = self.addToken(tk); err != nil {
+		if _, err = expr.addToken(tk); err != nil {
 			break
 		}
 	}
 	return
 }
 
-func (self *ast) addToken(tk *Token) (err error) {
-	_, err = self.addToken2(tk)
-	return
-}
+// func (expr *ast) addToken(tk *Token) (err error) {
+// 	_, err = expr.addToken2(tk)
+// 	return
+// }
 
-func (self *ast) addToken2(tk *Token) (t *term, err error) {
+func (expr *ast) addToken(tk *Token) (t *term, err error) {
 	if t = newTerm(tk); t != nil {
-		err = self.addTerm(t)
+		err = expr.addTerm(t)
 	} else {
 		err = tk.Errorf("unexpected token %q", tk.String())
 	}
 	return
 }
 
-func (self *ast) addTerm(node *term) (err error) {
-	if self.root == nil {
-		self.root = node
+func (expr *ast) addTerm(node *term) (err error) {
+	if expr.root == nil {
+		expr.root = node
 	} else {
-		self.root, err = self.insert(self.root, node)
+		expr.root, err = expr.insert(expr.root, node)
 	}
 	return
 }
 
-func (self *ast) insert(tree, node *term) (root *term, err error) {
+func (expr *ast) insert(tree, node *term) (root *term, err error) {
 	if tree.getPriority() < node.getPriority() {
 		root = tree
 		if tree.isComplete() {
 			var subRoot *term
 			last := tree.removeLastChild()
-			if subRoot, err = self.insert(last, node); err == nil {
+			if subRoot, err = expr.insert(last, node); err == nil {
 				subRoot.setParent(tree)
 			}
 		} else {
@@ -98,26 +96,20 @@ func (self *ast) insert(tree, node *term) (root *term, err error) {
 	return
 }
 
-func (self *ast) Finish() {
-	if self.root == nil && self.forest != nil && len(self.forest) >= 1 {
-		self.root = self.forest[len(self.forest)-1]
-		self.forest = self.forest[0 : len(self.forest)-1]
+func (expr *ast) Finish() {
+	if expr.root == nil && expr.forest != nil && len(expr.forest) >= 1 {
+		expr.root = expr.forest[len(expr.forest)-1]
+		expr.forest = expr.forest[0 : len(expr.forest)-1]
 	}
 }
 
-func (self *ast) Eval(ctx ExprContext) (result any, err error) {
-	return self.eval(ctx, true)
-}
+func (expr *ast) Eval(ctx ExprContext) (result any, err error) {
+	expr.Finish()
 
-func (self *ast) eval(ctx ExprContext, preset bool) (result any, err error) {
-	self.Finish()
-
-	if self.root != nil {
-		if preset {
-			initDefaultVars(ctx)
-		}
-		if self.forest != nil {
-			for _, root := range self.forest {
+	if expr.root != nil {
+		// initDefaultVars(ctx)
+		if expr.forest != nil {
+			for _, root := range expr.forest {
 				if result, err = root.compute(ctx); err == nil {
 					ctx.UnsafeSetVar(ControlLastResult, result)
 				} else {
@@ -127,8 +119,9 @@ func (self *ast) eval(ctx ExprContext, preset bool) (result any, err error) {
 			}
 		}
 		if err == nil {
-			result, err = self.root.compute(ctx)
-			ctx.UnsafeSetVar(ControlLastResult, result)
+			if result, err = expr.root.compute(ctx); err == nil {
+				ctx.UnsafeSetVar(ControlLastResult, result)
+			}
 		}
 		// } else {
 		// 	err = errors.New("empty expression")

bind-expr-functions.go

@@ -0,0 +1,59 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// function.go
+package expr
+
+// ---- Linking with Expr functions
+type exprFunctor struct {
+	baseFunctor
+	params []ExprFuncParam
+	expr   Expr
+	defCtx ExprContext
+}
+
+func (functor *exprFunctor) GetParams() (params []ExprFuncParam) {
+	return functor.params
+}
+
+func newExprFunctor(e Expr, params []ExprFuncParam, ctx ExprContext) *exprFunctor {
+	var defCtx ExprContext
+	if ctx != nil {
+		defCtx = ctx
+	}
+	return &exprFunctor{expr: e, params: params, defCtx: defCtx}
+}
+
+func (functor *exprFunctor) TypeName() string {
+	return "ExprFunctor"
+}
+
+func (functor *exprFunctor) GetDefinitionContext() ExprContext {
+	return functor.defCtx
+}
+
+func (functor *exprFunctor) InvokeNamed(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+	var missing []string
+	for _, p := range functor.params {
+		if arg, exists := args[p.Name()]; exists {
+			if funcArg, ok := arg.(Functor); ok {
+				paramSpecs := funcArg.GetParams()
+				ctx.RegisterFunc(p.Name(), funcArg, TypeAny, paramSpecs)
+			} else {
+				ctx.UnsafeSetVar(p.Name(), arg)
+			}
+		} else {
+			if missing == nil {
+				missing = make([]string, 0, 1)
+			}
+			missing = append(missing, p.Name())
+			// ctx.UnsafeSetVar(p.Name(), nil)
+		}
+	}
+	if missing != nil {
+		err = ErrMissingParams(name, missing)
+	} else {
+		result, err = functor.expr.Eval(ctx)
+	}
+	return
+}

bind-go-functions.go

@@ -0,0 +1,23 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// bind-go-function.go
+package expr
+
+// ---- Linking with Go functions
+type golangFunctor struct {
+	baseFunctor
+	f FuncTemplate
+}
+
+func NewGolangFunctor(f FuncTemplate) *golangFunctor {
+	return &golangFunctor{f: f}
+}
+
+func (functor *golangFunctor) TypeName() string {
+	return "GoFunctor"
+}
+
+func (functor *golangFunctor) InvokeNamed(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+	return functor.f(ctx, name, args)
+}

builtin-base.go

@@ -0,0 +1,316 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// builtin-base.go
+package expr
+
+import (
+	"fmt"
+	"math"
+	"strconv"
+	"strings"
+)
+
+const (
+	ParamDenominator = "denominator"
+)
+
+func isNilFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+	result = args[ParamValue] == nil
+	return
+}
+
+func isIntFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+	result = IsInteger(args[ParamValue])
+	return
+}
+
+func isFloatFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+	result = IsFloat(args[ParamValue])
+	return
+}
+
+func isBoolFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+	result = IsBool(args[ParamValue])
+	return
+}
+
+func isStringFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+	result = IsString(args[ParamValue])
+	return
+}
+
+func isFractionFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+	result = IsFract(args[ParamValue])
+	return
+}
+
+func isRationalFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+	result = IsRational(args[ParamValue])
+	return
+}
+
+func isListFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+	result = IsList(args[ParamValue])
+	return
+}
+
+func isDictionaryFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+	result = IsDict(args[ParamValue])
+	return
+}
+
+func boolFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+	switch v := args[ParamValue].(type) {
+	case int64:
+		result = (v != 0)
+	case *FractionType:
+		result = v.num != 0
+	case float64:
+		result = v != 0.0
+	case bool:
+		result = v
+	case string:
+		result = len(v) > 0
+	case *ListType:
+		result = len(*v) > 0
+	case *DictType:
+		result = len(*v) > 0
+	default:
+		err = ErrCantConvert(name, v, "bool")
+	}
+	return
+}
+
+func intFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+	switch v := args[ParamValue].(type) {
+	case int64:
+		result = v
+	case float64:
+		result = int64(math.Trunc(v))
+	case bool:
+		if v {
+			result = int64(1)
+		} else {
+			result = int64(0)
+		}
+	case string:
+		var i int
+		if i, err = strconv.Atoi(v); err == nil {
+			result = int64(i)
+		}
+	case *FractionType:
+		result = int64(v.num / v.den)
+	default:
+		err = ErrCantConvert(name, v, "int")
+	}
+	return
+}
+
+func decFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+	switch v := args[ParamValue].(type) {
+	case int64:
+		result = float64(v)
+	case float64:
+		result = v
+	case bool:
+		if v {
+			result = float64(1)
+		} else {
+			result = float64(0)
+		}
+	case string:
+		var f float64
+		if f, err = strconv.ParseFloat(v, 64); err == nil {
+			result = f
+		}
+	case *FractionType:
+		result = v.toFloat()
+	default:
+		err = ErrCantConvert(name, v, "float")
+	}
+	return
+}
+
+func stringFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+	switch v := args[ParamValue].(type) {
+	case int64:
+		result = strconv.FormatInt(v, 10)
+	case float64:
+		result = strconv.FormatFloat(v, 'g', -1, 64)
+	case bool:
+		if v {
+			result = "true"
+		} else {
+			result = "false"
+		}
+	case string:
+		result = v
+	case *FractionType:
+		result = v.ToString(0)
+	case Formatter:
+		result = v.ToString(0)
+	case fmt.Stringer:
+		result = v.String()
+	default:
+		err = ErrCantConvert(name, v, "string")
+	}
+	return
+}
+
+func fractFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+	switch v := args[ParamValue].(type) {
+	case int64:
+		var den int64 = 1
+
+		var ok bool
+		if den, ok = args[ParamDenominator].(int64); !ok {
+			err = ErrExpectedGot(name, "integer", args[ParamDenominator])
+		} else if den == 0 {
+			err = ErrFuncDivisionByZero(name)
+		}
+
+		if err == nil {
+			result = newFraction(v, den)
+		}
+	case float64:
+		result, err = float64ToFraction(v)
+	case bool:
+		if v {
+			result = newFraction(1, 1)
+		} else {
+			result = newFraction(0, 1)
+		}
+	case string:
+		result, err = makeGeneratingFraction(v)
+	case *FractionType:
+		result = v
+	default:
+		err = ErrCantConvert(name, v, "float")
+	}
+	return
+}
+
+// func iteratorFunc(ctx ExprContext, name string, args []any) (result any, err error) {
+// 	return
+// }
+
+func evalFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+	if source, ok := args[ParamSource].(string); ok {
+		var expr Expr
+
+		parser := NewParser()
+		if ctx == nil {
+			ctx = NewSimpleStore()
+		}
+
+		r := strings.NewReader(source)
+		scanner := NewScanner(r, DefaultTranslations())
+
+		if expr, err = parser.Parse(scanner); err == nil {
+			CtrlEnable(ctx, control_export_all)
+			result, err = expr.Eval(ctx)
+		}
+	} else {
+		err = ErrWrongParamType(name, ParamSource, TypeString, args[ParamSource])
+	}
+	return
+}
+
+func varFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+	var varName string
+	var ok bool
+
+	if varName, ok = args[ParamName].(string); !ok {
+		return nil, ErrWrongParamType(name, ParamName, TypeString, args[ParamName])
+	}
+
+	if result, ok = args[ParamValue]; ok && result != nil {
+		ctx.GetParent().UnsafeSetVar(varName, result)
+		// } else {
+		// 	err = ErrWrongParamType(name, ParamSource, TypeString, args[ParamSource])
+		// }
+	} else if result, ok = ctx.GetVar(varName); !ok {
+		err = ErrUnknownVar(name, varName)
+	}
+	return
+}
+
+func setFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+	var varName string
+	var ok bool
+
+	if varName, ok = args[ParamName].(string); !ok {
+		return nil, ErrWrongParamType(name, ParamName, TypeString, args[ParamName])
+	}
+
+	if result, ok = args[ParamValue]; ok {
+		ctx.GetParent().UnsafeSetVar(varName, result)
+	} else {
+		err = ErrWrongParamType(name, ParamValue, TypeAny, args[ParamValue])
+	}
+	return
+}
+
+func unsetFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+	var varName string
+	var ok bool
+
+	if varName, ok = args[ParamName].(string); !ok {
+		return nil, ErrWrongParamType(name, ParamName, TypeString, args[ParamName])
+	} else {
+		ctx.GetParent().DeleteVar(varName)
+		result = nil
+	}
+	return
+}
+
+//// import
+
+func ImportBuiltinsFuncs(ctx ExprContext) {
+	anyParams := []ExprFuncParam{
+		NewFuncParam(ParamValue),
+	}
+
+	ctx.RegisterFunc("isNil", NewGolangFunctor(isNilFunc), TypeBoolean, anyParams)
+	ctx.RegisterFunc("isInt", NewGolangFunctor(isIntFunc), TypeBoolean, anyParams)
+	ctx.RegisterFunc("isFloat", NewGolangFunctor(isFloatFunc), TypeBoolean, anyParams)
+	ctx.RegisterFunc("isBool", NewGolangFunctor(isBoolFunc), TypeBoolean, anyParams)
+	ctx.RegisterFunc("isString", NewGolangFunctor(isStringFunc), TypeBoolean, anyParams)
+	ctx.RegisterFunc("isFract", NewGolangFunctor(isFractionFunc), TypeBoolean, anyParams)
+	ctx.RegisterFunc("isRational", NewGolangFunctor(isRationalFunc), TypeBoolean, anyParams)
+	ctx.RegisterFunc("isList", NewGolangFunctor(isListFunc), TypeBoolean, anyParams)
+	ctx.RegisterFunc("isDict", NewGolangFunctor(isDictionaryFunc), TypeBoolean, anyParams)
+
+	ctx.RegisterFunc("bool", NewGolangFunctor(boolFunc), TypeBoolean, anyParams)
+	ctx.RegisterFunc("int", NewGolangFunctor(intFunc), TypeInt, anyParams)
+	ctx.RegisterFunc("dec", NewGolangFunctor(decFunc), TypeFloat, anyParams)
+	ctx.RegisterFunc("string", NewGolangFunctor(stringFunc), TypeString, anyParams)
+	ctx.RegisterFunc("fract", NewGolangFunctor(fractFunc), TypeFraction, []ExprFuncParam{
+		NewFuncParam(ParamValue),
+		NewFuncParamFlagDef(ParamDenominator, PfDefault, int64(1)),
+	})
+
+	ctx.RegisterFunc("eval", NewGolangFunctor(evalFunc), TypeAny, []ExprFuncParam{
+		NewFuncParam(ParamSource),
+	})
+
+	ctx.RegisterFunc("var", NewGolangFunctor(varFunc), TypeAny, []ExprFuncParam{
+		NewFuncParam(ParamName),
+		NewFuncParamFlagDef(ParamValue, PfDefault, nil),
+	})
+
+	ctx.RegisterFunc("set", NewGolangFunctor(setFunc), TypeAny, []ExprFuncParam{
+		NewFuncParam(ParamName),
+		NewFuncParam(ParamValue),
+	})
+
+	ctx.RegisterFunc("unset", NewGolangFunctor(unsetFunc), TypeAny, []ExprFuncParam{
+		NewFuncParam(ParamName),
+		NewFuncParam(ParamValue),
+	})
+}
+
+func init() {
+	RegisterBuiltinModule("base", ImportBuiltinsFuncs, "Base expression tools like isNil(), int(), etc.")
+}

builtin-fmt.go

@@ -0,0 +1,57 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// builtin-fmt.go
+package expr
+
+import (
+	"fmt"
+	"io"
+	"os"
+)
+
+func getStdout(ctx ExprContext) io.Writer {
+	var w io.Writer
+	if wany, exists := ctx.GetVar(ControlStdout); exists && wany != nil {
+		w, _ = wany.(io.Writer)
+	}
+	if w == nil {
+		w = os.Stdout
+	}
+	return w
+}
+
+func printFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+	var n int = 0
+	if v, exists := args[ParamItem]; exists && v != nil {
+		argv := v.([]any)
+		n, err = fmt.Fprint(getStdout(ctx), argv...)
+	}
+	result = int64(n)
+	return
+}
+
+func printLnFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+	var n int = 0
+	if v, exists := args[ParamItem]; exists && v != nil {
+		argv := v.([]any)
+		n, err = fmt.Fprintln(getStdout(ctx), argv...)
+	} else {
+		n, err = fmt.Fprintln(getStdout(ctx))
+	}
+	result = int64(n)
+	return
+}
+
+func ImportFmtFuncs(ctx ExprContext) {
+	ctx.RegisterFunc("print", NewGolangFunctor(printFunc), TypeInt, []ExprFuncParam{
+		NewFuncParamFlag(ParamItem, PfRepeat),
+	})
+	ctx.RegisterFunc("println", NewGolangFunctor(printLnFunc), TypeInt, []ExprFuncParam{
+		NewFuncParamFlag(ParamItem, PfRepeat),
+	})
+}
+
+func init() {
+	RegisterBuiltinModule("fmt", ImportFmtFuncs, "String and console formatting functions")
+}

builtin-import.go

@@ -0,0 +1,78 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// builtin-import.go
+package expr
+
+import (
+	"io"
+	"os"
+)
+
+func importFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+	return importGeneral(ctx, name, args)
+}
+
+func importAllFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+	CtrlEnable(ctx, control_export_all)
+	return importGeneral(ctx, name, args)
+}
+
+func importGeneral(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+	dirList := buildSearchDirList("sources", ENV_EXPR_SOURCE_PATH)
+	if v, exists := args[ParamFilepath]; exists && v != nil {
+		argv := v.([]any)
+		result, err = doImport(ctx, name, dirList, NewArrayIterator(argv))
+	}
+	return
+}
+
+func doImport(ctx ExprContext, name string, dirList []string, it Iterator) (result any, err error) {
+	var v any
+	var sourceFilepath string
+
+	for v, err = it.Next(); err == nil; v, err = it.Next() {
+		if err = checkStringParamExpected(name, v, it.Index()); err != nil {
+			break
+		}
+		if sourceFilepath, err = makeFilepath(v.(string), dirList); err != nil {
+			break
+		}
+		var file *os.File
+		if file, err = os.Open(sourceFilepath); err == nil {
+			defer file.Close()
+			var expr *ast
+			scanner := NewScanner(file, DefaultTranslations())
+			parser := NewParser()
+			if expr, err = parser.parseGeneral(scanner, allowMultiExpr|allowVarRef, SymEos); err == nil {
+				result, err = expr.Eval(ctx)
+			}
+			if err != nil {
+				break
+			}
+		} else {
+			break
+		}
+	}
+	if err != nil {
+		if err == io.EOF {
+			err = nil
+		} else {
+			result = nil
+		}
+	}
+	return
+}
+
+func ImportImportFuncs(ctx ExprContext) {
+	ctx.RegisterFunc("import", NewGolangFunctor(importFunc), TypeAny, []ExprFuncParam{
+		NewFuncParamFlag(ParamFilepath, PfRepeat),
+	})
+	ctx.RegisterFunc("importAll", NewGolangFunctor(importAllFunc), TypeAny, []ExprFuncParam{
+		NewFuncParamFlag(ParamFilepath, PfRepeat),
+	})
+}
+
+func init() {
+	RegisterBuiltinModule("import", ImportImportFuncs, "Functions import() and include()")
+}

builtin-iterator.go

@@ -0,0 +1,112 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// builtin-iterator.go
+package expr
+
+import (
+	"fmt"
+	"io"
+)
+
+const (
+	iterParamOperator = "operator"
+	iterParamVars     = "vars"
+	iterVarStatus     = "status"
+)
+
+func parseRunArgs(localCtx ExprContext, args map[string]any) (it Iterator, op Functor, err error) {
+	var ok bool
+
+	if it, ok = args[ParamIterator].(Iterator); !ok {
+		err = fmt.Errorf("paramter %q must be an iterator, passed %v [%s]", ParamIterator, args[ParamIterator], TypeName(args[ParamIterator]))
+		return
+	}
+
+	if args[iterParamOperator] != nil {
+		if op, ok = args[iterParamOperator].(Functor); !ok || op == nil {
+			err = fmt.Errorf("paramter %q must be a function, passed %v [%s]", iterParamOperator, args[iterParamOperator], TypeName(args[iterParamOperator]))
+			return
+		}
+	}
+
+	var vars *DictType
+	if vars, ok = args[iterParamVars].(*DictType); !ok && args[iterParamVars] != nil {
+		err = fmt.Errorf("paramter %q must be a dictionary, passed %v [%s]", iterParamVars, args[iterParamVars], TypeName(args[iterParamVars]))
+		return
+	}
+
+	if vars != nil {
+		for key, value := range *vars {
+			var varName string
+			if varName, ok = key.(string); ok {
+				localCtx.UnsafeSetVar(varName, value)
+			}
+		}
+	}
+
+	return
+}
+
+func runFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+	var it Iterator
+	var ok bool
+	var op Functor
+	var v any
+	// var usingDefaultOp = false
+	var params map[string]any
+	var item any
+
+	localCtx := ctx.Clone()
+	localCtx.UnsafeSetVar(iterVarStatus, nil)
+
+	if it, op, err = parseRunArgs(localCtx, args); err != nil {
+		return
+		// } else if op == nil {
+		// 	op = NewGolangFunctor(printLnFunc)
+		// 	usingDefaultOp = true
+	}
+
+	for item, err = it.Next(); err == nil; item, err = it.Next() {
+		// if usingDefaultOp {
+		// 	params = map[string]any{ParamItem: []any{item}}
+		// } else {
+		// params = map[string]any{ParamIndex: it.Index(), ParamItem: item}
+		// }
+
+		if op != nil {
+			params = map[string]any{ParamIndex: it.Index(), ParamItem: item}
+			if v, err = op.InvokeNamed(localCtx, iterParamOperator, params); err != nil {
+				break
+			} else {
+				var success bool
+				if success, ok = ToBool(v); !success || !ok {
+					break
+				}
+			}
+		}
+	}
+
+	if err == io.EOF {
+		err = nil
+	}
+	if err == nil {
+		if op == nil {
+			ctx.UnsafeSetVar(iterVarStatus, it.Count())
+		}
+		result, _ = localCtx.GetVar(iterVarStatus)
+	}
+	return
+}
+
+func ImportIterFuncs(ctx ExprContext) {
+	ctx.RegisterFunc("run", NewGolangFunctor(runFunc), TypeAny, []ExprFuncParam{
+		NewFuncParam(ParamIterator),
+		NewFuncParamFlag(iterParamOperator, PfOptional),
+		NewFuncParamFlag(iterParamVars, PfOptional),
+	})
+}
+
+func init() {
+	RegisterBuiltinModule("iterator", ImportIterFuncs, "Iterator helper functions")
+}

builtin-math-arith.go

@@ -1,7 +1,7 @@
 // Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
 // All rights reserved.
 
-// funcs-math.go
+// builtin-math-arith.go
 package expr
 
 import (
@@ -34,8 +34,8 @@ func doAdd(ctx ExprContext, name string, it Iterator, count, level int) (result
 			if v, err = doAdd(ctx, name, subIter, count, level); err != nil {
 				break
 			}
-			if extIter, ok := v.(ExtIterator); ok && extIter.HasOperation(cleanName) {
-				if _, err = extIter.CallOperation(cleanName, nil); err != nil {
+			if extIter, ok := v.(ExtIterator); ok && extIter.HasOperation(CleanName) {
+				if _, err = extIter.CallOperation(CleanName, nil); err != nil {
 					return
 				}
 			}
@@ -86,8 +86,9 @@ func doAdd(ctx ExprContext, name string, it Iterator, count, level int) (result
 	return
 }
 
-func addFunc(ctx ExprContext, name string, args []any) (result any, err error) {
-	result, err = doAdd(ctx, name, NewArrayIterator(args), 0, -1)
+func addFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+	argv := args[ParamValue].([]any)
+	result, err = doAdd(ctx, name, NewArrayIterator(argv), 0, -1)
 	return
 }
 
@@ -107,8 +108,8 @@ func doMul(ctx ExprContext, name string, it Iterator, count, level int) (result
 			if v, err = doMul(ctx, name, subIter, count, level); err != nil {
 				break
 			}
-			if extIter, ok := v.(ExtIterator); ok && extIter.HasOperation(cleanName) {
-				if _, err = extIter.CallOperation(cleanName, nil); err != nil {
+			if extIter, ok := v.(ExtIterator); ok && extIter.HasOperation(CleanName) {
+				if _, err = extIter.CallOperation(CleanName, nil); err != nil {
 					return
 				}
 			}
@@ -161,21 +162,22 @@ func doMul(ctx ExprContext, name string, it Iterator, count, level int) (result
 	return
 }
 
-func mulFunc(ctx ExprContext, name string, args []any) (result any, err error) {
-	result, err = doMul(ctx, name, NewArrayIterator(args), 0, -1)
+func mulFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+	argv := args[ParamValue].([]any)
+	result, err = doMul(ctx, name, NewArrayIterator(argv), 0, -1)
 	return
 }
 
 func ImportMathFuncs(ctx ExprContext) {
-	ctx.RegisterFunc("add", &golangFunctor{f: addFunc}, typeNumber, []ExprFuncParam{
-		newFuncParamFlagDef(paramValue, pfOptional|pfRepeat, 0),
+	ctx.RegisterFunc("add", NewGolangFunctor(addFunc), TypeNumber, []ExprFuncParam{
+		NewFuncParamFlagDef(ParamValue, PfDefault|PfRepeat, int64(0)),
 	})
 
-	ctx.RegisterFunc("mul", &golangFunctor{f: mulFunc}, typeNumber, []ExprFuncParam{
-		newFuncParamFlagDef(paramValue, pfOptional|pfRepeat, 1),
+	ctx.RegisterFunc("mul", NewGolangFunctor(mulFunc), TypeNumber, []ExprFuncParam{
+		NewFuncParamFlagDef(ParamValue, PfDefault|PfRepeat, int64(1)),
 	})
 }
 
 func init() {
-	registerImport("math.arith", ImportMathFuncs, "Functions add() and mul()")
+	RegisterBuiltinModule("math.arith", ImportMathFuncs, "Functions add() and mul()")
 }

builtin-os-file-iter.go

@@ -0,0 +1,149 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// builtin-os-file.go
+package expr
+
+import (
+	"fmt"
+	"io"
+	"slices"
+)
+
+const paramHandleOrPath = "handle-or-path"
+const fileReadTextIteratorType = "fileReadTextIterator"
+
+type fileReadTextIterator struct {
+	osReader  *osReader
+	index     int
+	count     int
+	line      string
+	autoClose bool
+}
+
+func newReadTextIterator(r *osReader, autoClose bool) *fileReadTextIterator {
+	return &fileReadTextIterator{osReader: r, index: -1, autoClose: autoClose}
+}
+
+func (it *fileReadTextIterator) TypeName() string {
+	return fileReadTextIteratorType
+}
+
+func (it *fileReadTextIterator) String() string {
+	if it.osReader != nil && it.osReader.fh != nil {
+		return fmt.Sprintf("$(%s@%q)", fileReadTextIteratorType, it.osReader.fh.Name())
+	}
+	return fmt.Sprintf("$(%s@<nil>)", fileReadTextIteratorType)
+}
+
+func (it *fileReadTextIterator) Count() int {
+	return it.count
+}
+
+func (it *fileReadTextIterator) Next() (item any, err error) { // must return io.EOF after the last item
+	if it.osReader.fh != nil {
+		if it.line, err = it.osReader.reader.ReadString('\n'); err == nil {
+			it.index++
+			it.count++
+			item = it.line[0 : len(it.line)-1]
+		} else if it.autoClose {
+			it.Clean()
+		}
+	}
+	return
+}
+
+func (it *fileReadTextIterator) Current() (item any, err error) {
+	if len(it.line) > 0 {
+		item = it.line[0 : len(it.line)-1]
+	}
+	return
+}
+
+func (it *fileReadTextIterator) Index() int {
+	return it.index
+}
+
+func (it *fileReadTextIterator) Reset() (err error) {
+	if _, err = it.osReader.fh.Seek(0, io.SeekStart); err == nil {
+		it.index = -1
+		it.count = 0
+		it.line = ""
+	}
+	return
+}
+
+func (it *fileReadTextIterator) HasOperation(name string) bool {
+	return slices.Contains([]string{NextName, ResetName, IndexName, CountName, CurrentName, CleanName}, name)
+}
+
+func (it *fileReadTextIterator) Clean() (err error) {
+	if it.osReader.fh != nil {
+		if err = it.osReader.fh.Close(); err == nil {
+			it.osReader = nil
+		}
+	}
+	return nil
+}
+
+func (it *fileReadTextIterator) CallOperation(name string, args map[string]any) (v any, err error) {
+	switch name {
+	case NextName:
+		v, err = it.Next()
+	case ResetName:
+		err = it.Reset()
+	case CleanName:
+		err = it.Clean()
+	case IndexName:
+		v = int64(it.Index())
+	case CurrentName:
+		v, err = it.Current()
+	case CountName:
+		v = it.count
+	default:
+		err = errNoOperation(name)
+	}
+	return
+}
+
+func fileReadIteratorFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+	var handle *osReader
+	var invalidFileHandle any
+	var ok, autoClose bool
+
+	result = nil
+	if handle, ok = args[paramHandleOrPath].(*osReader); !ok {
+		if fileName, ok := args[paramHandleOrPath].(string); ok && len(fileName) > 0 {
+			var handleAny any
+			if handleAny, err = openFileFunc(ctx, name, map[string]any{ParamFilepath: fileName}); err != nil {
+				return
+			}
+			if handleAny != nil {
+				handle = handleAny.(*osReader)
+				autoClose = true
+			}
+		} else {
+			invalidFileHandle = args[paramHandleOrPath]
+		}
+	}
+
+	if handle != nil {
+		result = newReadTextIterator(handle, autoClose)
+
+	}
+
+	if err == nil && (handle == nil || invalidFileHandle != nil) {
+		err = errInvalidFileHandle(name, invalidFileHandle)
+	}
+	return
+}
+
+// func ImportOsIterFuncs(ctx ExprContext) {
+// 	ctx.RegisterFunc("fileReadIterator", NewGolangFunctor(fileReadIteratorFunc), TypeIterator, []ExprFuncParam{
+// 		NewFuncParam(paramHandleOrPath),
+// 	})
+// }
+
+// func init() {
+// 	RegisterBuiltinModule("os.file", ImportOsIterFuncs, "Operating system file iterator functions")
+// }

builtin-os-file.go

@@ -0,0 +1,261 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// builtin-os-file.go
+package expr
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"os"
+)
+
+const (
+	osLimitCh = "limitCh"
+)
+
+type osHandle interface {
+	getFile() *os.File
+}
+
+type osWriter struct {
+	fh     *os.File
+	writer *bufio.Writer
+}
+
+func (h *osWriter) TypeName() string {
+	return "osWriter"
+}
+
+func (h *osWriter) String() string {
+	return "writer"
+}
+
+func (h *osWriter) getFile() *os.File {
+	return h.fh
+}
+
+type osReader struct {
+	fh     *os.File
+	reader *bufio.Reader
+}
+
+func (h *osReader) TypeName() string {
+	return "osReader"
+}
+
+func (h *osReader) String() string {
+	return "reader"
+}
+
+func (h *osReader) getFile() *os.File {
+	return h.fh
+}
+
+func errMissingFilePath(funcName string) error {
+	return fmt.Errorf("%s(): missing or invalid file path", funcName)
+}
+
+func errInvalidFileHandle(funcName string, v any) error {
+	if v != nil {
+		return fmt.Errorf("%s(): invalid file handle %v [%T]", funcName, v, v)
+	} else {
+		return fmt.Errorf("%s(): invalid file handle", funcName)
+	}
+}
+
+func createFileFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+	if filePath, ok := args[ParamFilepath].(string); ok && len(filePath) > 0 {
+		var fh *os.File
+		if fh, err = os.Create(filePath); err == nil {
+			result = &osWriter{fh: fh, writer: bufio.NewWriter(fh)}
+		}
+	} else {
+		err = errMissingFilePath(name)
+	}
+	return
+}
+
+func openFileFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+	if filePath, ok := args[ParamFilepath].(string); ok && len(filePath) > 0 {
+		var fh *os.File
+		if fh, err = os.Open(filePath); err == nil {
+			result = &osReader{fh: fh, reader: bufio.NewReader(fh)}
+		}
+	} else {
+		err = errMissingFilePath(name)
+	}
+	return
+}
+
+func appendFileFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+	if filePath, ok := args[ParamFilepath].(string); ok && len(filePath) > 0 {
+		var fh *os.File
+		if fh, err = os.OpenFile(filePath, os.O_APPEND|os.O_WRONLY|os.O_CREATE, 0660); err == nil {
+			result = &osWriter{fh: fh, writer: bufio.NewWriter(fh)}
+		}
+	} else {
+		err = errMissingFilePath(name)
+	}
+	return
+}
+
+func closeFileFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+	var handle osHandle
+	var invalidFileHandle any
+	var ok bool
+
+	if handle, ok = args[ParamHandle].(osHandle); !ok {
+		invalidFileHandle = args[ParamHandle]
+	}
+
+	if handle != nil {
+		if fh := handle.getFile(); fh != nil {
+			if w, ok := handle.(*osWriter); ok {
+				err = w.writer.Flush()
+			}
+
+			if err == nil {
+				err = fh.Close()
+			}
+		}
+	}
+	if err == nil && (handle == nil || invalidFileHandle != nil) {
+		err = errInvalidFileHandle(name, handle)
+	}
+	result = err == nil
+	return
+}
+
+func fileWriteTextFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+	var handle osHandle
+	var invalidFileHandle any
+	var ok bool
+
+	if handle, ok = args[ParamHandle].(osHandle); !ok {
+		invalidFileHandle = args[ParamHandle]
+	}
+
+	if handle != nil {
+		if w, ok := handle.(*osWriter); ok {
+			if v, exists := args[ParamItem]; exists {
+				argv := v.([]any)
+				result, err = fmt.Fprint(w.writer, argv...)
+			}
+		} else {
+			invalidFileHandle = handle
+		}
+	}
+
+	if err == nil && (handle == nil || invalidFileHandle != nil) {
+		err = errInvalidFileHandle(name, invalidFileHandle)
+	}
+	return
+}
+
+func fileReadTextFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+	var handle osHandle
+	var invalidFileHandle any
+	var ok bool
+
+	result = nil
+	if handle, ok = args[ParamHandle].(osHandle); !ok || args[ParamHandle] == nil {
+		invalidFileHandle = args[ParamHandle]
+	}
+
+	if handle != nil {
+		if r, ok := handle.(*osReader); ok {
+			var limit byte = '\n'
+			var v string
+			if s, ok := args[osLimitCh].(string); ok && len(s) > 0 {
+				limit = s[0]
+			}
+
+			v, err = r.reader.ReadString(limit)
+			if err == io.EOF {
+				err = nil
+			}
+			if len(v) > 0 {
+				if v[len(v)-1] == limit {
+					result = v[0 : len(v)-1]
+				} else {
+					result = v
+				}
+			}
+		} else {
+			invalidFileHandle = handle
+		}
+	}
+
+	if err == nil && (handle == nil || invalidFileHandle != nil) {
+		err = errInvalidFileHandle(name, invalidFileHandle)
+	}
+	return
+}
+
+func fileReadTextAllFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+	var handle osHandle
+	var invalidFileHandle any
+	var ok bool
+
+	result = nil
+	if handle, ok = args[ParamHandle].(osHandle); !ok || args[ParamHandle] == nil {
+		invalidFileHandle = args[ParamHandle]
+	}
+
+	if handle != nil {
+		if r, ok := handle.(*osReader); ok {
+			var b []byte
+			b, err = io.ReadAll(r.reader)
+			result = string(b)
+		} else {
+			invalidFileHandle = handle
+		}
+	}
+
+	if err == nil && (handle == nil || invalidFileHandle != nil) {
+		err = errInvalidFileHandle(name, invalidFileHandle)
+	}
+	return
+}
+
+func ImportOsFuncs(ctx ExprContext) {
+	ctx.RegisterFunc("fileOpen", NewGolangFunctor(openFileFunc), TypeFileHandle, []ExprFuncParam{
+		NewFuncParam(ParamFilepath),
+	})
+
+	ctx.RegisterFunc("fileAppend", NewGolangFunctor(appendFileFunc), TypeFileHandle, []ExprFuncParam{
+		NewFuncParam(ParamFilepath),
+	})
+
+	ctx.RegisterFunc("fileCreate", NewGolangFunctor(createFileFunc), TypeFileHandle, []ExprFuncParam{
+		NewFuncParam(ParamFilepath),
+	})
+
+	ctx.RegisterFunc("fileClose", NewGolangFunctor(closeFileFunc), TypeBoolean, []ExprFuncParam{
+		NewFuncParam(ParamHandle),
+	})
+
+	ctx.RegisterFunc("fileWriteText", NewGolangFunctor(fileWriteTextFunc), TypeInt, []ExprFuncParam{
+		NewFuncParam(ParamHandle),
+		NewFuncParamFlagDef(ParamItem, PfDefault|PfRepeat, ""),
+	})
+
+	ctx.RegisterFunc("fileReadText", NewGolangFunctor(fileReadTextFunc), TypeString, []ExprFuncParam{
+		NewFuncParam(ParamHandle),
+		NewFuncParamFlagDef(osLimitCh, PfDefault, "\n"),
+	})
+
+	ctx.RegisterFunc("fileReadTextAll", NewGolangFunctor(fileReadTextAllFunc), TypeString, []ExprFuncParam{
+		NewFuncParam(ParamHandle),
+	})
+
+	ctx.RegisterFunc("fileReadIterator", NewGolangFunctor(fileReadIteratorFunc), TypeIterator, []ExprFuncParam{
+		NewFuncParam(paramHandleOrPath),
+	})
+}
+
+func init() {
+	RegisterBuiltinModule("os.file", ImportOsFuncs, "Operating system file functions")
+}

builtin-string.go

@@ -0,0 +1,271 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// builtin-string.go
+package expr
+
+import (
+	"fmt"
+	"io"
+	"strings"
+)
+
+const (
+	strParamOther = "other"
+)
+
+// --- Start of function definitions
+func doJoinStr(funcName string, sep string, it Iterator) (result any, err error) {
+	var sb strings.Builder
+	var v any
+	for v, err = it.Next(); err == nil; v, err = it.Next() {
+		if it.Index() > 0 {
+			sb.WriteString(sep)
+		}
+		if s, ok := v.(string); ok {
+			sb.WriteString(s)
+		} else {
+			err = ErrExpectedGot(funcName, TypeString, v)
+			return
+		}
+	}
+	if err == io.EOF {
+		err = nil
+		result = sb.String()
+	}
+	return
+}
+
+func joinStrFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+	if sep, ok := args[ParamSeparator].(string); ok {
+		if v, exists := args[ParamItem]; exists {
+			argv := v.([]any)
+			if len(argv) == 1 {
+				if ls, ok := argv[0].(*ListType); ok {
+					result, err = doJoinStr(name, sep, NewListIterator(ls, nil))
+				} else if it, ok := argv[0].(Iterator); ok {
+					result, err = doJoinStr(name, sep, it)
+				} else if s, ok := argv[0].(string); ok {
+					result = s
+				} else {
+					err = ErrInvalidParameterValue(name, ParamItem, v)
+				}
+			} else {
+				result, err = doJoinStr(name, sep, NewArrayIterator(argv))
+			}
+		}
+	} else {
+		err = ErrWrongParamType(name, ParamSeparator, TypeString, args[ParamSeparator])
+	}
+	return
+}
+
+func subStrFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+	var start = 0
+	var count = -1
+	var source string
+	var ok bool
+
+	if source, ok = args[ParamSource].(string); !ok {
+		return nil, ErrWrongParamType(name, ParamSource, TypeString, args[ParamSource])
+	}
+
+	if start, err = ToGoInt(args[ParamStart], name+"()"); err != nil {
+		return
+	}
+
+	if count, err = ToGoInt(args[ParamCount], name+"()"); err != nil {
+		return
+	}
+
+	if start < 0 {
+		start = len(source) + start
+	}
+
+	if count < 0 {
+		count = len(source) - start
+	}
+	end := min(start+count, len(source))
+	result = source[start:end]
+	return
+}
+
+func trimStrFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+	var source string
+	var ok bool
+
+	if source, ok = args[ParamSource].(string); !ok {
+		return nil, ErrWrongParamType(name, ParamSource, TypeString, args[ParamSource])
+	}
+	result = strings.TrimSpace(source)
+	return
+}
+
+func startsWithStrFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+	var source, prefix string
+	var ok bool
+
+	result = false
+
+	if source, ok = args[ParamSource].(string); !ok {
+		return result, ErrWrongParamType(name, ParamSource, TypeString, args[ParamSource])
+	}
+
+	if prefix, ok = args[ParamPrefix].(string); !ok {
+		return result, ErrWrongParamType(name, ParamPrefix, TypeString, args[ParamPrefix])
+	}
+	if strings.HasPrefix(source, prefix) {
+		result = true
+	} else if v, exists := args[strParamOther]; exists {
+		argv := v.([]any)
+		for i, targetSpec := range argv {
+			if target, ok := targetSpec.(string); ok {
+				if strings.HasPrefix(source, target) {
+					result = true
+					break
+				}
+			} else {
+				err = fmt.Errorf("target item nr %d is %s, string expected", i+1, TypeName(targetSpec))
+				break
+			}
+		}
+	}
+	return
+}
+
+func endsWithStrFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+	var source, suffix string
+	var ok bool
+
+	result = false
+
+	if source, ok = args[ParamSource].(string); !ok {
+		return result, ErrWrongParamType(name, ParamSource, TypeString, args[ParamSource])
+	}
+
+	if suffix, ok = args[ParamSuffix].(string); !ok {
+		return result, ErrWrongParamType(name, ParamSuffix, TypeString, args[ParamSuffix])
+	}
+	if strings.HasPrefix(source, suffix) {
+		result = true
+	} else if v, exists := args[strParamOther]; exists {
+		argv := v.([]any)
+		for i, targetSpec := range argv {
+			if target, ok := targetSpec.(string); ok {
+				if strings.HasSuffix(source, target) {
+					result = true
+					break
+				}
+			} else {
+				err = fmt.Errorf("target item nr %d is %s, string expected", i+1, TypeName(targetSpec))
+				break
+			}
+		}
+	}
+	return
+}
+
+func splitStrFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+	var source, sep string
+	var count int = -1
+	var parts []string
+	var ok bool
+
+	if source, ok = args[ParamSource].(string); !ok {
+		return result, ErrWrongParamType(name, ParamSource, TypeString, args[ParamSource])
+	}
+
+	if sep, ok = args[ParamSeparator].(string); !ok {
+		return nil, fmt.Errorf("separator param must be string, got %s (%v)", TypeName(args[ParamSeparator]), args[ParamSeparator])
+	}
+
+	if count64, ok := args[ParamCount].(int64); ok { // TODO replace type assertion with toInt()
+		count = int(count64)
+	} else {
+		return nil, fmt.Errorf("part count must be integer, got %s (%v)", TypeName(args[ParamCount]), args[ParamCount])
+	}
+
+	if count > 0 {
+		parts = strings.SplitN(source, sep, count)
+	} else if count < 0 {
+		parts = strings.Split(source, sep)
+	} else {
+		parts = []string{}
+	}
+	list := make(ListType, len(parts))
+	for i, part := range parts {
+		list[i] = part
+	}
+	result = &list
+	return
+}
+
+func upperStrFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+	if source, ok := args[ParamSource].(string); ok {
+		result = strings.ToUpper(source)
+	} else {
+		err = ErrWrongParamType(name, ParamSource, TypeString, args[ParamSource])
+	}
+	return
+}
+
+func lowerStrFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+	if source, ok := args[ParamSource].(string); ok {
+		result = strings.ToLower(source)
+	} else {
+		err = ErrWrongParamType(name, ParamSource, TypeString, args[ParamSource])
+	}
+	return
+}
+
+// --- End of function definitions
+
+// Import above functions in the context
+func ImportStringFuncs(ctx ExprContext) {
+	ctx.RegisterFunc("strJoin", NewGolangFunctor(joinStrFunc), TypeString, []ExprFuncParam{
+		NewFuncParam(ParamSeparator),
+		NewFuncParamFlag(ParamItem, PfRepeat),
+	})
+
+	ctx.RegisterFunc("strSub", NewGolangFunctor(subStrFunc), TypeString, []ExprFuncParam{
+		NewFuncParam(ParamSource),
+		NewFuncParamFlagDef(ParamStart, PfDefault, int64(0)),
+		NewFuncParamFlagDef(ParamCount, PfDefault, int64(-1)),
+	})
+
+	ctx.RegisterFunc("strSplit", NewGolangFunctor(splitStrFunc), "list of "+TypeString, []ExprFuncParam{
+		NewFuncParam(ParamSource),
+		NewFuncParamFlagDef(ParamSeparator, PfDefault, ""),
+		NewFuncParamFlagDef(ParamCount, PfDefault, int64(-1)),
+	})
+
+	ctx.RegisterFunc("strTrim", NewGolangFunctor(trimStrFunc), TypeString, []ExprFuncParam{
+		NewFuncParam(ParamSource),
+	})
+
+	ctx.RegisterFunc("strStartsWith", NewGolangFunctor(startsWithStrFunc), TypeBoolean, []ExprFuncParam{
+		NewFuncParam(ParamSource),
+		NewFuncParam(ParamPrefix),
+		NewFuncParamFlag(strParamOther, PfRepeat),
+	})
+
+	ctx.RegisterFunc("strEndsWith", NewGolangFunctor(endsWithStrFunc), TypeBoolean, []ExprFuncParam{
+		NewFuncParam(ParamSource),
+		NewFuncParam(ParamSuffix),
+		NewFuncParamFlag(strParamOther, PfRepeat),
+	})
+
+	ctx.RegisterFunc("strUpper", NewGolangFunctor(upperStrFunc), TypeString, []ExprFuncParam{
+		NewFuncParam(ParamSource),
+	})
+
+	ctx.RegisterFunc("strLower", NewGolangFunctor(lowerStrFunc), TypeString, []ExprFuncParam{
+		NewFuncParam(ParamSource),
+	})
+}
+
+// Register the import function in the import-register.
+// That will allow to import all function of this module by the "builtin" operator."
+func init() {
+	RegisterBuiltinModule("string", ImportStringFuncs, "string utilities")
+}

builtins-register.go

@@ -0,0 +1,48 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// builtins-register.go
+package expr
+
+import (
+	"fmt"
+)
+
+type builtinModule struct {
+	importFunc  func(ExprContext)
+	description string
+	imported    bool
+}
+
+func newBuiltinModule(importFunc func(ExprContext), description string) *builtinModule {
+	return &builtinModule{importFunc, description, false}
+}
+
+var builtinModuleRegister map[string]*builtinModule
+
+func RegisterBuiltinModule(name string, importFunc func(ExprContext), description string) {
+	if builtinModuleRegister == nil {
+		builtinModuleRegister = make(map[string]*builtinModule)
+	}
+	if _, exists := builtinModuleRegister[name]; exists {
+		panic(fmt.Errorf("module %q already registered", name))
+	}
+	builtinModuleRegister[name] = newBuiltinModule(importFunc, description)
+}
+
+func IterateBuiltinModules(op func(name, description string, imported bool) bool) {
+	if op != nil {
+		for name, mod := range builtinModuleRegister {
+			if !op(name, mod.description, mod.imported) {
+				break
+			}
+		}
+	}
+}
+
+// ----
+func init() {
+	if builtinModuleRegister == nil {
+		builtinModuleRegister = make(map[string]*builtinModule)
+	}
+}

byte-slider.go

@@ -18,17 +18,17 @@ func NewByteSlider(size int) *ByteSlider {
 	}
 }
 
-func (self *ByteSlider) PushEnd(b byte) {
-	if self.length == cap(self.buf) {
-		self.length--
-		for i := 0; i < self.length; i++ {
-			self.buf[i] = self.buf[i+1]
+func (slider *ByteSlider) PushEnd(b byte) {
+	if slider.length == cap(slider.buf) {
+		slider.length--
+		for i := 0; i < slider.length; i++ {
+			slider.buf[i] = slider.buf[i+1]
 		}
 	}
-	self.buf[self.length] = b
-	self.length++
+	slider.buf[slider.length] = b
+	slider.length++
 }
 
-func (self *ByteSlider) Equal(target []byte) bool {
-	return target != nil && bytes.Equal(self.buf, target)
+func (slider *ByteSlider) Equal(target []byte) bool {
+	return target != nil && bytes.Equal(slider.buf, target)
 }

common-errors.go

@@ -6,50 +6,86 @@ package expr
 
 import (
 	"fmt"
+	"strings"
 )
 
-func errTooFewParams(minArgs, maxArgs, argCount int) (err error) {
+func ErrMissingParams(funcName string, missing []string) (err error) {
+	return fmt.Errorf("%s(): missing params -- %s", funcName, strings.Join(missing, ", "))
+}
+
+func ErrTooFewParams(funcName string, minArgs, maxArgs, argCount int) (err error) {
 	if maxArgs < 0 {
-		err = fmt.Errorf("too few params -- expected %d or more, got %d", minArgs, argCount)
+		err = fmt.Errorf("%s(): too few params -- expected %d or more, got %d", funcName, minArgs, argCount)
 	} else {
-		err = fmt.Errorf("too few params -- expected %d, got %d", minArgs, argCount)
+		err = fmt.Errorf("%s(): too few params -- expected %d, got %d", funcName, minArgs, argCount)
 	}
 	return
 }
 
-func errTooMuchParams(maxArgs, argCount int) (err error) {
-	err = fmt.Errorf("too much params -- expected %d, got %d", maxArgs, argCount)
+func ErrTooManyParams(funcName string, maxArgs, argCount int) (err error) {
+	err = fmt.Errorf("%s(): too many params -- expected %d, got %d", funcName, maxArgs, argCount)
 	return
 }
 
 // --- General errors
 
-func errCantConvert(funcName string, value any, kind string) error {
-	return fmt.Errorf("%s() can't convert %T to %s", funcName, value, kind)
+func ErrCantConvert(funcName string, value any, kind string) error {
+	return fmt.Errorf("%s(): can't convert %s to %s", funcName, TypeName(value), kind)
 }
 
-func errExpectedGot(funcName string, kind string, value any) error {
-	return fmt.Errorf("%s() expected %s, got %T (%v)", funcName, kind, value, value)
+func ErrExpectedGot(funcName string, kind string, value any) error {
+	return fmt.Errorf("%s(): expected %s, got %s (%v)", funcName, kind, TypeName(value), value)
 }
 
-func errDivisionByZero(funcName string) error {
-	return fmt.Errorf("%s() division by zero", funcName)
+func ErrFuncDivisionByZero(funcName string) error {
+	return fmt.Errorf("%s(): division by zero", funcName)
 }
 
+// func ErrDivisionByZero() error {
+// 	return fmt.Errorf("division by zero")
+// }
+
 // --- Parameter errors
 
-// func errOneParam(funcName string) error {
-// 	return fmt.Errorf("%s() requires exactly one param", funcName)
+// func ErrMissingRequiredParameter(funcName, paramName string) error {
+// 	return fmt.Errorf("%s(): missing required parameter %q", funcName, paramName)
 // }
 
-func errMissingRequiredParameter(funcName, paramName string) error {
-	return fmt.Errorf("%s() missing required parameter %q", funcName, paramName)
+func ErrInvalidParameterValue(funcName, paramName string, paramValue any) error {
+	return fmt.Errorf("%s(): invalid value %s (%v) for parameter %q", funcName, TypeName(paramValue), paramValue, paramName)
 }
 
-func errInvalidParameterValue(funcName, paramName string, paramValue any) error {
-	return fmt.Errorf("%s() invalid value %T (%v) for parameter %q", funcName, paramValue, paramValue, paramName)
+func undefArticle(s string) (article string) {
+	if len(s) > 0 && strings.Contains("aeiou", s[0:1]) {
+		article = "an"
+	} else {
+		article = "a"
+	}
+	return
 }
 
-func errWrongParamType(funcName, paramName, paramType string, paramValue any) error {
-	return fmt.Errorf("%s() the %q parameter must be a %s, got a %T (%v)", funcName, paramName, paramType, paramValue, paramValue)
+func prependUndefArticle(s string) (result string) {
+	return undefArticle(s) + " " + s
+}
+
+func ErrWrongParamType(funcName, paramName, paramType string, paramValue any) error {
+	var artWantType, artGotType string
+	gotType := TypeName(paramValue)
+	artGotType = prependUndefArticle(gotType)
+	artWantType = prependUndefArticle(paramType)
+	return fmt.Errorf("%s(): the %q parameter must be %s, got %s (%v)", funcName, paramName, artWantType, artGotType, paramValue)
+}
+
+func ErrUnknownParam(funcName, paramName string) error {
+	return fmt.Errorf("%s(): unknown parameter %q", funcName, paramName)
+}
+
+func ErrUnknownVar(funcName, varName string) error {
+	return fmt.Errorf("%s(): unknown variable %q", funcName, varName)
+}
+
+// --- Operator errors
+
+func ErrLeftOperandMustBeVariable(leftTerm, opTerm *term) error {
+	return leftTerm.Errorf("left operand of %q must be a variable", opTerm.source())
 }

common-params.go

@@ -5,26 +5,28 @@
 package expr
 
 const (
-	paramCount     = "count"
-	paramItem      = "item"
-	paramParts     = "parts"
-	paramSeparator = "separator"
-	paramSource    = "source"
-	paramSuffix    = "suffix"
-	paramPrefix    = "prefix"
-	paramStart     = "start"
-	paramEnd       = "end"
-	paramValue     = "value"
-	paramEllipsis  = "..."
-	typeFilepath   = "filepath"
-	typeDirpath    = "dirpath"
+	ParamArgs      = "args"
+	ParamCount     = "count"
+	ParamItem      = "item"
+	ParamIndex     = "index"
+	ParamParts     = "parts"
+	ParamSeparator = "separator"
+	ParamSource    = "source"
+	ParamSuffix    = "suffix"
+	ParamPrefix    = "prefix"
+	ParamStart     = "start"
+	ParamEnd       = "end"
+	ParamValue     = "value"
+	ParamName      = "name"
+	ParamEllipsis  = "..."
+	ParamFilepath  = "filepath"
+	ParamDirpath   = "dirpath"
+	ParamHandle    = "handle"
+	ParamResource  = "resource"
+	ParamIterator  = "iterator"
 )
 
-// const (
-// 	typeInteger  = "int"
-// 	typeFloat    = "float"
-// 	typeString   = "string"
-// 	typeFraction = "fract"
-// 	typeList     = "list"
-// 	typeDict     = "dict"
-// )
+// to be moved in its own source file
+const (
+	ConstLastIndex = 0xFFFF_FFFF
+)

common-type-names.go

@@ -5,14 +5,19 @@
 package expr
 
 const (
-	typeAny      = "any"
-	typeBoolean  = "boolean"
-	typeFloat    = "float"
-	typeFraction = "fraction"
-	typeHandle   = "handle"
-	typeInt      = "integer"
-	typeItem     = "item"
-	typeNumber   = "number"
-	typePair     = "pair"
-	typeString   = "string"
+	TypeAny           = "any"
+	TypeNil           = "nil"
+	TypeBoolean       = "boolean"
+	TypeFloat         = "float"
+	TypeFraction      = "fraction"
+	TypeFileHandle    = "file-handle"
+	TypeInt           = "integer"
+	TypeItem          = "item"
+	TypeIterator      = "iterator"
+	TypeNumber        = "number"
+	TypePair          = "pair"
+	TypeString        = "string"
+	TypeDict          = "dict"
+	TypeListOf        = "list-of-"
+	TypeListOfStrings = "list-of-strings"
 )

context-helpers.go

@@ -22,16 +22,14 @@ func exportFunc(ctx ExprContext, name string, info ExprFunc) {
 	if name[0] == '@' {
 		name = name[1:]
 	}
-	// ctx.RegisterFunc(name, info.Functor(), info.MinArgs(), info.MaxArgs())
-	// ctx.RegisterFuncInfo(name, info)
 	ctx.RegisterFunc(name, info.Functor(), info.ReturnType(), info.Params())
 }
 
 func exportObjects(destCtx, sourceCtx ExprContext) {
-	exportAll := isEnabled(sourceCtx, control_export_all)
+	exportAll := CtrlIsEnabled(sourceCtx, control_export_all)
 	// fmt.Printf("Exporting from sourceCtx [%p] to destCtx [%p] -- exportAll=%t\n", sourceCtx, destCtx, exportAll)
 	// Export variables
-	for _, refName := range sourceCtx.EnumVars(func(name string) bool { return exportAll || name[0] == '@' }) {
+	for _, refName := range sourceCtx.EnumVars(func(name string) bool { return (exportAll || name[0] == '@') && !(name[0] == '_') }) {
 		// fmt.Printf("\tExporting %q\n", refName)
 		refValue, _ := sourceCtx.GetVar(refName)
 		exportVar(destCtx, refName, refValue)
@@ -43,3 +41,9 @@ func exportObjects(destCtx, sourceCtx ExprContext) {
 		}
 	}
 }
+
+func exportObjectsToParent(sourceCtx ExprContext) {
+	if parentCtx := sourceCtx.GetParent(); parentCtx != nil {
+		exportObjects(parentCtx, sourceCtx)
+	}
+}

context.go

@@ -1,47 +0,0 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
-// All rights reserved.
-
-// context.go
-package expr
-
-// ---- Functor interface
-type Functor interface {
-	Invoke(ctx ExprContext, name string, args []any) (result any, err error)
-	SetFunc(info ExprFunc)
-	GetFunc() ExprFunc
-}
-
-// ---- Function Param Info
-type ExprFuncParam interface {
-	Name() string
-	Type() string
-	IsOptional() bool
-	IsRepeat() bool
-	DefaultValue() any
-}
-
-// ---- Function Info
-type ExprFunc interface {
-	Formatter
-	Name() string
-	MinArgs() int
-	MaxArgs() int
-	Functor() Functor
-	Params() []ExprFuncParam
-	ReturnType() string
-}
-
-// ----Expression Context
-type ExprContext interface {
-	Clone() ExprContext
-	GetVar(varName string) (value any, exists bool)
-	SetVar(varName string, value any)
-	UnsafeSetVar(varName string, value any)
-	EnumVars(func(name string) (accept bool)) (varNames []string)
-	EnumFuncs(func(name string) (accept bool)) (funcNames []string)
-	GetFuncInfo(name string) (item ExprFunc, exists bool)
-	Call(name string, args []any) (result any, err error)
-	// RegisterFunc(name string, f Functor, minArgs, maxArgs int)
-	RegisterFuncInfo(info ExprFunc)
-	RegisterFunc(name string, f Functor, returnType string, param []ExprFuncParam) error
-}

control.go

@@ -4,13 +4,14 @@
 // control.go
 package expr
 
-import "strings"
-
 // Preset control variables
 const (
-	ControlLastResult   = "last"
-	ControlBoolShortcut = "_bool_shortcut"
-	ControlImportPath   = "_import_path"
+	ControlPreset        = "_preset"
+	ControlLastResult    = "last"
+	ControlBoolShortcut  = "_bool_shortcut"
+	ControlSearchPath    = "_search_path"
+	ControlParentContext = "_parent_context"
+	ControlStdout        = "_stdout"
 )
 
 // Other control variables
@@ -20,43 +21,20 @@ const (
 
 // Initial values
 const (
-	init_import_path = "~/.local/lib/go-pkg/expr:/usr/local/lib/go-pkg/expr:/usr/lib/go-pkg/expr"
+	init_search_path = "~/.local/lib/go-pkg/expr:/usr/local/lib/go-pkg/expr:/usr/lib/go-pkg/expr"
 )
 
+func SetCtrl(ctx ExprContext, name string, value any) (current any) {
+	current, _ = ctx.GetVar(name)
+	ctx.UnsafeSetVar(name, value)
+	return
+}
+
 func initDefaultVars(ctx ExprContext) {
-	ctx.SetVar(ControlBoolShortcut, true)
-	ctx.SetVar(ControlImportPath, init_import_path)
-}
-
-func enable(ctx ExprContext, name string) {
-	if strings.HasPrefix(name, "_") {
-		ctx.SetVar(name, true)
-	} else {
-		ctx.SetVar("_"+name, true)
+	if _, exists := ctx.GetVar(ControlPreset); exists {
+		return
 	}
-}
-
-func disable(ctx ExprContext, name string) {
-	if strings.HasPrefix(name, "_") {
-		ctx.SetVar(name, false)
-	} else {
-		ctx.SetVar("_"+name, false)
-	}
-}
-
-func isEnabled(ctx ExprContext, name string) (status bool) {
-	if v, exists := ctx.GetVar(name); exists {
-		if b, ok := v.(bool); ok {
-			status = b
-		}
-	}
-	return
-}
-
-func getControlString(ctx ExprContext, name string) (s string, exists bool) {
-	var v any
-	if v, exists = ctx.GetVar(name); exists {
-		s, exists = v.(string)
-	}
-	return
+	ctx.UnsafeSetVar(ControlPreset, true)
+	ctx.UnsafeSetVar(ControlBoolShortcut, true)
+	ctx.UnsafeSetVar(ControlSearchPath, init_search_path)
 }

data-cursor.go

@@ -5,30 +5,51 @@
 package expr
 
 import (
-	"errors"
 	"io"
+	"slices"
 )
 
 type dataCursor struct {
-	ds          map[string]Functor
-	ctx         ExprContext
-	index       int
-	resource    any
-	nextFunc    Functor
-	cleanFunc   Functor
-	resetFunc   Functor
-	currentFunc Functor
+	ds        map[string]Functor
+	ctx       ExprContext
+	initState bool // true if no item has produced yet (this replace di initial Next() call in the contructor)
+	// cursorValid bool // true if resource is nil or if clean has not yet been called
+	index     int
+	count     int
+	current   any
+	lastErr   error
+	resource  any
+	nextFunc  Functor
+	cleanFunc Functor
+	resetFunc Functor
 }
 
-func newDataCursor(ctx ExprContext, ds map[string]Functor) (dc *dataCursor) {
+func NewDataCursor(ctx ExprContext, ds map[string]Functor, resource any) (dc *dataCursor) {
 	dc = &dataCursor{
-		ds:    ds,
-		index: -1,
-		ctx:   ctx.Clone(),
+		ds:        ds,
+		initState: true,
+		// cursorValid: true,
+		index:     -1,
+		count:     0,
+		current:   nil,
+		lastErr:   nil,
+		resource:  resource,
+		ctx:       ctx.Clone(),
+		nextFunc:  ds[NextName],
+		cleanFunc: ds[CleanName],
+		resetFunc: ds[ResetName],
 	}
 	return
 }
 
+func (dc *dataCursor) Context() ExprContext {
+	return dc.ctx
+}
+
+func (dc *dataCursor) TypeName() string {
+	return "DataCursor"
+}
+
 // func mapToString(m map[string]Functor) string {
 // 	var sb strings.Builder
 // 	sb.WriteByte('{')
@@ -58,7 +79,7 @@ func (dc *dataCursor) String() string {
 }
 
 func (dc *dataCursor) HasOperation(name string) (exists bool) {
-	exists = name == indexName
+	exists = slices.Contains([]string{CleanName, ResetName, CurrentName, IndexName}, name)
 	if !exists {
 		f, ok := dc.ds[name]
 		exists = ok && isFunctor(f)
@@ -66,89 +87,219 @@ func (dc *dataCursor) HasOperation(name string) (exists bool) {
 	return
 }
 
-func (dc *dataCursor) CallOperation(name string, args []any) (value any, err error) {
-	if name == indexName {
+func (dc *dataCursor) CallOperation(name string, args map[string]any) (value any, err error) {
+	if name == IndexName {
 		value = int64(dc.Index())
+	} else if name == CleanName {
+		err = dc.Clean()
+	} else if name == ResetName {
+		err = dc.Reset()
 	} else if functor, ok := dc.ds[name]; ok && isFunctor(functor) {
-		if functor == dc.cleanFunc {
-			value, err = dc.Clean()
-		} else if functor == dc.resetFunc {
-			value, err = dc.Reset()
-		} else {
-			ctx := cloneContext(dc.ctx)
-			value, err = functor.Invoke(ctx, name, []any{})
-			exportObjects(dc.ctx, ctx)
-		}
+		ctx := cloneContext(dc.ctx)
+		value, err = functor.InvokeNamed(ctx, name, args)
+		exportObjects(dc.ctx, ctx)
 	} else {
 		err = errNoOperation(name)
 	}
 	return
 }
 
-func (dc *dataCursor) Reset() (success bool, err error) {
+// func (dc *dataCursor) Reset() (err error) {
+// 	if dc.resetFunc != nil {
+// 		if dc.resource != nil {
+// 			ctx := cloneContext(dc.ctx)
+// 			actualParams := bindActualParams(dc.resetFunc, []any{dc.resource})
+// 			_, err = dc.resetFunc.InvokeNamed(ctx, ResetName, actualParams)
+// 			exportObjects(dc.ctx, ctx)
+// 			dc.index = -1
+// 			dc.count = 0
+// 			dc.initState = true
+// 			dc.current = nil
+// 			dc.lastErr = nil
+// 		} else {
+// 			err = errInvalidDataSource()
+// 		}
+// 	} else {
+// 		err = errNoOperation(ResetName)
+// 	}
+// 	return
+// }
+
+func (dc *dataCursor) Reset() (err error) {
 	if dc.resetFunc != nil {
-		if dc.resource != nil {
-			ctx := cloneContext(dc.ctx)
-			if _, err = dc.resetFunc.Invoke(ctx, resetName, []any{dc.resource}); err == nil {
-				dc.index = -1
-			}
-			exportObjects(dc.ctx, ctx)
-		} else {
-			err = errInvalidDataSource()
-		}
-	} else {
-		err = errNoOperation(resetName)
+		ctx := cloneContext(dc.ctx)
+		actualParams := bindActualParams(dc.resetFunc, []any{dc.resource})
+		_, err = dc.resetFunc.InvokeNamed(ctx, ResetName, actualParams)
+		exportObjects(dc.ctx, ctx)
 	}
-	success = err == nil
+	dc.index = -1
+	dc.count = 0
+	dc.initState = true
+	dc.current = nil
+	dc.lastErr = nil
 	return
 }
 
-func (dc *dataCursor) Clean() (success bool, err error) {
+func (dc *dataCursor) Clean() (err error) {
 	if dc.cleanFunc != nil {
-		if dc.resource != nil {
-			ctx := cloneContext(dc.ctx)
-			_, err = dc.cleanFunc.Invoke(ctx, cleanName, []any{dc.resource})
-			dc.resource = nil
-			exportObjects(dc.ctx, ctx)
-		} else {
-			err = errInvalidDataSource()
-		}
-	} else {
-		err = errors.New("no 'clean' function defined in the data-source")
+		ctx := cloneContext(dc.ctx)
+		actualParams := bindActualParams(dc.cleanFunc, []any{dc.resource})
+		_, err = dc.cleanFunc.InvokeNamed(ctx, CleanName, actualParams)
+		exportObjects(dc.ctx, ctx)
 	}
-	success = err == nil
+	dc.lastErr = io.EOF
 	return
 }
 
+// func (dc *dataCursor) Clean() (err error) {
+// 	if dc.cleanFunc != nil {
+// 		if dc.resource != nil {
+// 			ctx := cloneContext(dc.ctx)
+// 			actualParams := bindActualParams(dc.cleanFunc, []any{dc.resource})
+// 			_, err = dc.cleanFunc.InvokeNamed(ctx, CleanName, actualParams)
+// 			exportObjects(dc.ctx, ctx)
+// 		} else {
+// 			err = errInvalidDataSource()
+// 		}
+// 	} else {
+// 		err = errNoOperation(CleanName)
+// 	}
+// 	return
+// }
+
 func (dc *dataCursor) Current() (item any, err error) { // must return io.EOF at the last item
-	ctx := cloneContext(dc.ctx)
-	if item, err = dc.currentFunc.Invoke(ctx, currentName, []any{}); err == nil && item == nil {
+	dc.init()
+
+	if dc.current != nil {
+		item = dc.current
+	} else {
 		err = io.EOF
 	}
-	exportObjects(dc.ctx, ctx)
 	return
 }
 
-func (dc *dataCursor) Next() (item any, err error) { // must return io.EOF after the last item
-	if dc.resource != nil {
-		ctx := cloneContext(dc.ctx)
-		// fmt.Printf("Entering Inner-Ctx [%p]: %s\n", ctx, CtxToString(ctx, 0))
-		if item, err = dc.nextFunc.Invoke(ctx, nextName, []any{dc.resource}); err == nil {
-			if item == nil {
-				err = io.EOF
-			} else {
-				dc.index++
-			}
+func (dc *dataCursor) checkFilter(filter Functor, item any) (accepted bool, err error) {
+	var v any
+	var ok bool
+	ctx := cloneContext(dc.ctx)
+
+	actualParams := bindActualParams(filter, []any{item, dc.index})
+	if v, err = filter.InvokeNamed(ctx, FilterName, actualParams); err == nil && v != nil {
+		if accepted, ok = v.(bool); !ok {
+			accepted = true // NOTE: A non-boolean value that is not nil means the item has been accepted
 		}
-		// fmt.Printf("Exiting Inner-Ctx [%p]: %s\n", ctx, CtxToString(ctx, 0))
-		exportObjects(dc.ctx, ctx)
-		// fmt.Printf("Outer-Ctx [%p]: %s\n", dc.ctx, CtxToString(dc.ctx, 0))
-	} else {
-		err = errInvalidDataSource()
 	}
 	return
 }
 
+func (dc *dataCursor) mapItem(mapper Functor, item any) (mappedItem any, err error) {
+	ctx := cloneContext(dc.ctx)
+	actualParams := bindActualParams(mapper, []any{item, dc.index})
+	mappedItem, err = mapper.InvokeNamed(ctx, MapName, actualParams)
+	return
+}
+
+func (dc *dataCursor) init() {
+	if dc.initState {
+		dc.initState = false
+		dc.Next()
+	}
+}
+
+func (dc *dataCursor) Next() (current any, err error) { // must return io.EOF after the last item
+	if dc.initState {
+		dc.init()
+	} else if err = dc.lastErr; err != nil {
+		return
+	}
+	current = dc.current
+	filter := dc.ds[FilterName]
+	mapper := dc.ds[MapName]
+	var item any
+	for item == nil && dc.lastErr == nil {
+		ctx := cloneContext(dc.ctx)
+		dc.index++
+
+		actualParams := bindActualParams(dc.nextFunc, []any{dc.resource, dc.index})
+		if item, dc.lastErr = dc.nextFunc.InvokeNamed(ctx, NextName, actualParams); dc.lastErr == nil {
+			if item == nil {
+				dc.lastErr = io.EOF
+			} else {
+				accepted := true
+				if filter != nil {
+					if accepted, dc.lastErr = dc.checkFilter(filter, item); dc.lastErr != nil || !accepted {
+						item = nil
+					}
+				}
+				if accepted {
+					dc.count++
+				}
+				if item != nil && mapper != nil {
+					item, dc.lastErr = dc.mapItem(mapper, item)
+				}
+			}
+		}
+		exportObjects(dc.ctx, ctx)
+	}
+	dc.current = item
+	if dc.lastErr != nil {
+		dc.index--
+		dc.Clean()
+	}
+	return
+}
+
+// func (dc *dataCursor) Next() (current any, err error) { // must return io.EOF after the last item
+// 	if dc.initState {
+// 		dc.init()
+// 	} else if err = dc.lastErr; err != nil {
+// 		return
+// 	}
+// 	current = dc.current
+// 	if dc.resource != nil {
+// 		filter := dc.ds[FilterName]
+// 		mapper := dc.ds[MapName]
+// 		var item any
+// 		for item == nil && dc.lastErr == nil {
+// 			ctx := cloneContext(dc.ctx)
+// 			dc.index++
+
+// 			actualParams := bindActualParams(dc.nextFunc, []any{dc.resource, dc.index})
+// 			if item, dc.lastErr = dc.nextFunc.InvokeNamed(ctx, NextName, actualParams); dc.lastErr == nil {
+// 				if item == nil {
+// 					dc.lastErr = io.EOF
+// 				} else {
+// 					accepted := true
+// 					if filter != nil {
+// 						if accepted, dc.lastErr = dc.checkFilter(filter, item); dc.lastErr != nil || !accepted {
+// 							item = nil
+// 						}
+// 					}
+// 					if accepted {
+// 						dc.count++
+// 					}
+// 					if item != nil && mapper != nil {
+// 						item, dc.lastErr = dc.mapItem(mapper, item)
+// 					}
+// 				}
+// 			}
+// 			exportObjects(dc.ctx, ctx)
+// 		}
+// 		dc.current = item
+// 		if dc.lastErr != nil {
+// 			dc.index--
+// 			dc.Clean()
+// 		}
+// 	} else {
+// 		dc.lastErr = errInvalidDataSource()
+// 	}
+// 	return
+// }
+
 func (dc *dataCursor) Index() int {
-	return dc.index
+	return dc.index - 1
+}
+
+func (dc *dataCursor) Count() int {
+	return dc.count
 }

dict-iterator.go

@@ -0,0 +1,221 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// dict-iterator.go
+package expr
+
+import (
+	"fmt"
+	"io"
+	"slices"
+	"strings"
+)
+
+type dictIterMode int
+
+const (
+	dictIterModeKeys dictIterMode = iota
+	dictIterModeValues
+	dictIterModeItems
+)
+
+type DictIterator struct {
+	a        *DictType
+	count    int
+	index    int
+	keys     []any
+	iterMode dictIterMode
+}
+
+type sortType int
+
+const (
+	sortTypeNone sortType = iota
+	sortTypeAsc
+	sortTypeDesc
+	sortTypeDefault = sortTypeAsc
+)
+
+func (it *DictIterator) makeKeys(m map[any]any, sort sortType) {
+	it.keys = make([]any, 0, len(m))
+
+	if sort == sortTypeNone {
+		for keyAny := range m {
+			it.keys = append(it.keys, keyAny)
+		}
+	} else {
+		scalarMap := make(map[string]any, len(m))
+		scalerKeys := make([]string, 0, len(m))
+		for keyAny := range m {
+			keyStr := fmt.Sprint(keyAny)
+			scalarMap[keyStr] = keyAny
+			scalerKeys = append(scalerKeys, keyStr)
+		}
+
+		switch sort {
+		case sortTypeAsc:
+			slices.Sort(scalerKeys)
+		case sortTypeDesc:
+			slices.Sort(scalerKeys)
+			slices.Reverse(scalerKeys)
+		}
+		for _, keyStr := range scalerKeys {
+			it.keys = append(it.keys, scalarMap[keyStr])
+		}
+	}
+}
+
+func NewDictIterator(dict *DictType, args []any) (it *DictIterator, err error) {
+	var sortType = sortTypeNone
+	var s string
+	var argAny any
+
+	dictIt := &DictIterator{a: dict, count: 0, index: -1, keys: nil, iterMode: dictIterModeKeys}
+	if len(args) > 0 {
+		argAny = args[0]
+	} else {
+		argAny = "default"
+	}
+	if s, err = ToGoString(argAny, "sort type"); err == nil {
+		switch strings.ToLower(s) {
+		case "a", "asc":
+			sortType = sortTypeAsc
+		case "d", "desc":
+			sortType = sortTypeDesc
+		case "n", "none", "nosort", "no-sort":
+			sortType = sortTypeNone
+		case "", "default":
+			sortType = sortTypeDefault
+		default:
+			err = fmt.Errorf("invalid sort type %q", s)
+		}
+
+		if err == nil {
+			if len(args) > 1 {
+				argAny = args[1]
+			} else {
+				argAny = "default"
+			}
+
+			if s, err = ToGoString(argAny, "iteration mode"); err == nil {
+				switch strings.ToLower(s) {
+				case "k", "key", "keys":
+					dictIt.iterMode = dictIterModeKeys
+				case "v", "value", "values":
+					dictIt.iterMode = dictIterModeValues
+				case "i", "item", "items":
+					dictIt.iterMode = dictIterModeItems
+				case "", "default":
+					dictIt.iterMode = dictIterModeKeys
+				default:
+					err = fmt.Errorf("invalid iteration mode %q", s)
+				}
+			}
+		}
+	}
+
+	dictIt.makeKeys(*dict, sortType)
+	return dictIt, err
+}
+
+func NewMapIterator(m map[any]any) (it *DictIterator) {
+	it = &DictIterator{a: (*DictType)(&m), count: 0, index: -1, keys: nil}
+	it.makeKeys(m, sortTypeNone)
+	return
+}
+
+func (it *DictIterator) String() string {
+	var l = 0
+	if it.a != nil {
+		l = len(*it.a)
+	}
+	return fmt.Sprintf("$({#%d})", l)
+}
+
+func (it *DictIterator) TypeName() string {
+	return "DictIterator"
+}
+
+func (it *DictIterator) HasOperation(name string) bool {
+	// yes := name == NextName || name == ResetName || name == IndexName || name == CountName || name == CurrentName
+	yes := slices.Contains([]string{NextName, ResetName, IndexName, CountName, CurrentName, CleanName, KeyName, ValueName}, name)
+	return yes
+}
+
+func (it *DictIterator) CallOperation(name string, args map[string]any) (v any, err error) {
+	switch name {
+	case NextName:
+		v, err = it.Next()
+	case ResetName:
+		err = it.Reset()
+	case CleanName:
+		err = it.Clean()
+	case IndexName:
+		v = int64(it.Index())
+	case CurrentName:
+		v, err = it.Current()
+	case CountName:
+		v = it.count
+	case KeyName:
+		if it.index >= 0 && it.index < len(it.keys) {
+			v = it.keys[it.index]
+		} else {
+			err = io.EOF
+		}
+	case ValueName:
+		if it.index >= 0 && it.index < len(it.keys) {
+			a := *(it.a)
+			v = a[it.keys[it.index]]
+		} else {
+			err = io.EOF
+		}
+	default:
+		err = errNoOperation(name)
+	}
+	return
+}
+
+func (it *DictIterator) Current() (item any, err error) {
+	if it.index >= 0 && it.index < len(it.keys) {
+		switch it.iterMode {
+		case dictIterModeKeys:
+			item = it.keys[it.index]
+		case dictIterModeValues:
+			a := *(it.a)
+			item = a[it.keys[it.index]]
+		case dictIterModeItems:
+			a := *(it.a)
+			pair := []any{it.keys[it.index], a[it.keys[it.index]]}
+			item = newList(pair)
+		}
+	} else {
+		err = io.EOF
+	}
+	return
+}
+
+func (it *DictIterator) Next() (item any, err error) {
+	it.index++
+	if item, err = it.Current(); err != io.EOF {
+		it.count++
+	}
+	return
+}
+
+func (it *DictIterator) Index() int {
+	return it.index
+}
+
+func (it *DictIterator) Count() int {
+	return it.count
+}
+
+func (it *DictIterator) Reset() error {
+	it.index = -1
+	it.count = 0
+	return nil
+}
+
+func (it *DictIterator) Clean() error {
+	return nil
+}

dict-type.go

@@ -0,0 +1,166 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// dict-type.go
+package expr
+
+import (
+	"fmt"
+	"reflect"
+	"strings"
+)
+
+type DictType map[any]any
+
+func MakeDict() (dict *DictType) {
+	d := make(DictType)
+	dict = &d
+	return
+}
+
+func NewDict(dictAny map[any]any) (dict *DictType) {
+	var d DictType
+	if dictAny != nil {
+		d = make(DictType, len(dictAny))
+		for i, item := range dictAny {
+			d[i] = item
+		}
+	} else {
+		d = make(DictType)
+	}
+	dict = &d
+	return
+}
+
+func newDict(dictAny map[any]*term) (dict *DictType) {
+	// TODO Change with a call to NewDict()
+	var d DictType
+	if dictAny != nil {
+		d = make(DictType, len(dictAny))
+		for i, item := range dictAny {
+			d[i] = item
+		}
+	} else {
+		d = make(DictType)
+	}
+	dict = &d
+	return
+}
+
+func (dict *DictType) toMultiLine(sb *strings.Builder, opt FmtOpt) {
+	indent := GetFormatIndent(opt)
+	flags := GetFormatFlags(opt)
+	//sb.WriteString(strings.Repeat("  ", indent))
+	sb.WriteByte('{')
+
+	if len(*dict) > 0 {
+		innerOpt := MakeFormatOptions(flags, indent+1)
+		nest := strings.Repeat("  ", indent+1)
+		sb.WriteByte('\n')
+
+		first := true
+		for name, value := range *dict {
+			if first {
+				first = false
+			} else {
+				sb.WriteByte(',')
+				sb.WriteByte('\n')
+			}
+
+			sb.WriteString(nest)
+			if key, ok := name.(string); ok {
+				sb.WriteString(string('"') + key + string('"'))
+			} else {
+				sb.WriteString(fmt.Sprintf("%v", name))
+			}
+			sb.WriteString(": ")
+			if f, ok := value.(Formatter); ok {
+				sb.WriteString(f.ToString(innerOpt))
+			} else if _, ok = value.(Functor); ok {
+				sb.WriteString("func(){}")
+			} else {
+				sb.WriteString(fmt.Sprintf("%v", value))
+			}
+		}
+		sb.WriteByte('\n')
+		sb.WriteString(strings.Repeat("  ", indent))
+	}
+	sb.WriteString("}")
+}
+
+func (dict *DictType) ToString(opt FmtOpt) string {
+	var sb strings.Builder
+	flags := GetFormatFlags(opt)
+	if flags&MultiLine != 0 {
+		dict.toMultiLine(&sb, opt)
+	} else {
+		sb.WriteByte('{')
+		first := true
+		for key, value := range *dict {
+			if first {
+				first = false
+			} else {
+				sb.WriteString(", ")
+			}
+			if s, ok := key.(string); ok {
+				sb.WriteString(string('"') + s + string('"'))
+			} else {
+				sb.WriteString(fmt.Sprintf("%v", key))
+			}
+			sb.WriteString(": ")
+			if formatter, ok := value.(Formatter); ok {
+				sb.WriteString(formatter.ToString(opt))
+			} else if t, ok := value.(*term); ok {
+				sb.WriteString(t.String())
+			} else {
+				sb.WriteString(fmt.Sprintf("%#v", value))
+			}
+		}
+		sb.WriteByte('}')
+	}
+	return sb.String()
+}
+
+func (dict *DictType) String() string {
+	return dict.ToString(0)
+}
+
+func (dict *DictType) TypeName() string {
+	return "dict"
+}
+
+func (dict *DictType) hasKey(target any) (ok bool) {
+	for key := range *dict {
+		if ok = reflect.DeepEqual(key, target); ok {
+			break
+		}
+	}
+	return
+}
+
+func (dict *DictType) clone() (c *DictType) {
+	c = newDict(nil)
+	for k, v := range *dict {
+		(*c)[k] = v
+	}
+	return
+}
+
+func (dict *DictType) merge(second *DictType) {
+	if second != nil {
+		for k, v := range *second {
+			(*dict)[k] = v
+		}
+	}
+}
+
+func (dict *DictType) setItem(key any, value any) (err error) {
+	(*dict)[key] = value
+	return
+}
+
+////////////////
+
+type DictFormat interface {
+	ToDict() *DictType
+}

expr-context.go

@@ -0,0 +1,29 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// expr-context.go
+package expr
+
+// ----Expression Context
+type ExprContext interface {
+	Clone() ExprContext
+	SetParent(ctx ExprContext)
+	GetParent() (ctx ExprContext)
+	GetVar(varName string) (value any, exists bool)
+	GetLast() any
+	SetVar(varName string, value any)
+	UnsafeSetVar(varName string, value any)
+
+	EnumVars(func(name string) (accept bool)) (varNames []string)
+	VarCount() int
+	DeleteVar(varName string)
+
+	EnumFuncs(func(name string) (accept bool)) (funcNames []string)
+	FuncCount() int
+	DeleteFunc(funcName string)
+
+	GetFuncInfo(name string) (item ExprFunc, exists bool)
+	Call(name string, args map[string]any) (result any, err error)
+	RegisterFuncInfo(info ExprFunc)
+	RegisterFunc(name string, f Functor, returnType string, param []ExprFuncParam) (funcInfo ExprFunc, err error)
+}

expr-function.go

@@ -0,0 +1,39 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// expr-function.go
+package expr
+
+// ---- Functor interface
+type Functor interface {
+	Typer
+	InvokeNamed(ctx ExprContext, name string, args map[string]any) (result any, err error)
+	SetFunc(info ExprFunc)
+	GetFunc() ExprFunc
+	GetParams() []ExprFuncParam
+	GetDefinitionContext() ExprContext
+}
+
+// ---- Function Param Info
+type ExprFuncParam interface {
+	Name() string
+	Type() string
+	IsDefault() bool
+	IsOptional() bool
+	IsRepeat() bool
+	DefaultValue() any
+}
+
+// ---- Function Info
+type ExprFunc interface {
+	Formatter
+	Name() string
+	MinArgs() int
+	MaxArgs() int
+	Functor() Functor
+	Params() []ExprFuncParam
+	ParamSpec(paramName string) ExprFuncParam
+	ReturnType() string
+	PrepareCall(name string, actualParams map[string]any) (err error)
+	AllocContext(parentCtx ExprContext) (ctx ExprContext)
+}

expr.go

@@ -0,0 +1,12 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// expr.go
+package expr
+
+// ----Expression interface
+type Expr interface {
+	Typer
+	Eval(ctx ExprContext) (result any, err error)
+	String() string
+}

file-reader.expr

@@ -1,33 +0,0 @@
-builtin ["os.file", "base"];
-
-readInt=func(fh){
-	line=readFile(fh);
-	line ? [nil] {nil} :: {int(line)}
-};
-
-ds={
-	"init":func(filename){
-		fh=openFile(filename);
-		fh ? [nil] {nil} :: { @current=readInt(fh); @prev=@current };
-		fh
-	},
-	"current":func(){
-		prev
-	},
-	"next":func(fh){
-		current ? 
-			[nil] {current}
-			:: {@prev=current; @current=readInt(fh) but current}
-	},
-	"clean":func(fh){
-		closeFile(fh)
-	}
-}
-
-//;f=$(ds, "int.list")
-/*
-;f++
-;f++
-;f++
-*/
-//;add(f)

formatter.go

@@ -6,7 +6,7 @@ package expr
 
 import "fmt"
 
-type FmtOpt uint16
+type FmtOpt uint32 // lower 16 bits hold a bit-mask, higher 16 bits hold an indentation number
 
 const (
 	TTY FmtOpt = 1 << iota
@@ -30,6 +30,18 @@ func TruncateString(s string) (trunc string) {
 	return
 }
 
+func MakeFormatOptions(flags FmtOpt, indent int) FmtOpt {
+	return FmtOpt(indent<<16) | flags
+}
+
+func GetFormatFlags(opt FmtOpt) FmtOpt {
+	return opt & 0xFFFF
+}
+
+func GetFormatIndent(opt FmtOpt) int {
+	return int(opt >> 16)
+}
+
 type Formatter interface {
 	ToString(options FmtOpt) string
 }
@@ -51,8 +63,10 @@ type Typer interface {
 	TypeName() string
 }
 
-func getTypeName(v any) (name string) {
-	if typer, ok := v.(Typer); ok {
+func TypeName(v any) (name string) {
+	if v == nil {
+		name = "nil"
+	} else if typer, ok := v.(Typer); ok {
 		name = typer.TypeName()
 	} else if IsInteger(v) {
 		name = "integer"

fraction-type.go

@@ -33,52 +33,10 @@ func float64ToFraction(f float64) (fract *FractionType, err error) {
 	}
 	dec := fmt.Sprintf("%.12f", decPart)
 	s := fmt.Sprintf("%s%.f%s", sign, intPart, dec[1:])
-	// fmt.Printf("S: '%s'\n",s)
 	return makeGeneratingFraction(s)
 }
 
 // Based on https://cs.opensource.google/go/go/+/refs/tags/go1.22.3:src/math/big/rat.go;l=39
-/*
-func _float64ToFraction(f float64) (num, den int64, err error) {
-	const expMask = 1<<11 - 1
-	bits := math.Float64bits(f)
-	mantissa := bits & (1<<52 - 1)
-	exp := int((bits >> 52) & expMask)
-	switch exp {
-	case expMask: // non-finite
-		err = errors.New("infite")
-		return
-	case 0: // denormal
-		exp -= 1022
-	default: // normal
-		mantissa |= 1 << 52
-		exp -= 1023
-	}
-
-	shift := 52 - exp
-
-	// Optimization (?): partially pre-normalise.
-	for mantissa&1 == 0 && shift > 0 {
-		mantissa >>= 1
-		shift--
-	}
-
-	if f < 0 {
-		num = -int64(mantissa)
-	} else {
-		num = int64(mantissa)
-	}
-	den = int64(1)
-
-	if shift > 0 {
-		den = den << shift
-	} else {
-		num = num << (-shift)
-	}
-	return
-}
-*/
-
 func makeGeneratingFraction(s string) (f *FractionType, err error) {
 	var num, den int64
 	var sign int64 = 1
@@ -92,9 +50,10 @@ func makeGeneratingFraction(s string) (f *FractionType, err error) {
 	} else if s[0] == '+' {
 		s = s[1:]
 	}
-	if strings.HasSuffix(s, "()") {
-		s = s[0 : len(s)-2]
-	}
+	//	if strings.HasSuffix(s, "()") {
+	//		s = s[0 : len(s)-2]
+	//	}
+	s = strings.TrimSuffix(s, "()")
 	parts = strings.SplitN(s, ".", 2)
 	if num, err = strconv.ParseInt(parts[0], 10, 64); err != nil {
 		return
@@ -112,7 +71,7 @@ func makeGeneratingFraction(s string) (f *FractionType, err error) {
 			}
 			for _, c := range dec[0:lsd] {
 				if c < '0' || c > '9' {
-					return nil, errExpectedGot("fract", "digit", c)
+					return nil, ErrExpectedGot("fract", "digit", c)
 				}
 				num = num*10 + int64(c-'0')
 				den = den * 10
@@ -123,7 +82,7 @@ func makeGeneratingFraction(s string) (f *FractionType, err error) {
 			mul := int64(1)
 			for _, c := range subParts[0] {
 				if c < '0' || c > '9' {
-					return nil, errExpectedGot("fract", "digit", c)
+					return nil, ErrExpectedGot("fract", "digit", c)
 				}
 				num = num*10 + int64(c-'0')
 				sub = sub*10 + int64(c-'0')
@@ -136,7 +95,7 @@ func makeGeneratingFraction(s string) (f *FractionType, err error) {
 				p := subParts[1][0 : len(subParts[1])-1]
 				for _, c := range p {
 					if c < '0' || c > '9' {
-						return nil, errExpectedGot("fract", "digit", c)
+						return nil, ErrExpectedGot("fract", "digit", c)
 					}
 					num = num*10 + int64(c-'0')
 					den = den*10 + 9
@@ -165,36 +124,38 @@ func (f *FractionType) String() string {
 func (f *FractionType) ToString(opt FmtOpt) string {
 	var sb strings.Builder
 	if opt&MultiLine == 0 {
-		sb.WriteString(fmt.Sprintf("%d|%d", f.num, f.den))
+		sb.WriteString(fmt.Sprintf("%d:%d", f.num, f.den))
 	} else {
-		var s, num string
+		var sign, num string
 		if f.num < 0 && opt&TTY == 0 {
 			num = strconv.FormatInt(-f.num, 10)
-			s = "-"
+			sign = "-"
 		} else {
 			num = strconv.FormatInt(f.num, 10)
 		}
 		den := strconv.FormatInt(f.den, 10)
 		size := max(len(num), len(den))
 		if opt&TTY != 0 {
-			sb.WriteString(fmt.Sprintf("\x1b[4m%[1]*s\x1b[0m\n", -size, fmt.Sprintf("%[1]*s", (size+len(num))/2, s+num)))
+			sNum := fmt.Sprintf("\x1b[4m%[1]*s\x1b[0m\n", -size, fmt.Sprintf("%[1]*s", (size+len(num))/2, sign+num))
+			sb.WriteString(sNum)
 		} else {
-			if len(s) > 0 {
+			if len(sign) > 0 {
 				sb.WriteString("  ")
 			}
 			sb.WriteString(fmt.Sprintf("%[1]*s", -size, fmt.Sprintf("%[1]*s", (size+len(num))/2, num)))
 			sb.WriteByte('\n')
-			if len(s) > 0 {
-				sb.WriteString(s)
+			if len(sign) > 0 {
+				sb.WriteString(sign)
 				sb.WriteByte(' ')
 			}
 			sb.WriteString(strings.Repeat("-", size))
 			sb.WriteByte('\n')
-			if len(s) > 0 {
+			if len(sign) > 0 {
 				sb.WriteString("  ")
 			}
 		}
-		sb.WriteString(fmt.Sprintf("%[1]*s", -size, fmt.Sprintf("%[1]*s", (size+len(den))/2, den)))
+		sDen := fmt.Sprintf("%[1]*s", size, fmt.Sprintf("%[1]*s", (size+len(den))/2, den))
+		sb.WriteString(sDen)
 	}
 
 	return sb.String()
@@ -254,7 +215,7 @@ func anyToFract(v any) (f *FractionType, err error) {
 		}
 	}
 	if f == nil {
-		err = errExpectedGot("fract", typeFraction, v)
+		err = ErrExpectedGot("fract", TypeFraction, v)
 	}
 	return
 }
@@ -353,7 +314,6 @@ func divAnyFract(af1, af2 any) (quot any, err error) {
 	if f2.num == 0 {
 		err = errors.New("division by zero")
 		return
-		return
 	}
 	if f1.num == 0 || f2.den == 0 {
 		quot = 0

func-base.go

@@ -1,186 +0,0 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
-// All rights reserved.
-
-// func-builtins.go
-package expr
-
-import (
-	"math"
-	"strconv"
-)
-
-func isNilFunc(ctx ExprContext, name string, args []any) (result any, err error) {
-	result = args[0] == nil
-	return
-}
-
-func isIntFunc(ctx ExprContext, name string, args []any) (result any, err error) {
-	result = IsInteger(args[0])
-	return
-}
-
-func isFloatFunc(ctx ExprContext, name string, args []any) (result any, err error) {
-	result = IsFloat(args[0])
-	return
-}
-
-func isBoolFunc(ctx ExprContext, name string, args []any) (result any, err error) {
-	result = IsBool(args[0])
-	return
-}
-
-func isStringFunc(ctx ExprContext, name string, args []any) (result any, err error) {
-	result = IsString(args[0])
-	return
-}
-
-func isFractionFunc(ctx ExprContext, name string, args []any) (result any, err error) {
-	result = IsFract(args[0])
-	return
-}
-
-func isRationalFunc(ctx ExprContext, name string, args []any) (result any, err error) {
-	result = IsRational(args[0])
-	return
-}
-
-func isListFunc(ctx ExprContext, name string, args []any) (result any, err error) {
-	result = IsList(args[0])
-	return
-}
-
-func isDictionaryFunc(ctx ExprContext, name string, args []any) (result any, err error) {
-	result = IsDict(args[0])
-	return
-}
-
-func boolFunc(ctx ExprContext, name string, args []any) (result any, err error) {
-	switch v := args[0].(type) {
-	case int64:
-		result = (v != 0)
-	case *FractionType:
-		result = v.num != 0
-	case float64:
-		result = v != 0.0
-	case bool:
-		result = v
-	case string:
-		result = len(v) > 0
-	default:
-		err = errCantConvert(name, v, "bool")
-	}
-	return
-}
-
-func intFunc(ctx ExprContext, name string, args []any) (result any, err error) {
-	switch v := args[0].(type) {
-	case int64:
-		result = v
-	case float64:
-		result = int64(math.Trunc(v))
-	case bool:
-		if v {
-			result = int64(1)
-		} else {
-			result = int64(0)
-		}
-	case string:
-		var i int
-		if i, err = strconv.Atoi(v); err == nil {
-			result = int64(i)
-		}
-	default:
-		err = errCantConvert(name, v, "int")
-	}
-	return
-}
-
-func decFunc(ctx ExprContext, name string, args []any) (result any, err error) {
-	switch v := args[0].(type) {
-	case int64:
-		result = float64(v)
-	case float64:
-		result = v
-	case bool:
-		if v {
-			result = float64(1)
-		} else {
-			result = float64(0)
-		}
-	case string:
-		var f float64
-		if f, err = strconv.ParseFloat(v, 64); err == nil {
-			result = f
-		}
-	case *FractionType:
-		result = v.toFloat()
-	default:
-		err = errCantConvert(name, v, "float")
-	}
-	return
-}
-
-func fractFunc(ctx ExprContext, name string, args []any) (result any, err error) {
-	switch v := args[0].(type) {
-	case int64:
-		var den int64 = 1
-		if len(args) > 1 {
-			var ok bool
-			if den, ok = args[1].(int64); !ok {
-				err = errExpectedGot(name, "integer", args[1])
-			} else if den == 0 {
-				err = errDivisionByZero(name)
-			}
-		}
-		if err == nil {
-			result = newFraction(v, den)
-		}
-	case float64:
-		result, err = float64ToFraction(v)
-	case bool:
-		if v {
-			result = newFraction(1, 1)
-		} else {
-			result = newFraction(0, 1)
-		}
-	case string:
-		result, err = makeGeneratingFraction(v)
-	case *FractionType:
-		result = v
-	default:
-		err = errCantConvert(name, v, "float")
-	}
-	return
-}
-
-func iteratorFunc(ctx ExprContext, name string, args []any) (result any, err error) {
-	return
-}
-
-func ImportBuiltinsFuncs(ctx ExprContext) {
-	anyParams := []ExprFuncParam{
-		newFuncParam(paramValue),
-	}
-
-	ctx.RegisterFunc("isNil", newGolangFunctor(isNilFunc), typeBoolean, anyParams)
-	ctx.RegisterFunc("isInt", newGolangFunctor(isIntFunc), typeBoolean, anyParams)
-	ctx.RegisterFunc("isFloat", newGolangFunctor(isFloatFunc), typeBoolean, anyParams)
-	ctx.RegisterFunc("isBool", newGolangFunctor(isBoolFunc), typeBoolean, anyParams)
-	ctx.RegisterFunc("isString", newGolangFunctor(isStringFunc), typeBoolean, anyParams)
-	ctx.RegisterFunc("isFract", newGolangFunctor(isFractionFunc), typeBoolean, anyParams)
-	ctx.RegisterFunc("isRational", newGolangFunctor(isRationalFunc), typeBoolean, anyParams)
-	ctx.RegisterFunc("isList", newGolangFunctor(isListFunc), typeBoolean, anyParams)
-	ctx.RegisterFunc("isDict", newGolangFunctor(isDictionaryFunc), typeBoolean, anyParams)
-
-	ctx.RegisterFunc("bool", newGolangFunctor(boolFunc), typeBoolean, anyParams)
-	ctx.RegisterFunc("int", newGolangFunctor(intFunc), typeInt, anyParams)
-	ctx.RegisterFunc("dec", newGolangFunctor(decFunc), typeFloat, anyParams)
-	ctx.RegisterFunc("fract", newGolangFunctor(fractFunc), typeFraction, []ExprFuncParam{
-		newFuncParam(paramValue),
-		newFuncParamFlagDef("denominator", pfOptional, 1),
-	})
-}
-
-func init() {
-	registerImport("base", ImportBuiltinsFuncs, "Base expression tools like isNil(), int(), etc.")
-}

func-import.go

@@ -1,150 +0,0 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
-// All rights reserved.
-
-// func-import.go
-package expr
-
-import (
-	"errors"
-	"fmt"
-	"io"
-	"os"
-	"path"
-	"path/filepath"
-	"strings"
-)
-
-const ENV_EXPR_PATH = "EXPR_PATH"
-
-func importFunc(ctx ExprContext, name string, args []any) (result any, err error) {
-	return importGeneral(ctx, name, args)
-}
-
-func importAllFunc(ctx ExprContext, name string, args []any) (result any, err error) {
-	enable(ctx, control_export_all)
-	return importGeneral(ctx, name, args)
-}
-
-func importGeneral(ctx ExprContext, name string, args []any) (result any, err error) {
-	var dirList []string
-
-	dirList = addEnvImportDirs(dirList)
-	dirList = addPresetImportDirs(ctx, dirList)
-	result, err = doImport(ctx, name, dirList, NewArrayIterator(args))
-	return
-}
-
-func checkStringParamExpected(funcName string, paramValue any, paramPos int) (err error) {
-	if !(IsString(paramValue) /*|| isList(paramValue)*/) {
-		err = fmt.Errorf("%s(): param nr %d has wrong type %T, string expected", funcName, paramPos+1, paramValue)
-	}
-	return
-}
-
-func addEnvImportDirs(dirList []string) []string {
-	if dirSpec, exists := os.LookupEnv(ENV_EXPR_PATH); exists {
-		dirs := strings.Split(dirSpec, ":")
-		if dirList == nil {
-			dirList = dirs
-		} else {
-			dirList = append(dirList, dirs...)
-		}
-	}
-	return dirList
-}
-
-func addPresetImportDirs(ctx ExprContext, dirList []string) []string {
-	if dirSpec, exists := getControlString(ctx, ControlImportPath); exists {
-		dirs := strings.Split(dirSpec, ":")
-		if dirList == nil {
-			dirList = dirs
-		} else {
-			dirList = append(dirList, dirs...)
-		}
-	}
-	return dirList
-}
-
-func isFile(filePath string) bool {
-	info, err := os.Stat(filePath)
-	return (err == nil || errors.Is(err, os.ErrExist)) && info.Mode().IsRegular()
-}
-
-func searchAmongPath(filename string, dirList []string) (filePath string) {
-	for _, dir := range dirList {
-		if fullPath := path.Join(dir, filename); isFile(fullPath) {
-			filePath = fullPath
-			break
-		}
-	}
-	return
-}
-
-func isPathRelative(filePath string) bool {
-	unixPath := filepath.ToSlash(filePath)
-	return strings.HasPrefix(unixPath, "./") || strings.HasPrefix(unixPath, "../")
-}
-
-func makeFilepath(filename string, dirList []string) (filePath string, err error) {
-	if path.IsAbs(filename) || isPathRelative(filename) {
-		if isFile(filename) {
-			filePath = filename
-		}
-	} else {
-		filePath = searchAmongPath(filename, dirList)
-	}
-	if len(filePath) == 0 {
-		err = fmt.Errorf("source file %q not found", filename)
-	}
-	return
-}
-
-func doImport(ctx ExprContext, name string, dirList []string, it Iterator) (result any, err error) {
-	var v any
-	var sourceFilepath string
-
-	for v, err = it.Next(); err == nil; v, err = it.Next() {
-		if err = checkStringParamExpected(name, v, it.Index()); err != nil {
-			break
-		}
-		if sourceFilepath, err = makeFilepath(v.(string), dirList); err != nil {
-			break
-		}
-		var file *os.File
-		if file, err = os.Open(sourceFilepath); err == nil {
-			defer file.Close()
-			var expr *ast
-			scanner := NewScanner(file, DefaultTranslations())
-			parser := NewParser(ctx)
-			if expr, err = parser.parseGeneral(scanner, true, true); err == nil {
-				result, err = expr.eval(ctx, false)
-			}
-			if err != nil {
-				break
-			}
-		} else {
-			break
-		}
-	}
-	if err != nil {
-		if err == io.EOF {
-			err = nil
-		} else {
-			result = nil
-		}
-	}
-	return
-}
-
-func ImportImportFuncs(ctx ExprContext) {
-	ctx.RegisterFunc("import", newGolangFunctor(importFunc), typeAny, []ExprFuncParam{
-		newFuncParamFlag(typeFilepath, pfRepeat),
-	})
-	ctx.RegisterFunc("importAll", newGolangFunctor(importAllFunc), typeAny, []ExprFuncParam{
-		newFuncParamFlag(typeFilepath, pfRepeat),
-	})
-}
-
-func init() {
-	registerImport("import", ImportImportFuncs, "Functions import() and include()")
-}

func-os.go

@@ -1,185 +0,0 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
-// All rights reserved.
-
-// func-os.go
-package expr
-
-import (
-	"bufio"
-	"fmt"
-	"io"
-	"os"
-)
-
-type osHandle interface {
-	getFile() *os.File
-}
-
-type osWriter struct {
-	fh     *os.File
-	writer *bufio.Writer
-}
-
-func (h *osWriter) getFile() *os.File {
-	return h.fh
-}
-
-type osReader struct {
-	fh     *os.File
-	reader *bufio.Reader
-}
-
-func (h *osReader) getFile() *os.File {
-	return h.fh
-}
-
-func createFileFunc(ctx ExprContext, name string, args []any) (result any, err error) {
-	var filePath string
-	if len(args) > 0 {
-		filePath, _ = args[0].(string)
-	}
-
-	if len(filePath) > 0 {
-		var fh *os.File
-		if fh, err = os.Create(filePath); err == nil {
-			result = &osWriter{fh: fh, writer: bufio.NewWriter(fh)}
-		}
-	} else {
-		err = fmt.Errorf("%s(): missing the file path", name)
-	}
-	return
-}
-
-func openFileFunc(ctx ExprContext, name string, args []any) (result any, err error) {
-	var filePath string
-	if len(args) > 0 {
-		filePath, _ = args[0].(string)
-	}
-
-	if len(filePath) > 0 {
-		var fh *os.File
-		if fh, err = os.Open(filePath); err == nil {
-			result = &osReader{fh: fh, reader: bufio.NewReader(fh)}
-		}
-	} else {
-		err = fmt.Errorf("%s(): missing the file path", name)
-	}
-	return
-}
-
-func appendFileFunc(ctx ExprContext, name string, args []any) (result any, err error) {
-	var filePath string
-	if len(args) > 0 {
-		filePath, _ = args[0].(string)
-	}
-
-	if len(filePath) > 0 {
-		var fh *os.File
-		if fh, err = os.OpenFile(filePath, os.O_APPEND|os.O_WRONLY|os.O_CREATE, 0660); err == nil {
-			result = &osWriter{fh: fh, writer: bufio.NewWriter(fh)}
-		}
-	} else {
-		err = fmt.Errorf("%s(): missing the file path", name)
-	}
-	return
-}
-
-func closeFileFunc(ctx ExprContext, name string, args []any) (result any, err error) {
-	var handle osHandle
-
-	if len(args) > 0 {
-		handle, _ = args[0].(osHandle)
-	}
-
-	if handle != nil {
-		if fh := handle.getFile(); fh != nil {
-			if w, ok := handle.(*osWriter); ok {
-				err = w.writer.Flush()
-			}
-			if err == nil {
-				err = fh.Close()
-			}
-		}
-	} else {
-		err = fmt.Errorf("%s(): invalid file handle", name)
-	}
-	result = err == nil
-	return
-}
-
-func writeFileFunc(ctx ExprContext, name string, args []any) (result any, err error) {
-	var handle osHandle
-
-	if len(args) > 0 {
-		handle, _ = args[0].(osHandle)
-	}
-
-	if handle != nil {
-		if fh := handle.getFile(); fh != nil {
-			if w, ok := handle.(*osWriter); ok {
-				result, err = fmt.Fprint(w.writer, args[1:]...)
-			}
-		}
-	}
-	return
-}
-
-func readFileFunc(ctx ExprContext, name string, args []any) (result any, err error) {
-	var handle osHandle
-	result = nil
-	if len(args) > 0 {
-		handle, _ = args[0].(osHandle)
-	}
-
-	if handle != nil {
-		if fh := handle.getFile(); fh != nil {
-			if r, ok := handle.(*osReader); ok {
-				var limit byte = '\n'
-				var v string
-				if len(args) > 1 {
-					if s, ok := args[1].(string); ok && len(s) > 0 {
-						limit = s[0]
-					}
-				}
-				if v, err = r.reader.ReadString(limit); err == nil {
-					if len(v) > 0 && v[len(v)-1] == limit {
-						result = v[0 : len(v)-1]
-					} else {
-						result = v
-					}
-				}
-				if err == io.EOF {
-					err = nil
-				}
-			}
-		}
-	}
-	return
-}
-
-func ImportOsFuncs(ctx ExprContext) {
-	ctx.RegisterFunc("openFile", newGolangFunctor(openFileFunc), typeHandle, []ExprFuncParam{
-		newFuncParam(typeFilepath),
-	})
-	ctx.RegisterFunc("appendFile", newGolangFunctor(appendFileFunc), typeHandle, []ExprFuncParam{
-		newFuncParam(typeFilepath),
-	})
-	ctx.RegisterFunc("createFile", newGolangFunctor(createFileFunc), typeHandle, []ExprFuncParam{
-		newFuncParam(typeFilepath),
-	})
-	ctx.RegisterFunc("writeFile", newGolangFunctor(writeFileFunc), typeInt, []ExprFuncParam{
-		newFuncParam(typeHandle),
-		newFuncParamFlagDef(typeItem, pfOptional|pfRepeat, ""),
-	})
-	ctx.RegisterFunc("readFile", newGolangFunctor(readFileFunc), typeString, []ExprFuncParam{
-		newFuncParam(typeHandle),
-		newFuncParamFlagDef("limitCh", pfOptional, "\\n"),
-	})
-	ctx.RegisterFunc("closeFile", newGolangFunctor(closeFileFunc), typeBoolean, []ExprFuncParam{
-		newFuncParam(typeHandle),
-	})
-}
-
-func init() {
-	registerImport("os.file", ImportOsFuncs, "Operating system file functions")
-}

func-string.go

@@ -1,222 +0,0 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
-// All rights reserved.
-
-// func-string.go
-package expr
-
-import (
-	"fmt"
-	"io"
-	"strings"
-)
-
-// --- Start of function definitions
-func doJoinStr(funcName string, sep string, it Iterator) (result any, err error) {
-	var sb strings.Builder
-	var v any
-	for v, err = it.Next(); err == nil; v, err = it.Next() {
-		if it.Index() > 0 {
-			sb.WriteString(sep)
-		}
-		if s, ok := v.(string); ok {
-			sb.WriteString(s)
-		} else {
-			err = errExpectedGot(funcName, typeString, v)
-			return
-		}
-	}
-	if err == nil || err == io.EOF {
-		err = nil
-		result = sb.String()
-	}
-	return
-}
-
-func joinStrFunc(ctx ExprContext, name string, args []any) (result any, err error) {
-	//	if len(args) < 1 {
-	//		return nil, errMissingRequiredParameter(name, paramSeparator)
-	//	}
-	if sep, ok := args[0].(string); ok {
-		if len(args) == 1 {
-			result = ""
-		} else if len(args) == 2 {
-			if ls, ok := args[1].(*ListType); ok {
-				result, err = doJoinStr(name, sep, NewListIterator(ls, nil))
-			} else if it, ok := args[1].(Iterator); ok {
-				result, err = doJoinStr(name, sep, it)
-			} else {
-				err = errInvalidParameterValue(name, paramParts, args[1])
-			}
-		} else {
-			result, err = doJoinStr(name, sep, NewArrayIterator(args[1:]))
-		}
-	} else {
-		err = errWrongParamType(name, paramSeparator, typeString, args[0])
-	}
-	return
-}
-
-func subStrFunc(ctx ExprContext, name string, args []any) (result any, err error) {
-	var start = 0
-	var count = -1
-	var source string
-	var ok bool
-
-	if source, ok = args[0].(string); !ok {
-		return nil, errWrongParamType(name, paramSource, typeString, args[0])
-	}
-	if len(args) > 1 {
-		if start, err = toInt(args[1], name+"()"); err != nil {
-			return
-		}
-		if len(args) > 2 {
-			if count, err = toInt(args[2], name+"()"); err != nil {
-				return
-			}
-		}
-		if start < 0 {
-			start = len(source) + start
-		}
-	}
-	if count < 0 {
-		count = len(source) - start
-	}
-	end := min(start+count, len(source))
-	result = source[start:end]
-	return
-}
-
-func trimStrFunc(ctx ExprContext, name string, args []any) (result any, err error) {
-	var source string
-	var ok bool
-
-	if source, ok = args[0].(string); !ok {
-		return nil, errWrongParamType(name, paramSource, typeString, args[0])
-	}
-	result = strings.TrimSpace(source)
-	return
-}
-
-func startsWithStrFunc(ctx ExprContext, name string, args []any) (result any, err error) {
-	var source string
-	var ok bool
-
-	result = false
-
-	if source, ok = args[0].(string); !ok {
-		return result, errWrongParamType(name, paramSource, typeString, args[0])
-	}
-	for i, targetSpec := range args[1:] {
-		if target, ok := targetSpec.(string); ok {
-			if strings.HasPrefix(source, target) {
-				result = true
-				break
-			}
-		} else {
-			err = fmt.Errorf("target item nr %d is %T, expected string", i+1, targetSpec)
-			break
-		}
-	}
-	return
-}
-
-func endsWithStrFunc(ctx ExprContext, name string, args []any) (result any, err error) {
-	var source string
-	var ok bool
-
-	result = false
-
-	if source, ok = args[0].(string); !ok {
-		return result, errWrongParamType(name, paramSource, typeString, args[0])
-	}
-	for i, targetSpec := range args[1:] {
-		if target, ok := targetSpec.(string); ok {
-			if strings.HasSuffix(source, target) {
-				result = true
-				break
-			}
-		} else {
-			err = fmt.Errorf("target item nr %d is %T, expected string", i+1, targetSpec)
-			break
-		}
-	}
-	return
-}
-
-func splitStrFunc(ctx ExprContext, name string, args []any) (result any, err error) {
-	var source, sep string
-	var count int = -1
-	var parts []string
-	var ok bool
-
-	if source, ok = args[0].(string); !ok {
-		return result, errWrongParamType(name, paramSource, typeString, args[0])
-	}
-	if len(args) >= 2 {
-		if sep, ok = args[1].(string); !ok {
-			return nil, fmt.Errorf("separator param must be string, got %T (%v)", args[1], args[1])
-		}
-		if len(args) >= 3 {
-			if count64, ok := args[2].(int64); ok { // TODO replace type assertion with toInt()
-				count = int(count64)
-			} else {
-				return nil, fmt.Errorf("part count must be integer, got %T (%v)", args[2], args[2])
-			}
-		}
-	}
-	if count > 0 {
-		parts = strings.SplitN(source, sep, count)
-	} else if count < 0 {
-		parts = strings.Split(source, sep)
-	} else {
-		parts = []string{}
-	}
-	list := make(ListType, len(parts))
-	for i, part := range parts {
-		list[i] = part
-	}
-	result = &list
-	return
-}
-
-// --- End of function definitions
-
-// Import above functions in the context
-func ImportStringFuncs(ctx ExprContext) {
-	ctx.RegisterFunc("joinStr", newGolangFunctor(joinStrFunc), typeString, []ExprFuncParam{
-		newFuncParam(paramSeparator),
-		newFuncParamFlagDef(paramItem, pfOptional|pfRepeat, ""),
-	})
-
-	ctx.RegisterFunc("subStr", newGolangFunctor(subStrFunc), typeString, []ExprFuncParam{
-		newFuncParam(paramSource),
-		newFuncParamFlagDef(paramStart, pfOptional, 0),
-		newFuncParamFlagDef(paramCount, pfOptional, -1),
-	})
-
-	ctx.RegisterFunc("splitStr", newGolangFunctor(splitStrFunc), "list of "+typeString, []ExprFuncParam{
-		newFuncParam(paramSource),
-		newFuncParamFlagDef(paramSeparator, pfOptional, ""),
-		newFuncParamFlagDef(paramCount, pfOptional, -1),
-	})
-
-	ctx.RegisterFunc("trimStr", newGolangFunctor(trimStrFunc), typeString, []ExprFuncParam{
-		newFuncParam(paramSource),
-	})
-
-	ctx.RegisterFunc("startsWithStr", newGolangFunctor(startsWithStrFunc), typeBoolean, []ExprFuncParam{
-		newFuncParam(paramSource),
-		newFuncParamFlag(paramPrefix, pfRepeat),
-	})
-
-	ctx.RegisterFunc("endsWithStr", newGolangFunctor(endsWithStrFunc), typeBoolean, []ExprFuncParam{
-		newFuncParam(paramSource),
-		newFuncParamFlag(paramSuffix, pfRepeat),
-	})
-}
-
-// Register the import function in the import-register.
-// That will allow to import all function of this module by the "builtin" operator."
-func init() {
-	registerImport("string", ImportStringFuncs, "string utilities")
-}

function.go

@@ -6,11 +6,12 @@ package expr
 
 import (
 	"fmt"
+	"strconv"
 	"strings"
 )
 
 // ---- Function template
-type FuncTemplate func(ctx ExprContext, name string, args []any) (result any, err error)
+type FuncTemplate func(ctx ExprContext, name string, args map[string]any) (result any, err error)
 
 // ---- Common functor definition
 type baseFunctor struct {
@@ -21,11 +22,19 @@ func (functor *baseFunctor) ToString(opt FmtOpt) (s string) {
 	if functor.info != nil {
 		s = functor.info.ToString(opt)
 	} else {
-		s = "func() {<body>}"
+		s = "func(){}"
 	}
 	return s
 }
 
+func (functor *baseFunctor) GetParams() (params []ExprFuncParam) {
+	if functor.info != nil {
+		return functor.info.Params()
+	} else {
+		return []ExprFuncParam{}
+	}
+}
+
 func (functor *baseFunctor) SetFunc(info ExprFunc) {
 	functor.info = info
 }
@@ -34,57 +43,17 @@ func (functor *baseFunctor) GetFunc() ExprFunc {
 	return functor.info
 }
 
-// ---- Linking with the functions of Go
-type golangFunctor struct {
-	baseFunctor
-	f FuncTemplate
-}
-
-func newGolangFunctor(f FuncTemplate) *golangFunctor {
-	return &golangFunctor{f: f}
-}
-
-func (functor *golangFunctor) Invoke(ctx ExprContext, name string, args []any) (result any, err error) {
-	return functor.f(ctx, name, args)
-}
-
-// ---- Linking with the functions of Expr
-type exprFunctor struct {
-	baseFunctor
-	params []string
-	expr   Expr
-}
-
-func newExprFunctor(e Expr, params []string) *exprFunctor {
-	return &exprFunctor{expr: e, params: params}
-}
-
-func (functor *exprFunctor) Invoke(ctx ExprContext, name string, args []any) (result any, err error) {
-	for i, p := range functor.params {
-		if i < len(args) {
-			arg := args[i]
-			if funcArg, ok := arg.(Functor); ok {
-				// ctx.RegisterFunc(p, functor, 0, -1)
-				ctx.RegisterFunc(p, funcArg, typeAny, []ExprFuncParam{
-					newFuncParam(paramValue),
-				})
-			} else {
-				ctx.UnsafeSetVar(p, arg)
-			}
-		} else {
-			ctx.UnsafeSetVar(p, nil)
-		}
-	}
-	result, err = functor.expr.eval(ctx, false)
-	return
+func (functor *baseFunctor) GetDefinitionContext() ExprContext {
+	return nil
 }
 
 // ---- Function Parameters
 type paramFlags uint16
 
 const (
-	pfOptional paramFlags = 1 << iota
-	pfRepeat
+	PfDefault paramFlags = 1 << iota
+	PfOptional
+	PfRepeat
 )
 
 type funcParamInfo struct {
@@ -93,15 +62,15 @@ type funcParamInfo struct {
 	defaultValue any
 }
 
-func newFuncParam(name string) ExprFuncParam {
+func NewFuncParam(name string) ExprFuncParam {
 	return &funcParamInfo{name: name}
 }
 
-func newFuncParamFlag(name string, flags paramFlags) ExprFuncParam {
+func NewFuncParamFlag(name string, flags paramFlags) ExprFuncParam {
 	return &funcParamInfo{name: name, flags: flags}
 }
 
-func newFuncParamFlagDef(name string, flags paramFlags, defValue any) *funcParamInfo {
+func NewFuncParamFlagDef(name string, flags paramFlags, defValue any) *funcParamInfo {
 	return &funcParamInfo{name: name, flags: flags, defaultValue: defValue}
 }
 
@@ -110,15 +79,19 @@ func (param *funcParamInfo) Name() string {
 }
 
 func (param *funcParamInfo) Type() string {
-	return "any"
+	return TypeAny
+}
+
+func (param *funcParamInfo) IsDefault() bool {
+	return (param.flags & PfDefault) != 0
 }
 
 func (param *funcParamInfo) IsOptional() bool {
-	return (param.flags & pfOptional) != 0
+	return (param.flags & PfOptional) != 0
 }
 
 func (param *funcParamInfo) IsRepeat() bool {
-	return (param.flags & pfRepeat) != 0
+	return (param.flags & PfRepeat) != 0
 }
 
 func (param *funcParamInfo) DefaultValue() any {
@@ -126,49 +99,47 @@ func (param *funcParamInfo) DefaultValue() any {
 }
 
 // --- Functions
+
+// funcInfo implements ExprFunc
 type funcInfo struct {
-	name       string
-	minArgs    int
-	maxArgs    int
-	functor    Functor
-	params     []ExprFuncParam
-	returnType string
+	name         string
+	minArgs      int
+	maxArgs      int
+	functor      Functor
+	formalParams []ExprFuncParam
+	returnType   string
 }
 
 func newFuncInfo(name string, functor Functor, returnType string, params []ExprFuncParam) (info *funcInfo, err error) {
 	var minArgs = 0
 	var maxArgs = 0
-	if params != nil {
-		for _, p := range params {
-			if maxArgs == -1 {
-				return nil, fmt.Errorf("no more params can be specified after the ellipsis symbol: %q", p.Name())
-			}
-			if p.IsOptional() {
-				maxArgs++
-			} else if maxArgs == minArgs {
-				minArgs++
-				maxArgs++
-			} else {
-				return nil, fmt.Errorf("can't specify non-optional param after optional ones: %q", p.Name())
-			}
-			if p.IsRepeat() {
-				maxArgs = -1
-			}
+	for _, p := range params {
+		if maxArgs == -1 {
+			return nil, fmt.Errorf("no more params can be specified after the ellipsis symbol: %q", p.Name())
+		}
+		if p.IsDefault() || p.IsOptional() {
+			maxArgs++
+		} else if maxArgs == minArgs {
+			minArgs++
+			maxArgs++
+		} else {
+			return nil, fmt.Errorf("can't specify non-optional param after optional ones: %q", p.Name())
+		}
+		if p.IsRepeat() {
+			minArgs--
+			maxArgs = -1
 		}
 	}
+
 	info = &funcInfo{
-		name: name, minArgs: minArgs, maxArgs: maxArgs, functor: functor, returnType: returnType, params: params,
+		name: name, minArgs: minArgs, maxArgs: maxArgs, functor: functor, returnType: returnType, formalParams: params,
 	}
 	functor.SetFunc(info)
 	return info, nil
 }
 
-func newUnnamedFuncInfo(functor Functor, returnType string, params []ExprFuncParam) (info *funcInfo, err error) {
-	return newFuncInfo("unnamed", functor, returnType, params)
-}
-
 func (info *funcInfo) Params() []ExprFuncParam {
-	return info.params
+	return info.formalParams
 }
 
 func (info *funcInfo) ReturnType() string {
@@ -183,14 +154,14 @@ func (info *funcInfo) ToString(opt FmtOpt) string {
 		sb.WriteString(info.Name())
 	}
 	sb.WriteByte('(')
-	if info.params != nil {
-		for i, p := range info.params {
+	if info.formalParams != nil {
+		for i, p := range info.formalParams {
 			if i > 0 {
 				sb.WriteString(", ")
 			}
 			sb.WriteString(p.Name())
 
-			if p.IsOptional() {
+			if p.IsDefault() {
 				sb.WriteByte('=')
 				if s, ok := p.DefaultValue().(string); ok {
 					sb.WriteByte('"')
@@ -205,13 +176,13 @@ func (info *funcInfo) ToString(opt FmtOpt) string {
 	if info.maxArgs < 0 {
 		sb.WriteString(" ...")
 	}
-	sb.WriteString("): ")
+	sb.WriteString("):")
 	if len(info.returnType) > 0 {
 		sb.WriteString(info.returnType)
 	} else {
-		sb.WriteString(typeAny)
+		sb.WriteString(TypeAny)
 	}
-	sb.WriteString(" {<body>}")
+	sb.WriteString("{}")
 	return sb.String()
 }
 
@@ -230,3 +201,186 @@ func (info *funcInfo) MaxArgs() int {
 func (info *funcInfo) Functor() Functor {
 	return info.functor
 }
+
+func (info *funcInfo) AllocContext(parentCtx ExprContext) (ctx ExprContext) {
+	if defCtx := info.functor.GetDefinitionContext(); defCtx != nil {
+		ctx = defCtx.Clone()
+		ctx.SetParent(defCtx)
+	} else {
+		ctx = parentCtx.Clone()
+		ctx.SetParent(parentCtx)
+	}
+	return
+}
+
+func (info *funcInfo) ParamSpec(paramName string) ExprFuncParam {
+	for _, spec := range info.formalParams {
+		if spec.Name() == paramName {
+			return spec
+		}
+	}
+	return nil
+}
+
+func initActualParams(ctx ExprContext, info ExprFunc, callTerm *term) (actualParams map[string]any, err error) {
+	var varArgs []any
+	var varName string
+
+	namedParamsStarted := false
+
+	formalParams := info.Params()
+	actualParams = make(map[string]any, len(formalParams))
+	if callTerm == nil {
+		return
+	}
+
+	for i, tree := range callTerm.children {
+		var paramValue any
+		paramCtx := ctx.Clone()
+		if paramValue, err = tree.compute(paramCtx); err != nil {
+			break
+		}
+		if paramName, namedParam := getAssignVarName(tree); namedParam {
+			if info.ParamSpec(paramName) == nil {
+				err = fmt.Errorf("%s(): unknown param %q", info.Name(), paramName)
+				break
+			}
+			actualParams[paramName] = paramValue
+			namedParamsStarted = true
+		} else if !namedParamsStarted {
+			if varArgs != nil {
+				varArgs = append(varArgs, paramValue)
+			} else if i < len(formalParams) {
+				spec := formalParams[i]
+				if spec.IsRepeat() {
+					varArgs = make([]any, 0, len(callTerm.children)-i)
+					varArgs = append(varArgs, paramValue)
+					varName = spec.Name()
+				} else {
+					actualParams[spec.Name()] = paramValue
+				}
+			} else {
+				err = ErrTooManyParams(info.Name(), len(formalParams), len(callTerm.children))
+				break
+			}
+		} else {
+			err = fmt.Errorf("%s(): positional param nr %d not allowed after named params", info.Name(), i+1)
+			break
+		}
+	}
+	if err == nil {
+		if varArgs != nil {
+			actualParams[varName] = varArgs
+		}
+	}
+	return
+}
+
+func (info *funcInfo) PrepareCall(name string, actualParams map[string]any) (err error) {
+	passedCount := len(actualParams)
+	if info.MinArgs() > passedCount {
+		err = ErrTooFewParams(name, info.MinArgs(), info.MaxArgs(), passedCount)
+		return
+	}
+
+	if passedCount < len(info.formalParams) {
+		for _, p := range info.formalParams {
+			if _, exists := actualParams[p.Name()]; !exists {
+				if !p.IsDefault() {
+					break
+				}
+				if p.IsRepeat() {
+					varArgs := make([]any, 1)
+					varArgs[0] = p.DefaultValue()
+					actualParams[p.Name()] = varArgs
+				} else {
+					actualParams[p.Name()] = p.DefaultValue()
+				}
+			}
+		}
+	}
+
+	if info.MaxArgs() >= 0 && info.MaxArgs() < len(actualParams) {
+		err = ErrTooManyParams(name, info.MaxArgs(), len(actualParams))
+	}
+	return
+}
+
+// ----- Call a function ---
+
+func getAssignVarName(t *term) (name string, ok bool) {
+	if ok = t.symbol() == SymEqual; ok {
+		name = t.children[0].source()
+	}
+	return
+}
+
+func CallFunctionByTerm(parentCtx ExprContext, name string, callTerm *term) (result any, err error) {
+	var actualParams map[string]any
+	if info, exists := GetFuncInfo(parentCtx, name); exists {
+		if actualParams, err = initActualParams(parentCtx, info, callTerm); err == nil {
+			ctx := info.AllocContext(parentCtx)
+			if err = info.PrepareCall(name, actualParams); err == nil {
+				functor := info.Functor()
+				result, err = functor.InvokeNamed(ctx, name, actualParams)
+				exportObjectsToParent(ctx)
+			}
+		}
+	} else {
+		err = fmt.Errorf("unknown function %s()", name)
+	}
+	return
+}
+
+func CallFunctionByArgs(parentCtx ExprContext, name string, args []any) (result any, err error) {
+	var actualParams map[string]any
+	if info, exists := GetFuncInfo(parentCtx, name); exists {
+		functor := info.Functor()
+		actualParams = bindActualParams(functor, args)
+		ctx := info.AllocContext(parentCtx)
+		if err = info.PrepareCall(name, actualParams); err == nil {
+			result, err = functor.InvokeNamed(ctx, name, actualParams)
+			exportObjectsToParent(ctx)
+		}
+	} else {
+		err = fmt.Errorf("unknown function %s()", name)
+	}
+	return
+}
+
+func CallFunctionByParams(parentCtx ExprContext, name string, actualParams map[string]any) (result any, err error) {
+	//var actualParams map[string]any
+	if info, exists := GetFuncInfo(parentCtx, name); exists {
+		functor := info.Functor()
+		ctx := info.AllocContext(parentCtx)
+		if err = info.PrepareCall(name, actualParams); err == nil {
+			result, err = functor.InvokeNamed(ctx, name, actualParams)
+			exportObjectsToParent(ctx)
+		}
+	} else {
+		err = fmt.Errorf("unknown function %s()", name)
+	}
+	return
+}
+
+func GetParam(args map[string]any, paramName string, paramNum int) (value any, exists bool) {
+	if value, exists = args[paramName]; !exists {
+		if paramNum > 0 && paramNum <= len(args) {
+			value, exists = args["arg"+strconv.Itoa(paramNum)]
+		}
+	}
+	return
+}
+
+func bindActualParams(functor Functor, args []any) (actualParams map[string]any) {
+	formalParams := functor.GetParams()
+	actualParams = make(map[string]any, len(args))
+	for i, arg := range args {
+		if i < len(formalParams) {
+			actualParams[formalParams[i].Name()] = arg
+		} else {
+			actualParams["arg"+strconv.Itoa(i+1)] = arg
+		}
+	}
+	return
+}

global-context.go

@@ -4,13 +4,16 @@
 // global-context.go
 package expr
 
-import "path/filepath"
+import (
+	"path/filepath"
+	"strings"
+)
 
 var globalCtx *SimpleStore
 
 func ImportInContext(name string) (exists bool) {
-	var mod *module
-	if mod, exists = moduleRegister[name]; exists {
+	var mod *builtinModule
+	if mod, exists = builtinModuleRegister[name]; exists {
 		mod.importFunc(globalCtx)
 		mod.imported = true
 	}
@@ -19,7 +22,7 @@ func ImportInContext(name string) (exists bool) {
 
 func ImportInContextByGlobPattern(pattern string) (count int, err error) {
 	var matched bool
-	for name, mod := range moduleRegister {
+	for name, mod := range builtinModuleRegister {
 		if matched, err = filepath.Match(pattern, name); err == nil {
 			if matched {
 				count++
@@ -40,16 +43,114 @@ func GetVar(ctx ExprContext, name string) (value any, exists bool) {
 	return
 }
 
-func GetFuncInfo(ctx ExprContext, name string) (item ExprFunc, exists bool, ownerCtx ExprContext) {
-	if item, exists = ctx.GetFuncInfo(name); exists {
-		ownerCtx = ctx
-	} else if item, exists = globalCtx.GetFuncInfo(name); exists {
-		ownerCtx = globalCtx
+func GetLocalFuncInfo(ctx ExprContext, name string) (item ExprFunc, exists bool) {
+	var v any
+	if len(name) > 0 {
+		if v, exists = ctx.GetVar(name); exists && isFunctor(v) {
+			f, _ := v.(Functor)
+			item = f.GetFunc()
+		} else {
+			item, exists = ctx.GetFuncInfo(name)
+		}
+	}
+	return
+}
+
+func GetFuncInfo(ctx ExprContext, name string) (item ExprFunc, exists bool) {
+	// if len(name) > 0 {
+	// 	if item, exists = GetLocalFuncInfo(ctx, name); exists {
+	// 		ownerCtx = ctx
+	// 	} else if item, exists = globalCtx.GetFuncInfo(name); exists {
+	// 		ownerCtx = globalCtx
+	// 	}
+	// }
+	item, exists, _ = GetFuncInfoAndOwner(ctx, name)
+	return
+}
+
+func GetFuncInfoAndOwner(ctx ExprContext, name string) (item ExprFunc, exists bool, ownerCtx ExprContext) {
+	if len(name) > 0 {
+		if item, exists = GetLocalFuncInfo(ctx, name); exists {
+			ownerCtx = ctx
+		} else if item, exists = globalCtx.GetFuncInfo(name); exists {
+			ownerCtx = globalCtx
+		}
+	}
+	return
+}
+
+func GlobalCtrlSet(name string, newValue any) (currentValue any) {
+	if !strings.HasPrefix(name, "_") {
+		name = "_" + name
+	}
+	currentValue, _ = globalCtx.GetVar(name)
+
+	globalCtx.SetVar(name, newValue)
+	return currentValue
+}
+
+func GlobalCtrlGet(name string) (currentValue any) {
+	if !strings.HasPrefix(name, "_") {
+		name = "_" + name
+	}
+	currentValue, _ = globalCtx.GetVar(name)
+	return currentValue
+}
+
+func CtrlEnable(ctx ExprContext, name string) (currentStatus bool) {
+	if !strings.HasPrefix(name, "_") {
+		name = "_" + name
+	}
+	if v, exists := ctx.GetVar(name); exists && IsBool(v) {
+		currentStatus, _ = v.(bool)
+	}
+
+	ctx.SetVar(name, true)
+	return currentStatus
+}
+
+func CtrlDisable(ctx ExprContext, name string) (currentStatus bool) {
+	if !strings.HasPrefix(name, "_") {
+		name = "_" + name
+	}
+	if v, exists := ctx.GetVar(name); exists && IsBool(v) {
+		currentStatus, _ = v.(bool)
+	}
+
+	ctx.SetVar(name, false)
+	return currentStatus
+}
+
+func CtrlIsEnabled(ctx ExprContext, name string) (status bool) {
+	var v any
+	var exists bool
+
+	if !strings.HasPrefix(name, "_") {
+		name = "_" + name
+	}
+
+	if v, exists = ctx.GetVar(name); !exists {
+		v, exists = globalCtx.GetVar(name)
+	}
+
+	if exists {
+		if b, ok := v.(bool); ok {
+			status = b
+		}
+	}
+	return
+}
+
+func getControlString(name string) (s string, exists bool) {
+	var v any
+	if v, exists = globalCtx.GetVar(name); exists {
+		s, exists = v.(string)
 	}
 	return
 }
 
 func init() {
 	globalCtx = NewSimpleStore()
+	initDefaultVars(globalCtx)
 	ImportBuiltinsFuncs(globalCtx)
 }

go.mod

@@ -1,3 +1,7 @@
 module git.portale-stac.it/go-pkg/expr
 
-go 1.21.6
+go 1.22.0
+
+toolchain go1.23.3
+
+require golang.org/x/exp v0.0.0-20241204233417-43b7b7cde48d

go.sum

@@ -0,0 +1,4 @@
+github.com/yqylovy/goimportdot v0.0.0-20170519021755-eb181a7eeabe h1:bWYrKmmfv37uNgXTdwkLSKYiYPJ1yfWmjBnvtMyAYzk=
+github.com/yqylovy/goimportdot v0.0.0-20170519021755-eb181a7eeabe/go.mod h1:alTKUpAJ/zbp17qvZwcFNwzufrb5DljMDY4mgJlIHao=
+golang.org/x/exp v0.0.0-20241204233417-43b7b7cde48d h1:0olWaB5pg3+oychR51GUVCEsGkeCU/2JxjBgIo4f3M0=
+golang.org/x/exp v0.0.0-20241204233417-43b7b7cde48d/go.mod h1:qj5a5QZpwLU2NLQudwIN5koi3beDhSAlJwa67PuM98c=

helpers.go

@@ -16,10 +16,10 @@ func EvalString(ctx ExprContext, source string) (result any, err error) {
 
 	r := strings.NewReader(source)
 	scanner := NewScanner(r, DefaultTranslations())
-	parser := NewParser(ctx)
+	parser := NewParser()
 
 	if tree, err = parser.Parse(scanner); err == nil {
-		result, err = tree.eval(ctx, true)
+		result, err = tree.Eval(ctx)
 	}
 	return
 }
@@ -38,10 +38,10 @@ func EvalStringV(source string, args []Arg) (result any, err error) {
 	for _, arg := range args {
 		if isFunc(arg.Value) {
 			if f, ok := arg.Value.(FuncTemplate); ok {
-				functor := newGolangFunctor(f)
+				functor := NewGolangFunctor(f)
 				// ctx.RegisterFunc(arg.Name, functor, 0, -1)
-				ctx.RegisterFunc(arg.Name, functor, typeAny, []ExprFuncParam{
-					newFuncParamFlagDef(paramValue, pfOptional|pfRepeat, 0),
+				ctx.RegisterFunc(arg.Name, functor, TypeAny, []ExprFuncParam{
+					NewFuncParamFlagDef(ParamValue, PfDefault|PfRepeat, 0),
 				})
 			} else {
 				err = fmt.Errorf("invalid function specification: %q", arg.Name)
@@ -68,7 +68,7 @@ func EvalStringV(source string, args []Arg) (result any, err error) {
 func EvalStream(ctx ExprContext, r io.Reader) (result any, err error) {
 	var tree *ast
 	scanner := NewScanner(r, DefaultTranslations())
-	parser := NewParser(ctx)
+	parser := NewParser()
 
 	if tree, err = parser.Parse(scanner); err == nil {
 		result, err = tree.Eval(ctx)

import-utils.go

@@ -0,0 +1,124 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// import-utils.go
+package expr
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"path"
+	"path/filepath"
+	"strings"
+)
+
+const (
+	ENV_EXPR_SOURCE_PATH = "EXPR_PATH"
+	ENV_EXPR_PLUGIN_PATH = "EXPR_PLUGIN_PATH"
+)
+
+func checkStringParamExpected(funcName string, paramValue any, paramPos int) (err error) {
+	if !(IsString(paramValue) /*|| isList(paramValue)*/) {
+		err = fmt.Errorf("%s(): param nr %d has wrong type %s, string expected", funcName, paramPos+1, TypeName(paramValue))
+	}
+	return
+}
+
+// func addSourceEnvImportDirs(varName string, dirList []string) []string {
+// 	return addEnvImportDirs(ENV_EXPR_SOURCE_PATH, dirList)
+// }
+
+// func addPluginEnvImportDirs(varName string, dirList []string) []string {
+// 	return addEnvImportDirs(ENV_EXPR_PLUGIN_PATH, dirList)
+// }
+
+func addEnvImportDirs(envVarName string, dirList []string) []string {
+	if dirSpec, exists := os.LookupEnv(envVarName); exists {
+		dirs := strings.Split(dirSpec, ":")
+		if dirList == nil {
+			dirList = dirs
+		} else {
+			dirList = append(dirList, dirs...)
+		}
+	}
+	return dirList
+}
+
+func addSearchDirs(endingPath string, dirList []string) []string {
+	if dirSpec, exists := getControlString(ControlSearchPath); exists {
+		dirs := strings.Split(dirSpec, ":")
+		if dirList == nil {
+			dirList = dirs
+		} else {
+			if len(endingPath) > 0 {
+				for _, d := range dirs {
+					dirList = append(dirList, path.Join(d, endingPath))
+				}
+			} else {
+				dirList = append(dirList, dirs...)
+			}
+		}
+	}
+	return dirList
+}
+
+func buildSearchDirList(endingPath, envVarName string) (dirList []string) {
+	dirList = addEnvImportDirs(envVarName, dirList)
+	dirList = addSearchDirs(endingPath, dirList)
+	return
+}
+
+func isFile(filePath string) bool {
+	info, err := os.Stat(filePath)
+	return (err == nil || errors.Is(err, os.ErrExist)) && info.Mode().IsRegular()
+}
+
+func searchAmongPath(filename string, dirList []string) (filePath string) {
+	var err error
+
+	suffix := SHAREDLIBRARY_EXTENSION
+	if strings.HasSuffix(filename, ".debug") {
+		suffix += ".debug"
+	}
+
+	for _, dir := range dirList {
+		if dir, err = ExpandPath(dir); err != nil {
+			continue
+		}
+		if fullPath := path.Join(dir, filename); isFile(fullPath) {
+			filePath = fullPath
+			break
+		}
+
+		subdir := strings.TrimSuffix(filename, suffix)
+		if fullPath := path.Join(dir, subdir, filename); isFile(fullPath) {
+			filePath = fullPath
+			break
+		}
+	}
+	return
+}
+
+func isPathRelative(filePath string) bool {
+	unixPath := filepath.ToSlash(filePath)
+	return strings.HasPrefix(unixPath, "./") || strings.HasPrefix(unixPath, "../")
+}
+
+func makeFilepath(filename string, dirList []string) (filePath string, err error) {
+	if filename, err = ExpandPath(filename); err != nil {
+		return
+	}
+
+	if path.IsAbs(filename) || isPathRelative(filename) {
+		if isFile(filename) {
+			filePath = filename
+		}
+	} else {
+		filePath = searchAmongPath(filename, dirList)
+	}
+	if len(filePath) == 0 {
+		err = fmt.Errorf("file %q not found", filename)
+	}
+	return
+}

iter-factory.go

@@ -0,0 +1,25 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// iter-factory.go
+package expr
+
+func NewIterator(value any) (it Iterator, err error) {
+	if value == nil {
+		return NewArrayIterator([]any{}), nil
+	}
+
+	switch v := value.(type) {
+	case *ListType:
+		it = NewListIterator(v, nil)
+	case *DictType:
+		it, err = NewDictIterator(v, nil)
+	case []any:
+		it = NewArrayIterator(v)
+	case Iterator:
+		it = v
+	default:
+		it = NewArrayIterator([]any{value})
+	}
+	return
+}

iterator.go

@@ -5,38 +5,47 @@
 package expr
 
 import (
-	"errors"
+	// "errors"
 	"fmt"
 )
 
 // Operator names
 
 const (
-	initName    = "init"
-	cleanName   = "clean"
-	resetName   = "reset"
-	nextName    = "next"
-	currentName = "current"
-	indexName   = "index"
-	countName   = "count"
+	InitName    = "init"
+	CleanName   = "clean"
+	ResetName   = "reset"
+	NextName    = "next"
+	CurrentName = "current"
+	IndexName   = "index"
+	CountName   = "count"
+	FilterName  = "filter"
+	MapName     = "map"
+	KeyName     = "key"
+	ValueName   = "value"
 )
 
 type Iterator interface {
+	Typer
+	fmt.Stringer
 	Next() (item any, err error) // must return io.EOF after the last item
 	Current() (item any, err error)
 	Index() int
+	Count() int
+	HasOperation(name string) bool
+	CallOperation(name string, args map[string]any) (value any, err error)
 }
 
 type ExtIterator interface {
 	Iterator
-	HasOperation(name string) bool
-	CallOperation(name string, args []any) (value any, err error)
+	Reset() error
+	Clean() error
 }
 
 func errNoOperation(name string) error {
-	return fmt.Errorf("no %q function defined in the data-source", name)
+	return fmt.Errorf("no %s() function defined in the data-source", name)
 }
 
-func errInvalidDataSource() error {
-	return errors.New("invalid data-source")
-}
+// func errInvalidDataSource() error {
+// 	return errors.New("invalid data-source")
+// }

lib-ext-darwin.go

@@ -0,0 +1,9 @@
+//go:build darwin
+
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// lib-ext-darwin.go
+package expr
+
+const SHAREDLIBRARY_EXTENSION = ".dylib"

lib-ext-linux.go

@@ -0,0 +1,9 @@
+//go:build linux
+
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// lib-ext-linux.go
+package expr
+
+const SHAREDLIBRARY_EXTENSION = ".so"

lib-ext-windows.go

@@ -0,0 +1,9 @@
+//go:build windows
+
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// lib-ext-windows.go
+package expr
+
+const SHAREDLIBRARY_EXTENSION = ".dll"

list-iterator.go

@@ -1,7 +1,7 @@
 // Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
 // All rights reserved.
 
-// iter-list.go
+// list-iterator.go
 package expr
 
 import (
@@ -26,21 +26,21 @@ func NewListIterator(list *ListType, args []any) (it *ListIterator) {
 	}
 	it = &ListIterator{a: list, count: 0, index: -1, start: 0, stop: listLen - 1, step: 1}
 	if argc >= 1 {
-		if i, err := toInt(args[0], "start index"); err == nil {
+		if i, err := ToGoInt(args[0], "start index"); err == nil {
 			if i < 0 {
 				i = listLen + i
 			}
 			it.start = i
 		}
 		if argc >= 2 {
-			if i, err := toInt(args[1], "stop index"); err == nil {
+			if i, err := ToGoInt(args[1], "stop index"); err == nil {
 				if i < 0 {
 					i = listLen + i
 				}
 				it.stop = i
 			}
 			if argc >= 3 {
-				if i, err := toInt(args[2], "step"); err == nil {
+				if i, err := ToGoInt(args[2], "step"); err == nil {
 					if i < 0 {
 						i = -i
 					}
@@ -62,41 +62,36 @@ func NewArrayIterator(array []any) (it *ListIterator) {
 	return
 }
 
-func NewAnyIterator(value any) (it *ListIterator) {
-	if value == nil {
-		it = NewArrayIterator([]any{})
-	} else if list, ok := value.(*ListType); ok {
-		it = NewListIterator(list, nil)
-	} else if array, ok := value.([]any); ok {
-		it = NewArrayIterator(array)
-	} else if it1, ok := value.(*ListIterator); ok {
-		it = it1
-	} else {
-		it = NewArrayIterator([]any{value})
-	}
-	return
-}
-
 func (it *ListIterator) String() string {
 	var l = 0
 	if it.a != nil {
 		l = len(*it.a)
 	}
-	return fmt.Sprintf("$(#%d)", l)
+	return fmt.Sprintf("$([#%d])", l)
+}
+
+func (it *ListIterator) TypeName() string {
+	return "ListIterator"
 }
 
 func (it *ListIterator) HasOperation(name string) bool {
-	yes := name == resetName || name == indexName || name == countName
+	yes := name == NextName || name == ResetName || name == IndexName || name == CountName || name == CurrentName
 	return yes
 }
 
-func (it *ListIterator) CallOperation(name string, args []any) (v any, err error) {
+func (it *ListIterator) CallOperation(name string, args map[string]any) (v any, err error) {
 	switch name {
-	case resetName:
-		v, err = it.Reset()
-	case indexName:
+	case NextName:
+		v, err = it.Next()
+	case ResetName:
+		err = it.Reset()
+	case CleanName:
+		err = it.Clean()
+	case IndexName:
 		v = int64(it.Index())
-	case countName:
+	case CurrentName:
+		v, err = it.Current()
+	case CountName:
 		v = it.count
 	default:
 		err = errNoOperation(name)
@@ -106,10 +101,19 @@ func (it *ListIterator) CallOperation(name string, args []any) (v any, err error
 
 func (it *ListIterator) Current() (item any, err error) {
 	a := *(it.a)
-	if it.index >= 0 && it.index <= it.stop {
-		item = a[it.index]
+	if it.start <= it.stop {
+		if it.stop < len(a) && it.index >= it.start && it.index <= it.stop {
+			item = a[it.index]
+		} else {
+			err = io.EOF
+		}
 	} else {
-		err = io.EOF
+		if it.start < len(a) && it.index >= it.stop && it.index <= it.start {
+			item = a[it.index]
+		} else {
+			err = io.EOF
+		}
+
 	}
 	return
 }
@@ -126,7 +130,16 @@ func (it *ListIterator) Index() int {
 	return it.index
 }
 
-func (it *ListIterator) Reset() (bool, error) {
-	it.index = it.start
-	return true, nil
+func (it *ListIterator) Count() int {
+	return it.count
+}
+
+func (it *ListIterator) Reset() error {
+	it.index = it.start - it.step
+	it.count = 0
+	return nil
+}
+
+func (it *ListIterator) Clean() error {
+	return nil
 }

list-type.go

@@ -13,31 +13,64 @@ import (
 type ListType []any
 
 func newListA(listAny ...any) (list *ListType) {
+	if listAny == nil {
+		listAny = []any{}
+	}
 	return newList(listAny)
 }
 
 func newList(listAny []any) (list *ListType) {
+	return NewList(listAny)
+}
+
+func NewList(listAny []any) (list *ListType) {
 	if listAny != nil {
 		ls := make(ListType, len(listAny))
-		for i, item := range listAny {
-			ls[i] = item
-		}
+		//		for i, item := range listAny {
+		//			ls[i] = item
+		//		}
+		copy(ls, listAny)
 		list = &ls
 	}
 	return
 }
 
+func MakeList(length, capacity int) (list *ListType) {
+	if capacity < length {
+		capacity = length
+	}
+	ls := make(ListType, length, capacity)
+	list = &ls
+	return
+}
+
+func ListFromStrings(stringList []string) (list *ListType) {
+	list = MakeList(len(stringList), 0)
+	for i, s := range stringList {
+		(*list)[i] = s
+	}
+	return
+}
+
 func (ls *ListType) ToString(opt FmtOpt) (s string) {
+	indent := GetFormatIndent(opt)
+	flags := GetFormatFlags(opt)
+
 	var sb strings.Builder
 	sb.WriteByte('[')
 	if len(*ls) > 0 {
-		if opt&MultiLine != 0 {
-			sb.WriteString("\n  ")
+		innerOpt := MakeFormatOptions(flags, indent+1)
+		nest := strings.Repeat("  ", indent+1)
+
+		if flags&MultiLine != 0 {
+			sb.WriteByte('\n')
+			sb.WriteString(nest)
 		}
 		for i, item := range []any(*ls) {
 			if i > 0 {
-				if opt&MultiLine != 0 {
-					sb.WriteString(",\n  ")
+				if flags&MultiLine != 0 {
+					sb.WriteString(",\n")
+					sb.WriteString(nest)
 				} else {
 					sb.WriteString(", ")
 				}
@@ -46,17 +79,20 @@ func (ls *ListType) ToString(opt FmtOpt) (s string) {
 				sb.WriteByte('"')
 				sb.WriteString(s)
 				sb.WriteByte('"')
+			} else if formatter, ok := item.(Formatter); ok {
+				sb.WriteString(formatter.ToString(innerOpt))
 			} else {
 				sb.WriteString(fmt.Sprintf("%v", item))
 			}
 		}
-		if opt&MultiLine != 0 {
+		if flags&MultiLine != 0 {
 			sb.WriteByte('\n')
+			sb.WriteString(strings.Repeat("  ", indent))
 		}
 	}
 	sb.WriteByte(']')
 	s = sb.String()
-	if opt&Truncate != 0 && len(s) > TruncateSize {
+	if flags&Truncate != 0 && len(s) > TruncateSize {
 		s = TruncateString(s)
 	}
 	return
@@ -70,16 +106,16 @@ func (ls *ListType) TypeName() string {
 	return "list"
 }
 
-func (list *ListType) indexDeepCmp(target any) (index int) {
-	index = -1
-	for i, item := range *list {
-		if reflect.DeepEqual(item, target) {
-			index = i
-			break
-		}
-	}
-	return
-}
+// func (list *ListType) indexDeepCmp(target any) (index int) {
+// 	index = -1
+// 	for i, item := range *list {
+// 		if reflect.DeepEqual(item, target) {
+// 			index = i
+// 			break
+// 		}
+// 	}
+// 	return
+// }
 
 func (ls *ListType) contains(t *ListType) (answer bool) {
 	if len(*ls) >= len(*t) {
@@ -93,6 +129,20 @@ func (ls *ListType) contains(t *ListType) (answer bool) {
 	return
 }
 
+func (ls1 *ListType) Equals(ls2 ListType) (answer bool) {
+	if ls2 != nil && len(*ls1) == len(ls2) {
+		answer = true
+		for index, i1 := range *ls1 {
+			// if i1 != (ls2)[index] {
+			if !reflect.DeepEqual(i1, ls2[index]) {
+				answer = false
+				break
+			}
+		}
+	}
+	return
+}
+
 func (list *ListType) indexDeepSameCmp(target any) (index int) {
 	var eq bool
 	var err error
@@ -147,3 +197,16 @@ func deepSame(a, b any, deepCmp deepFuncTemplate) (eq bool, err error) {
 
 	return
 }
+
+func (list *ListType) setItem(index int64, value any) (err error) {
+	if index >= 0 && index < int64(len(*list)) {
+		(*list)[index] = value
+	} else {
+		err = fmt.Errorf("index %d out of bounds (0, %d)", index, len(*list)-1)
+	}
+	return
+}
+
+func (list *ListType) appendItem(value any) {
+	*list = append(*list, value)
+}

module-register.go

@@ -1,73 +0,0 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
-// All rights reserved.
-
-// module-register.go
-package expr
-
-import (
-	"fmt"
-)
-
-type module struct {
-	importFunc  func(ExprContext)
-	description string
-	imported    bool
-}
-
-func newModule(importFunc func(ExprContext), description string) *module {
-	return &module{importFunc, description, false}
-}
-
-var moduleRegister map[string]*module
-
-func registerImport(name string, importFunc func(ExprContext), description string) {
-	if moduleRegister == nil {
-		moduleRegister = make(map[string]*module)
-	}
-	if _, exists := moduleRegister[name]; exists {
-		panic(fmt.Errorf("module %q already registered", name))
-	}
-	moduleRegister[name] = newModule(importFunc, description)
-}
-
-// func ImportInContext(ctx ExprContext, name string) (exists bool) {
-// 	var mod *module
-// 	if mod, exists = moduleRegister[name]; exists {
-// 		mod.importFunc(ctx)
-// 		mod.imported = true
-// 	}
-// 	return
-// }
-
-// func ImportInContextByGlobPattern(ctx ExprContext, pattern string) (count int, err error) {
-// 	var matched bool
-// 	for name, mod := range moduleRegister {
-// 		if matched, err = filepath.Match(pattern, name); err == nil {
-// 			if matched {
-// 				count++
-// 				mod.importFunc(ctx)
-// 				mod.imported = true
-// 			}
-// 		} else {
-// 			break
-// 		}
-// 	}
-// 	return
-// }
-
-func IterateModules(op func(name, description string, imported bool) bool) {
-	if op != nil {
-		for name, mod := range moduleRegister {
-			if !op(name, mod.description, mod.imported) {
-				break
-			}
-		}
-	}
-}
-
-// ----
-func init() {
-	if moduleRegister == nil {
-		moduleRegister = make(map[string]*module)
-	}
-}

operand-dict.go

@@ -4,124 +4,6 @@
 // operand-dict.go
 package expr
 
-import (
-	"fmt"
-	"reflect"
-	"strings"
-)
-
-type DictType map[any]any
-
-func newDict(dictAny map[any]*term) (dict *DictType) {
-	var d DictType
-	if dictAny != nil {
-		d = make(DictType, len(dictAny))
-		for i, item := range dictAny {
-			d[i] = item
-		}
-	} else {
-		d = make(DictType)
-	}
-	dict = &d
-	return
-}
-
-func (dict *DictType) toMultiLine(sb *strings.Builder, indent int) {
-	sb.WriteString(strings.Repeat("\t", indent))
-	sb.WriteString("{\n")
-
-	first := true
-	for name, value := range *dict {
-		if first {
-			first = false
-		} else {
-			sb.WriteByte(',')
-			sb.WriteByte('\n')
-		}
-
-		sb.WriteString(strings.Repeat("\t", indent+1))
-		if key, ok := name.(string); ok {
-			sb.WriteString(string('"') + key + string('"'))
-		} else {
-			sb.WriteString(fmt.Sprintf("%v", name))
-		}
-		sb.WriteString(": ")
-		if f, ok := value.(Formatter); ok {
-			sb.WriteString(f.ToString(MultiLine))
-		} else if _, ok = value.(Functor); ok {
-			sb.WriteString("func(){}")
-		} else {
-			sb.WriteString(fmt.Sprintf("%v", value))
-		}
-	}
-	sb.WriteString(strings.Repeat("\t", indent))
-	sb.WriteString("\n}")
-}
-
-func (dict *DictType) ToString(opt FmtOpt) string {
-	var sb strings.Builder
-	if opt&MultiLine != 0 {
-		dict.toMultiLine(&sb, 0)
-	} else {
-		sb.WriteByte('{')
-		first := true
-		for key, value := range *dict {
-			if first {
-				first = false
-			} else {
-				sb.WriteString(", ")
-			}
-			if s, ok := key.(string); ok {
-				sb.WriteString(string('"') + s + string('"'))
-			} else {
-				sb.WriteString(fmt.Sprintf("%v", key))
-			}
-			sb.WriteString(": ")
-			if formatter, ok := value.(Formatter); ok {
-				sb.WriteString(formatter.ToString(opt))
-			} else if t, ok := value.(*term); ok {
-				sb.WriteString(t.String())
-			} else {
-				sb.WriteString(fmt.Sprintf("%#v", value))
-			}
-		}
-		sb.WriteByte('}')
-	}
-	return sb.String()
-}
-
-func (dict *DictType) String() string {
-	return dict.ToString(0)
-}
-
-func (dict *DictType) TypeName() string {
-	return "dict"
-}
-
-func (dict *DictType) hasKey(target any) (ok bool) {
-	for key := range *dict {
-		if ok = reflect.DeepEqual(key, target); ok {
-			break
-		}
-	}
-	return
-}
-
-func (dict *DictType) clone() (c *DictType) {
-	c = newDict(nil)
-	for k, v := range *dict {
-		(*c)[k] = v
-	}
-	return
-}
-
-func (dict *DictType) merge(second *DictType) {
-	if second != nil {
-		for k, v := range *second {
-			(*dict)[k] = v
-		}
-	}
-}
 
 // -------- dict term
 func newDictTerm(args map[any]*term) *term {
@@ -136,8 +18,8 @@ func newDictTerm(args map[any]*term) *term {
 }
 
 // -------- dict func
-func evalDict(ctx ExprContext, self *term) (v any, err error) {
-	dict, _ := self.value().(map[any]*term)
+func evalDict(ctx ExprContext, opTerm *term) (v any, err error) {
+	dict, _ := opTerm.value().(map[any]*term)
 	items := make(DictType, len(dict))
 	for key, tree := range dict {
 		var param any

operand-expr.go

@@ -20,11 +20,11 @@ func newExprTerm(root *term) *term {
 }
 
 // -------- eval expr
-func evalExpr(ctx ExprContext, self *term) (v any, err error) {
-	if expr, ok := self.value().(*term); ok {
+func evalExpr(ctx ExprContext, opTerm *term) (v any, err error) {
+	if expr, ok := opTerm.value().(*term); ok {
 		v, err = expr.compute(ctx)
 	} else {
-		err = fmt.Errorf("expression expected, got %T", self.value())
+		err = fmt.Errorf("expression expected, got %T", opTerm.value())
 	}
 	return
 }

operand-func.go

@@ -6,7 +6,6 @@ package expr
 
 import (
 	"errors"
-	"fmt"
 )
 
 // -------- function call term
@@ -22,43 +21,26 @@ func newFuncCallTerm(tk *Token, args []*term) *term {
 }
 
 // -------- eval func call
-func checkFunctionCall(ctx ExprContext, name string, params []any) (err error) {
-	if info, exists, owner := GetFuncInfo(ctx, name); exists {
-		if info.MinArgs() > len(params) {
-			err = errTooFewParams(info.MinArgs(), info.MaxArgs(), len(params))
-		}
-		if err == nil && info.MaxArgs() >= 0 && info.MaxArgs() < len(params) {
-			err = errTooMuchParams(info.MaxArgs(), len(params))
-		}
-		if err == nil && owner != ctx {
-			// ctx.RegisterFunc(name, info.Functor(), info.MinArgs(), info.MaxArgs())
-			ctx.RegisterFuncInfo(info)
-		}
-	} else {
-		err = fmt.Errorf("unknown function %s()", name)
-	}
-	return
-}
+// func _evalFuncCall(ctx ExprContext, opTerm *term) (v any, err error) {
+// 	name, _ := opTerm.tk.Value.(string)
+// 	params := make([]any, len(opTerm.children), len(opTerm.children)+5)
+// 	for i, tree := range opTerm.children {
+// 		var param any
+// 		if param, err = tree.compute(ctx); err != nil {
+// 			break
+// 		}
+// 		params[i] = param
+// 	}
 
-func evalFuncCall(parentCtx ExprContext, self *term) (v any, err error) {
-	ctx := cloneContext(parentCtx)
-	name, _ := self.tk.Value.(string)
-	// fmt.Printf("Call %s(), context: %p\n", name, ctx)
-	params := make([]any, len(self.children))
-	for i, tree := range self.children {
-		var param any
-		if param, err = tree.compute(ctx); err != nil {
-			break
-		}
-		params[i] = param
-	}
-	if err == nil {
-		if err = checkFunctionCall(ctx, name, params); err == nil {
-			if v, err = ctx.Call(name, params); err == nil {
-				exportObjects(parentCtx, ctx)
-			}
-		}
-	}
+// 	if err == nil {
+// 		v, err = CallFunction(ctx, name, params)
+// 	}
+// 	return
+// }
+
+func evalFuncCall(ctx ExprContext, opTerm *term) (v any, err error) {
+	name, _ := opTerm.tk.Value.(string)
+	v, err = CallFunctionByTerm(ctx, name, opTerm)
 	return
 }
 
@@ -75,44 +57,23 @@ func newFuncDefTerm(tk *Token, args []*term) *term {
 }
 
 // -------- eval func def
-// TODO
-// type funcDefFunctor struct {
-// 	params []string
-// 	expr   Expr
-// }
-
-// func (funcDef *funcDefFunctor) Invoke(ctx ExprContext, name string, args []any) (result any, err error) {
-// 	for i, p := range funcDef.params {
-// 		if i < len(args) {
-// 			arg := args[i]
-// 			if functor, ok := arg.(Functor); ok {
-// 				// ctx.RegisterFunc(p, functor, 0, -1)
-// 				ctx.RegisterFunc2(p, functor, typeAny, []ExprFuncParam{
-// 					newFuncParam(paramValue),
-// 				})
-// 			} else {
-// 				ctx.UnsafeSetVar(p, arg)
-// 			}
-// 		} else {
-// 			ctx.UnsafeSetVar(p, nil)
-// 		}
-// 	}
-// 	result, err = funcDef.expr.eval(ctx, false)
-// 	return
-// }
-
-func evalFuncDef(ctx ExprContext, self *term) (v any, err error) {
-	bodySpec := self.value()
+func evalFuncDef(ctx ExprContext, opTerm *term) (v any, err error) {
+	bodySpec := opTerm.value()
 	if expr, ok := bodySpec.(*ast); ok {
-		paramList := make([]string, 0, len(self.children))
-		for _, param := range self.children {
-			paramList = append(paramList, param.source())
+		paramList := make([]ExprFuncParam, 0, len(opTerm.children))
+		for _, param := range opTerm.children {
+			var defValue any
+			flags := paramFlags(0)
+			if len(param.children) > 0 {
+				flags |= PfDefault
+				if defValue, err = param.children[0].compute(ctx); err != nil {
+					return
+				}
+			}
+			info := NewFuncParamFlagDef(param.source(), flags, defValue)
+			paramList = append(paramList, info)
 		}
-		v = newExprFunctor(expr, paramList)
-		// v = &funcDefFunctor{
-		// 	params: paramList,
-		// 	expr:   expr,
-		// }
+		v = newExprFunctor(expr, paramList, ctx)
 	} else {
 		err = errors.New("invalid function definition: the body specification must be an expression")
 	}

operand-iterator.go

@@ -5,29 +5,12 @@
 package expr
 
 import (
-	"fmt"
 	"slices"
 	"strings"
 )
 
 // -------- iterator term
 
-func newDsIteratorTerm(tk *Token, dsTerm *term, args []*term) *term {
-	tk.Sym = SymIterator
-
-	children := make([]*term, 0, 1+len(args))
-	children = append(children, dsTerm)
-	children = append(children, args...)
-	return &term{
-		tk:       *tk,
-		parent:   nil,
-		children: children,
-		position: posLeaf,
-		priority: priValue,
-		evalFunc: evalIterator,
-	}
-}
-
 func newIteratorTerm(tk *Token, args []*term) *term {
 	tk.Sym = SymIterator
 	return &term{
@@ -42,9 +25,9 @@ func newIteratorTerm(tk *Token, args []*term) *term {
 
 // -------- eval iterator
 
-func evalTermArray(ctx ExprContext, a []*term) (values []any, err error) {
-	values = make([]any, len(a))
-	for i, t := range a {
+func evalTermArray(ctx ExprContext, terms []*term) (values []any, err error) {
+	values = make([]any, len(terms))
+	for i, t := range terms {
 		var value any
 		if value, err = t.compute(ctx); err == nil {
 			values[i] = value
@@ -55,26 +38,24 @@ func evalTermArray(ctx ExprContext, a []*term) (values []any, err error) {
 	return
 }
 
-func evalFirstChild(ctx ExprContext, self *term) (value any, err error) {
-	if len(self.children) < 1 || self.children[0] == nil {
-		err = self.Errorf("missing the data-source parameter")
+func evalFirstChild(ctx ExprContext, iteratorTerm *term) (value any, err error) {
+	if len(iteratorTerm.children) < 1 || iteratorTerm.children[0] == nil {
+		err = iteratorTerm.Errorf("missing the data-source parameter")
 		return
 	}
 
-	value, err = self.children[0].compute(ctx)
+	value, err = iteratorTerm.children[0].compute(ctx)
 	return
 }
 
-func getDataSourceDict(ctx ExprContext, self *term, firstChildValue any) (ds map[string]Functor, err error) {
-	// if dictAny, ok := firstChildValue.(map[any]any); ok {
+func getDataSourceDict(iteratorTerm *term, firstChildValue any) (ds map[string]Functor, err error) {
 	if dictAny, ok := firstChildValue.(*DictType); ok {
-		requiredFields := []string{currentName, nextName}
-		fieldsMask := 0b11
+		requiredFields := []string{NextName}
+		fieldsMask := 0b1
 		foundFields := 0
 		ds = make(map[string]Functor)
 		for keyAny, item := range *dictAny {
 			if key, ok := keyAny.(string); ok {
-				//if functor, ok := item.(*funcDefFunctor); ok {
 				if functor, ok := item.(Functor); ok {
 					ds[key] = functor
 					if index := slices.Index(requiredFields, key); index >= 0 {
@@ -91,80 +72,77 @@ func getDataSourceDict(ctx ExprContext, self *term, firstChildValue any) (ds map
 					missingFields = append(missingFields, field)
 				}
 			}
-			err = fmt.Errorf("the data-source must provide a non-nil %q operator(s)", strings.Join(missingFields, ", "))
+			err = iteratorTerm.children[0].Errorf("the data-source must provide a non-nil %q operator(s)", strings.Join(missingFields, ", "))
 		}
 	}
 	return
 }
 
-func evalIterator(ctx ExprContext, self *term) (v any, err error) {
+func evalIterator(ctx ExprContext, opTerm *term) (v any, err error) {
 	var firstChildValue any
 	var ds map[string]Functor
 
-	if firstChildValue, err = evalFirstChild(ctx, self); err != nil {
+	if firstChildValue, err = evalFirstChild(ctx, opTerm); err != nil {
 		return
 	}
 
-	if ds, err = getDataSourceDict(ctx, self, firstChildValue); err != nil {
+	if ds, err = getDataSourceDict(opTerm, firstChildValue); err != nil && ds == nil {
 		return
 	}
+	err = nil
 
 	if ds != nil {
-		dc := newDataCursor(ctx, ds)
-		if initFunc, exists := ds[initName]; exists && initFunc != nil {
-			var args []any
-			if len(self.children) > 1 {
-				if args, err = evalTermArray(ctx, self.children[1:]); err != nil {
+		if len(ds) > 0 {
+			var dc *dataCursor
+			dcCtx := ctx.Clone()
+			if initFunc, exists := ds[InitName]; exists && initFunc != nil {
+				var args []any
+				var resource any
+				if len(opTerm.children) > 1 {
+					if args, err = evalTermArray(ctx, opTerm.children[1:]); err != nil {
+						return
+					}
+				} else {
+					args = []any{}
+				}
+
+				actualParams := bindActualParams(initFunc, args)
+
+				initCtx := ctx.Clone()
+				if resource, err = initFunc.InvokeNamed(initCtx, InitName, actualParams); err != nil {
 					return
 				}
+				exportObjects(dcCtx, initCtx)
+				dc = NewDataCursor(dcCtx, ds, resource)
 			} else {
-				args = []any{}
+				dc = NewDataCursor(dcCtx, ds, nil)
 			}
 
-			initCtx := dc.ctx.Clone()
-			if dc.resource, err = initFunc.Invoke(initCtx, initName, args); err != nil {
-				return
+			v = dc
+		} else {
+			if dictIt, ok := firstChildValue.(*DictType); ok {
+				var args []any
+				if args, err = evalSibling(ctx, opTerm.children, nil); err == nil {
+					v, err = NewDictIterator(dictIt, args)
+				}
+			} else {
+				err = opTerm.children[0].Errorf("the data-source must be a dictionary")
 			}
-			exportObjects(dc.ctx, initCtx)
 		}
-
-		dc.nextFunc, _ = ds[nextName]
-		dc.currentFunc, _ = ds[currentName]
-		dc.cleanFunc, _ = ds[cleanName]
-		dc.resetFunc, _ = ds[resetName]
-
-		v = dc
 	} else if list, ok := firstChildValue.(*ListType); ok {
 		var args []any
-		if args, err = evalSibling(ctx, self.children, nil); err == nil {
+		if args, err = evalSibling(ctx, opTerm.children, nil); err == nil {
 			v = NewListIterator(list, args)
 		}
 	} else {
 		var list []any
-		if list, err = evalSibling(ctx, self.children, firstChildValue); err == nil {
+		if list, err = evalSibling(ctx, opTerm.children, firstChildValue); err == nil {
 			v = NewArrayIterator(list)
 		}
 	}
 	return
 }
 
-// func evalChildren(ctx ExprContext, terms []*term, firstChildValue any) (list *ListType, err error) {
-// 	items := make(ListType, len(terms))
-// 	for i, tree := range terms {
-// 		var param any
-// 		if i == 0 && firstChildValue != nil {
-// 			param = firstChildValue
-// 		} else if param, err = tree.compute(ctx); err != nil {
-// 			break
-// 		}
-// 		items[i] = param
-// 	}
-// 	if err == nil {
-// 		list = &items
-// 	}
-// 	return
-// }
-
 func evalSibling(ctx ExprContext, terms []*term, firstChildValue any) (list []any, err error) {
 	items := make([]any, 0, len(terms))
 	for i, tree := range terms {

operand-list.go

@@ -21,8 +21,8 @@ func newListTerm(row, col int, args []*term) *term {
 }
 
 // -------- list func
-func evalList(ctx ExprContext, self *term) (v any, err error) {
-	list, _ := self.value().([]*term)
+func evalList(ctx ExprContext, opTerm *term) (v any, err error) {
+	list, _ := opTerm.value().([]*term)
 	items := make(ListType, len(list))
 	for i, tree := range list {
 		var param any

operand-literal.go

@@ -17,8 +17,8 @@ func newLiteralTerm(tk *Token) *term {
 }
 
 // -------- eval func
-func evalLiteral(ctx ExprContext, self *term) (v any, err error) {
-	v = self.tk.Value
+func evalLiteral(ctx ExprContext, opTerm *term) (v any, err error) {
+	v = opTerm.tk.Value
 	return
 }
 

operand-selector-case.go

@@ -41,10 +41,10 @@ func newSelectorCaseTerm(row, col int, filterList *term, caseExpr Expr) *term {
 }
 
 // -------- eval selector case
-func evalSelectorCase(ctx ExprContext, self *term) (v any, err error) {
+func evalSelectorCase(ctx ExprContext, opTerm *term) (v any, err error) {
 	var ok bool
-	if v, ok = self.value().(*selectorCase); !ok {
-		err = fmt.Errorf("selector-case expected, got %T", self.value())
+	if v, ok = opTerm.value().(*selectorCase); !ok {
+		err = fmt.Errorf("selector-case expected, got %T", opTerm.value())
 	}
 	return
 }

operand-var.go

@@ -9,9 +9,7 @@ import "fmt"
 // -------- variable term
 func newVarTerm(tk *Token) *term {
 	t := &term{
-		tk: *tk,
-		// class:    classVar,
-		// kind:     kindUnknown,
+		tk:       *tk,
 		parent:   nil,
 		children: nil,
 		position: posLeaf,
@@ -23,11 +21,11 @@ func newVarTerm(tk *Token) *term {
 }
 
 // -------- eval func
-func evalVar(ctx ExprContext, self *term) (v any, err error) {
+func evalVar(ctx ExprContext, opTerm *term) (v any, err error) {
 	var exists bool
-	name := self.source()
+	name := opTerm.source()
 	if v, exists = GetVar(ctx, name); !exists {
-		if info, exists, _ := GetFuncInfo(ctx, name); exists {
+		if info, exists := GetFuncInfo(ctx, name); exists {
 			v = info.Functor()
 		} else {
 			err = fmt.Errorf("undefined variable or function %q", name)

operator-assign.go

@@ -16,38 +16,189 @@ func newAssignTerm(tk *Token) (inst *term) {
 	}
 }
 
-func evalAssign(ctx ExprContext, self *term) (v any, err error) {
-	if err = self.checkOperands(); err != nil {
+func assignCollectionItem(ctx ExprContext, collectionTerm, keyListTerm *term, value any) (err error) {
+	var collectionValue, keyListValue, keyValue any
+	var keyList *ListType
+	var ok bool
+
+	if collectionValue, err = collectionTerm.compute(ctx); err != nil {
 		return
 	}
 
-	leftTerm := self.children[0]
-	if leftTerm.tk.Sym != SymVariable {
-		err = leftTerm.tk.Errorf("left operand of %q must be a variable", self.tk.source)
+	if keyListValue, err = keyListTerm.compute(ctx); err != nil {
+		return
+	} else if keyList, ok = keyListValue.(*ListType); !ok || len(*keyList) != 1 {
+		err = keyListTerm.Errorf("index/key specification expected, got %v [%s]", keyListValue, TypeName(keyListValue))
+		return
+	}
+	if keyValue = (*keyList)[0]; keyValue == nil {
+		err = keyListTerm.Errorf("index/key is nil")
 		return
 	}
 
-	rightChild := self.children[1]
+	switch collection := collectionValue.(type) {
+	case *ListType:
+		if index, ok := keyValue.(int64); ok {
+			err = collection.setItem(index, value)
+		} else {
+			err = keyListTerm.Errorf("integer expected, got %v [%s]", keyValue, TypeName(keyValue))
+		}
+	case *DictType:
+		err = collection.setItem(keyValue, value)
+	default:
+		err = collectionTerm.Errorf("collection expected")
+	}
+	return
+}
+
+func assignValue(ctx ExprContext, leftTerm *term, v any) (err error) {
+	if leftTerm.symbol() == SymIndex {
+		err = assignCollectionItem(ctx, leftTerm.children[0], leftTerm.children[1], v)
+	} else {
+		ctx.UnsafeSetVar(leftTerm.source(), v)
+	}
+	return
+}
+
+func evalAssign(ctx ExprContext, opTerm *term) (v any, err error) {
+	if err = opTerm.checkOperands(); err != nil {
+		return
+	}
+
+	leftTerm := opTerm.children[0]
+	leftSym := leftTerm.symbol()
+	if leftSym != SymVariable && leftSym != SymIndex {
+		err = leftTerm.tk.Errorf("left operand of %q must be a variable or a collection's item", opTerm.tk.source)
+		return
+	}
+
+	rightChild := opTerm.children[1]
 
 	if v, err = rightChild.compute(ctx); err == nil {
 		if functor, ok := v.(Functor); ok {
-			funcName := rightChild.source()
-			if info, exists, _ := GetFuncInfo(ctx, funcName); exists {
-				// ctx.RegisterFuncInfo(info)
-				ctx.RegisterFunc(leftTerm.source(), info.Functor(), info.ReturnType(), info.Params())
-			} else if funcDef, ok := functor.(*exprFunctor); ok {
-				paramSpecs := ForAll(funcDef.params, newFuncParam)
-				// paramCount := len(funcDef.params)
-				// paramSpecs := make([]ExprFuncParam, paramCount)
-				// for i := range paramSpecs {
-				// 	paramSpecs[i] = newFuncParam(funcDef.params[i])
-				// }
-				ctx.RegisterFunc(leftTerm.source(), functor, typeAny, paramSpecs)
+			if leftSym == SymVariable {
+				if info := functor.GetFunc(); info != nil {
+					ctx.RegisterFunc(leftTerm.source(), info.Functor(), info.ReturnType(), info.Params())
+				} else if funcDef, ok := functor.(*exprFunctor); ok {
+					paramSpecs := ForAll(funcDef.params, func(p ExprFuncParam) ExprFuncParam { return p })
+
+					ctx.RegisterFunc(leftTerm.source(), functor, TypeAny, paramSpecs)
+				} else {
+					err = opTerm.Errorf("unknown function %s()", rightChild.source())
+				}
 			} else {
-				err = self.Errorf("unknown function %s()", funcName)
+				err = assignValue(ctx, leftTerm, v)
 			}
 		} else {
-			ctx.UnsafeSetVar(leftTerm.source(), v)
+			err = assignValue(ctx, leftTerm, v)
+		}
+	}
+	if err != nil {
+		v = nil
+	}
+	return
+}
+
+//-------- assign term
+
+func newOpAssignTerm(tk *Token) (inst *term) {
+	return &term{
+		tk:       *tk,
+		children: make([]*term, 0, 2),
+		position: posInfix,
+		priority: priAssign,
+		evalFunc: evalOpAssign,
+	}
+}
+
+func getCollectionItemValue(ctx ExprContext, collectionTerm, keyListTerm *term) (value any, err error) {
+	var collectionValue, keyListValue, keyValue any
+	var keyList *ListType
+	var ok bool
+
+	if collectionValue, err = collectionTerm.compute(ctx); err != nil {
+		return
+	}
+
+	if keyListValue, err = keyListTerm.compute(ctx); err != nil {
+		return
+	} else if keyList, ok = keyListValue.(*ListType); !ok || len(*keyList) != 1 {
+		err = keyListTerm.Errorf("index/key specification expected, got %v [%s]", keyListValue, TypeName(keyListValue))
+		return
+	}
+	if keyValue = (*keyList)[0]; keyValue == nil {
+		err = keyListTerm.Errorf("index/key is nil")
+		return
+	}
+
+	switch collection := collectionValue.(type) {
+	case *ListType:
+		if index, ok := keyValue.(int64); ok {
+			value = (*collection)[index]
+		} else {
+			err = keyListTerm.Errorf("integer expected, got %v [%s]", keyValue, TypeName(keyValue))
+		}
+	case *DictType:
+		value = (*collection)[keyValue]
+	default:
+		err = collectionTerm.Errorf("collection expected")
+	}
+	return
+}
+
+func getAssignValue(ctx ExprContext, leftTerm *term) (value any, err error) {
+	if leftTerm.symbol() == SymIndex {
+		value, err = getCollectionItemValue(ctx, leftTerm.children[0], leftTerm.children[1])
+	} else {
+		value, _ = ctx.GetVar(leftTerm.source())
+	}
+	return
+}
+
+func evalOpAssign(ctx ExprContext, opTerm *term) (v any, err error) {
+	var rightValue, leftValue any
+	if err = opTerm.checkOperands(); err != nil {
+		return
+	}
+
+	leftTerm := opTerm.children[0]
+	leftSym := leftTerm.symbol()
+	if leftSym != SymVariable && leftSym != SymIndex {
+		err = leftTerm.tk.Errorf("left operand of %q must be a variable or a collection's item", opTerm.tk.source)
+		return
+	}
+
+	rightChild := opTerm.children[1]
+
+	if rightValue, err = rightChild.compute(ctx); err == nil {
+		if leftValue, err = getAssignValue(ctx, leftTerm); err == nil {
+			switch opTerm.symbol() {
+			case SymPlusEqual:
+				v, err = sumValues(opTerm, leftValue, rightValue)
+			case SymMinusEqual:
+				v, err = diffValues(opTerm, leftValue, rightValue)
+			case SymStarEqual:
+				v, err = mulValues(opTerm, leftValue, rightValue)
+			case SymSlashEqual:
+				v, err = divValues(opTerm, leftValue, rightValue)
+			case SymPercEqual:
+				v, err = remainderValues(opTerm, leftValue, rightValue)
+			case SymAmpersandEqual:
+				v, err = bitwiseAnd(opTerm, leftValue, rightValue)
+			case SymVertBarEqual:
+				v, err = bitwiseOr(opTerm, leftValue, rightValue)
+			case SymCaretEqual:
+				v, err = bitwiseXor(opTerm, leftValue, rightValue)
+			case SymDoubleLessEqual:
+				v, err = bitLeftShift(opTerm, leftValue, rightValue)
+			case SymDoubleGreaterEqual:
+				v, err = bitRightShift(opTerm, leftValue, rightValue)
+			default:
+				err = opTerm.Errorf("unsupported assign operator %q", opTerm.source())
+			}
+			if err == nil {
+				err = assignValue(ctx, leftTerm, v)
+			}
 		}
 	}
 	return
@@ -56,4 +207,14 @@ func evalAssign(ctx ExprContext, self *term) (v any, err error) {
 // init
 func init() {
 	registerTermConstructor(SymEqual, newAssignTerm)
+	registerTermConstructor(SymPlusEqual, newOpAssignTerm)
+	registerTermConstructor(SymMinusEqual, newOpAssignTerm)
+	registerTermConstructor(SymStarEqual, newOpAssignTerm)
+	registerTermConstructor(SymSlashEqual, newOpAssignTerm)
+	registerTermConstructor(SymPercEqual, newOpAssignTerm)
+	registerTermConstructor(SymDoubleLessEqual, newOpAssignTerm)
+	registerTermConstructor(SymDoubleGreaterEqual, newOpAssignTerm)
+	registerTermConstructor(SymAmpersandEqual, newOpAssignTerm)
+	registerTermConstructor(SymVertBarEqual, newOpAssignTerm)
+	registerTermConstructor(SymCaretEqual, newOpAssignTerm)
 }

operator-bitwise.go

@@ -0,0 +1,154 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// operator-bitwise.go
+package expr
+
+//-------- Bitwise NOT term
+
+func newBitwiseNotTerm(tk *Token) (inst *term) {
+	return &term{
+		tk:       *tk,
+		children: make([]*term, 0, 1),
+		position: posPrefix,
+		priority: priBitwiseNot,
+		evalFunc: evalBitwiseNot,
+	}
+}
+
+func evalBitwiseNot(ctx ExprContext, opTerm *term) (v any, err error) {
+	var value any
+
+	if value, err = opTerm.evalPrefix(ctx); err != nil {
+		return
+	}
+
+	if IsInteger(value) {
+		i, _ := value.(int64)
+		v = ^i
+	} else {
+		err = opTerm.errIncompatibleType(value)
+	}
+	return
+}
+
+//-------- Bitwise AND term
+
+func newBitwiseAndTerm(tk *Token) (inst *term) {
+	return &term{
+		tk:       *tk,
+		children: make([]*term, 0, 2),
+		position: posInfix,
+		priority: priBitwiseAnd,
+		evalFunc: evalBitwiseAnd,
+	}
+}
+
+func bitwiseAnd(opTerm *term, leftValue, rightValue any) (v any, err error) {
+	var leftInt, rightInt int64
+	var lok, rok bool
+
+	leftInt, lok = leftValue.(int64)
+	rightInt, rok = rightValue.(int64)
+
+	if lok && rok {
+		v = leftInt & rightInt
+	} else {
+		err = opTerm.errIncompatibleTypes(leftValue, rightValue)
+	}
+	return
+}
+
+func evalBitwiseAnd(ctx ExprContext, opTerm *term) (v any, err error) {
+	var leftValue, rightValue any
+
+	if leftValue, rightValue, err = opTerm.evalInfix(ctx); err != nil {
+		return
+	}
+	v, err = bitwiseAnd(opTerm, leftValue, rightValue)
+	return
+}
+
+//-------- Bitwise OR term
+
+func newBitwiseOrTerm(tk *Token) (inst *term) {
+	return &term{
+		tk:       *tk,
+		children: make([]*term, 0, 2),
+		position: posInfix,
+		priority: priBitwiseOr,
+		evalFunc: evalBitwiseOr,
+	}
+}
+
+func bitwiseOr(opTerm *term, leftValue, rightValue any) (v any, err error) {
+	var leftInt, rightInt int64
+	var lok, rok bool
+
+	leftInt, lok = leftValue.(int64)
+	rightInt, rok = rightValue.(int64)
+
+	if lok && rok {
+		v = leftInt | rightInt
+	} else {
+		err = opTerm.errIncompatibleTypes(leftValue, rightValue)
+	}
+	return
+}
+
+func evalBitwiseOr(ctx ExprContext, opTerm *term) (v any, err error) {
+	var leftValue, rightValue any
+
+	if leftValue, rightValue, err = opTerm.evalInfix(ctx); err != nil {
+		return
+	}
+
+	v, err = bitwiseOr(opTerm, leftValue, rightValue)
+	return
+}
+
+//-------- Bitwise XOR term
+
+func newBitwiseXorTerm(tk *Token) (inst *term) {
+	return &term{
+		tk:       *tk,
+		children: make([]*term, 0, 2),
+		position: posInfix,
+		priority: priBitwiseOr,
+		evalFunc: evalBitwiseXor,
+	}
+}
+
+func bitwiseXor(opTerm *term, leftValue, rightValue any) (v any, err error) {
+	var leftInt, rightInt int64
+	var lok, rok bool
+
+	leftInt, lok = leftValue.(int64)
+	rightInt, rok = rightValue.(int64)
+
+	if lok && rok {
+		v = leftInt ^ rightInt
+	} else {
+		err = opTerm.errIncompatibleTypes(leftValue, rightValue)
+	}
+	return
+}
+
+func evalBitwiseXor(ctx ExprContext, opTerm *term) (v any, err error) {
+	var leftValue, rightValue any
+
+	if leftValue, rightValue, err = opTerm.evalInfix(ctx); err != nil {
+		return
+	}
+
+	v, err = bitwiseXor(opTerm, leftValue, rightValue)
+	return
+}
+
+// init
+func init() {
+	registerTermConstructor(SymTilde, newBitwiseNotTerm)
+	registerTermConstructor(SymAmpersand, newBitwiseAndTerm)
+	registerTermConstructor(SymVertBar, newBitwiseOrTerm)
+	registerTermConstructor(SymCaret, newBitwiseXorTerm)
+}

operator-bool.go

@@ -18,17 +18,17 @@ func newNotTerm(tk *Token) (inst *term) {
 	}
 }
 
-func evalNot(ctx ExprContext, self *term) (v any, err error) {
+func evalNot(ctx ExprContext, opTerm *term) (v any, err error) {
 	var rightValue any
 
-	if rightValue, err = self.evalPrefix(ctx); err != nil {
+	if rightValue, err = opTerm.evalPrefix(ctx); err != nil {
 		return
 	}
 
-	if b, ok := toBool(rightValue); ok {
+	if b, ok := ToBool(rightValue); ok {
 		v = !b
 	} else {
-		err = self.errIncompatibleType(rightValue)
+		err = opTerm.errIncompatibleType(rightValue)
 	}
 	return
 }
@@ -37,9 +37,7 @@ func evalNot(ctx ExprContext, self *term) (v any, err error) {
 
 func newAndTerm(tk *Token) (inst *term) {
 	return &term{
-		tk: *tk,
-		// class:    classOperator,
-		// kind:     kindBool,
+		tk:       *tk,
 		children: make([]*term, 0, 2),
 		position: posInfix,
 		priority: priAnd,
@@ -48,7 +46,7 @@ func newAndTerm(tk *Token) (inst *term) {
 }
 
 func evalAnd(ctx ExprContext, self *term) (v any, err error) {
-	if isEnabled(ctx, ControlBoolShortcut) {
+	if CtrlIsEnabled(ctx, ControlBoolShortcut) {
 		v, err = evalAndWithShortcut(ctx, self)
 	} else {
 		v, err = evalAndWithoutShortcut(ctx, self)
@@ -65,8 +63,8 @@ func evalAndWithoutShortcut(ctx ExprContext, self *term) (v any, err error) {
 		return
 	}
 
-	leftBool, lok = toBool(leftValue)
-	rightBool, rok = toBool(rightValue)
+	leftBool, lok = ToBool(leftValue)
+	rightBool, rok = ToBool(rightValue)
 
 	if lok && rok {
 		v = leftBool && rightBool
@@ -87,13 +85,13 @@ func evalAndWithShortcut(ctx ExprContext, self *term) (v any, err error) {
 		return
 	}
 
-	if leftBool, lok := toBool(leftValue); !lok {
-		err = fmt.Errorf("got %T as left operand type of 'and' operator, it must be bool", leftBool)
+	if leftBool, lok := ToBool(leftValue); !lok {
+		err = fmt.Errorf("got %s as left operand type of 'AND' operator, it must be bool", TypeName(leftValue))
 		return
 	} else if !leftBool {
 		v = false
 	} else if rightValue, err = self.children[1].compute(ctx); err == nil {
-		if rightBool, rok := toBool(rightValue); rok {
+		if rightBool, rok := ToBool(rightValue); rok {
 			v = rightBool
 		} else {
 			err = self.errIncompatibleTypes(leftValue, rightValue)
@@ -106,9 +104,7 @@ func evalAndWithShortcut(ctx ExprContext, self *term) (v any, err error) {
 
 func newOrTerm(tk *Token) (inst *term) {
 	return &term{
-		tk: *tk,
-		// class:    classOperator,
-		// kind:     kindBool,
+		tk:       *tk,
 		children: make([]*term, 0, 2),
 		position: posInfix,
 		priority: priOr,
@@ -117,7 +113,7 @@ func newOrTerm(tk *Token) (inst *term) {
 }
 
 func evalOr(ctx ExprContext, self *term) (v any, err error) {
-	if isEnabled(ctx, ControlBoolShortcut) {
+	if CtrlIsEnabled(ctx, ControlBoolShortcut) {
 		v, err = evalOrWithShortcut(ctx, self)
 	} else {
 		v, err = evalOrWithoutShortcut(ctx, self)
@@ -134,8 +130,8 @@ func evalOrWithoutShortcut(ctx ExprContext, self *term) (v any, err error) {
 		return
 	}
 
-	leftBool, lok = toBool(leftValue)
-	rightBool, rok = toBool(rightValue)
+	leftBool, lok = ToBool(leftValue)
+	rightBool, rok = ToBool(rightValue)
 
 	if lok && rok {
 		v = leftBool || rightBool
@@ -156,13 +152,13 @@ func evalOrWithShortcut(ctx ExprContext, self *term) (v any, err error) {
 		return
 	}
 
-	if leftBool, lok := toBool(leftValue); !lok {
-		err = fmt.Errorf("got %T as left operand type of 'or' operator, it must be bool", leftBool)
+	if leftBool, lok := ToBool(leftValue); !lok {
+		err = fmt.Errorf("got %s as left operand type of 'OR' operator, it must be bool", TypeName(leftValue))
 		return
 	} else if leftBool {
 		v = true
 	} else if rightValue, err = self.children[1].compute(ctx); err == nil {
-		if rightBool, rok := toBool(rightValue); rok {
+		if rightBool, rok := ToBool(rightValue); rok {
 			v = rightBool
 		} else {
 			err = self.errIncompatibleTypes(leftValue, rightValue)

operator-builtin.go

@@ -18,10 +18,10 @@ func newBuiltinTerm(tk *Token) (inst *term) {
 	}
 }
 
-func evalBuiltin(ctx ExprContext, self *term) (v any, err error) {
+func evalBuiltin(ctx ExprContext, opTerm *term) (v any, err error) {
 	var childValue any
 
-	if childValue, err = self.evalPrefix(ctx); err != nil {
+	if childValue, err = opTerm.evalPrefix(ctx); err != nil {
 		return
 	}
 
@@ -31,17 +31,20 @@ func evalBuiltin(ctx ExprContext, self *term) (v any, err error) {
 		count, err = ImportInContextByGlobPattern(module)
 	} else {
 		var moduleSpec any
-		it := NewAnyIterator(childValue)
+		var it Iterator
+		if it, err = NewIterator(childValue); err != nil {
+			return
+		}
 		for moduleSpec, err = it.Next(); err == nil; moduleSpec, err = it.Next() {
 			if module, ok := moduleSpec.(string); ok {
 				if ImportInContext(module) {
 					count++
 				} else {
-					err = self.Errorf("unknown module %q", module)
+					err = opTerm.Errorf("unknown builtin module %q", module)
 					break
 				}
 			} else {
-				err = self.Errorf("expected string at item nr %d, got %T", it.Index()+1, moduleSpec)
+				err = opTerm.Errorf("expected string at item nr %d, got %s", it.Index()+1, TypeName(moduleSpec))
 				break
 			}
 		}

operator-but.go

@@ -16,8 +16,8 @@ func newButTerm(tk *Token) (inst *term) {
 	}
 }
 
-func evalBut(ctx ExprContext, self *term) (v any, err error) {
-	_, v, err = self.evalInfix(ctx)
+func evalBut(ctx ExprContext, opTerm *term) (v any, err error) {
+	_, v, err = opTerm.evalInfix(ctx)
 	return
 }
 

operator-coalesce.go

@@ -1,85 +0,0 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
-// All rights reserved.
-
-// operator-coalesce.go
-package expr
-
-//-------- null coalesce term
-
-func newNullCoalesceTerm(tk *Token) (inst *term) {
-	return &term{
-		tk:       *tk,
-		children: make([]*term, 0, 2),
-		position: posInfix,
-		priority: priCoalesce,
-		evalFunc: evalNullCoalesce,
-	}
-}
-
-func evalNullCoalesce(ctx ExprContext, self *term) (v any, err error) {
-	var rightValue any
-
-	if err = self.checkOperands(); err != nil {
-		return
-	}
-
-	leftTerm := self.children[0]
-	if leftTerm.tk.Sym != SymVariable {
-		err = leftTerm.Errorf("left operand of %q must be a variable", self.tk.source)
-		return
-	}
-
-	if leftValue, exists := ctx.GetVar(leftTerm.source()); exists {
-		v = leftValue
-	} else if rightValue, err = self.children[1].compute(ctx); err == nil {
-		v = rightValue
-	}
-	return
-}
-
-//-------- coalesce assign term
-
-func newCoalesceAssignTerm(tk *Token) (inst *term) {
-	return &term{
-		tk:       *tk,
-		children: make([]*term, 0, 2),
-		position: posInfix,
-		priority: priCoalesce,
-		evalFunc: evalAssignCoalesce,
-	}
-}
-
-func evalAssignCoalesce(ctx ExprContext, self *term) (v any, err error) {
-	var rightValue any
-
-	if err = self.checkOperands(); err != nil {
-		return
-	}
-
-	leftTerm := self.children[0]
-	if leftTerm.tk.Sym != SymVariable {
-		err = leftTerm.Errorf("left operand of %q must be a variable", self.tk.source)
-		return
-	}
-
-	if leftValue, exists := ctx.GetVar(leftTerm.source()); exists {
-		v = leftValue
-	} else if rightValue, err = self.children[1].compute(ctx); err == nil {
-		if functor, ok := rightValue.(Functor); ok {
-			//ctx.RegisterFunc(leftTerm.source(), functor, 0, -1)
-			ctx.RegisterFunc(leftTerm.source(), functor, typeAny, []ExprFuncParam{
-				newFuncParamFlag(paramValue, pfOptional|pfRepeat),
-			})
-		} else {
-			v = rightValue
-			ctx.UnsafeSetVar(leftTerm.source(), rightValue)
-		}
-	}
-	return
-}
-
-// init
-func init() {
-	registerTermConstructor(SymDoubleQuestion, newNullCoalesceTerm)
-	registerTermConstructor(SymQuestionEqual, newCoalesceAssignTerm)
-}

operator-context.go

@@ -16,25 +16,28 @@ func newContextTerm(tk *Token) (inst *term) {
 	}
 }
 
-func evalContextValue(ctx ExprContext, self *term) (v any, err error) {
+func evalContextValue(ctx ExprContext, opTerm *term) (v any, err error) {
 	var childValue any
 
 	var sourceCtx ExprContext
-	if self.children == nil || len(self.children) == 0 {
+	if len(opTerm.children) == 0 {
 		sourceCtx = ctx
-	} else if self.children[0].symbol() == SymVariable && self.children[0].source() == "global" {
+	} else if opTerm.children[0].symbol() == SymVariable && opTerm.children[0].source() == "global" {
 		sourceCtx = globalCtx
-	} else if childValue, err = self.evalPrefix(ctx); err == nil {
+	} else if childValue, err = opTerm.evalPrefix(ctx); err == nil {
 		if dc, ok := childValue.(*dataCursor); ok {
 			sourceCtx = dc.ctx
 		}
 	}
 
 	if sourceCtx != nil {
-		if formatter, ok := sourceCtx.(Formatter); ok {
+		if formatter, ok := sourceCtx.(DictFormat); ok {
+			v = formatter.ToDict()
+		} else if formatter, ok := sourceCtx.(Formatter); ok {
 			v = formatter.ToString(0)
 		} else {
-			keys := sourceCtx.EnumVars(func(name string) bool { return name[0] != '_' })
+			// keys := sourceCtx.EnumVars(func(name string) bool { return name[0] != '_' })
+			keys := sourceCtx.EnumVars(nil)
 			d := make(map[string]any)
 			for _, key := range keys {
 				d[key], _ = sourceCtx.GetVar(key)
@@ -46,7 +49,7 @@ func evalContextValue(ctx ExprContext, self *term) (v any, err error) {
 			v = d
 		}
 	} else {
-		err = self.errIncompatibleType(childValue)
+		err = opTerm.errIncompatibleType(childValue)
 	}
 	return
 }

operator-ctrl.go

@@ -16,8 +16,8 @@ func newExportAllTerm(tk *Token) (inst *term) {
 	}
 }
 
-func evalExportAll(ctx ExprContext, self *term) (v any, err error) {
-	enable(ctx, control_export_all)
+func evalExportAll(ctx ExprContext, opTerm *term) (v any, err error) {
+	CtrlEnable(ctx, control_export_all)
 	return
 }
 

operator-default.go

@@ -0,0 +1,124 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// operator-default.go
+package expr
+
+//-------- default term
+
+func newDefaultTerm(tk *Token) (inst *term) {
+	return &term{
+		tk:       *tk,
+		children: make([]*term, 0, 2),
+		position: posInfix,
+		priority: priDefault,
+		evalFunc: evalDefault,
+	}
+}
+
+func evalDefault(ctx ExprContext, opTerm *term) (v any, err error) {
+	var rightValue any
+
+	if err = opTerm.checkOperands(); err != nil {
+		return
+	}
+
+	leftTerm := opTerm.children[0]
+	if leftTerm.tk.Sym != SymVariable {
+		// err = leftTerm.Errorf("left operand of %q must be a variable", self.tk.source)
+		err = ErrLeftOperandMustBeVariable(leftTerm, opTerm)
+		return
+	}
+
+	if leftValue, exists := ctx.GetVar(leftTerm.source()); exists {
+		v = leftValue
+	} else if rightValue, err = opTerm.children[1].compute(ctx); err == nil {
+		v = rightValue
+	}
+	return
+}
+
+//-------- alternate term
+
+func newAlternateTerm(tk *Token) (inst *term) {
+	return &term{
+		tk:       *tk,
+		children: make([]*term, 0, 2),
+		position: posInfix,
+		priority: priDefault,
+		evalFunc: evalAlternate,
+	}
+}
+
+func evalAlternate(ctx ExprContext, opTerm *term) (v any, err error) {
+	var rightValue any
+
+	if err = opTerm.checkOperands(); err != nil {
+		return
+	}
+
+	leftTerm := opTerm.children[0]
+	if leftTerm.tk.Sym != SymVariable {
+		// err = leftTerm.Errorf("left operand of %q must be a variable", self.tk.source)
+		err = ErrLeftOperandMustBeVariable(leftTerm, opTerm)
+		return
+	}
+
+	if leftValue, exists := ctx.GetVar(leftTerm.source()); exists && leftValue != nil {
+		if rightValue, err = opTerm.children[1].compute(ctx); err == nil {
+			v = rightValue
+		}
+	} else {
+		v = leftValue
+	}
+	return
+}
+
+//-------- default assign term
+
+func newDefaultAssignTerm(tk *Token) (inst *term) {
+	return &term{
+		tk:       *tk,
+		children: make([]*term, 0, 2),
+		position: posInfix,
+		priority: priDefault,
+		evalFunc: evalAssignDefault,
+	}
+}
+
+func evalAssignDefault(ctx ExprContext, opTerm *term) (v any, err error) {
+	var rightValue any
+
+	if err = opTerm.checkOperands(); err != nil {
+		return
+	}
+
+	leftTerm := opTerm.children[0]
+	if leftTerm.tk.Sym != SymVariable {
+		// err = leftTerm.Errorf("left operand of %q must be a variable", self.tk.source)
+		err = ErrLeftOperandMustBeVariable(leftTerm, opTerm)
+		return
+	}
+
+	if leftValue, exists := ctx.GetVar(leftTerm.source()); exists {
+		v = leftValue
+	} else if rightValue, err = opTerm.children[1].compute(ctx); err == nil {
+		if functor, ok := rightValue.(Functor); ok {
+			//ctx.RegisterFunc(leftTerm.source(), functor, 0, -1)
+			ctx.RegisterFunc(leftTerm.source(), functor, TypeAny, []ExprFuncParam{
+				NewFuncParamFlag(ParamValue, PfDefault|PfRepeat),
+			})
+		} else {
+			v = rightValue
+			ctx.UnsafeSetVar(leftTerm.source(), rightValue)
+		}
+	}
+	return
+}
+
+// init
+func init() {
+	registerTermConstructor(SymDoubleQuestion, newDefaultTerm)
+	registerTermConstructor(SymQuestionEqual, newDefaultAssignTerm)
+	registerTermConstructor(SymQuestionExclam, newAlternateTerm)
+}

operator-digest.go

@@ -0,0 +1,70 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// operator-digest.go
+package expr
+
+import (
+	"fmt"
+	"io"
+)
+
+//-------- digest term
+
+func newDigestTerm(tk *Token) (inst *term) {
+	return &term{
+		tk:       *tk,
+		children: make([]*term, 0, 2),
+		position: posInfix,
+		priority: priIterOp,
+		evalFunc: evalDigest,
+	}
+}
+
+func evalDigest(ctx ExprContext, opTerm *term) (v any, err error) {
+	var leftValue, rightValue any
+	var it Iterator
+	var item, lastValue any
+
+	if err = opTerm.checkOperands(); err != nil {
+		return
+	}
+
+	if leftValue, err = opTerm.children[0].compute(ctx); err != nil {
+		return
+	}
+
+	if it, err = NewIterator(leftValue); err != nil {
+		return nil, fmt.Errorf("left operand of DIGEST must be an iterable data-source; got %s", TypeName(leftValue))
+	}
+
+	lastValue = nil
+	for item, err = it.Next(); err == nil; item, err = it.Next() {
+		ctx.SetVar("_", item)
+		ctx.SetVar("_index", it.Index())
+		ctx.SetVar("_count", it.Count())
+		if rightValue, err = opTerm.children[1].compute(ctx); err == nil {
+			if rightValue == nil {
+				break
+			} else {
+				lastValue = rightValue
+			}
+		}
+		ctx.DeleteVar("_count")
+		ctx.DeleteVar("_index")
+		ctx.DeleteVar("_")
+		if err != nil {
+			break
+		}
+	}
+	if err == io.EOF {
+		err = nil
+	}
+	v = lastValue
+	return
+}
+
+// init
+func init() {
+	registerTermConstructor(SymKwDigest, newDigestTerm)
+}

operator-dot.go

@@ -15,24 +15,24 @@ func newDotTerm(tk *Token) (inst *term) {
 	}
 }
 
-func evalDot(ctx ExprContext, self *term) (v any, err error) {
+func evalDot(ctx ExprContext, opTerm *term) (v any, err error) {
 	var leftValue, rightValue any
 
-	if err = self.checkOperands(); err != nil {
+	if err = opTerm.checkOperands(); err != nil {
 		return
 	}
-	if leftValue, err = self.children[0].compute(ctx); err != nil {
+	if leftValue, err = opTerm.children[0].compute(ctx); err != nil {
 		return
 	}
 
-	indexTerm := self.children[1]
+	indexTerm := opTerm.children[1]
 
 	switch unboxedValue := leftValue.(type) {
 	case ExtIterator:
 		if indexTerm.symbol() == SymVariable /*|| indexTerm.symbol() == SymString */ {
 			opName := indexTerm.source()
 			if unboxedValue.HasOperation(opName) {
-				v, err = unboxedValue.CallOperation(opName, []any{})
+				v, err = unboxedValue.CallOperation(opName, map[string]any{})
 			} else {
 				err = indexTerm.Errorf("this iterator do not support the %q command", opName)
 				v = false
@@ -41,8 +41,8 @@ func evalDot(ctx ExprContext, self *term) (v any, err error) {
 			err = indexTerm.tk.ErrorExpectedGot("identifier")
 		}
 	default:
-		if rightValue, err = self.children[1].compute(ctx); err == nil {
-			err = self.errIncompatibleTypes(leftValue, rightValue)
+		if rightValue, err = opTerm.children[1].compute(ctx); err == nil {
+			err = opTerm.errIncompatibleTypes(leftValue, rightValue)
 		}
 	}
 	return

operator-fact.go

@@ -18,10 +18,10 @@ func newFactTerm(tk *Token) (inst *term) {
 	}
 }
 
-func evalFact(ctx ExprContext, self *term) (v any, err error) {
+func evalFact(ctx ExprContext, opTerm *term) (v any, err error) {
 	var leftValue any
 
-	if leftValue, err = self.evalPrefix(ctx); err != nil {
+	if leftValue, err = opTerm.evalPrefix(ctx); err != nil {
 		return
 	}
 
@@ -36,7 +36,7 @@ func evalFact(ctx ExprContext, self *term) (v any, err error) {
 			err = fmt.Errorf("factorial of a negative integer (%d) is not allowed", i)
 		}
 	} else {
-		err = self.errIncompatibleType(leftValue)
+		err = opTerm.errIncompatibleType(leftValue)
 	}
 	return
 }

operator-filter.go

@@ -0,0 +1,72 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// operator-filter.go
+package expr
+
+import (
+	"fmt"
+	"io"
+)
+
+//-------- map term
+
+func newFilterTerm(tk *Token) (inst *term) {
+	return &term{
+		tk:       *tk,
+		children: make([]*term, 0, 2),
+		position: posInfix,
+		priority: priIterOp,
+		evalFunc: evalFilter,
+	}
+}
+
+func evalFilter(ctx ExprContext, opTerm *term) (v any, err error) {
+	var leftValue, rightValue any
+	var it Iterator
+	var item any
+
+	if err = opTerm.checkOperands(); err != nil {
+		return
+	}
+
+	if leftValue, err = opTerm.children[0].compute(ctx); err != nil {
+		return
+	}
+
+	if it, err = NewIterator(leftValue); err != nil {
+		return nil, fmt.Errorf("left operand of FILTER must be an iterable data-source; got %s", TypeName(leftValue))
+	}
+
+	values := newListA()
+	for item, err = it.Next(); err == nil; item, err = it.Next() {
+		ctx.SetVar("_", item)
+		ctx.SetVar("_index", it.Index())
+		ctx.SetVar("_count", it.Count())
+		if rightValue, err = opTerm.children[1].compute(ctx); err == nil {
+			if success, valid := ToBool(rightValue); valid {
+				if success {
+					values.appendItem(item)
+				}
+			} else {
+				err = fmt.Errorf("filter expression must return a boolean or a castable to boolean, got %v [%T]", rightValue, rightValue)
+			}
+		}
+		ctx.DeleteVar("_count")
+		ctx.DeleteVar("_index")
+		ctx.DeleteVar("_")
+		if err != nil {
+			break
+		}
+	}
+	if err == io.EOF {
+		err = nil
+	}
+	v = values
+	return
+}
+
+// init
+func init() {
+	registerTermConstructor(SymKwFilter, newFilterTerm)
+}

operator-fraction.go

@@ -7,7 +7,6 @@ package expr
 //https://www.youmath.it/lezioni/algebra-elementare/lezioni-di-algebra-e-aritmetica-per-scuole-medie/553-dalle-frazioni-a-numeri-decimali.html
 
 import (
-	"errors"
 	"fmt"
 )
 
@@ -24,12 +23,12 @@ func newFractionTerm(tk *Token) *term {
 }
 
 // -------- eval func
-func evalFraction(ctx ExprContext, self *term) (v any, err error) {
+func evalFraction(ctx ExprContext, opTerm *term) (v any, err error) {
 	var numValue, denValue any
 	var num, den int64
 	var ok bool
 
-	if numValue, denValue, err = self.evalInfix(ctx); err != nil {
+	if numValue, denValue, err = opTerm.evalInfix(ctx); err != nil {
 		return
 	}
 	if num, ok = numValue.(int64); !ok {
@@ -41,7 +40,7 @@ func evalFraction(ctx ExprContext, self *term) (v any, err error) {
 		return
 	}
 	if den == 0 {
-		err = errors.New("division by zero")
+		err = opTerm.errDivisionByZero()
 		return
 	}
 
@@ -49,18 +48,23 @@ func evalFraction(ctx ExprContext, self *term) (v any, err error) {
 		den = -den
 		num = -num
 	}
-	g := gcd(num, den)
-	num = num / g
-	den = den / g
-	if den == 1 {
-		v = num
+	if num != 0 {
+		g := gcd(num, den)
+		num = num / g
+		den = den / g
+		if den == 1 {
+			v = num
+		} else {
+			v = &FractionType{num, den}
+		}
 	} else {
-		v = &FractionType{num, den}
+		v = &FractionType{0, den}
 	}
 	return
 }
 
 // init
 func init() {
-	registerTermConstructor(SymVertBar, newFractionTerm)
+	// registerTermConstructor(SymVertBar, newFractionTerm)
+	registerTermConstructor(SymColon, newFractionTerm)
 }

operator-in.go

@@ -21,10 +21,10 @@ func newInTerm(tk *Token) (inst *term) {
 // 	return
 // }
 
-func evalIn(ctx ExprContext, self *term) (v any, err error) {
+func evalIn(ctx ExprContext, opTerm *term) (v any, err error) {
 	var leftValue, rightValue any
 
-	if leftValue, rightValue, err = self.evalInfix(ctx); err != nil {
+	if leftValue, rightValue, err = opTerm.evalInfix(ctx); err != nil {
 		return
 	}
 
@@ -35,7 +35,7 @@ func evalIn(ctx ExprContext, self *term) (v any, err error) {
 		dict, _ := rightValue.(*DictType)
 		v = dict.hasKey(leftValue)
 	} else {
-		err = self.errIncompatibleTypes(leftValue, rightValue)
+		err = opTerm.errIncompatibleTypes(leftValue, rightValue)
 	}
 	return
 }

operator-include.go

@@ -16,37 +16,40 @@ func newIncludeTerm(tk *Token) (inst *term) {
 	}
 }
 
-func evalInclude(ctx ExprContext, self *term) (v any, err error) {
+func evalInclude(ctx ExprContext, opTerm *term) (v any, err error) {
 	var childValue any
 
-	if childValue, err = self.evalPrefix(ctx); err != nil {
+	if childValue, err = opTerm.evalPrefix(ctx); err != nil {
 		return
 	}
 
 	count := 0
 	if IsList(childValue) {
-		list, _ := childValue.([]any)
-		for i, filePathSpec := range list {
+		list, _ := childValue.(*ListType)
+		for i, filePathSpec := range *list {
 			if filePath, ok := filePathSpec.(string); ok {
 				if v, err = EvalFile(ctx, filePath); err == nil {
 					count++
 				} else {
-					err = self.Errorf("can't load file %q", filePath)
+					err = opTerm.Errorf("can't load file %q", filePath)
 					break
 				}
 			} else {
-				err = self.Errorf("expected string at item nr %d, got %T", i+1, filePathSpec)
+				err = opTerm.Errorf("expected string at item nr %d, got %T", i+1, filePathSpec)
 				break
 			}
 		}
 	} else if IsString(childValue) {
 		filePath, _ := childValue.(string)
-		v, err = EvalFile(ctx, filePath)
+		if v, err = EvalFile(ctx, filePath); err == nil {
+			count++
+		}
 	} else {
-		err = self.errIncompatibleType(childValue)
+		err = opTerm.errIncompatibleType(childValue)
 	}
-	if err == nil {
-		v = count
+	if err != nil {
+		//v = count
+		v = nil
 	}
 	return
 }

operator-index.go

@@ -15,7 +15,7 @@ func newIndexTerm(tk *Token) (inst *term) {
 	}
 }
 
-func verifyKey(indexTerm *term, indexList *ListType) (index any, err error) {
+func verifyKey(indexList *ListType) (index any, err error) {
 	index = (*indexList)[0]
 	return
 }
@@ -23,7 +23,7 @@ func verifyKey(indexTerm *term, indexList *ListType) (index any, err error) {
 func verifyIndex(indexTerm *term, indexList *ListType, maxValue int) (index int, err error) {
 	var v int
 
-	if v, err = toInt((*indexList)[0], "index expression"); err == nil {
+	if v, err = ToGoInt((*indexList)[0], "index expression"); err == nil {
 		if v < 0 && v >= -maxValue {
 			v = maxValue + v
 		}
@@ -40,11 +40,14 @@ func verifyRange(indexTerm *term, indexList *ListType, maxValue int) (startIndex
 	v, _ := ((*indexList)[0]).(*intPair)
 	startIndex = v.a
 	endIndex = v.b
+	if endIndex == ConstLastIndex {
+		endIndex = maxValue
+	}
 	if startIndex < 0 && startIndex >= -maxValue {
 		startIndex = maxValue + startIndex
 	}
 	if endIndex < 0 && endIndex >= -maxValue {
-		endIndex = maxValue + endIndex + 1
+		endIndex = maxValue + endIndex
 	}
 	if startIndex < 0 || startIndex > maxValue {
 		err = indexTerm.Errorf("range start-index %d is out of bounds", startIndex)
@@ -56,18 +59,18 @@ func verifyRange(indexTerm *term, indexList *ListType, maxValue int) (startIndex
 	return
 }
 
-func evalIndex(ctx ExprContext, self *term) (v any, err error) {
+func evalIndex(ctx ExprContext, opTerm *term) (v any, err error) {
 	var leftValue, rightValue any
 	var indexList *ListType
 	var ok bool
 
-	if leftValue, rightValue, err = self.evalInfix(ctx); err != nil {
+	if leftValue, rightValue, err = opTerm.evalInfix(ctx); err != nil {
 		return
 	}
 
-	indexTerm := self.children[1]
+	indexTerm := opTerm.children[1]
 	if indexList, ok = rightValue.(*ListType); !ok {
-		err = self.Errorf("invalid index expression")
+		err = opTerm.Errorf("invalid index expression")
 		return
 	} else if len(*indexList) != 1 {
 		err = indexTerm.Errorf("one index only is allowed")
@@ -87,15 +90,9 @@ func evalIndex(ctx ExprContext, self *term) (v any, err error) {
 				v = string(unboxedValue[index])
 			}
 		case *DictType:
-			var ok bool
-			var indexValue any
-			if indexValue, err = verifyKey(indexTerm, indexList); err == nil {
-				if v, ok = (*unboxedValue)[indexValue]; !ok {
-					err = indexTerm.Errorf("key %v does not belong to the dictionary", rightValue)
-				}
-			}
+			v, err = getDictItem(unboxedValue, indexTerm, indexList, rightValue)
 		default:
-			err = self.errIncompatibleTypes(leftValue, rightValue)
+			err = opTerm.errIncompatibleTypes(leftValue, rightValue)
 		}
 	} else if isIntPair((*indexList)[0]) {
 		switch unboxedValue := leftValue.(type) {
@@ -111,7 +108,25 @@ func evalIndex(ctx ExprContext, self *term) (v any, err error) {
 				v = unboxedValue[start:end]
 			}
 		default:
-			err = self.errIncompatibleTypes(leftValue, rightValue)
+			err = opTerm.errIncompatibleTypes(leftValue, rightValue)
+		}
+	} else if IsDict(leftValue) {
+		d := leftValue.(*DictType)
+		v, err = getDictItem(d, indexTerm, indexList, rightValue)
+	} else {
+		rightChild := opTerm.children[1]
+		err = rightChild.Errorf("invalid index type: %v", (*indexList)[0])
+	}
+	return
+}
+
+func getDictItem(d *DictType, indexTerm *term, indexList *ListType, rightValue any) (v any, err error) {
+	var ok bool
+	var indexValue any
+
+	if indexValue, err = verifyKey(indexList); err == nil {
+		if v, ok = (*d)[indexValue]; !ok {
+			err = indexTerm.Errorf("key %v does not belong to the dictionary", rightValue)
 		}
 	}
 	return

operator-insert.go

@@ -4,15 +4,15 @@
 // operator-insert.go
 package expr
 
-//-------- insert term
+//-------- prepend term
 
-func newInsertTerm(tk *Token) (inst *term) {
+func newPrependTerm(tk *Token) (inst *term) {
 	return &term{
 		tk:       *tk,
 		children: make([]*term, 0, 2),
 		position: posInfix,
-		priority: priAssign,
-		evalFunc: evalInsert,
+		priority: priInsert,
+		evalFunc: evalPrepend,
 	}
 }
 
@@ -21,15 +21,15 @@ func newAppendTerm(tk *Token) (inst *term) {
 		tk:       *tk,
 		children: make([]*term, 0, 2),
 		position: posInfix,
-		priority: priAssign,
+		priority: priInsert,
 		evalFunc: evalAppend,
 	}
 }
 
-func evalInsert(ctx ExprContext, self *term) (v any, err error) {
+func evalPrepend(ctx ExprContext, opTerm *term) (v any, err error) {
 	var leftValue, rightValue any
 
-	if leftValue, rightValue, err = self.evalInfix(ctx); err != nil {
+	if leftValue, rightValue, err = opTerm.evalInfix(ctx); err != nil {
 		return
 	}
 
@@ -37,19 +37,19 @@ func evalInsert(ctx ExprContext, self *term) (v any, err error) {
 		list, _ := rightValue.(*ListType)
 		newList := append(ListType{leftValue}, *list...)
 		v = &newList
-		if self.children[1].symbol() == SymVariable {
-			ctx.UnsafeSetVar(self.children[1].source(), v)
+		if opTerm.children[1].symbol() == SymVariable {
+			ctx.UnsafeSetVar(opTerm.children[1].source(), v)
 		}
 	} else {
-		err = self.errIncompatibleTypes(leftValue, rightValue)
+		err = opTerm.errIncompatibleTypes(leftValue, rightValue)
 	}
 	return
 }
 
-func evalAppend(ctx ExprContext, self *term) (v any, err error) {
+func evalAppend(ctx ExprContext, opTerm *term) (v any, err error) {
 	var leftValue, rightValue any
 
-	if leftValue, rightValue, err = self.evalInfix(ctx); err != nil {
+	if leftValue, rightValue, err = opTerm.evalInfix(ctx); err != nil {
 		return
 	}
 
@@ -57,11 +57,11 @@ func evalAppend(ctx ExprContext, self *term) (v any, err error) {
 		list, _ := leftValue.(*ListType)
 		newList := append(*list, rightValue)
 		v = &newList
-		if self.children[0].symbol() == SymVariable {
-			ctx.UnsafeSetVar(self.children[0].source(), v)
+		if opTerm.children[0].symbol() == SymVariable {
+			ctx.UnsafeSetVar(opTerm.children[0].source(), v)
 		}
 	} else {
-		err = self.errIncompatibleTypes(leftValue, rightValue)
+		err = opTerm.errIncompatibleTypes(leftValue, rightValue)
 	}
 	return
 }
@@ -86,6 +86,6 @@ func evalAppend(ctx ExprContext, self *term) (v any, err error) {
 
 // init
 func init() {
-	registerTermConstructor(SymInsert, newInsertTerm)
-	registerTermConstructor(SymAppend, newAppendTerm)
+	registerTermConstructor(SymPlusGreater, newPrependTerm)
+	registerTermConstructor(SymLessPlus, newAppendTerm)
 }

operator-iter-value.go

@@ -11,27 +11,28 @@ func newIterValueTerm(tk *Token) (inst *term) {
 		tk:       *tk,
 		children: make([]*term, 0, 1),
 		position: posPrefix,
-		priority: priIterValue,
+		priority: priDereference,
 		evalFunc: evalIterValue,
 	}
 }
 
-func evalIterValue(ctx ExprContext, self *term) (v any, err error) {
+func evalIterValue(ctx ExprContext, opTerm *term) (v any, err error) {
 	var childValue any
 
-	if childValue, err = self.evalPrefix(ctx); err != nil {
+	if childValue, err = opTerm.evalPrefix(ctx); err != nil {
 		return
 	}
 
 	if it, ok := childValue.(Iterator); ok {
 		v, err = it.Current()
 	} else {
-		err = self.errIncompatibleType(childValue)
+		err = opTerm.errIncompatibleType(childValue)
 	}
 	return
 }
 
 // init
 func init() {
-	registerTermConstructor(SymOpenClosedRound, newIterValueTerm)
+	//	registerTermConstructor(SymOpenClosedRound, newIterValueTerm)
+	registerTermConstructor(SymDereference, newIterValueTerm)
 }

operator-join.go

@@ -0,0 +1,65 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// operator-join.go
+package expr
+
+import (
+	"fmt"
+	"io"
+)
+
+//-------- join term
+
+func newJoinTerm(tk *Token) (inst *term) {
+	return &term{
+		tk:       *tk,
+		children: make([]*term, 0, 2),
+		position: posInfix,
+		priority: priIterOp,
+		evalFunc: evalJoin,
+	}
+}
+
+func evalJoin(ctx ExprContext, opTerm *term) (v any, err error) {
+	var leftValue, rightValue any
+	var itLeft, itRight Iterator
+	var item any
+
+	if err = opTerm.checkOperands(); err != nil {
+		return
+	}
+
+	if leftValue, err = opTerm.children[0].compute(ctx); err != nil {
+		return
+	}
+
+	if rightValue, err = opTerm.children[1].compute(ctx); err != nil {
+		return
+	}
+
+	if itLeft, err = NewIterator(leftValue); err != nil {
+		return nil, fmt.Errorf("left operand of JOIN must be an iterable data-source; got %s", TypeName(leftValue))
+	}
+
+	if itRight, err = NewIterator(rightValue); err != nil {
+		return nil, fmt.Errorf("right operand of JOIN must be an iterable data-source; got %s", TypeName(rightValue))
+	}
+
+	values := newListA()
+	for _, it := range []Iterator{itLeft, itRight} {
+		for item, err = it.Next(); err == nil; item, err = it.Next() {
+			values.appendItem(item)
+		}
+	}
+	if err == io.EOF {
+		err = nil
+	}
+	v = values
+	return
+}
+
+// init
+func init() {
+	registerTermConstructor(SymKwJoin, newJoinTerm)
+}

operator-length.go

@@ -16,10 +16,10 @@ func newLengthTerm(tk *Token) (inst *term) {
 	}
 }
 
-func evalLength(ctx ExprContext, self *term) (v any, err error) {
+func evalLength(ctx ExprContext, opTerm *term) (v any, err error) {
 	var childValue any
 
-	if childValue, err = self.evalPrefix(ctx); err != nil {
+	if childValue, err = opTerm.evalPrefix(ctx); err != nil {
 		return
 	}
 
@@ -30,18 +30,18 @@ func evalLength(ctx ExprContext, self *term) (v any, err error) {
 		s, _ := childValue.(string)
 		v = int64(len(s))
 	} else if IsDict(childValue) {
-		// m, _ := childValue.(map[any]any)
 		m, _ := childValue.(*DictType)
 		v = int64(len(*m))
 	} else if it, ok := childValue.(Iterator); ok {
-		if extIt, ok := childValue.(ExtIterator); ok && extIt.HasOperation(countName) {
-			count, _ := extIt.CallOperation(countName, nil)
-			v, _ = toInt(count, "")
-		} else {
-			v = int64(it.Index() + 1)
-		}
+		v = int64(it.Count())
+		// if extIt, ok := childValue.(ExtIterator); ok && extIt.HasOperation(CountName) {
+		// 	count, _ := extIt.CallOperation(CountName, nil)
+		// 	v, _ = ToGoInt(count, "")
+		// } else {
+		// 	v = int64(it.Index() + 1)
+		// }
 	} else {
-		err = self.errIncompatibleType(childValue)
+		err = opTerm.errIncompatibleType(childValue)
 	}
 	return
 }

operator-map.go

@@ -0,0 +1,66 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// operator-map.go
+package expr
+
+import (
+	"fmt"
+	"io"
+)
+
+//-------- map term
+
+func newMapTerm(tk *Token) (inst *term) {
+	return &term{
+		tk:       *tk,
+		children: make([]*term, 0, 2),
+		position: posInfix,
+		priority: priIterOp,
+		evalFunc: evalMap,
+	}
+}
+
+func evalMap(ctx ExprContext, opTerm *term) (v any, err error) {
+	var leftValue, rightValue any
+	var it Iterator
+	var item any
+
+	if err = opTerm.checkOperands(); err != nil {
+		return
+	}
+
+	if leftValue, err = opTerm.children[0].compute(ctx); err != nil {
+		return
+	}
+
+	if it, err = NewIterator(leftValue); err != nil {
+		return nil, fmt.Errorf("left operand of MAP must be an iterable data-source; got %s", TypeName(leftValue))
+	}
+
+	values := newListA()
+	for item, err = it.Next(); err == nil; item, err = it.Next() {
+		ctx.SetVar("_", item)
+		ctx.SetVar("_index", it.Index())
+		ctx.SetVar("_count", it.Count())
+		if rightValue, err = opTerm.children[1].compute(ctx); err == nil {
+			values.appendItem(rightValue)
+		}
+		ctx.DeleteVar("_count")
+		ctx.DeleteVar("_index")
+		ctx.DeleteVar("_")
+		if err != nil {
+			break
+		}
+	}
+	if err == io.EOF {
+		err = nil
+	}
+	v = values
+	return
+}
+
+// init
+func init() {
+	registerTermConstructor(SymKwMap, newMapTerm)
+}

operator-plugin.go

@@ -0,0 +1,36 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// operator-plugin.go
+package expr
+
+//-------- plugin term
+
+func newPluginTerm(tk *Token) (inst *term) {
+	return &term{
+		tk:       *tk,
+		children: make([]*term, 0, 1),
+		position: posPrefix,
+		priority: priSign,
+		evalFunc: evalPlugin,
+	}
+}
+
+func evalPlugin(ctx ExprContext, opTerm *term) (v any, err error) {
+	var childValue any
+	var count int
+
+	if childValue, err = opTerm.evalPrefix(ctx); err != nil {
+		return
+	}
+
+	if count, err = importPluginFromSearchPath(childValue); err == nil {
+		v = int64(count)
+	}
+	return
+}
+
+// init
+func init() {
+	registerTermConstructor(SymKwPlugin, newPluginTerm)
+}

operator-post-inc-dec.go

@@ -0,0 +1,93 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// operator-post-inc-dec.go
+package expr
+
+// -------- post increment term
+
+func newPostIncTerm(tk *Token) *term {
+	return &term{
+		tk:       *tk,
+		parent:   nil,
+		children: make([]*term, 0, 1),
+		position: posPostfix,
+		priority: priIncDec,
+		evalFunc: evalPostInc,
+	}
+}
+
+func evalPostInc(ctx ExprContext, opTerm *term) (v any, err error) {
+	var childValue any
+	if childValue, err = opTerm.evalPrefix(ctx); err != nil {
+		return
+	}
+
+	if it, ok := childValue.(Iterator); ok {
+		var namePrefix string
+		v, err = it.Next()
+
+		if opTerm.children[0].symbol() == SymVariable {
+			namePrefix = opTerm.children[0].source()
+		}
+		ctx.UnsafeSetVar(namePrefix+"_index", it.Index())
+		if c, err1 := it.Current(); err1 == nil {
+			ctx.UnsafeSetVar(namePrefix+"_current", c)
+		}
+
+		if it.HasOperation(KeyName) {
+			if k, err1 := it.CallOperation(KeyName, nil); err1 == nil {
+				ctx.UnsafeSetVar(namePrefix+"_key", k)
+			}
+		}
+		if it.HasOperation(ValueName) {
+			if v1, err1 := it.CallOperation(ValueName, nil); err1 == nil {
+				ctx.UnsafeSetVar(namePrefix+"_value", v1)
+			}
+		}
+	} else if IsInteger(childValue) && opTerm.children[0].symbol() == SymVariable {
+		v = childValue
+		i, _ := childValue.(int64)
+		ctx.SetVar(opTerm.children[0].source(), i+1)
+	} else {
+		err = opTerm.errIncompatibleType(childValue)
+	}
+	return
+}
+
+// -------- post decrement term
+
+func newPostDecTerm(tk *Token) *term {
+	return &term{
+		tk:       *tk,
+		parent:   nil,
+		children: make([]*term, 0, 1),
+		position: posPostfix,
+		priority: priIncDec,
+		evalFunc: evalPostDec,
+	}
+}
+
+func evalPostDec(ctx ExprContext, opTerm *term) (v any, err error) {
+	var childValue any
+	if childValue, err = opTerm.evalPrefix(ctx); err != nil {
+		return
+	}
+
+	/* if it, ok := childValue.(Iterator); ok {
+		v, err = it.Next()
+	} else  */if IsInteger(childValue) && opTerm.children[0].symbol() == SymVariable {
+		v = childValue
+		i, _ := childValue.(int64)
+		ctx.SetVar(opTerm.children[0].source(), i-1)
+	} else {
+		err = opTerm.errIncompatibleType(childValue)
+	}
+	return
+}
+
+// init
+func init() {
+	registerTermConstructor(SymDoublePlus, newPostIncTerm)
+	registerTermConstructor(SymDoubleMinus, newPostDecTerm)
+}

operator-post-inc.go

@@ -1,41 +0,0 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
-// All rights reserved.
-
-// operator-post-inc.go
-package expr
-
-// -------- post increment term
-
-func newPostIncTerm(tk *Token) *term {
-	return &term{
-		tk:       *tk,
-		parent:   nil,
-		children: make([]*term, 0, 1),
-		position: posPostfix,
-		priority: priIncDec,
-		evalFunc: evalPostInc,
-	}
-}
-
-func evalPostInc(ctx ExprContext, self *term) (v any, err error) {
-	var childValue any
-	if childValue, err = self.evalPrefix(ctx); err != nil {
-		return
-	}
-
-	if it, ok := childValue.(Iterator); ok {
-		v, err = it.Next()
-	} else if IsInteger(childValue) && self.children[0].symbol() == SymVariable {
-		v = childValue
-		i, _ := childValue.(int64)
-		ctx.SetVar(self.children[0].source(), i+1)
-	} else {
-		err = self.errIncompatibleType(childValue)
-	}
-	return
-}
-
-// init
-func init() {
-	registerTermConstructor(SymDoublePlus, newPostIncTerm)
-}

operator-pre-inc-dec.go

@@ -0,0 +1,69 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// operator-pre-inc-dec.go
+package expr
+
+// -------- pre increment term
+
+func newPreIncTerm(tk *Token) *term {
+	return &term{
+		tk:       *tk,
+		parent:   nil,
+		children: make([]*term, 0, 1),
+		position: posPrefix,
+		priority: priIncDec,
+		evalFunc: evalPreInc,
+	}
+}
+
+func evalPreInc(ctx ExprContext, opTerm *term) (v any, err error) {
+	var childValue any
+	if childValue, err = opTerm.evalPrefix(ctx); err != nil {
+		return
+	}
+
+	if IsInteger(childValue) && opTerm.children[0].symbol() == SymVariable {
+		i := childValue.(int64) + 1
+		ctx.SetVar(opTerm.children[0].source(), i)
+		v = i
+	} else {
+		err = opTerm.errIncompatibleType(childValue)
+	}
+	return
+}
+
+// -------- pre decrement term
+
+func newPreDecTerm(tk *Token) *term {
+	return &term{
+		tk:       *tk,
+		parent:   nil,
+		children: make([]*term, 0, 1),
+		position: posPrefix,
+		priority: priIncDec,
+		evalFunc: evalPreDec,
+	}
+}
+
+func evalPreDec(ctx ExprContext, opTerm *term) (v any, err error) {
+	var childValue any
+	if childValue, err = opTerm.evalPrefix(ctx); err != nil {
+		return
+	}
+
+	if IsInteger(childValue) && opTerm.children[0].symbol() == SymVariable {
+		i := childValue.(int64) - 1
+		ctx.SetVar(opTerm.children[0].source(), i)
+		v = i
+	} else {
+		err = opTerm.errIncompatibleType(childValue)
+	}
+	return
+}
+
+// init
+func init() {
+	registerTermConstructor(SymPreInc, newPreIncTerm)
+	registerTermConstructor(SymPreDec, newPreDecTerm)
+}

operator-prod.go

@@ -5,7 +5,6 @@
 package expr
 
 import (
-	"errors"
 	"strings"
 )
 
@@ -13,9 +12,7 @@ import (
 
 func newMultiplyTerm(tk *Token) (inst *term) {
 	return &term{
-		tk: *tk,
-		// class:    classOperator,
-		// kind:     kindUnknown,
+		tk:       *tk,
 		children: make([]*term, 0, 2),
 		position: posInfix,
 		priority: priProduct,
@@ -23,13 +20,7 @@ func newMultiplyTerm(tk *Token) (inst *term) {
 	}
 }
 
-func evalMultiply(ctx ExprContext, self *term) (v any, err error) {
-	var leftValue, rightValue any
-
-	if leftValue, rightValue, err = self.evalInfix(ctx); err != nil {
-		return
-	}
-
+func mulValues(opTerm *term, leftValue, rightValue any) (v any, err error) {
 	if IsString(leftValue) && IsInteger(rightValue) {
 		s, _ := leftValue.(string)
 		n, _ := rightValue.(int64)
@@ -45,18 +36,26 @@ func evalMultiply(ctx ExprContext, self *term) (v any, err error) {
 			v = leftInt * rightInt
 		}
 	} else {
-		err = self.errIncompatibleTypes(leftValue, rightValue)
+		err = opTerm.errIncompatibleTypes(leftValue, rightValue)
 	}
 	return
 }
 
+func evalMultiply(ctx ExprContext, prodTerm *term) (v any, err error) {
+	var leftValue, rightValue any
+
+	if leftValue, rightValue, err = prodTerm.evalInfix(ctx); err != nil {
+		return
+	}
+
+	return mulValues(prodTerm, leftValue, rightValue)
+}
+
 //-------- divide term
 
 func newDivideTerm(tk *Token) (inst *term) {
 	return &term{
-		tk: *tk,
-		// class:    classOperator,
-		// kind:     kindUnknown,
+		tk:       *tk,
 		children: make([]*term, 0, 2),
 		position: posInfix,
 		priority: priProduct,
@@ -64,18 +63,12 @@ func newDivideTerm(tk *Token) (inst *term) {
 	}
 }
 
-func evalDivide(ctx ExprContext, self *term) (v any, err error) {
-	var leftValue, rightValue any
-
-	if leftValue, rightValue, err = self.evalInfix(ctx); err != nil {
-		return
-	}
-
+func divValues(opTerm *term, leftValue, rightValue any) (v any, err error) {
 	if isNumOrFract(leftValue) && isNumOrFract(rightValue) {
 		if IsFloat(leftValue) || IsFloat(rightValue) {
 			d := numAsFloat(rightValue)
 			if d == 0.0 {
-				err = errors.New("division by zero")
+				err = opTerm.errDivisionByZero()
 			} else {
 				v = numAsFloat(leftValue) / d
 			}
@@ -84,17 +77,52 @@ func evalDivide(ctx ExprContext, self *term) (v any, err error) {
 		} else {
 			leftInt, _ := leftValue.(int64)
 			if rightInt, _ := rightValue.(int64); rightInt == 0 {
-				err = errors.New("division by zero")
+				err = opTerm.errDivisionByZero()
 			} else {
 				v = leftInt / rightInt
 			}
 		}
+	} else if IsString(leftValue) && IsString(rightValue) {
+		source := leftValue.(string)
+		sep := rightValue.(string)
+		v = ListFromStrings(strings.Split(source, sep))
+	} else if IsString(leftValue) && IsInteger(rightValue) {
+		source := leftValue.(string)
+		partSize := int(rightValue.(int64))
+		if partSize == 0 {
+			err = opTerm.errDivisionByZero()
+		} else {
+			partCount := len(source) / partSize
+			remainder := len(source) % partSize
+			listSize := partCount
+			if remainder > 0 {
+				listSize++
+			}
+			parts := make([]any, 0, listSize)
+			for i := 0; i < partCount; i++ {
+				parts = append(parts, source[i*partSize:(i+1)*partSize])
+			}
+			if remainder > 0 {
+				parts = append(parts, source[len(source)-remainder:])
+			}
+			v = newList(parts)
+		}
 	} else {
-		err = self.errIncompatibleTypes(leftValue, rightValue)
+		err = opTerm.errIncompatibleTypes(leftValue, rightValue)
 	}
 	return
 }
 
+func evalDivide(ctx ExprContext, opTerm *term) (v any, err error) {
+	var leftValue, rightValue any
+
+	if leftValue, rightValue, err = opTerm.evalInfix(ctx); err != nil {
+		return
+	}
+
+	return divValues(opTerm, leftValue, rightValue)
+}
+
 //-------- divide as float term
 
 func newDivideAsFloatTerm(tk *Token) (inst *term) {
@@ -107,65 +135,66 @@ func newDivideAsFloatTerm(tk *Token) (inst *term) {
 	}
 }
 
-func evalDivideAsFloat(ctx ExprContext, self *term) (v any, err error) {
+func evalDivideAsFloat(ctx ExprContext, floatDivTerm *term) (v any, err error) {
 	var leftValue, rightValue any
 
-	if leftValue, rightValue, err = self.evalInfix(ctx); err != nil {
+	if leftValue, rightValue, err = floatDivTerm.evalInfix(ctx); err != nil {
 		return
 	}
 
 	if isNumOrFract(leftValue) && isNumOrFract(rightValue) {
 		d := numAsFloat(rightValue)
 		if d == 0.0 {
-			err = errors.New("division by zero")
+			err = floatDivTerm.errDivisionByZero()
 		} else {
 			v = numAsFloat(leftValue) / d
 		}
 	} else {
-		err = self.errIncompatibleTypes(leftValue, rightValue)
+		err = floatDivTerm.errIncompatibleTypes(leftValue, rightValue)
 	}
 	return
 }
 
 //-------- reminder term
 
-func newReminderTerm(tk *Token) (inst *term) {
+func newRemainderTerm(tk *Token) (inst *term) {
 	return &term{
-		tk: *tk,
-		// class:    classOperator,
-		// kind:     kindUnknown,
+		tk:       *tk,
 		children: make([]*term, 0, 2),
 		position: posInfix,
 		priority: priProduct,
-		evalFunc: evalReminder,
+		evalFunc: evalRemainder,
 	}
 }
-
-func evalReminder(ctx ExprContext, self *term) (v any, err error) {
-	var leftValue, rightValue any
-
-	if leftValue, rightValue, err = self.evalInfix(ctx); err != nil {
-		return
-	}
-
+func remainderValues(opTerm *term, leftValue, rightValue any) (v any, err error) {
 	if IsInteger(leftValue) && IsInteger(rightValue) {
 		rightInt, _ := rightValue.(int64)
 		if rightInt == 0 {
-			err = errors.New("division by zero")
+			err = opTerm.errDivisionByZero()
 		} else {
 			leftInt, _ := leftValue.(int64)
 			v = leftInt % rightInt
 		}
 	} else {
-		err = self.errIncompatibleTypes(leftValue, rightValue)
+		err = opTerm.errIncompatibleTypes(leftValue, rightValue)
 	}
 	return
 }
 
+func evalRemainder(ctx ExprContext, remainderTerm *term) (v any, err error) {
+	var leftValue, rightValue any
+
+	if leftValue, rightValue, err = remainderTerm.evalInfix(ctx); err != nil {
+		return
+	}
+
+	return remainderValues(remainderTerm, leftValue, rightValue)
+}
+
 // init
 func init() {
 	registerTermConstructor(SymStar, newMultiplyTerm)
 	registerTermConstructor(SymSlash, newDivideTerm)
 	registerTermConstructor(SymDotSlash, newDivideAsFloatTerm)
-	registerTermConstructor(SymPercent, newReminderTerm)
+	registerTermConstructor(SymPercent, newRemainderTerm)
 }

operator-range.go

@@ -12,7 +12,7 @@ type intPair struct {
 }
 
 func (p *intPair) TypeName() string {
-	return typePair
+	return TypePair
 }
 
 func (p *intPair) ToString(opt FmtOpt) string {
@@ -29,30 +29,35 @@ func newRangeTerm(tk *Token) (inst *term) {
 		tk:       *tk,
 		children: make([]*term, 0, 2),
 		position: posInfix,
-		priority: priDot,
+		priority: priRange,
 		evalFunc: evalRange,
 	}
 }
 
-func evalRange(ctx ExprContext, self *term) (v any, err error) {
+func changeColonToRange(t *term) {
+	if t.tk.IsSymbol(SymColon) {
+		t.tk.Sym = SymRange
+		t.evalFunc = evalRange
+	}
+}
+
+func evalRange(ctx ExprContext, opTerm *term) (v any, err error) {
 	var leftValue, rightValue any
 
-	// if err = self.checkOperands(); err != nil {
-	// 	return
-	// }
-	if len(self.children) == 0 {
+	if len(opTerm.children) == 0 {
 		leftValue = int64(0)
 		rightValue = int64(-1)
-	} else if len(self.children) == 1 {
-		if leftValue, err = self.children[0].compute(ctx); err != nil {
+	} else if len(opTerm.children) == 1 {
+		if leftValue, err = opTerm.children[0].compute(ctx); err != nil {
 			return
 		}
-		rightValue = int64(-1)
-	} else if leftValue, rightValue, err = self.evalInfix(ctx); err != nil {
+		rightValue = int64(ConstLastIndex)
+	} else if leftValue, rightValue, err = opTerm.evalInfix(ctx); err != nil {
 		return
 	}
 	if !(IsInteger(leftValue) && IsInteger(rightValue)) {
-		err = self.errIncompatibleTypes(leftValue, rightValue)
+		// err = opTerm.errIncompatibleTypes(leftValue, rightValue)
+		err = errRangeInvalidSpecification(opTerm)
 		return
 	}
 
@@ -63,7 +68,15 @@ func evalRange(ctx ExprContext, self *term) (v any, err error) {
 	return
 }
 
+func errRangeInvalidSpecification(t *term) error {
+	return t.Errorf("invalid range specification")
+}
+
+func errRangeUnexpectedExpression(t *term) error {
+	return t.Errorf("unexpected range expression")
+}
+
 // init
 func init() {
-	registerTermConstructor(SymColon, newRangeTerm)
+	registerTermConstructor(SymRange, newRangeTerm)
 }

operator-rel.go

@@ -45,10 +45,10 @@ func equals(a, b any, deepCmp deepFuncTemplate) (eq bool, err error) {
 	return
 }
 
-func evalEqual(ctx ExprContext, self *term) (v any, err error) {
+func evalEqual(ctx ExprContext, opTerm *term) (v any, err error) {
 	var leftValue, rightValue any
 
-	if leftValue, rightValue, err = self.evalInfix(ctx); err != nil {
+	if leftValue, rightValue, err = opTerm.evalInfix(ctx); err != nil {
 		return
 	}
 
@@ -68,9 +68,9 @@ func newNotEqualTerm(tk *Token) (inst *term) {
 	}
 }
 
-func evalNotEqual(ctx ExprContext, self *term) (v any, err error) {
-	if v, err = evalEqual(ctx, self); err == nil {
-		b, _ := toBool(v)
+func evalNotEqual(ctx ExprContext, opTerm *term) (v any, err error) {
+	if v, err = evalEqual(ctx, opTerm); err == nil {
+		b, _ := ToBool(v)
 		v = !b
 	}
 	return
@@ -119,13 +119,13 @@ func lessThan(self *term, a, b any) (isLess bool, err error) {
 	return
 }
 
-func evalLess(ctx ExprContext, self *term) (v any, err error) {
+func evalLess(ctx ExprContext, opTerm *term) (v any, err error) {
 	var leftValue, rightValue any
 
-	if leftValue, rightValue, err = self.evalInfix(ctx); err != nil {
+	if leftValue, rightValue, err = opTerm.evalInfix(ctx); err != nil {
 		return
 	}
-	v, err = lessThan(self, leftValue, rightValue)
+	v, err = lessThan(opTerm, leftValue, rightValue)
 	return
 }
 
@@ -154,14 +154,14 @@ func lessThanOrEqual(self *term, a, b any) (isLessEq bool, err error) {
 	return
 }
 
-func evalLessEqual(ctx ExprContext, self *term) (v any, err error) {
+func evalLessEqual(ctx ExprContext, opTerm *term) (v any, err error) {
 	var leftValue, rightValue any
 
-	if leftValue, rightValue, err = self.evalInfix(ctx); err != nil {
+	if leftValue, rightValue, err = opTerm.evalInfix(ctx); err != nil {
 		return
 	}
 
-	v, err = lessThanOrEqual(self, leftValue, rightValue)
+	v, err = lessThanOrEqual(opTerm, leftValue, rightValue)
 
 	return
 }
@@ -178,14 +178,14 @@ func newGreaterTerm(tk *Token) (inst *term) {
 	}
 }
 
-func evalGreater(ctx ExprContext, self *term) (v any, err error) {
+func evalGreater(ctx ExprContext, opTerm *term) (v any, err error) {
 	var leftValue, rightValue any
 
-	if leftValue, rightValue, err = self.evalInfix(ctx); err != nil {
+	if leftValue, rightValue, err = opTerm.evalInfix(ctx); err != nil {
 		return
 	}
 
-	v, err = lessThan(self, rightValue, leftValue)
+	v, err = lessThan(opTerm, rightValue, leftValue)
 	return
 }
 
@@ -201,14 +201,14 @@ func newGreaterEqualTerm(tk *Token) (inst *term) {
 	}
 }
 
-func evalGreaterEqual(ctx ExprContext, self *term) (v any, err error) {
+func evalGreaterEqual(ctx ExprContext, opTerm *term) (v any, err error) {
 	var leftValue, rightValue any
 
-	if leftValue, rightValue, err = self.evalInfix(ctx); err != nil {
+	if leftValue, rightValue, err = opTerm.evalInfix(ctx); err != nil {
 		return
 	}
 
-	v, err = lessThanOrEqual(self, rightValue, leftValue)
+	v, err = lessThanOrEqual(opTerm, rightValue, leftValue)
 	return
 }
 

operator-selector.go

@@ -19,17 +19,27 @@ func newSelectorTerm(tk *Token) (inst *term) {
 func trySelectorCase(ctx ExprContext, exprValue, caseSel any, caseIndex int) (match bool, selectedValue any, err error) {
 	caseData, _ := caseSel.(*selectorCase)
 	if caseData.filterList == nil {
-		selectedValue, err = caseData.caseExpr.eval(ctx, false)
+		selectedValue, err = caseData.caseExpr.Eval(ctx)
 		match = true
 	} else if filterList, ok := caseData.filterList.value().([]*term); ok {
-		if len(filterList) == 0 && exprValue == int64(caseIndex) {
-			selectedValue, err = caseData.caseExpr.eval(ctx, false)
-			match = true
+		if len(filterList) == 0 {
+			var valueAsInt = int64(0)
+			if b, ok := exprValue.(bool); ok {
+				if !b {
+					valueAsInt = 1
+				}
+			} else if valueAsInt, ok = exprValue.(int64); !ok {
+				return
+			}
+			if valueAsInt == int64(caseIndex) {
+				selectedValue, err = caseData.caseExpr.Eval(ctx)
+				match = true
+			}
 		} else {
 			var caseValue any
 			for _, caseTerm := range filterList {
 				if caseValue, err = caseTerm.compute(ctx); err != nil || caseValue == exprValue {
-					selectedValue, err = caseData.caseExpr.eval(ctx, false)
+					selectedValue, err = caseData.caseExpr.Eval(ctx)
 					match = true
 					break
 				}
@@ -39,19 +49,19 @@ func trySelectorCase(ctx ExprContext, exprValue, caseSel any, caseIndex int) (ma
 	return
 }
 
-func evalSelector(ctx ExprContext, self *term) (v any, err error) {
+func evalSelector(ctx ExprContext, opTerm *term) (v any, err error) {
 	var exprValue any
 	var match bool
 
-	if err = self.checkOperands(); err != nil {
+	if err = opTerm.checkOperands(); err != nil {
 		return
 	}
-	exprTerm := self.children[0]
+	exprTerm := opTerm.children[0]
 	if exprValue, err = exprTerm.compute(ctx); err != nil {
 		return
 	}
 
-	caseListTerm := self.children[1]
+	caseListTerm := opTerm.children[1]
 	caseList, _ := caseListTerm.value().([]*term)
 	for i, caseTerm := range caseList {
 		caseSel := caseTerm.value()

operator-shift.go

@@ -0,0 +1,77 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// operator-shift.go
+package expr
+
+//-------- bit right shift term
+
+func newRightShiftTerm(tk *Token) (inst *term) {
+	return &term{
+		tk:       *tk,
+		children: make([]*term, 0, 2),
+		position: posInfix,
+		priority: priBinShift,
+		evalFunc: evalRightShift,
+	}
+}
+
+func bitRightShift(opTerm *term, leftValue, rightValue any) (v any, err error) {
+	if IsInteger(leftValue) && IsInteger(rightValue) {
+		leftInt := leftValue.(int64)
+		rightInt := rightValue.(int64)
+		v = leftInt >> rightInt
+	} else {
+		err = opTerm.errIncompatibleTypes(leftValue, rightValue)
+	}
+	return
+}
+
+func evalRightShift(ctx ExprContext, opTerm *term) (v any, err error) {
+	var leftValue, rightValue any
+
+	if leftValue, rightValue, err = opTerm.evalInfix(ctx); err != nil {
+		return
+	}
+
+	v, err = bitRightShift(opTerm, leftValue, rightValue)
+	return
+}
+
+func newLeftShiftTerm(tk *Token) (inst *term) {
+	return &term{
+		tk:       *tk,
+		children: make([]*term, 0, 2),
+		position: posInfix,
+		priority: priBinShift,
+		evalFunc: evalLeftShift,
+	}
+}
+
+func bitLeftShift(opTerm *term, leftValue, rightValue any) (v any, err error) {
+	if IsInteger(leftValue) && IsInteger(rightValue) {
+		leftInt := leftValue.(int64)
+		rightInt := rightValue.(int64)
+		v = leftInt << rightInt
+	} else {
+		err = opTerm.errIncompatibleTypes(leftValue, rightValue)
+	}
+	return
+}
+
+func evalLeftShift(ctx ExprContext, opTerm *term) (v any, err error) {
+	var leftValue, rightValue any
+
+	if leftValue, rightValue, err = opTerm.evalInfix(ctx); err != nil {
+		return
+	}
+
+	v, err = bitLeftShift(opTerm, leftValue, rightValue)
+	return
+}
+
+// init
+func init() {
+	registerTermConstructor(SymDoubleGreater, newRightShiftTerm)
+	registerTermConstructor(SymDoubleLess, newLeftShiftTerm)
+}

operator-sign.go

@@ -28,29 +28,29 @@ func newMinusSignTerm(tk *Token) (inst *term) {
 	}
 }
 
-func evalSign(ctx ExprContext, self *term) (v any, err error) {
+func evalSign(ctx ExprContext, opTerm *term) (v any, err error) {
 	var rightValue any
 
-	if rightValue, err = self.evalPrefix(ctx); err != nil {
+	if rightValue, err = opTerm.evalPrefix(ctx); err != nil {
 		return
 	}
 
 	if IsFloat(rightValue) {
-		if self.tk.Sym == SymChangeSign {
+		if opTerm.tk.Sym == SymChangeSign {
 			f, _ := rightValue.(float64)
 			v = -f
 		} else {
 			v = rightValue
 		}
 	} else if IsInteger(rightValue) {
-		if self.tk.Sym == SymChangeSign {
+		if opTerm.tk.Sym == SymChangeSign {
 			i, _ := rightValue.(int64)
 			v = -i
 		} else {
 			v = rightValue
 		}
 	} else {
-		err = self.errIncompatibleType(rightValue)
+		err = opTerm.errIncompatibleType(rightValue)
 	}
 	return
 }

operator-sum.go

@@ -21,13 +21,7 @@ func newPlusTerm(tk *Token) (inst *term) {
 	}
 }
 
-func evalPlus(ctx ExprContext, self *term) (v any, err error) {
-	var leftValue, rightValue any
-
-	if leftValue, rightValue, err = self.evalInfix(ctx); err != nil {
-		return
-	}
-
+func sumValues(plusTerm *term, leftValue, rightValue any) (v any, err error) {
 	if (IsString(leftValue) && isNumberString(rightValue)) || (IsString(rightValue) && isNumberString(leftValue)) {
 		v = fmt.Sprintf("%v%v", leftValue, rightValue)
 	} else if IsNumber(leftValue) && IsNumber(rightValue) {
@@ -44,12 +38,8 @@ func evalPlus(ctx ExprContext, self *term) (v any, err error) {
 		rightList, _ = rightValue.(*ListType)
 
 		sumList := make(ListType, 0, len(*leftList)+len(*rightList))
-		for _, item := range *leftList {
-			sumList = append(sumList, item)
-		}
-		for _, item := range *rightList {
-			sumList = append(sumList, item)
-		}
+		sumList = append(sumList, *leftList...)
+		sumList = append(sumList, *rightList...)
 		v = &sumList
 	} else if (isFraction(leftValue) && IsNumber(rightValue)) || (isFraction(rightValue) && IsNumber(leftValue)) {
 		if IsFloat(leftValue) || IsFloat(rightValue) {
@@ -63,10 +53,22 @@ func evalPlus(ctx ExprContext, self *term) (v any, err error) {
 		c := leftDict.clone()
 		c.merge(rightDict)
 		v = c
+	} else if isFraction(leftValue) && isFraction(rightValue) {
+		v, err = sumAnyFract(leftValue, rightValue)
 	} else {
-		err = self.errIncompatibleTypes(leftValue, rightValue)
+		err = plusTerm.errIncompatibleTypes(leftValue, rightValue)
 	}
-	return
+	return v, err
+}
+
+func evalPlus(ctx ExprContext, plusTerm *term) (v any, err error) {
+	var leftValue, rightValue any
+
+	if leftValue, rightValue, err = plusTerm.evalInfix(ctx); err != nil {
+		return
+	}
+
+	return sumValues(plusTerm, leftValue, rightValue)
 }
 
 //-------- minus term
@@ -81,13 +83,7 @@ func newMinusTerm(tk *Token) (inst *term) {
 	}
 }
 
-func evalMinus(ctx ExprContext, self *term) (v any, err error) {
-	var leftValue, rightValue any
-
-	if leftValue, rightValue, err = self.evalInfix(ctx); err != nil {
-		return
-	}
-
+func diffValues(minusTerm *term, leftValue, rightValue any) (v any, err error) {
 	if isNumOrFract(leftValue) && isNumOrFract(rightValue) {
 		if IsFloat(leftValue) || IsFloat(rightValue) {
 			v = numAsFloat(leftValue) - numAsFloat(rightValue)
@@ -109,11 +105,21 @@ func evalMinus(ctx ExprContext, self *term) (v any, err error) {
 		}
 		v = &diffList
 	} else {
-		err = self.errIncompatibleTypes(leftValue, rightValue)
+		err = minusTerm.errIncompatibleTypes(leftValue, rightValue)
 	}
 	return
 }
 
+func evalMinus(ctx ExprContext, minusTerm *term) (v any, err error) {
+	var leftValue, rightValue any
+
+	if leftValue, rightValue, err = minusTerm.evalInfix(ctx); err != nil {
+		return
+	}
+
+	return diffValues(minusTerm, leftValue, rightValue)
+}
+
 // init
 func init() {
 	registerTermConstructor(SymPlus, newPlusTerm)

operator-unset.go

@@ -0,0 +1,69 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// operator-unset.go
+package expr
+
+import "strings"
+
+//-------- unset term
+
+func newUnsetTerm(tk *Token) (inst *term) {
+	return &term{
+		tk:       *tk,
+		children: make([]*term, 0, 1),
+		position: posPrefix,
+		priority: priSign,
+		evalFunc: evalUnset,
+	}
+}
+
+func deleteContextItem(ctx ExprContext, opTerm *term, item any) (deleted bool, err error) {
+	if name, ok := item.(string); ok {
+		var size int
+		if strings.HasSuffix(name, "()") {
+			size = ctx.FuncCount()
+			ctx.DeleteFunc(strings.TrimRight(name, "()"))
+			deleted = ctx.FuncCount() < size
+		} else {
+			size = ctx.VarCount()
+			ctx.DeleteVar(name)
+			deleted = ctx.VarCount() < size
+		}
+	} else {
+		err = opTerm.errIncompatibleType(item)
+	}
+	return
+}
+
+func evalUnset(ctx ExprContext, opTerm *term) (v any, err error) {
+	var childValue any
+	var deleted bool
+
+	if childValue, err = opTerm.evalPrefix(ctx); err != nil {
+		return
+	}
+
+	count := 0
+	if IsList(childValue) {
+		list, _ := childValue.(*ListType)
+		for _, item := range *list {
+			if deleted, err = deleteContextItem(ctx, opTerm, item); err != nil {
+				break
+			} else if deleted {
+				count++
+			}
+		}
+	} else if deleted, err = deleteContextItem(ctx, opTerm, childValue); err == nil && deleted {
+		count++
+	}
+	if err == nil {
+		v = int64(count)
+	}
+	return
+}
+
+// init
+func init() {
+	registerTermConstructor(SymKwUnset, newUnsetTerm)
+}

parser.go

@@ -6,51 +6,83 @@ package expr
 
 import (
 	"errors"
-	"fmt"
+
+	"golang.org/x/exp/constraints"
 )
 
 //-------- parser
 
-type parser struct {
-	ctx ExprContext
+type parserContext uint16
+
+const (
+	parserNoFlags                = 0
+	allowMultiExpr parserContext = 1 << iota
+	allowVarRef
+	selectorContext
+	listContext                                // squareContext for list
+	indexContext                               // squareContext for index
+	allowIndex                                 // allow index in squareContext
+	squareContext = listContext | indexContext // Square parenthesis for list or index
+)
+
+func hasFlag[T constraints.Unsigned](set T, singleFlag T) bool {
+	return (set & singleFlag) != 0
 }
 
-func NewParser(ctx ExprContext) (p *parser) {
-	p = &parser{
-		ctx: ctx,
+func addFlags[T constraints.Unsigned](set T, flags T) T {
+	return set | flags
+}
+
+func addFlagsCond[T constraints.Unsigned](set T, flags T, cond bool) (newSet T) {
+	if cond {
+		newSet = set | flags
+	} else {
+		newSet = set
 	}
+	return
+}
+
+func remFlags[T constraints.Unsigned](set T, flags T) T {
+	return set & (^flags)
+}
+
+type parser struct {
+}
+
+func NewParser() (p *parser) {
+	p = &parser{}
 	return p
 }
 
-func (self *parser) parseFuncCall(scanner *scanner, allowVarRef bool, tk *Token) (tree *term, err error) {
-	// name, _ := tk.Value.(string)
-	// funcObj := self.ctx.GetFuncInfo(name)
-	// if funcObj == nil {
-	// 	err = fmt.Errorf("unknown function %s()", name)
-	// 	return
-	// }
-	// maxArgs := funcObj.MaxArgs()
-	// if maxArgs < 0 {
-	// 	maxArgs = funcObj.MinArgs() + 10
-	// }
-	// args := make([]*term, 0, maxArgs)
+func (parser *parser) Next(scanner *scanner) (tk *Token) {
+	for tk = scanner.Next(); tk.IsSymbol(SymComment); tk = scanner.Next() {
+	}
+	return
+}
+
+func (parser *parser) parseFuncCall(scanner *scanner, ctx parserContext, tk *Token) (tree *term, err error) {
 	args := make([]*term, 0, 10)
+	itemExpected := false
 	lastSym := SymUnknown
 	for lastSym != SymClosedRound && lastSym != SymEos {
 		var subTree *ast
-		if subTree, err = self.parseItem(scanner, allowVarRef, SymComma, SymClosedRound); err == nil {
-			if subTree.root != nil {
-				args = append(args, subTree.root)
-			}
-		} else {
+		if subTree, err = parser.parseItem(scanner, ctx, SymComma, SymClosedRound); err != nil {
 			break
 		}
+		prev := scanner.Previous()
+		if subTree.root != nil {
+			args = append(args, subTree.root)
+		} else if itemExpected {
+			err = prev.ErrorExpectedGot("function-param-value")
+			break
+		}
+
+		itemExpected = prev.Sym == SymComma
 		lastSym = scanner.Previous().Sym
 	}
 	if err == nil {
-		// TODO Check arguments
 		if lastSym != SymClosedRound {
-			err = errors.New("unterminate arguments list")
+			err = errors.New("unterminated arguments list")
 		} else {
 			tree = newFuncCallTerm(tk, args)
 		}
@@ -58,73 +90,40 @@ func (self *parser) parseFuncCall(scanner *scanner, allowVarRef bool, tk *Token)
 	return
 }
 
-// func (self *parser) parseFuncDef(scanner *scanner) (tree *term, err error) {
-// 	// Example: "add = func(x,y) {x+y}
-// 	var body *ast
-// 	args := make([]*term, 0)
-// 	lastSym := SymUnknown
-// 	itemExpected := false
-// 	tk := scanner.Previous()
-// 	for lastSym != SymClosedRound && lastSym != SymEos {
-// 		var subTree *ast
-// 		if subTree, err = self.parseItem(scanner, true, SymComma, SymClosedRound); err == nil {
-// 			if subTree.root != nil {
-// 				if subTree.root.symbol() == SymIdentifier {
-// 					args = append(args, subTree.root)
-// 				} else {
-// 					err = tk.ErrorExpectedGotString("param-name", subTree.root.String())
-// 				}
-// 			} else if itemExpected {
-// 				prev := scanner.Previous()
-// 				err = prev.ErrorExpectedGot("function-param")
-// 				break
-// 			}
-// 		} else {
-// 			break
-// 		}
-// 		lastSym = scanner.Previous().Sym
-// 		itemExpected = lastSym == SymComma
-// 	}
-
-// 	if err == nil && lastSym != SymClosedRound {
-// 		err = tk.ErrorExpectedGot(")")
-// 	}
-// 	if err == nil {
-// 		tk = scanner.Next()
-// 		if tk.Sym == SymOpenBrace {
-// 			body, err = self.parseGeneral(scanner, true, true, SymClosedBrace)
-// 		} else {
-// 			err = tk.ErrorExpectedGot("{")
-// 		}
-// 	}
-// 	if err == nil {
-// 		// TODO Check arguments
-// 		if scanner.Previous().Sym != SymClosedBrace {
-// 			err = scanner.Previous().ErrorExpectedGot("}")
-// 		} else {
-// 			tk = scanner.makeValueToken(SymExpression, "", body)
-// 			tree = newFuncDefTerm(tk, args)
-// 		}
-// 	}
-// 	return
-// }
-
-func (self *parser) parseFuncDef(scanner *scanner) (tree *term, err error) {
+func (parser *parser) parseFuncDef(scanner *scanner) (tree *term, err error) {
 	// Example: "add = func(x,y) {x+y}
 	var body *ast
 	args := make([]*term, 0)
 	lastSym := SymUnknown
+	defaultParamsStarted := false
 	itemExpected := false
 	tk := scanner.Previous()
 	for lastSym != SymClosedRound && lastSym != SymEos {
-		tk = scanner.Next()
+		tk = parser.Next(scanner)
 		if tk.IsSymbol(SymIdentifier) {
 			param := newTerm(tk)
+			if len(args) > 0 {
+				if pos := paramAlreadyDefined(args, param); pos > 0 {
+					err = tk.Errorf("parameter %q at position %d already defined at position %d", param.source(), len(args)+1, pos)
+					break
+				}
+			}
 			args = append(args, param)
-			tk = scanner.Next()
+			tk = parser.Next(scanner)
+			if tk.Sym == SymEqual {
+				var paramExpr *ast
+				defaultParamsStarted = true
+				if paramExpr, err = parser.parseItem(scanner, parserNoFlags, SymComma, SymClosedRound); err != nil {
+					break
+				}
+				param.forceChild(paramExpr.root)
+			} else if defaultParamsStarted {
+				err = tk.Errorf("can't mix default and non-default parameters")
+				break
+			}
 		} else if itemExpected {
 			prev := scanner.Previous()
-			err = prev.ErrorExpectedGot("function-param")
+			err = prev.ErrorExpectedGot("function-param-spec")
 			break
 		}
 		lastSym = scanner.Previous().Sym
@@ -135,15 +134,14 @@ func (self *parser) parseFuncDef(scanner *scanner) (tree *term, err error) {
 		err = tk.ErrorExpectedGot(")")
 	}
 	if err == nil {
-		tk = scanner.Next()
+		tk = parser.Next(scanner)
 		if tk.IsSymbol(SymOpenBrace) {
-			body, err = self.parseGeneral(scanner, true, true, SymClosedBrace)
+			body, err = parser.parseGeneral(scanner, allowMultiExpr|allowVarRef, SymClosedBrace)
 		} else {
 			err = tk.ErrorExpectedGot("{")
 		}
 	}
 	if err == nil {
-		// TODO Check arguments
 		if scanner.Previous().Sym != SymClosedBrace {
 			err = scanner.Previous().ErrorExpectedGot("}")
 		} else {
@@ -154,27 +152,43 @@ func (self *parser) parseFuncDef(scanner *scanner) (tree *term, err error) {
 	return
 }
 
-func (self *parser) parseList(scanner *scanner, parsingIndeces bool, allowVarRef bool) (subtree *term, err error) {
+func paramAlreadyDefined(args []*term, param *term) (position int) {
+	position = 0
+	for i, arg := range args {
+		if arg.source() == param.source() {
+			position = i + 1
+		}
+	}
+	return
+}
+
+func (parser *parser) parseList(scanner *scanner, ctx parserContext) (listTerm *term, err error) {
 	r, c := scanner.lastPos()
 	args := make([]*term, 0)
 	lastSym := SymUnknown
 	itemExpected := false
+	itemCtx := remFlags(ctx, allowIndex)
 	for lastSym != SymClosedSquare && lastSym != SymEos {
-		var subTree *ast
 		zeroRequired := scanner.current.Sym == SymColon
-		if subTree, err = self.parseItem(scanner, allowVarRef, SymComma, SymClosedSquare); err == nil {
-			root := subTree.root
+		var itemTree *ast
+		if itemTree, err = parser.parseItem(scanner, itemCtx, SymComma, SymClosedSquare); err == nil {
+			root := itemTree.root
 			if root != nil {
-				if !parsingIndeces && root.symbol() == SymColon {
-					err = root.Errorf("unexpected range expression")
+				if hasFlag(ctx, allowIndex) && root.symbol() == SymColon {
+					changeColonToRange(root)
+				}
+				if !hasFlag(ctx, allowIndex) && root.symbol() == SymRange {
+					// err = root.Errorf("unexpected range expression")
+					err = errRangeUnexpectedExpression(root)
 					break
 				}
 				args = append(args, root)
-				if parsingIndeces && root.symbol() == SymColon && zeroRequired { //len(root.children) == 0 {
+				if hasFlag(ctx, allowIndex) && root.symbol() == SymRange && zeroRequired { //len(root.children) == 0 {
 					if len(root.children) == 1 {
 						root.children = append(root.children, root.children[0])
 					} else if len(root.children) > 1 {
-						err = root.Errorf("invalid range specification")
+						// err = root.Errorf("invalid range specification")
+						err = errRangeInvalidSpecification(root)
 						break
 					}
 					zeroTk := NewValueToken(root.tk.row, root.tk.col, SymInteger, "0", int64(0))
@@ -191,26 +205,28 @@ func (self *parser) parseList(scanner *scanner, parsingIndeces bool, allowVarRef
 			break
 		}
 		lastSym = scanner.Previous().Sym
-		itemExpected = lastSym == SymComma
+		if itemExpected = lastSym == SymComma; itemExpected {
+			remFlags(ctx, allowIndex)
+		}
 	}
 	if err == nil {
 		if lastSym != SymClosedSquare {
 			err = scanner.Previous().ErrorExpectedGot("]")
 		} else {
-			subtree = newListTerm(r, c, args)
+			listTerm = newListTerm(r, c, args)
 		}
 	}
 	return
 }
 
-func (self *parser) parseIterDef(scanner *scanner, allowVarRef bool) (subtree *term, err error) {
+func (parser *parser) parseIterDef(scanner *scanner, ctx parserContext) (subtree *term, err error) {
 	tk := scanner.Previous()
 	args := make([]*term, 0)
 	lastSym := SymUnknown
 	itemExpected := false
 	for lastSym != SymClosedRound && lastSym != SymEos {
 		var subTree *ast
-		if subTree, err = self.parseItem(scanner, allowVarRef, SymComma, SymClosedRound); err == nil {
+		if subTree, err = parser.parseItem(scanner, ctx, SymComma, SymClosedRound); err == nil {
 			if subTree.root != nil {
 				args = append(args, subTree.root)
 			} else if itemExpected {
@@ -225,7 +241,6 @@ func (self *parser) parseIterDef(scanner *scanner, allowVarRef bool) (subtree *t
 		itemExpected = lastSym == SymComma
 	}
 	if err == nil {
-		// TODO Check arguments
 		if lastSym != SymClosedRound {
 			err = scanner.Previous().ErrorExpectedGot(")")
 		} else {
@@ -235,8 +250,8 @@ func (self *parser) parseIterDef(scanner *scanner, allowVarRef bool) (subtree *t
 	return
 }
 
-func (self *parser) parseDictKey(scanner *scanner, allowVarRef bool) (key any, err error) {
-	tk := scanner.Next()
+func (parser *parser) parseDictKey(scanner *scanner) (key any, err error) {
+	tk := parser.Next(scanner)
 	if tk.Sym == SymError {
 		err = tk.Error()
 		return
@@ -245,27 +260,26 @@ func (self *parser) parseDictKey(scanner *scanner, allowVarRef bool) (key any, e
 		return
 	}
 	if tk.Sym == SymInteger || tk.Sym == SymString {
-		tkSep := scanner.Next()
+		tkSep := parser.Next(scanner)
 		if tkSep.Sym != SymColon {
 			err = tkSep.ErrorExpectedGot(":")
 		} else {
 			key = tk.Value
 		}
 	} else {
-		// err = tk.Errorf("expected dictionary key or closed brace, got %q", tk)
 		err = tk.ErrorExpectedGot("dictionary-key or }")
 	}
 	return
 }
 
-func (self *parser) parseDictionary(scanner *scanner, allowVarRef bool) (subtree *term, err error) {
+func (parser *parser) parseDictionary(scanner *scanner, ctx parserContext) (subtree *term, err error) {
 	args := make(map[any]*term, 0)
 	lastSym := SymUnknown
 	itemExpected := false
 	for lastSym != SymClosedBrace && lastSym != SymEos {
 		var subTree *ast
 		var key any
-		if key, err = self.parseDictKey(scanner, allowVarRef); err != nil {
+		if key, err = parser.parseDictKey(scanner); err != nil {
 			break
 		} else if key == nil {
 			tk := scanner.Previous()
@@ -275,10 +289,10 @@ func (self *parser) parseDictionary(scanner *scanner, allowVarRef bool) (subtree
 			}
 			break
 		}
-		if subTree, err = self.parseItem(scanner, allowVarRef, SymComma, SymClosedBrace); err == nil {
+		if subTree, err = parser.parseItem(scanner, ctx, SymComma, SymClosedBrace); err == nil {
 			if subTree.root != nil {
 				args[key] = subTree.root
-			} else if key != nil {
+			} else /*if key != nil*/ {
 				prev := scanner.Previous()
 				err = prev.ErrorExpectedGot("dictionary-value")
 				break
@@ -290,21 +304,20 @@ func (self *parser) parseDictionary(scanner *scanner, allowVarRef bool) (subtree
 		itemExpected = lastSym == SymComma
 	}
 	if err == nil {
-		// TODO Check arguments
 		if lastSym != SymClosedBrace {
 			err = scanner.Previous().ErrorExpectedGot("}")
 		} else {
 			subtree = newDictTerm(args)
-			// subtree = newMapTerm(args)
 		}
 	}
 	return
 }
 
-func (self *parser) parseSelectorCase(scanner *scanner, allowVarRef bool, defaultCase bool) (caseTerm *term, err error) {
+func (parser *parser) parseSelectorCase(scanner *scanner, ctx parserContext, defaultCase bool) (caseTerm *term, err error) {
 	var filterList *term
 	var caseExpr *ast
-	tk := scanner.Next()
+	ctx = remFlags(ctx, allowIndex)
+	tk := parser.Next(scanner)
 	startRow := tk.row
 	startCol := tk.col
 	if tk.Sym == SymOpenSquare {
@@ -312,10 +325,10 @@ func (self *parser) parseSelectorCase(scanner *scanner, allowVarRef bool, defaul
 			err = tk.Errorf("case list in default clause")
 			return
 		}
-		if filterList, err = self.parseList(scanner, false, allowVarRef); err != nil {
+		if filterList, err = parser.parseList(scanner, remFlags(ctx, allowIndex)); err != nil {
 			return
 		}
-		tk = scanner.Next()
+		tk = parser.Next(scanner)
 		startRow = tk.row
 		startCol = tk.col
 	} else if !defaultCase {
@@ -323,7 +336,7 @@ func (self *parser) parseSelectorCase(scanner *scanner, allowVarRef bool, defaul
 	}
 
 	if tk.Sym == SymOpenBrace {
-		if caseExpr, err = self.parseGeneral(scanner, true, allowVarRef, SymClosedBrace); err != nil {
+		if caseExpr, err = parser.parseGeneral(scanner, ctx|allowMultiExpr, SymClosedBrace); err != nil {
 			return
 		}
 	} else {
@@ -349,25 +362,28 @@ func addSelectorCase(selectorTerm, caseTerm *term) {
 	caseTerm.parent = selectorTerm
 }
 
-func (self *parser) parseSelector(scanner *scanner, tree *ast, allowVarRef bool) (selectorTerm *term, err error) {
+func (parser *parser) parseSelector(scanner *scanner, tree *ast, ctx parserContext) (selectorTerm *term, err error) {
 	var caseTerm *term
+
+	ctx = remFlags(ctx, allowIndex)
 	tk := scanner.makeToken(SymSelector, '?')
-	if selectorTerm, err = tree.addToken2(tk); err != nil {
+	if selectorTerm, err = tree.addToken(tk); err != nil {
 		return
 	}
 
-	if caseTerm, err = self.parseSelectorCase(scanner, allowVarRef, false); err == nil {
+	if caseTerm, err = parser.parseSelectorCase(scanner, ctx|allowVarRef, false); err == nil {
 		addSelectorCase(selectorTerm, caseTerm)
 	}
 	return
 }
 
-func (self *parser) parseItem(scanner *scanner, allowVarRef bool, termSymbols ...Symbol) (tree *ast, err error) {
-	return self.parseGeneral(scanner, false, allowVarRef, termSymbols...)
+func (parser *parser) parseItem(scanner *scanner, ctx parserContext, termSymbols ...Symbol) (tree *ast, err error) {
+	return parser.parseGeneral(scanner, ctx|allowVarRef, termSymbols...)
 }
 
-func (self *parser) Parse(scanner *scanner, termSymbols ...Symbol) (tree *ast, err error) {
-	return self.parseGeneral(scanner, true, false, termSymbols...)
+func (parser *parser) Parse(scanner *scanner, termSymbols ...Symbol) (tree *ast, err error) {
+	termSymbols = append(termSymbols, SymEos)
+	return parser.parseGeneral(scanner, allowMultiExpr, termSymbols...)
 }
 
 func couldBeACollection(t *term) bool {
@@ -378,22 +394,57 @@ func couldBeACollection(t *term) bool {
 	return sym == SymList || sym == SymString || sym == SymDict || sym == SymExpression || sym == SymVariable
 }
 
-func (self *parser) parseGeneral(scanner *scanner, allowForest bool, allowVarRef bool, termSymbols ...Symbol) (tree *ast, err error) {
+func listSubTree(tree *ast, listTerm *term, allowIndeces bool) (root *term, err error) {
+	var tk *Token
+	if allowIndeces {
+		tk = NewToken(listTerm.tk.row, listTerm.tk.col, SymIndex, listTerm.source())
+		root = newTerm(tk)
+		if err = tree.addTerm(root); err == nil {
+			err = tree.addTerm(listTerm)
+		}
+	} else {
+		root = listTerm
+		err = tree.addTerm(listTerm)
+	}
+	return
+}
+
+func changePrefix(tk *Token) {
+	switch tk.Sym {
+	case SymMinus:
+		tk.SetSymbol(SymChangeSign)
+	case SymPlus:
+		tk.SetSymbol(SymUnchangeSign)
+	case SymStar:
+		tk.SetSymbol(SymDereference)
+	case SymExclamation:
+		tk.SetSymbol(SymNot)
+	case SymDoublePlus:
+		tk.SetSymbol(SymPreInc)
+	case SymDoubleMinus:
+		tk.SetSymbol(SymPreDec)
+	}
+}
+
+func (parser *parser) parseGeneral(scanner *scanner, ctx parserContext, termSymbols ...Symbol) (tree *ast, err error) {
 	var selectorTerm *term = nil
 	var currentTerm *term = nil
 	var tk *Token
+
 	tree = NewAst()
 	firstToken := true
-	lastSym := SymUnknown
-	for tk = scanner.Next(); err == nil && tk != nil && !tk.IsTerm(termSymbols); tk = scanner.Next() {
-		if tk.Sym == SymComment {
-			continue
-		}
+	// lastSym := SymUnknown
+	for tk = parser.Next(scanner); err == nil && tk != nil && !tk.IsTerm(termSymbols); /*&& !areSymbolsOutOfCtx(tk, selectorTerm, SymColon, SymDoubleColon)*/ tk = parser.Next(scanner) {
+		// if tk.Sym == SymComment {
+		// 	continue
+		// }
 
 		if tk.Sym == SymSemiColon {
-			if allowForest {
+			if hasFlag(ctx, allowMultiExpr) {
 				tree.ToForest()
 				firstToken = true
+				currentTerm = nil
+				selectorTerm = nil
 				continue
 			} else {
 				err = tk.Errorf(`unexpected token %q, expected ",", "]", or ")"`, tk.source)
@@ -403,83 +454,82 @@ func (self *parser) parseGeneral(scanner *scanner, allowForest bool, allowVarRef
 
 		//fmt.Println("Token:", tk)
 		if firstToken {
-			if tk.Sym == SymMinus {
-				tk.Sym = SymChangeSign
-			} else if tk.Sym == SymPlus {
-				tk.Sym = SymUnchangeSign
-			}
+			changePrefix(tk)
+			// if tk.Sym == SymMinus {
+			// 	tk.Sym = SymChangeSign
+			// } else if tk.Sym == SymPlus {
+			// 	tk.Sym = SymUnchangeSign
+			// } else if tk.IsSymbol(SymStar) {
+			// 	tk.SetSymbol(SymDereference)
+			// } else if tk.IsSymbol(SymExclamation) {
+			// 	tk.SetSymbol(SymNot)
+			// }
 			firstToken = false
 		}
 
 		switch tk.Sym {
 		case SymOpenRound:
 			var subTree *ast
-			if subTree, err = self.parseGeneral(scanner, false, allowVarRef, SymClosedRound); err == nil {
-				subTree.root.priority = priValue
-				err = tree.addTerm(newExprTerm(subTree.root))
-				currentTerm = subTree.root
+			if subTree, err = parser.parseGeneral(scanner, ctx, SymClosedRound); err == nil {
+				exprTerm := newExprTerm(subTree.root)
+				err = tree.addTerm(exprTerm)
+				currentTerm = exprTerm
+				// subTree.root.priority = priValue
+				// err = tree.addTerm(newExprTerm(subTree.root))
+				// currentTerm = subTree.root
 			}
 		case SymFuncCall:
 			var funcCallTerm *term
-			if funcCallTerm, err = self.parseFuncCall(scanner, allowVarRef, tk); err == nil {
+			if funcCallTerm, err = parser.parseFuncCall(scanner, ctx, tk); err == nil {
 				err = tree.addTerm(funcCallTerm)
 				currentTerm = funcCallTerm
 			}
 		case SymOpenSquare:
 			var listTerm *term
-			parsingIndeces := couldBeACollection(currentTerm)
-			if listTerm, err = self.parseList(scanner, parsingIndeces, allowVarRef); err == nil {
-				if parsingIndeces {
-					indexTk := NewToken(listTerm.tk.row, listTerm.tk.col, SymIndex, listTerm.source())
-					indexTerm := newTerm(indexTk)
-					if err = tree.addTerm(indexTerm); err == nil {
-						err = tree.addTerm(listTerm)
-					}
-				} else {
-					err = tree.addTerm(listTerm)
-				}
-				currentTerm = listTerm
+			newCtx := addFlagsCond(addFlags(ctx, squareContext), allowIndex, couldBeACollection(currentTerm))
+			if listTerm, err = parser.parseList(scanner, newCtx); err == nil {
+				currentTerm, err = listSubTree(tree, listTerm, hasFlag(newCtx, allowIndex))
 			}
 		case SymOpenBrace:
 			if currentTerm != nil && currentTerm.symbol() == SymColon {
 				err = currentTerm.Errorf(`selector-case outside of a selector context`)
 			} else {
 				var mapTerm *term
-				if mapTerm, err = self.parseDictionary(scanner, allowVarRef); err == nil {
+				if mapTerm, err = parser.parseDictionary(scanner, ctx); err == nil {
 					err = tree.addTerm(mapTerm)
 					currentTerm = mapTerm
 				}
 			}
-		case SymEqual:
-			if err = checkPrevSymbol(lastSym, SymIdentifier, tk); err == nil {
-				currentTerm, err = tree.addToken2(tk)
-			}
+		case SymEqual, SymPlusEqual, SymMinusEqual, SymStarEqual, SymSlashEqual, SymPercEqual, SymAmpersandEqual, SymVertBarEqual, SymDoubleLessEqual, SymDoubleGreaterEqual, SymCaretEqual:
+			currentTerm, err = tree.addToken(tk)
+			firstToken = true
 		case SymFuncDef:
 			var funcDefTerm *term
-			if funcDefTerm, err = self.parseFuncDef(scanner); err == nil {
+			if funcDefTerm, err = parser.parseFuncDef(scanner); err == nil {
 				err = tree.addTerm(funcDefTerm)
 				currentTerm = funcDefTerm
 			}
 		case SymDollarRound:
 			var iterDefTerm *term
-			if iterDefTerm, err = self.parseIterDef(scanner, allowVarRef); err == nil {
+			if iterDefTerm, err = parser.parseIterDef(scanner, ctx); err == nil {
 				err = tree.addTerm(iterDefTerm)
 				currentTerm = iterDefTerm
 			}
 		case SymIdentifier:
-			if tk.source[0] == '@' && !allowVarRef {
+			if tk.source[0] == '@' && !hasFlag(ctx, allowVarRef) {
 				err = tk.Errorf("variable references are not allowed in top level expressions: %q", tk.source)
 			} else {
-				currentTerm, err = tree.addToken2(tk)
+				currentTerm, err = tree.addToken(tk)
 			}
 		case SymQuestion:
-			if selectorTerm, err = self.parseSelector(scanner, tree, allowVarRef); err == nil {
+			if selectorTerm, err = parser.parseSelector(scanner, tree, ctx); err == nil {
 				currentTerm = selectorTerm
+				addFlags(ctx, selectorContext)
 			}
 		case SymColon, SymDoubleColon:
 			var caseTerm *term
 			if selectorTerm != nil {
-				if caseTerm, err = self.parseSelectorCase(scanner, allowVarRef, tk.Sym == SymDoubleColon); err == nil {
+				if caseTerm, err = parser.parseSelectorCase(scanner, ctx, tk.Sym == SymDoubleColon); err == nil {
 					addSelectorCase(selectorTerm, caseTerm)
 					currentTerm = caseTerm
 					if tk.Sym == SymDoubleColon {
@@ -487,27 +537,35 @@ func (self *parser) parseGeneral(scanner *scanner, allowForest bool, allowVarRef
 					}
 				}
 			} else {
-				currentTerm, err = tree.addToken2(tk)
+				currentTerm, err = tree.addToken(tk)
+				if tk.IsOneOfA(SymColon, SymRange) {
+					// Colon outside a selector term acts like a separator
+					firstToken = true
+				}
 			}
 		default:
-			currentTerm, err = tree.addToken2(tk)
+			currentTerm, err = tree.addToken(tk)
 		}
 
 		if currentTerm != nil && currentTerm.tk.Sym != SymSelector && currentTerm.parent != nil && currentTerm.parent.tk.Sym != SymSelector {
 			selectorTerm = nil
-
+			remFlags(ctx, selectorContext)
 		}
-		lastSym = tk.Sym
+		// lastSym = tk.Sym
 	}
-	if err == nil {
-		err = tk.Error()
-	}
-	return
-}
 
-func checkPrevSymbol(lastSym, wantedSym Symbol, tk *Token) (err error) {
-	if lastSym != wantedSym {
-		err = fmt.Errorf(`assign operator (%q) must be preceded by a variable`, tk.source)
+	if err == nil {
+		if !tk.IsOneOf(termSymbols) {
+			var symDesc string
+			if tk.IsSymbol(SymError) {
+				symDesc = tk.ErrorText()
+			} else {
+				symDesc = SymToString(tk.Sym)
+			}
+			err = tk.ErrorExpectedGotStringWithPrefix("expected one of", SymListToString(termSymbols, true), symDesc)
+		} else {
+			err = tk.Error()
+		}
 	}
 	return
 }

plugins.go

@@ -0,0 +1,133 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// plugin.go
+package expr
+
+import (
+	"fmt"
+	"io"
+	"os"
+	"plugin"
+	"strings"
+)
+
+var pluginRegister map[string]*plugin.Plugin
+
+func registerPlugin(name string, p *plugin.Plugin) (err error) {
+	if pluginExists(name) {
+		err = fmt.Errorf("plugin %q already loaded", name)
+	} else {
+		pluginRegister[name] = p
+	}
+	return
+}
+
+func pluginExists(name string) (exists bool) {
+	_, exists = pluginRegister[name]
+	return
+}
+
+func makePluginName(name string) (decorated string) {
+	var template string
+	if execName, err := os.Executable(); err != nil || !strings.Contains(execName, "debug") {
+		template = "expr-%s-plugin%s"
+	} else {
+		template = "expr-%s-plugin%s.debug"
+	}
+	decorated = fmt.Sprintf(template, name, SHAREDLIBRARY_EXTENSION)
+	return
+}
+
+func importPlugin( /*ctx ExprContext,*/ dirList []string, name string) (err error) {
+	var filePath string
+	var p *plugin.Plugin
+	var sym plugin.Symbol
+	var moduleName string
+	var importFunc func(ExprContext)
+	var ok bool
+
+	decoratedName := makePluginName(name)
+
+	if filePath, err = makeFilepath(decoratedName, dirList); err != nil {
+		return
+	}
+
+	if p, err = plugin.Open(filePath); err != nil {
+		return
+	}
+
+	if sym, err = p.Lookup("MODULE_NAME"); err != nil {
+		return
+	}
+
+	if moduleName = *sym.(*string); moduleName == "" {
+		err = fmt.Errorf("plugin %q does not provide a valid module name", decoratedName)
+		return
+	}
+
+	if sym, err = p.Lookup("DEPENDENCIES"); err != nil {
+		return
+	}
+	if deps := *sym.(*[]string); len(deps) > 0 {
+		// var count int
+		if err = loadModules(dirList, deps); err != nil {
+			return
+		}
+	}
+
+	if sym, err = p.Lookup("ImportFuncs"); err != nil {
+		return
+	}
+
+	if importFunc, ok = sym.(func(ExprContext)); !ok {
+		err = fmt.Errorf("plugin %q does not provide a valid import function", decoratedName)
+		return
+	}
+
+	registerPlugin(moduleName, p)
+	importFunc(globalCtx)
+
+	return
+}
+
+func importPluginFromSearchPath(name any) (count int, err error) {
+	var moduleSpec any
+	var it Iterator
+	dirList := buildSearchDirList("plugin", ENV_EXPR_PLUGIN_PATH)
+	count = 0
+	if it, err = NewIterator(name); err != nil {
+		return
+	}
+	for moduleSpec, err = it.Next(); err == nil; moduleSpec, err = it.Next() {
+		if module, ok := moduleSpec.(string); ok {
+			if err = importPlugin(dirList, module); err != nil {
+				break
+			}
+			count++
+		} else {
+			err = fmt.Errorf("expected string as item nr %d, got %s", it.Index()+1, TypeName(moduleSpec))
+			break
+		}
+	}
+	if err == io.EOF {
+		err = nil
+	}
+	return
+}
+
+func loadModules(dirList []string, moduleNames []string) (err error) {
+	for _, name := range moduleNames {
+		if err1 := importPlugin(dirList, name); err1 != nil {
+			if !ImportInContext(name) {
+				err = err1
+				break
+			}
+		}
+	}
+	return
+}
+
+func init() {
+	pluginRegister = make(map[string]*plugin.Plugin)
+}

scanner.go

@@ -16,6 +16,7 @@ import (
 type scanner struct {
 	current      *Token
 	prev         *Token
+	stage        *Token
 	stream       *bufio.Reader
 	row          int
 	column       int
@@ -39,9 +40,9 @@ func DefaultTranslations() map[Symbol]Symbol {
 		SymKwAnd:           SymAnd,
 		SymDoubleVertBar:   SymOr,
 		SymKwOr:            SymOr,
-		SymTilde:           SymNot,
-		SymKwNot:           SymNot,
-		SymLessGreater:     SymNotEqual,
+		// SymTilde:           SymNot,
+		SymKwNot:       SymNot,
+		SymLessGreater: SymNotEqual,
 	}
 }
 
@@ -49,250 +50,314 @@ func DefaultTranslations() map[Symbol]Symbol {
 // 	return self.current
 // }
 
-func (self *scanner) readChar() (ch byte, err error) {
-	if ch, err = self.stream.ReadByte(); err == nil {
+func (scanner *scanner) readChar() (ch byte, err error) {
+	if ch, err = scanner.stream.ReadByte(); err == nil {
 		if ch == '\n' {
-			self.row++
-			self.column = 0
+			scanner.row++
+			scanner.column = 0
 		} else {
-			self.column++
+			scanner.column++
 		}
 	}
 	return
 }
 
-func (self *scanner) unreadChar() (err error) {
-	if err = self.stream.UnreadByte(); err == nil {
-		if self.column--; self.column == 0 {
-			if self.row--; self.row == 0 {
+func (scanner *scanner) unreadChar() (err error) {
+	if err = scanner.stream.UnreadByte(); err == nil {
+		if scanner.column--; scanner.column == 0 {
+			if scanner.row--; scanner.row == 0 {
 				err = errors.New("unread beyond the stream boundary")
 			} else {
-				self.column = 1
+				scanner.column = 1
 			}
 		}
 	}
 	return
 }
 
-func (self *scanner) lastPos() (r, c int) {
-	if self.prev != nil {
-		r = self.prev.row
-		c = self.prev.col
+func (scanner *scanner) UnreadToken() (err error) {
+	if scanner.stage == nil {
+		scanner.stage = scanner.current
+		scanner.current = scanner.prev
+	} else {
+		err = fmt.Errorf("staging already present, currently one level only of staging is allowed")
 	}
 	return
 }
 
-func (self *scanner) Previous() *Token {
-	return self.prev
+func (scanner *scanner) lastPos() (r, c int) {
+	if scanner.prev != nil {
+		r = scanner.prev.row
+		c = scanner.prev.col
+	}
+	return
 }
 
-func (self *scanner) Next() (tk *Token) {
-	self.prev = self.current
-	tk = self.current
-	self.current = self.fetchNextToken()
+func (scanner *scanner) Previous() *Token {
+	return scanner.prev
+}
+
+func (scanner *scanner) Next() (tk *Token) {
+	scanner.prev = scanner.current
+	tk = scanner.current
+	if scanner.stage != nil {
+		scanner.current = scanner.stage
+		scanner.stage = nil
+	} else {
+		scanner.current = scanner.fetchNextToken()
+	}
 	return tk
 }
 
-func (self *scanner) fetchNextToken() (tk *Token) {
+func (scanner *scanner) fetchNextToken() (tk *Token) {
 	var ch byte
-	if err := self.skipBlanks(); err != nil {
-		return self.makeErrorToken(err)
+	if err := scanner.skipBlanks(); err != nil {
+		return scanner.makeErrorToken(err)
 	}
 
 	escape := false
 	for {
-		ch, _ = self.readChar()
+		ch, _ = scanner.readChar()
 		switch ch {
 		case '+':
-			if next, _ := self.peek(); next == '+' {
-				tk = self.moveOn(SymDoublePlus, ch, next)
+			if next, _ := scanner.peek(); next == '+' {
+				tk = scanner.moveOn(SymDoublePlus, ch, next)
 			} else if next == '=' {
-				tk = self.moveOn(SymPlusEqual, ch, next)
+				tk = scanner.moveOn(SymPlusEqual, ch, next)
+			} else if next == '>' {
+				tk = scanner.moveOn(SymPlusGreater, ch, next)
 			} else {
-				tk = self.makeToken(SymPlus, ch)
+				tk = scanner.makeToken(SymPlus, ch)
 			}
 		case '-':
-			if next, _ := self.peek(); next == '-' {
-				tk = self.moveOn(SymDoubleMinus, ch, next)
+			if next, _ := scanner.peek(); next == '-' {
+				tk = scanner.moveOn(SymDoubleMinus, ch, next)
 			} else if next == '=' {
-				tk = self.moveOn(SymMinusEqual, ch, next)
+				tk = scanner.moveOn(SymMinusEqual, ch, next)
 			} else {
-				tk = self.makeToken(SymMinus, ch)
+				tk = scanner.makeToken(SymMinus, ch)
 			}
 		case '*':
-			if next, _ := self.peek(); next == '*' {
-				tk = self.moveOn(SymDoubleStar, ch, next)
+			if next, _ := scanner.peek(); next == '*' {
+				tk = scanner.moveOn(SymDoubleStar, ch, next)
 				// } else if next == '/' {
 				// 	tk = self.moveOn(SymClosedComment, ch, next)
+			} else if next, _ = scanner.peek(); next == '=' {
+				tk = scanner.moveOn(SymStarEqual, ch, next)
 			} else {
-				tk = self.makeToken(SymStar, ch)
+				tk = scanner.makeToken(SymStar, ch)
 			}
 		case '/':
-			if next, _ := self.peek(); next == '*' {
-				self.readChar()
-				tk = self.fetchBlockComment()
+			if next, _ := scanner.peek(); next == '*' {
+				scanner.readChar()
+				tk = scanner.fetchBlockComment()
+			} else if next, _ = scanner.peek(); next == '=' {
+				tk = scanner.moveOn(SymSlashEqual, ch, next)
 			} else if next == '/' {
-				self.readChar()
-				tk = self.fetchOnLineComment()
+				scanner.readChar()
+				tk = scanner.fetchOnLineComment()
 			} else {
-				tk = self.makeToken(SymSlash, ch)
+				tk = scanner.makeToken(SymSlash, ch)
 			}
 		case '\\':
 			if escape {
-				tk = self.makeToken(SymBackSlash, ch)
+				tk = scanner.makeToken(SymBackSlash, ch)
 				escape = false
 			} else {
 				escape = true
 			}
 		case '|':
-			if next, _ := self.peek(); next == '|' {
-				tk = self.moveOn(SymDoubleVertBar, ch, next)
+			if next, _ := scanner.peek(); next == '|' {
+				tk = scanner.moveOn(SymDoubleVertBar, ch, next)
+			} else if next, _ = scanner.peek(); next == '=' {
+				tk = scanner.moveOn(SymVertBarEqual, ch, next)
 			} else {
-				tk = self.makeToken(SymVertBar, ch)
+				tk = scanner.makeToken(SymVertBar, ch)
 			}
 		case ',':
-			tk = self.makeToken(SymComma, ch)
+			tk = scanner.makeToken(SymComma, ch)
 		case '^':
-			tk = self.makeToken(SymCaret, ch)
-		case ':':
-			if next, _ := self.peek(); next == ':' {
-				tk = self.moveOn(SymDoubleColon, ch, next)
+			if next, _ := scanner.peek(); next == '=' {
+				tk = scanner.moveOn(SymCaretEqual, ch, next)
 			} else {
-				tk = self.makeToken(SymColon, ch)
+				tk = scanner.makeToken(SymCaret, ch)
+			}
+		case ':':
+			if next, _ := scanner.peek(); next == ':' {
+				tk = scanner.moveOn(SymDoubleColon, ch, next)
+			} else {
+				tk = scanner.makeToken(SymColon, ch)
 			}
 		case ';':
-			tk = self.makeToken(SymSemiColon, ch)
+			tk = scanner.makeToken(SymSemiColon, ch)
 		case '.':
 			//if next, _ := self.peek(); next >= '0' && next <= '9' {
 			//	tk = self.parseNumber(ch)
 			//} else if next == '/' {
-			if next, _ := self.peek(); next == '/' {
-				tk = self.moveOn(SymDotSlash, ch, next)
+			if next, _ := scanner.peek(); next == '/' {
+				tk = scanner.moveOn(SymDotSlash, ch, next)
 			} else if next == '.' {
-				if next1, _ := self.peek(); next1 == '.' {
-					tk = self.moveOn(SymTripleDot, ch, next, next1)
+				if next1, _ := scanner.peek(); next1 == '.' {
+					tk = scanner.moveOn(SymTripleDot, ch, next, next1)
 				} else {
-					tk = self.moveOn(SymDoubleDot, ch, next)
+					tk = scanner.moveOn(SymDoubleDot, ch, next)
 				}
 			} else {
-				tk = self.makeToken(SymDot, ch)
+				tk = scanner.makeToken(SymDot, ch)
 			}
 		case '\'':
-			tk = self.makeToken(SymQuote, ch)
-		case '"':
 			if escape {
-				tk = self.makeToken(SymDoubleQuote, ch)
+				tk = scanner.makeToken(SymQuote, ch)
 				escape = false
 			} else {
-				tk = self.fetchString()
+				tk = scanner.fetchString(ch, true)
+			}
+		case '"':
+			if escape {
+				tk = scanner.makeToken(SymDoubleQuote, ch)
+				escape = false
+			} else {
+				tk = scanner.fetchString(ch, true)
 			}
 		case '`':
-			tk = self.makeToken(SymBackTick, ch)
+			tk = scanner.makeToken(SymBackTick, ch)
 		case '!':
-			if next, _ := self.peek(); next == '=' {
-				tk = self.moveOn(SymNotEqual, ch, next)
+			if next, _ := scanner.peek(); next == '=' {
+				tk = scanner.moveOn(SymNotEqual, ch, next)
 			} else {
-				tk = self.makeToken(SymExclamation, ch)
+				tk = scanner.makeToken(SymExclamation, ch)
 			}
 		case '?':
-			if next, _ := self.peek(); next == '?' {
-				tk = self.moveOn(SymDoubleQuestion, ch, next)
-			} else if next, _ := self.peek(); next == '=' {
-				tk = self.moveOn(SymQuestionEqual, ch, next)
+			if next, _ := scanner.peek(); next == '?' {
+				tk = scanner.moveOn(SymDoubleQuestion, ch, next)
+			} else if next == '=' {
+				tk = scanner.moveOn(SymQuestionEqual, ch, next)
+			} else if next == '!' {
+				tk = scanner.moveOn(SymQuestionExclam, ch, next)
 			} else {
-				tk = self.makeToken(SymQuestion, ch)
+				tk = scanner.makeToken(SymQuestion, ch)
 			}
 		case '&':
-			if next, _ := self.peek(); next == '&' {
-				tk = self.moveOn(SymDoubleAmpersand, ch, next)
+			if next, _ := scanner.peek(); next == '&' {
+				tk = scanner.moveOn(SymDoubleAmpersand, ch, next)
+			} else if next, _ = scanner.peek(); next == '=' {
+				tk = scanner.moveOn(SymAmpersandEqual, ch, next)
 			} else {
-				tk = self.makeToken(SymAmpersand, ch)
+				tk = scanner.makeToken(SymAmpersand, ch)
 			}
 		case '%':
-			tk = self.makeToken(SymPercent, ch)
+			if next, _ := scanner.peek(); next == '=' {
+				tk = scanner.moveOn(SymPercEqual, ch, next)
+			} else {
+				tk = scanner.makeToken(SymPercent, ch)
+			}
 		case '#':
-			tk = self.makeToken(SymHash, ch)
+			tk = scanner.makeToken(SymHash, ch)
 		case '@':
-			if next, _ := self.peek(); (next >= 'a' && next <= 'z') || (next >= 'A' && next <= 'Z') {
-				self.readChar()
-				if tk = self.fetchIdentifier(next); tk.Sym == SymIdentifier {
+			if next, _ := scanner.peek(); (next >= 'a' && next <= 'z') || (next >= 'A' && next <= 'Z') {
+				scanner.readChar()
+				if tk = scanner.fetchIdentifier(next); tk.Sym == SymIdentifier {
 					//tk.Sym = SymIdRef
 					tk.source = "@" + tk.source
 				} else {
-					tk = self.makeErrorToken(fmt.Errorf("invalid variable reference %q", tk.source))
+					tk = scanner.makeErrorToken(fmt.Errorf("invalid variable reference %q", tk.source))
 				}
 			} else if next == '@' {
-				tk = self.moveOn(SymDoubleAt, ch, next)
+				tk = scanner.moveOn(SymDoubleAt, ch, next)
 			} else {
-				tk = self.makeToken(SymAt, ch)
+				tk = scanner.makeToken(SymAt, ch)
 			}
 		case '_':
-			tk = self.makeToken(SymUndescore, ch)
+			tk = scanner.makeToken(SymUndescore, ch)
 		case '=':
-			if next, _ := self.peek(); next == '=' {
-				tk = self.moveOn(SymDoubleEqual, ch, next)
+			if next, _ := scanner.peek(); next == '=' {
+				tk = scanner.moveOn(SymDoubleEqual, ch, next)
 			} else {
-				tk = self.makeToken(SymEqual, ch)
+				tk = scanner.makeToken(SymEqual, ch)
 			}
 		case '<':
-			if next, _ := self.peek(); next == '=' {
-				tk = self.moveOn(SymLessOrEqual, ch, next)
+			if next, _ := scanner.peek(); next == '=' {
+				tk = scanner.moveOn(SymLessOrEqual, ch, next)
 			} else if next == '<' {
-				tk = self.moveOn(SymAppend, ch, next)
+				scanner.readChar()
+				next2, _ := scanner.readChar()
+				scanner.unreadChar()
+				if next2 == '=' {
+					tk = scanner.moveOn(SymDoubleLessEqual, ch, next, next2)
+				} else {
+					tk = scanner.accept(SymDoubleLess, ch, next)
+				}
 			} else if next == '>' {
-				tk = self.moveOn(SymLessGreater, ch, next)
+				tk = scanner.moveOn(SymLessGreater, ch, next)
+			} else if next == '+' {
+				tk = scanner.moveOn(SymLessPlus, ch, next)
 			} else {
-				tk = self.makeToken(SymLess, ch)
+				tk = scanner.makeToken(SymLess, ch)
 			}
 		case '>':
-			if next, _ := self.peek(); next == '=' {
-				tk = self.moveOn(SymGreaterOrEqual, ch, next)
+			if next, _ := scanner.peek(); next == '=' {
+				tk = scanner.moveOn(SymGreaterOrEqual, ch, next)
 			} else if next == '>' {
-				tk = self.moveOn(SymInsert, ch, next)
+				scanner.readChar()
+				next2, _ := scanner.readChar()
+				scanner.unreadChar()
+				if next2 == '=' {
+					tk = scanner.moveOn(SymDoubleGreaterEqual, ch, next, next2)
+				} else {
+					tk = scanner.accept(SymDoubleGreater, ch, next)
+				}
 			} else {
-				tk = self.makeToken(SymGreater, ch)
+				tk = scanner.makeToken(SymGreater, ch)
 			}
 		case '$':
-			if next, _ := self.peek(); next == '(' {
-				tk = self.moveOn(SymDollarRound, ch, next)
+			if next, _ := scanner.peek(); next == '(' {
+				tk = scanner.moveOn(SymDollarRound, ch, next)
 				tk.source += ")"
 			} else if next == '$' {
-				tk = self.moveOn(SymDoubleDollar, ch, next)
+				tk = scanner.moveOn(SymDoubleDollar, ch, next)
+			} else if next == '{' {
+				scanner.readChar()
+				if tk = scanner.fetchString('}', false); tk != nil {
+					tk.Sym = SymIdentifier
+				}
+			} else if next == '_' || (next >= 'a' && next <= 'z') || (next >= 'A' && next <= 'Z') {
+				scanner.readChar()
+				tk = scanner.fetchIdentifier(next)
 			} else {
-				tk = self.makeToken(SymDollar, ch)
+				tk = scanner.makeToken(SymDollar, ch)
 			}
 		case '(':
-			if next, _ := self.peek(); next == ')' {
-				tk = self.moveOn(SymOpenClosedRound, ch, next)
-			} else {
-				tk = self.makeToken(SymOpenRound, ch)
-			}
+			//			if next, _ := scanner.peek(); next == ')' {
+			//				tk = scanner.moveOn(SymOpenClosedRound, ch, next)
+			//			} else {
+			tk = scanner.makeToken(SymOpenRound, ch)
+			//			}
 		case ')':
-			tk = self.makeToken(SymClosedRound, ch)
+			tk = scanner.makeToken(SymClosedRound, ch)
 		case '[':
-			tk = self.makeToken(SymOpenSquare, ch)
+			tk = scanner.makeToken(SymOpenSquare, ch)
 		case ']':
-			tk = self.makeToken(SymClosedSquare, ch)
+			tk = scanner.makeToken(SymClosedSquare, ch)
 		case '{':
-			tk = self.makeToken(SymOpenBrace, ch)
+			tk = scanner.makeToken(SymOpenBrace, ch)
 		case '}':
-			tk = self.makeToken(SymClosedBrace, ch)
+			tk = scanner.makeToken(SymClosedBrace, ch)
 		case '~':
-			tk = self.makeToken(SymTilde, ch)
+			tk = scanner.makeToken(SymTilde, ch)
 		case 0:
 			if escape {
-				tk = self.makeErrorToken(errors.New("incomplete escape sequence"))
+				tk = scanner.makeErrorToken(errors.New("incomplete escape sequence"))
 			}
 			escape = false
 		default:
 			if /*ch == '_' ||*/ (ch >= 'a' && ch <= 'z') || (ch >= 'A' && ch <= 'Z') {
-				if tk = self.fetchIdentifier(ch); tk.Sym == SymKwFunc {
-					if next, _ := self.peek(); next == '(' {
-						tk = self.moveOn(SymFuncDef, ch, next)
+				if tk = scanner.fetchIdentifier(ch); tk.Sym == SymKwFunc {
+					if next, _ := scanner.peek(); next == '(' {
+						tk = scanner.moveOn(SymFuncDef, ch, next)
 					}
 				}
 			} else if ch >= '0' && ch <= '9' {
-				tk = self.parseNumber(ch)
+				tk = scanner.parseNumber(ch)
 			}
 		}
 		if !escape {
@@ -300,14 +365,14 @@ func (self *scanner) fetchNextToken() (tk *Token) {
 		}
 	}
 	if tk == nil {
-		tk = NewErrorToken(self.row, self.column, fmt.Errorf("unknown symbol '%c'", ch))
+		tk = NewErrorToken(scanner.row, scanner.column, fmt.Errorf("unknown symbol '%c'", ch))
 	}
 	return
 }
 
-func (self *scanner) sync(err error) error {
+func (scanner *scanner) sync(err error) error {
 	if err == nil {
-		err = self.unreadChar()
+		err = scanner.unreadChar()
 	}
 	return err
 }
@@ -328,32 +393,32 @@ func isHexDigit(ch byte) bool {
 	return (ch >= '0' && ch <= '9') || (ch >= 'a' && ch <= 'f') || (ch >= 'A' && ch <= 'F')
 }
 
-func (self *scanner) initBase(sb *strings.Builder, currentFirstCh byte) (firstCh byte, numBase int, digitFunc func(byte) bool, err error) {
+func (scanner *scanner) initBase(currentFirstCh byte) (firstCh byte, numBase int, digitFunc func(byte) bool, err error) {
 	var ch byte
 	var digitType string
 	firstCh = currentFirstCh
 	digitFunc = isDecimalDigit
 	numBase = 10
 
-	if ch, err = self.peek(); err == nil {
+	if ch, err = scanner.peek(); err == nil {
 		if ch == 'b' || ch == 'B' {
 			numBase = 2
 			digitType = "binary"
-			self.readChar()
+			scanner.readChar()
 			digitFunc = isBinaryDigit
-			firstCh, err = self.readChar()
+			firstCh, err = scanner.readChar()
 		} else if ch == 'o' || ch == 'O' {
 			numBase = 8
 			digitType = "octal"
-			self.readChar()
+			scanner.readChar()
 			digitFunc = isOctalDigit
-			firstCh, err = self.readChar()
+			firstCh, err = scanner.readChar()
 		} else if ch == 'x' || ch == 'X' {
 			numBase = 16
 			digitType = "hex"
-			self.readChar()
+			scanner.readChar()
 			digitFunc = isHexDigit
-			firstCh, err = self.readChar()
+			firstCh, err = scanner.readChar()
 		}
 		if err == nil && !digitFunc(firstCh) {
 			if len(digitType) == 0 {
@@ -367,7 +432,7 @@ func (self *scanner) initBase(sb *strings.Builder, currentFirstCh byte) (firstCh
 	return
 }
 
-func (self *scanner) parseNumber(firstCh byte) (tk *Token) {
+func (scanner *scanner) parseNumber(firstCh byte) (tk *Token) {
 	var err error
 	var ch byte
 	var sym Symbol = SymInteger
@@ -376,9 +441,9 @@ func (self *scanner) parseNumber(firstCh byte) (tk *Token) {
 	var numBase = 10
 
 	if firstCh == '0' {
-		firstCh, numBase, isDigit, err = self.initBase(&sb, firstCh)
+		firstCh, numBase, isDigit, err = scanner.initBase(firstCh)
 	}
-	for ch = firstCh; err == nil && isDigit(ch); ch, err = self.readChar() {
+	for ch = firstCh; err == nil && isDigit(ch); ch, err = scanner.readChar() {
 		sb.WriteByte(ch)
 	}
 
@@ -386,9 +451,9 @@ func (self *scanner) parseNumber(firstCh byte) (tk *Token) {
 		if err == nil && ch == '.' {
 			sym = SymFloat
 			sb.WriteByte(ch)
-			ch, err = self.readChar()
+			ch, err = scanner.readChar()
 			if ch >= '0' && ch <= '9' {
-				for ; err == nil && (ch >= '0' && ch <= '9'); ch, err = self.readChar() {
+				for ; err == nil && (ch >= '0' && ch <= '9'); ch, err = scanner.readChar() {
 					sb.WriteByte(ch)
 				}
 			}
@@ -397,32 +462,32 @@ func (self *scanner) parseNumber(firstCh byte) (tk *Token) {
 			if ch == 'e' || ch == 'E' {
 				sym = SymFloat
 				sb.WriteByte(ch)
-				if ch, err = self.readChar(); err == nil {
+				if ch, err = scanner.readChar(); err == nil {
 					if ch == '+' || ch == '-' {
 						sb.WriteByte(ch)
-						ch, err = self.readChar()
+						ch, err = scanner.readChar()
 					}
 					if ch >= '0' && ch <= '9' {
-						for ; err == nil && (ch >= '0' && ch <= '9'); ch, err = self.readChar() {
+						for ; err == nil && (ch >= '0' && ch <= '9'); ch, err = scanner.readChar() {
 							sb.WriteByte(ch)
 						}
 					} else {
-						err = fmt.Errorf("[%d:%d] expected integer exponent, got %c", self.row, self.column, ch)
+						err = fmt.Errorf("[%d:%d] expected integer exponent, got %c", scanner.row, scanner.column, ch)
 					}
 				}
 			} else if ch == '(' {
 				sym = SymFraction
 				sb.WriteByte(ch)
-				ch, err = self.readChar()
-				for ; err == nil && (ch >= '0' && ch <= '9'); ch, err = self.readChar() {
+				ch, err = scanner.readChar()
+				for ; err == nil && (ch >= '0' && ch <= '9'); ch, err = scanner.readChar() {
 					sb.WriteByte(ch)
 				}
 				if err == nil {
 					if ch != ')' {
-						err = fmt.Errorf("[%d:%d] expected ')', got '%c'", self.row, self.column, ch)
+						err = fmt.Errorf("[%d:%d] expected ')', got '%c'", scanner.row, scanner.column, ch)
 					} else {
 						sb.WriteByte(ch)
-						_, err = self.readChar()
+						_, err = scanner.readChar()
 					}
 				}
 			}
@@ -430,10 +495,10 @@ func (self *scanner) parseNumber(firstCh byte) (tk *Token) {
 	}
 
 	if err != nil && err != io.EOF {
-		tk = self.makeErrorToken(err)
+		tk = scanner.makeErrorToken(err)
 	} else {
 		var value any
-		err = self.sync(err)
+		_ = scanner.sync(err) // TODO: Check this function
 		txt := sb.String()
 		if sym == SymFloat {
 			value, err = strconv.ParseFloat(txt, 64)
@@ -443,39 +508,39 @@ func (self *scanner) parseNumber(firstCh byte) (tk *Token) {
 			value, err = strconv.ParseInt(txt, numBase, 64)
 		}
 		if err == nil {
-			tk = self.makeValueToken(sym, txt, value)
+			tk = scanner.makeValueToken(sym, txt, value)
 		} else {
-			tk = self.makeErrorToken(err)
+			tk = scanner.makeErrorToken(err)
 		}
 	}
 	return
 }
 
-func (self *scanner) fetchIdentifier(firstCh byte) (tk *Token) {
+func (scanner *scanner) fetchIdentifier(firstCh byte) (tk *Token) {
 	var err error
 	var sb strings.Builder
-	for ch := firstCh; err == nil && (ch == '_' || (ch >= 'a' && ch <= 'z') || (ch >= 'A' && ch <= 'Z') || (ch >= '0' && ch <= '9')); ch, err = self.readChar() {
+	for ch := firstCh; err == nil && (ch == '_' || (ch >= 'a' && ch <= 'z') || (ch >= 'A' && ch <= 'Z') || (ch >= '0' && ch <= '9')); ch, err = scanner.readChar() {
 		sb.WriteByte(ch)
 	}
 
 	if err != nil && err != io.EOF {
-		tk = self.makeErrorToken(err)
-	} else if err = self.sync(err); err != nil && err != io.EOF {
-		tk = self.makeErrorToken(err)
+		tk = scanner.makeErrorToken(err)
+	} else if err = scanner.sync(err); err != nil && err != io.EOF {
+		tk = scanner.makeErrorToken(err)
 	} else {
 		txt := sb.String()
 		uptxt := strings.ToUpper(txt)
 		if sym, ok := keywords[uptxt]; ok {
-			tk = self.makeKeywordToken(sym, uptxt)
+			tk = scanner.makeKeywordToken(sym, uptxt)
 		} else if uptxt == `TRUE` {
-			tk = self.makeValueToken(SymBool, txt, true)
+			tk = scanner.makeValueToken(SymBool, txt, true)
 		} else if uptxt == `FALSE` {
-			tk = self.makeValueToken(SymBool, txt, false)
-		} else if ch, _ := self.peek(); ch == '(' {
-			self.readChar()
-			tk = self.makeValueToken(SymFuncCall, txt+"(", txt)
+			tk = scanner.makeValueToken(SymBool, txt, false)
+		} else if ch, _ := scanner.peek(); ch == '(' {
+			scanner.readChar()
+			tk = scanner.makeValueToken(SymFuncCall, txt+"(", txt)
 		} else {
-			tk = self.makeValueToken(SymIdentifier, txt, txt)
+			tk = scanner.makeValueToken(SymIdentifier, txt, txt)
 		}
 	}
 
@@ -495,29 +560,29 @@ func (self *scanner) fetchIdentifier(firstCh byte) (tk *Token) {
 	return
 }
 
-func (self *scanner) fetchBlockComment() *Token {
-	return self.fetchUntil(SymComment, false, '*', '/')
+func (scanner *scanner) fetchBlockComment() *Token {
+	return scanner.fetchUntil(SymComment, false, '*', '/')
 }
 
-func (self *scanner) fetchOnLineComment() *Token {
-	return self.fetchUntil(SymComment, true, '\n')
+func (scanner *scanner) fetchOnLineComment() *Token {
+	return scanner.fetchUntil(SymComment, true, '\n')
 }
 
-func (self *scanner) fetchUntil(sym Symbol, allowEos bool, endings ...byte) (tk *Token) {
+func (scanner *scanner) fetchUntil(sym Symbol, allowEos bool, endings ...byte) (tk *Token) {
 	var err error
 	var ch byte
 	var sb strings.Builder
 	var value string
 	ring := NewByteSlider(len(endings))
 	endReached := false
-	for ch, err = self.readChar(); err == nil && !endReached; {
+	for ch, err = scanner.readChar(); err == nil && !endReached; {
 		sb.WriteByte(ch)
 		ring.PushEnd(ch)
 		if ring.Equal(endings) {
 			value = sb.String()[0 : sb.Len()-len(endings)]
 			endReached = true
 		} else {
-			ch, err = self.readChar()
+			ch, err = scanner.readChar()
 		}
 	}
 	if !endReached && allowEos {
@@ -526,18 +591,18 @@ func (self *scanner) fetchUntil(sym Symbol, allowEos bool, endings ...byte) (tk
 	}
 
 	if endReached {
-		tk = self.makeValueToken(sym, "", value)
+		tk = scanner.makeValueToken(sym, "", value)
 	} else {
-		tk = self.makeErrorToken(err)
+		tk = scanner.makeErrorToken(err)
 	}
 	return
 }
 
-func (self *scanner) fetchString() (tk *Token) {
+func (scanner *scanner) fetchString(termCh byte, addQuote bool) (tk *Token) {
 	var err error
 	var ch, prev byte
 	var sb strings.Builder
-	for ch, err = self.readChar(); err == nil; ch, err = self.readChar() {
+	for ch, err = scanner.readChar(); err == nil; ch, err = scanner.readChar() {
 		if prev == '\\' {
 			switch ch {
 			case '"':
@@ -554,7 +619,7 @@ func (self *scanner) fetchString() (tk *Token) {
 				sb.WriteByte(ch)
 			}
 			prev = 0
-		} else if ch == '"' {
+		} else if ch == termCh {
 			break
 		} else {
 			prev = ch
@@ -565,65 +630,76 @@ func (self *scanner) fetchString() (tk *Token) {
 	}
 	if err != nil {
 		if err == io.EOF {
-			tk = self.makeErrorToken(errors.New("missing string termination \""))
+			tk = scanner.makeErrorToken(errors.New(string(termCh)))
 		} else {
-			tk = self.makeErrorToken(err)
+			tk = scanner.makeErrorToken(err)
 		}
 	} else {
 		txt := sb.String()
-		tk = self.makeValueToken(SymString, `"`+txt+`"`, txt)
+		if addQuote {
+			tk = scanner.makeValueToken(SymString, `"`+txt+`"`, txt)
+		} else {
+			tk = scanner.makeValueToken(SymString, txt, txt)
+		}
 	}
 	return
 }
 
-func (self *scanner) peek() (next byte, err error) {
+func (scanner *scanner) peek() (next byte, err error) {
 	var one []byte
-	if one, err = self.stream.Peek(1); err == nil {
+	if one, err = scanner.stream.Peek(1); err == nil {
 		next = one[0]
 	}
 	return
 }
 
-func (self *scanner) skipBlanks() (err error) {
+func (scanner *scanner) skipBlanks() (err error) {
 	var one []byte
-	for one, err = self.stream.Peek(1); err == nil && one[0] <= 32; one, err = self.stream.Peek(1) {
-		self.readChar()
+	for one, err = scanner.stream.Peek(1); err == nil && one[0] <= 32; one, err = scanner.stream.Peek(1) {
+		scanner.readChar()
 	}
 	return
 }
 
-func (self *scanner) translate(sym Symbol) Symbol {
-	if self.translations != nil {
-		if translatedSym, ok := self.translations[sym]; ok {
+func (scanner *scanner) translate(sym Symbol) Symbol {
+	if scanner.translations != nil {
+		if translatedSym, ok := scanner.translations[sym]; ok {
 			return translatedSym
 		}
 	}
 	return sym
 }
 
-func (self *scanner) moveOn(sym Symbol, chars ...byte) (tk *Token) {
-	tk = NewToken(self.row, self.column, self.translate(sym), string(chars))
-	for i := 1; i < len(chars); i++ {
-		self.readChar()
+func (scanner *scanner) moveOn(sym Symbol, chars ...byte) (tk *Token) {
+	tk = NewToken(scanner.row, scanner.column, scanner.translate(sym), string(chars))
+	// for i := 1; i < len(chars); i++ {
+	if len(chars) > 1 {
+		scanner.readChar()
 	}
+	// }
 	return
 }
 
-func (self *scanner) makeToken(sym Symbol, chars ...byte) (tk *Token) {
-	tk = NewToken(self.row, self.column, self.translate(sym), string(chars))
+func (scanner *scanner) accept(sym Symbol, chars ...byte) (tk *Token) {
+	tk = NewToken(scanner.row, scanner.column, scanner.translate(sym), string(chars))
 	return
 }
 
-func (self *scanner) makeKeywordToken(sym Symbol, upperCaseKeyword string) (tk *Token) {
-	tk = NewToken(self.row, self.column, self.translate(sym), upperCaseKeyword)
+func (scanner *scanner) makeToken(sym Symbol, chars ...byte) (tk *Token) {
+	tk = NewToken(scanner.row, scanner.column, scanner.translate(sym), string(chars))
 	return
 }
 
-func (self *scanner) makeValueToken(sym Symbol, source string, value any) (tk *Token) {
-	tk = NewValueToken(self.row, self.column, self.translate(sym), source, value)
+func (scanner *scanner) makeKeywordToken(sym Symbol, upperCaseKeyword string) (tk *Token) {
+	tk = NewToken(scanner.row, scanner.column, scanner.translate(sym), upperCaseKeyword)
 	return
 }
 
-func (self *scanner) makeErrorToken(err error) *Token {
-	return NewErrorToken(self.row, self.column, err)
+func (scanner *scanner) makeValueToken(sym Symbol, source string, value any) (tk *Token) {
+	tk = NewValueToken(scanner.row, scanner.column, scanner.translate(sym), source, value)
+	return
+}
+
+func (scanner *scanner) makeErrorToken(err error) *Token {
+	return NewErrorToken(scanner.row, scanner.column, err)
 }

simple-func-store.go.bak

@@ -1,244 +0,0 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
-// All rights reserved.
-
-// simple-func-store.go
-package expr
-
-import (
-	"fmt"
-	"slices"
-	"strings"
-)
-
-type SimpleFuncStore struct {
-	SimpleVarStore
-	funcStore map[string]*funcInfo
-}
-
-type paramFlags uint16
-
-const (
-	pfOptional paramFlags = 1 << iota
-	pfRepeat
-)
-
-type funcParamInfo struct {
-	name         string
-	flags        paramFlags
-	defaultValue any
-}
-
-func newFuncParam(name string) *funcParamInfo {
-	return &funcParamInfo{name: name}
-}
-
-func newFuncParamFlag(name string, flags paramFlags) *funcParamInfo {
-	return &funcParamInfo{name: name, flags: flags}
-}
-
-func newFuncParamFlagDef(name string, flags paramFlags, defValue any) *funcParamInfo {
-	return &funcParamInfo{name: name, flags: flags, defaultValue: defValue}
-}
-
-func (param *funcParamInfo) Name() string {
-	return param.name
-}
-
-func (param *funcParamInfo) Type() string {
-	return "any"
-}
-
-func (param *funcParamInfo) IsOptional() bool {
-	return (param.flags & pfOptional) != 0
-}
-
-func (param *funcParamInfo) IsRepeat() bool {
-	return (param.flags & pfRepeat) != 0
-}
-
-func (param *funcParamInfo) DefaultValue() any {
-	return param.defaultValue
-}
-
-type funcInfo struct {
-	name       string
-	minArgs    int
-	maxArgs    int
-	functor    Functor
-	params     []ExprFuncParam
-	returnType string
-}
-
-func (info *funcInfo) Params() []ExprFuncParam {
-	return info.params
-}
-
-func (info *funcInfo) ReturnType() string {
-	return info.returnType
-}
-
-func (info *funcInfo) ToString(opt FmtOpt) string {
-	var sb strings.Builder
-	sb.WriteByte('(')
-	if info.params != nil {
-		for i, p := range info.params {
-			if i > 0 {
-				sb.WriteString(", ")
-			}
-			sb.WriteString(p.Name())
-			if p.IsOptional() {
-				sb.WriteByte('=')
-				if s, ok := p.DefaultValue().(string); ok {
-					sb.WriteByte('"')
-					sb.WriteString(s)
-					sb.WriteByte('"')
-				} else {
-					sb.WriteString(fmt.Sprintf("%v", p.DefaultValue()))
-				}
-			}
-		}
-	}
-	if info.maxArgs < 0 {
-		sb.WriteString(" ...")
-	}
-	sb.WriteString(") -> ")
-	if len(info.returnType) > 0 {
-		sb.WriteString(info.returnType)
-	} else {
-		sb.WriteString(typeAny)
-	}
-	return sb.String()
-}
-
-func (info *funcInfo) Name() string {
-	return info.name
-}
-
-func (info *funcInfo) MinArgs() int {
-	return info.minArgs
-}
-
-func (info *funcInfo) MaxArgs() int {
-	return info.maxArgs
-}
-
-func (info *funcInfo) Functor() Functor {
-	return info.functor
-}
-
-func NewSimpleFuncStore() *SimpleFuncStore {
-	ctx := &SimpleFuncStore{
-		SimpleVarStore: SimpleVarStore{varStore: make(map[string]any)},
-		funcStore:      make(map[string]*funcInfo),
-	}
-	//ImportBuiltinsFuncs(ctx)
-	return ctx
-}
-
-func (ctx *SimpleFuncStore) Clone() ExprContext {
-	svs := ctx.SimpleVarStore
-	return &SimpleFuncStore{
-		// SimpleVarStore: SimpleVarStore{varStore: CloneMap(ctx.varStore)},
-		SimpleVarStore: SimpleVarStore{varStore: svs.cloneVars()},
-		funcStore:      CloneFilteredMap(ctx.funcStore, func(name string) bool { return name[0] != '@' }),
-	}
-}
-
-func funcsCtxToBuilder(sb *strings.Builder, ctx ExprContext, indent int) {
-	sb.WriteString("funcs: {\n")
-	first := true
-	names := ctx.EnumFuncs(func(name string) bool { return true })
-	slices.Sort(names)
-	for _, name := range names {
-		if first {
-			first = false
-		} else {
-			sb.WriteByte(',')
-			sb.WriteByte('\n')
-		}
-		value, _ := ctx.GetFuncInfo(name)
-		sb.WriteString(strings.Repeat("\t", indent+1))
-		sb.WriteString(name)
-		//sb.WriteString("=")
-		if formatter, ok := value.(Formatter); ok {
-			sb.WriteString(formatter.ToString(0))
-		} else {
-			sb.WriteString(fmt.Sprintf("%v", value))
-		}
-	}
-	sb.WriteString("\n}\n")
-}
-
-func (ctx *SimpleFuncStore) ToString(opt FmtOpt) string {
-	var sb strings.Builder
-	sb.WriteString(ctx.SimpleVarStore.ToString(opt))
-	funcsCtxToBuilder(&sb, ctx, 0)
-	return sb.String()
-}
-
-func (ctx *SimpleFuncStore) GetFuncInfo(name string) (info ExprFunc, exists bool) {
-	info, exists = ctx.funcStore[name]
-	return
-}
-
-// func (ctx *SimpleFuncStore) RegisterFunc(name string, functor Functor, minArgs, maxArgs int) {
-// 	ctx.funcStore[name] = &funcInfo{name: name, minArgs: minArgs, maxArgs: maxArgs, functor: functor}
-// }
-
-func (ctx *SimpleFuncStore) RegisterFuncInfo(info ExprFunc) {
-	ctx.funcStore[info.Name()], _ = info.(*funcInfo)
-}
-
-func (ctx *SimpleFuncStore) RegisterFunc2(name string, functor Functor, returnType string, params []ExprFuncParam) error {
-	var minArgs = 0
-	var maxArgs = 0
-	if params != nil {
-		for _, p := range params {
-			if maxArgs == -1 {
-				return fmt.Errorf("no more params can be specified after the ellipsis symbol: %q", p.Name())
-				// } else if p.IsRepeat() {
-				// 	maxArgs = -1
-				// 	continue
-			}
-			if p.IsOptional() {
-				maxArgs++
-			} else if maxArgs == minArgs {
-				minArgs++
-				maxArgs++
-			} else {
-				return fmt.Errorf("can't specify non-optional param after optional ones: %q", p.Name())
-			}
-			if p.IsRepeat() {
-				maxArgs = -1
-			}
-		}
-	}
-	ctx.funcStore[name] = &funcInfo{
-		name: name, minArgs: minArgs, maxArgs: maxArgs, functor: functor, returnType: returnType, params: params,
-	}
-	return nil
-}
-
-func (ctx *SimpleFuncStore) EnumFuncs(acceptor func(name string) (accept bool)) (funcNames []string) {
-	funcNames = make([]string, 0)
-	for name := range ctx.funcStore {
-		if acceptor != nil {
-			if acceptor(name) {
-				funcNames = append(funcNames, name)
-			}
-		} else {
-			funcNames = append(funcNames, name)
-		}
-	}
-	return
-}
-
-func (ctx *SimpleFuncStore) Call(name string, args []any) (result any, err error) {
-	if info, exists := ctx.funcStore[name]; exists {
-		functor := info.functor
-		result, err = functor.Invoke(ctx, name, args)
-	} else {
-		err = fmt.Errorf("unknown function %s()", name)
-	}
-	return
-}

simple-store.go

@@ -7,95 +7,96 @@ package expr
 import (
 	"fmt"
 	"slices"
-	"strings"
+	// "strings"
 )
 
 type SimpleStore struct {
+	parent    ExprContext
 	varStore  map[string]any
-	funcStore map[string]*funcInfo
+	funcStore map[string]ExprFunc
 }
 
 func NewSimpleStore() *SimpleStore {
 	ctx := &SimpleStore{
 		varStore:  make(map[string]any),
-		funcStore: make(map[string]*funcInfo),
+		funcStore: make(map[string]ExprFunc),
 	}
-	//ImportBuiltinsFuncs(ctx)
 	return ctx
 }
 
+func (ss *SimpleStore) Init() {
+	ss.varStore = make(map[string]any)
+	ss.funcStore = make(map[string]ExprFunc)
+}
+
+func filterRefName(name string) bool  { return name[0] != '@' }
+//func filterPrivName(name string) bool { return name[0] != '_' }
+
+func (ctx *SimpleStore) SetParent(parentCtx ExprContext) {
+	ctx.parent = parentCtx
+}
+
+func (ctx *SimpleStore) GetParent() ExprContext {
+	return ctx.parent
+}
+
 func (ctx *SimpleStore) Clone() ExprContext {
-	return &SimpleStore{
-		varStore:  CloneFilteredMap(ctx.varStore, func(name string) bool { return name[0] != '@' }),
-		funcStore: CloneFilteredMap(ctx.funcStore, func(name string) bool { return name[0] != '@' }),
+	clone := &SimpleStore{
+		varStore:  CloneFilteredMap(ctx.varStore, filterRefName),
+		funcStore: CloneFilteredMap(ctx.funcStore, filterRefName),
 	}
+	return clone
 }
 
-func varsCtxToBuilder(sb *strings.Builder, ctx ExprContext, indent int) {
-	sb.WriteString("vars: {\n")
-	first := true
-	for _, name := range ctx.EnumVars(func(name string) bool { return name[0] != '_' }) {
-		if first {
-			first = false
-		} else {
-			sb.WriteByte(',')
-			sb.WriteByte('\n')
-		}
+// func (ctx *SimpleStore) Merge(src ExprContext) {
+// 	for _, name := range src.EnumVars(filterRefName) {
+// 		ctx.varStore[name], _ = src.GetVar(name)
+// 	}
+// 	for _, name := range src.EnumFuncs(filterRefName) {
+// 		ctx.funcStore[name], _ = src.GetFuncInfo(name)
+// 	}
+// }
 
+func (ctx *SimpleStore) ToString(opt FmtOpt) string {
+	dict := ctx.ToDict()
+	return dict.ToString(opt)
+}
+
+func (ctx *SimpleStore) varsToDict(dict *DictType) *DictType {
+	names := ctx.EnumVars(nil)
+	slices.Sort(names)
+	for _, name := range ctx.EnumVars(nil) {
 		value, _ := ctx.GetVar(name)
-		sb.WriteString(strings.Repeat("\t", indent+1))
-		sb.WriteString(name)
-		sb.WriteString(": ")
 		if f, ok := value.(Formatter); ok {
-			sb.WriteString(f.ToString(0))
+			(*dict)[name] = f.ToString(0)
 		} else if _, ok = value.(Functor); ok {
-			sb.WriteString("func(){}")
-			// } else if _, ok = value.(map[any]any); ok {
-			// 	sb.WriteString("dict{}")
+			(*dict)[name] = "func(){}"
 		} else {
-			sb.WriteString(fmt.Sprintf("%v", value))
+			(*dict)[name] = fmt.Sprintf("%v", value)
 		}
 	}
-	sb.WriteString(strings.Repeat("\t", indent))
-	sb.WriteString("\n}\n")
+	return dict
 }
 
-func varsCtxToString(ctx ExprContext, indent int) string {
-	var sb strings.Builder
-	varsCtxToBuilder(&sb, ctx, indent)
-	return sb.String()
-}
-
-func funcsCtxToBuilder(sb *strings.Builder, ctx ExprContext, indent int) {
-	sb.WriteString("funcs: {\n")
-	first := true
+func (ctx *SimpleStore) funcsToDict(dict *DictType) *DictType {
 	names := ctx.EnumFuncs(func(name string) bool { return true })
 	slices.Sort(names)
 	for _, name := range names {
-		if first {
-			first = false
-		} else {
-			sb.WriteByte(',')
-			sb.WriteByte('\n')
-		}
 		value, _ := ctx.GetFuncInfo(name)
-		sb.WriteString(strings.Repeat("\t", indent+1))
-		sb.WriteString(name)
-		//sb.WriteString("=")
 		if formatter, ok := value.(Formatter); ok {
-			sb.WriteString(formatter.ToString(0))
+			(*dict)[name] = formatter.ToString(0)
 		} else {
-			sb.WriteString(fmt.Sprintf("%v", value))
+			(*dict)[name] = fmt.Sprintf("%v", value)
 		}
 	}
-	sb.WriteString("\n}\n")
+	return dict
 }
 
-func (ctx *SimpleStore) ToString(opt FmtOpt) string {
-	var sb strings.Builder
-	varsCtxToBuilder(&sb, ctx, 0)
-	funcsCtxToBuilder(&sb, ctx, 0)
-	return sb.String()
+func (ctx *SimpleStore) ToDict() (dict *DictType) {
+	dict = MakeDict()
+	(*dict)["variables"] = ctx.varsToDict(MakeDict())
+	(*dict)["functions"] = ctx.funcsToDict(MakeDict())
+	return
 }
 
 func (ctx *SimpleStore) GetVar(varName string) (v any, exists bool) {
@@ -103,6 +104,11 @@ func (ctx *SimpleStore) GetVar(varName string) (v any, exists bool) {
 	return
 }
 
+func (ctx *SimpleStore) GetLast() (v any) {
+	v = ctx.varStore["last"]
+	return
+}
+
 func (ctx *SimpleStore) UnsafeSetVar(varName string, value any) {
 	// fmt.Printf("[%p] setVar(%v, %v)\n", ctx, varName, value)
 	ctx.varStore[varName] = value
@@ -131,6 +137,14 @@ func (ctx *SimpleStore) EnumVars(acceptor func(name string) (accept bool)) (varN
 	return
 }
 
+func (ctx *SimpleStore) VarCount() int {
+	return len(ctx.varStore)
+}
+
+func (ctx *SimpleStore) DeleteVar(varName string) {
+	delete(ctx.varStore, varName)
+}
+
 func (ctx *SimpleStore) GetFuncInfo(name string) (info ExprFunc, exists bool) {
 	info, exists = ctx.funcStore[name]
 	return
@@ -140,10 +154,11 @@ func (ctx *SimpleStore) RegisterFuncInfo(info ExprFunc) {
 	ctx.funcStore[info.Name()], _ = info.(*funcInfo)
 }
 
-func (ctx *SimpleStore) RegisterFunc(name string, functor Functor, returnType string, params []ExprFuncParam) (err error) {
+func (ctx *SimpleStore) RegisterFunc(name string, functor Functor, returnType string, params []ExprFuncParam)  (exprFunc ExprFunc, err error) {
 	var info *funcInfo
 	if info, err = newFuncInfo(name, functor, returnType, params); err == nil {
 		ctx.funcStore[name] = info
+		exprFunc = info
 	}
 	return
 }
@@ -162,10 +177,18 @@ func (ctx *SimpleStore) EnumFuncs(acceptor func(name string) (accept bool)) (fun
 	return
 }
 
-func (ctx *SimpleStore) Call(name string, args []any) (result any, err error) {
-	if info, exists := ctx.funcStore[name]; exists {
-		functor := info.functor
-		result, err = functor.Invoke(ctx, name, args)
+func (ctx *SimpleStore) FuncCount() int {
+	return len(ctx.funcStore)
+}
+
+func (ctx *SimpleStore) DeleteFunc(funcName string) {
+	delete(ctx.funcStore, funcName)
+}
+
+func (ctx *SimpleStore) Call(name string, args map[string]any) (result any, err error) {
+	if info, exists := GetLocalFuncInfo(ctx, name); exists {
+		functor := info.Functor()
+		result, err = functor.InvokeNamed(ctx, name, args)
 	} else {
 		err = fmt.Errorf("unknown function %s()", name)
 	}

simple-var-store.go.bak

@@ -1,126 +0,0 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
-// All rights reserved.
-
-// simple-var-store.go
-package expr
-
-import (
-	"fmt"
-	"strings"
-)
-
-type SimpleVarStore struct {
-	varStore map[string]any
-}
-
-func NewSimpleVarStore() *SimpleVarStore {
-	return &SimpleVarStore{
-		varStore: make(map[string]any),
-	}
-}
-
-func (ctx *SimpleVarStore) cloneVars() (vars map[string]any) {
-	return CloneFilteredMap(ctx.varStore, func(name string) bool { return name[0] != '@' })
-}
-
-func (ctx *SimpleVarStore) Clone() (clone ExprContext) {
-	// fmt.Println("*** Cloning context ***")
-	clone = &SimpleVarStore{
-		varStore: ctx.cloneVars(),
-	}
-	return clone
-}
-
-func (ctx *SimpleVarStore) GetVar(varName string) (v any, exists bool) {
-	v, exists = ctx.varStore[varName]
-	return
-}
-
-func (ctx *SimpleVarStore) UnsafeSetVar(varName string, value any) {
-	// fmt.Printf("[%p] setVar(%v, %v)\n", ctx, varName, value)
-	ctx.varStore[varName] = value
-}
-
-func (ctx *SimpleVarStore) SetVar(varName string, value any) {
-	// fmt.Printf("[%p] SetVar(%v, %v)\n", ctx, varName, value)
-	if allowedValue, ok := fromGenericAny(value); ok {
-		ctx.varStore[varName] = allowedValue
-	} else {
-		panic(fmt.Errorf("unsupported type %T of value %v", value, value))
-	}
-}
-
-func (ctx *SimpleVarStore) EnumVars(acceptor func(name string) (accept bool)) (varNames []string) {
-	varNames = make([]string, 0)
-	for name := range ctx.varStore {
-		if acceptor != nil {
-			if acceptor(name) {
-				varNames = append(varNames, name)
-			}
-		} else {
-			varNames = append(varNames, name)
-		}
-	}
-	return
-}
-
-func (ctx *SimpleVarStore) GetFuncInfo(name string) (f ExprFunc, exists bool) {
-	return
-}
-
-func (ctx *SimpleVarStore) Call(name string, args []any) (result any, err error) {
-	return
-}
-
-// func (ctx *SimpleVarStore) RegisterFunc(name string, functor Functor, minArgs, maxArgs int) {
-// }
-func (ctx *SimpleVarStore) RegisterFuncInfo(info ExprFunc) {
-}
-func (ctx *SimpleVarStore) RegisterFunc2(name string, f Functor, returnType string, param []ExprFuncParam) error {
-	return nil
-}
-
-func (ctx *SimpleVarStore) EnumFuncs(acceptor func(name string) (accept bool)) (funcNames []string) {
-	return
-}
-
-func varsCtxToBuilder(sb *strings.Builder, ctx ExprContext, indent int) {
-	sb.WriteString("vars: {\n")
-	first := true
-	for _, name := range ctx.EnumVars(func(name string) bool { return name[0] != '_' }) {
-		if first {
-			first = false
-		} else {
-			sb.WriteByte(',')
-			sb.WriteByte('\n')
-		}
-
-		value, _ := ctx.GetVar(name)
-		sb.WriteString(strings.Repeat("\t", indent+1))
-		sb.WriteString(name)
-		sb.WriteString(": ")
-		if f, ok := value.(Formatter); ok {
-			sb.WriteString(f.ToString(0))
-		} else if _, ok = value.(Functor); ok {
-			sb.WriteString("func(){}")
-			// } else if _, ok = value.(map[any]any); ok {
-			// 	sb.WriteString("dict{}")
-		} else {
-			sb.WriteString(fmt.Sprintf("%v", value))
-		}
-	}
-	sb.WriteString(strings.Repeat("\t", indent))
-	sb.WriteString("\n}\n")
-}
-
-func varsCtxToString(ctx ExprContext, indent int) string {
-	var sb strings.Builder
-	varsCtxToBuilder(&sb, ctx, indent)
-	return sb.String()
-}
-
-func (ctx *SimpleVarStore) ToString(opt FmtOpt) string {
-	var sb strings.Builder
-	varsCtxToBuilder(&sb, ctx, 0)
-	return sb.String()
-}

symbol-map.go

@@ -0,0 +1,202 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// Symbol.go
+package expr
+
+import (
+	"strings"
+)
+
+var symbolMap map[Symbol]symbolSpec
+
+type symbolClass int16
+
+const (
+	symClassOperator symbolClass = iota
+	symClassCommand
+	symClassIdentifier
+	symClassDelimiter
+	symClassParenthesis
+	symClassDeclaration
+	symClassValue
+	symClassOther
+)
+
+type symbolSpec struct {
+	repr   string
+	kind   symbolClass
+	opType termPosition
+}
+
+func init() {
+
+	symbolMap = map[Symbol]symbolSpec{
+		SymUnknown:            {"<unknown>", symClassOther, posLeaf},  //  -1: Unknown symbol
+		SymNone:               {"<null>", symClassOther, posLeaf},     //   0: Null value for variable of type symbol
+		SymError:              {"<error>", symClassOther, posLeaf},    //   1: Error reading from stream
+		SymEos:                {"<eos>", symClassOther, posLeaf},      //   2: End of stream
+		SymMinus:              {"-", symClassOperator, posInfix},      //   3: '-'
+		SymMinusEqual:         {"-=", symClassOperator, posInfix},     //   4: '-='
+		SymDoubleMinus:        {"--", symClassOperator, posPostfix},   //   5: '--'
+		SymPlus:               {"+", symClassOperator, posInfix},      //   6: '+'
+		SymPlusEqual:          {"+=", symClassOperator, posInfix},     //   7: '+='
+		SymDoublePlus:         {"++", symClassOperator, posPostfix},   //   8: '++'
+		SymStar:               {"*", symClassOperator, posInfix},      //   9: '*'
+		SymDoubleStar:         {"**", symClassOperator, posInfix},     //  10: '**'
+		SymSlash:              {"/", symClassOperator, posInfix},      //  11: '/'
+		SymBackSlash:          {"\\", symClassOperator, posLeaf},      //  12: '\'
+		SymVertBar:            {"|", symClassOperator, posInfix},      //  13: '|'
+		SymDoubleVertBar:      {"||", symClassOperator, posInfix},     //  14: '||'
+		SymComma:              {",", symClassOperator, posInfix},      //  15: ','
+		SymColon:              {":", symClassOperator, posInfix},      //  16: ':'
+		SymSemiColon:          {";", symClassOperator, posInfix},      //  17: ';'
+		SymDot:                {".", symClassOperator, posInfix},      //  18: '.'
+		SymDotSlash:           {"./", symClassOperator, posInfix},     //  19: './'
+		SymQuote:              {"'", symClassDelimiter, posLeaf},      //  20: '\''
+		SymDoubleQuote:        {"\"", symClassDelimiter, posLeaf},     //  21: '"'
+		SymBackTick:           {"`", symClassDelimiter, posLeaf},      //  22: '`'
+		SymExclamation:        {"!", symClassOperator, posPostfix},    //  23: '!'
+		SymQuestion:           {"?", symClassOperator, posInfix},      //  24: '?'
+		SymAmpersand:          {"&", symClassOperator, posInfix},      //  25: '&'
+		SymDoubleAmpersand:    {"&&", symClassOperator, posInfix},     //  26: '&&'
+		SymPercent:            {"%", symClassOperator, posInfix},      //  27: '%'
+		SymAt:                 {"@", symClassOperator, posPrefix},     //  28: '@'
+		SymUndescore:          {"_", symClassIdentifier, posLeaf},     //  29: '_'
+		SymEqual:              {"=", symClassOperator, posInfix},      //  30: '='
+		SymDoubleEqual:        {"==", symClassOperator, posInfix},     //  31: '=='
+		SymLess:               {"<", symClassOperator, posInfix},      //  32: '<'
+		SymLessOrEqual:        {"<=", symClassOperator, posInfix},     //  33: '<='
+		SymGreater:            {">", symClassOperator, posInfix},      //  34: '>'
+		SymGreaterOrEqual:     {">=", symClassOperator, posInfix},     //  35: '>='
+		SymLessGreater:        {"<>", symClassOperator, posInfix},     //  36: '<>'
+		SymNotEqual:           {"!=", symClassOperator, posInfix},     //  37: '!='
+		SymDollar:             {"$", symClassOperator, posPrefix},     //  38: '$'
+		SymHash:               {"#", symClassOperator, posPrefix},     //  39: '#'
+		SymOpenRound:          {"(", symClassParenthesis, posPrefix},  //  40: '('
+		SymClosedRound:        {")", symClassParenthesis, posPostfix}, //  41: ')'
+		SymOpenSquare:         {"[", symClassParenthesis, posPrefix},  //  42: '['
+		SymClosedSquare:       {"]", symClassParenthesis, posPostfix}, //  43: ']'
+		SymOpenBrace:          {"{", symClassParenthesis, posPrefix},  //  44: '{'
+		SymClosedBrace:        {"}", symClassParenthesis, posPostfix}, //  45: '}'
+		SymTilde:              {"~", symClassOperator, posPrefix},     //  46: '~'
+		SymDoubleQuestion:     {"??", symClassOperator, posInfix},     //  47: '??'
+		SymQuestionEqual:      {"?=", symClassOperator, posInfix},     //  48: '?='
+		SymQuestionExclam:     {"?!", symClassOperator, posInfix},     //  49: '?!'
+		SymDoubleAt:           {"@@", symClassCommand, posLeaf},       //  50: '@@'
+		SymDoubleColon:        {"::", symClassOperator, posInfix},     //  51: '::'
+		SymDoubleGreater:      {">>", symClassOperator, posInfix},     //  52: '>>'
+		SymDoubleLess:         {"<<", symClassOperator, posInfix},     //  53: '<<'
+		SymCaret:              {"^", symClassOperator, posInfix},      //  54: '^'
+		SymDollarRound:        {"$(", symClassOperator, posPrefix},    //  55: '$('
+		SymOpenClosedRound:    {"()", symClassOperator, posPostfix},   //  56: '()'
+		SymDoubleDollar:       {"$$", symClassCommand, posLeaf},       //  57: '$$'
+		SymDoubleDot:          {"..", symClassOperator, posInfix},     //  58: '..'
+		SymTripleDot:          {"...", symClassOperator, posPostfix},  //  59: '...'
+		SymStarEqual:          {"*=", symClassOperator, posInfix},     //  60: '*='
+		SymSlashEqual:         {"/=", symClassOperator, posInfix},     //  61: '/='
+		SymPercEqual:          {"%=", symClassOperator, posInfix},     //  62: '%='
+		SymDoubleLessEqual:    {"<<=", symClassOperator, posInfix},    //  63: '<<='
+		SymDoubleGreaterEqual: {">>=", symClassOperator, posInfix},    //  64: '>>='
+		SymAmpersandEqual:     {"&=", symClassOperator, posInfix},     //  65: '&='
+		SymVertBarEqual:       {"|=", symClassOperator, posInfix},     //  65: '|='
+		SymCaretEqual:         {"^=", symClassOperator, posInfix},     //  66: '^='
+		SymPlusGreater:        {"+>", symClassOperator, posInfix},     //  67: '+>'
+		SymLessPlus:           {"<+", symClassOperator, posInfix},     //  68: '<+'
+		SymPreInc:             {"++", symClassOperator, posPrefix},    //    : '++'
+		SymPreDec:             {"--", symClassOperator, posPrefix},    //    : '--'
+		// SymChangeSign
+		// SymUnchangeSign
+		// SymIdentifier
+		// SymBool
+		// SymInteger
+		// SymVariable
+		// SymFloat
+		// SymFraction
+		// SymString
+		// SymIterator
+		// SymOr:  "or",
+		// SymAnd: "and",
+		// SymNot: "not",
+		// SymComment
+		// SymFuncCall
+		// SymFuncDef
+		// SymList
+		// SymDict
+		// SymIndex
+		// SymExpression
+		// SymSelector     // <selector> ::= <expr> "?" <selector-case> {":" <selector-case>} ["::" <default-selector-case>]
+		// SymSelectorCase // <selector-case> ::= [<list>] "{" <multi-expr> "}"
+		// // SymOpenComment                       //   0: '/*'
+		// // SymClosedComment                     //   0: '*/'
+		// // SymOneLineComment                    //   0: '//'
+		// keywordBase
+		SymKwAnd:     {"and", symClassOperator, posInfix},
+		SymKwNot:     {"not", symClassOperator, posInfix},
+		SymKwOr:      {"or", symClassOperator, posInfix},
+		SymKwBut:     {"but", symClassOperator, posInfix},
+		SymKwMap:     {"map", symClassOperator, posInfix},
+		SymKwFilter:  {"filter", symClassOperator, posInfix},
+		SymKwDigest:  {"digest", symClassOperator, posInfix},
+		SymKwJoin:    {"join", symClassOperator, posInfix},
+		SymKwFunc:    {"func(", symClassDeclaration, posPrefix},
+		SymKwBuiltin: {"builtin", symClassOperator, posPrefix},
+		SymKwPlugin:  {"plugin", symClassOperator, posPrefix},
+		SymKwIn:      {"in", symClassOperator, posInfix},
+		SymKwInclude: {"include", symClassOperator, posPrefix},
+		SymKwNil:     {"nil", symClassValue, posLeaf},
+		SymKwUnset:   {"unset", symClassOperator, posPrefix},
+	}
+}
+
+func SymToString(sym Symbol) string {
+	if s, ok := symbolMap[sym]; ok {
+		return s.repr
+	}
+	return ""
+}
+
+func SymListToString(symList []Symbol, quote bool) string {
+	var sb strings.Builder
+	if len(symList) == 0 {
+		sb.WriteString("<nothing>")
+	} else {
+		for _, sym := range symList {
+			if sb.Len() > 0 {
+				sb.WriteByte(',')
+				sb.WriteByte(' ')
+			}
+			if quote {
+				sb.WriteByte('`')
+			}
+			sb.WriteString(SymToString(sym))
+			if quote {
+				sb.WriteByte('`')
+			}
+		}
+	}
+	return sb.String()
+}
+
+func StringEndsWithOperator(s string) bool {
+	return endingOperator(s) != SymNone
+}
+
+func endingOperator(s string) (sym Symbol) {
+	var matchLength = 0
+	sym = SymNone
+	lower := strings.TrimRight(strings.ToLower(s), " \t")
+	for symbol, spec := range symbolMap {
+		if strings.HasSuffix(lower, spec.repr) {
+			if len(spec.repr) > matchLength {
+				matchLength = len(spec.repr)
+				if spec.kind == symClassOperator && (spec.opType == posInfix || spec.opType == posPrefix) {
+					sym = symbol
+				} else {
+					sym = SymNone
+				}
+			}
+		}
+	}
+	return
+}

symbol.go

@@ -7,68 +7,82 @@ package expr
 type Symbol int16
 
 const (
-	SymUnknown         Symbol = iota - 1 //  -1: Unknown symbol
-	SymNone                              //   0: Null value for variable of type symbol
-	SymError                             //   1: Error reading from stream
-	SymEos                               //   2: End of stream
-	SymMinus                             //   3: '-'
-	SymMinusEqual                        //   4: '-='
-	SymDoubleMinus                       //   5: '--'
-	SymPlus                              //   6: '+'
-	SymPlusEqual                         //   7: '+='
-	SymDoublePlus                        //   8: '++'
-	SymStar                              //   9: '*'
-	SymDoubleStar                        //  10: '**'
-	SymSlash                             //  11: '/'
-	SymBackSlash                         //  12: '\'
-	SymVertBar                           //  13: '|'
-	SymDoubleVertBar                     //  14: '||'
-	SymComma                             //  15: ','
-	SymColon                             //  16: ':'
-	SymSemiColon                         //  17: ';'
-	SymDot                               //  18: '.'
-	SymDotSlash                          //  19: './'
-	SymQuote                             //  20: '\''
-	SymDoubleQuote                       //  21: '"'
-	SymBackTick                          //  22: '`'
-	SymExclamation                       //  23: '!'
-	SymQuestion                          //  24: '?'
-	SymAmpersand                         //  25: '&'
-	SymDoubleAmpersand                   //  26: '&&'
-	SymPercent                           //  27: '%'
-	SymAt                                //  28: '@'
-	SymUndescore                         //  29: '_'
-	SymEqual                             //  30: '='
-	SymDoubleEqual                       //  31: '=='
-	SymLess                              //  32: '<'
-	SymLessOrEqual                       //  33: '<='
-	SymGreater                           //  34: '>'
-	SymGreaterOrEqual                    //  35: '>='
-	SymLessGreater                       //  36: '<>'
-	SymNotEqual                          //  37: '!='
-	SymDollar                            //  38: '$'
-	SymHash                              //  39: '#'
-	SymOpenRound                         //  40: '('
-	SymClosedRound                       //  41: ')'
-	SymOpenSquare                        //  42: '['
-	SymClosedSquare                      //  43: ']'
-	SymOpenBrace                         //  44: '{'
-	SymClosedBrace                       //  45: '}'
-	SymTilde                             //  46: '~'
-	SymDoubleQuestion                    //  47: '??'
-	SymQuestionEqual                     //  48: '?='
-	SymDoubleAt                          //  49: '@@'
-	SymDoubleColon                       //  50: '::'
-	SymInsert                            //  51: '>>'
-	SymAppend                            //  52: '<<'
-	SymCaret                             //  53: '^'
-	SymDollarRound                       //  54: '$('
-	SymOpenClosedRound                   //  55: '()'
-	SymDoubleDollar                      //  56: '$$'
-	SymDoubleDot                         //  57: '..'
-	SymTripleDot                         //  58: '...'
+	SymUnknown            Symbol = iota - 1 //  -1: Unknown symbol
+	SymNone                                 //   0: Null value for variable of type symbol
+	SymError                                //   1: Error reading from stream
+	SymEos                                  //   2: End of stream
+	SymMinus                                //   3: '-'
+	SymMinusEqual                           //   4: '-='
+	SymDoubleMinus                          //   5: '--'
+	SymPlus                                 //   6: '+'
+	SymPlusEqual                            //   7: '+='
+	SymDoublePlus                           //   8: '++'
+	SymStar                                 //   9: '*'
+	SymDoubleStar                           //  10: '**'
+	SymSlash                                //  11: '/'
+	SymBackSlash                            //  12: '\'
+	SymVertBar                              //  13: '|'
+	SymDoubleVertBar                        //  14: '||'
+	SymComma                                //  15: ','
+	SymColon                                //  16: ':'
+	SymSemiColon                            //  17: ';'
+	SymDot                                  //  18: '.'
+	SymDotSlash                             //  19: './'
+	SymQuote                                //  20: '\''
+	SymDoubleQuote                          //  21: '"'
+	SymBackTick                             //  22: '`'
+	SymExclamation                          //  23: '!'
+	SymQuestion                             //  24: '?'
+	SymAmpersand                            //  25: '&'
+	SymDoubleAmpersand                      //  26: '&&'
+	SymPercent                              //  27: '%'
+	SymAt                                   //  28: '@'
+	SymUndescore                            //  29: '_'
+	SymEqual                                //  30: '='
+	SymDoubleEqual                          //  31: '=='
+	SymLess                                 //  32: '<'
+	SymLessOrEqual                          //  33: '<='
+	SymGreater                              //  34: '>'
+	SymGreaterOrEqual                       //  35: '>='
+	SymLessGreater                          //  36: '<>'
+	SymNotEqual                             //  37: '!='
+	SymDollar                               //  38: '$'
+	SymHash                                 //  39: '#'
+	SymOpenRound                            //  40: '('
+	SymClosedRound                          //  41: ')'
+	SymOpenSquare                           //  42: '['
+	SymClosedSquare                         //  43: ']'
+	SymOpenBrace                            //  44: '{'
+	SymClosedBrace                          //  45: '}'
+	SymTilde                                //  46: '~'
+	SymDoubleQuestion                       //  47: '??'
+	SymQuestionEqual                        //  48: '?='
+	SymQuestionExclam                       //  49: '?!'
+	SymDoubleAt                             //  50: '@@'
+	SymDoubleColon                          //  51: '::'
+	SymDoubleGreater                        //  52: '>>'
+	SymDoubleLess                           //  53: '<<'
+	SymCaret                                //  54: '^'
+	SymDollarRound                          //  55: '$('
+	SymOpenClosedRound                      //  56: '()'
+	SymDoubleDollar                         //  57: '$$'
+	SymDoubleDot                            //  58: '..'
+	SymTripleDot                            //  59: '...'
+	SymStarEqual                            //  60: '*='
+	SymSlashEqual                           //  61: '/='
+	SymPercEqual                            //  62: '%='
+	SymDoubleLessEqual                      //  63: '<<='
+	SymDoubleGreaterEqual                   //  64: '>>='
+	SymAmpersandEqual                       //  65: '&='
+	SymVertBarEqual                         //  65: '|='
+	SymCaretEqual                           //  66: '^='
+	SymPlusGreater                          //  67: '+>'
+	SymLessPlus                             //  68: '<+'
 	SymChangeSign
 	SymUnchangeSign
+	SymDereference
+	SymPreInc
+	SymPreDec
 	SymIdentifier
 	SymBool
 	SymInteger
@@ -86,6 +100,7 @@ const (
 	SymList
 	SymDict
 	SymIndex
+	SymRange // [index : index]
 	SymExpression
 	SymSelector     // <selector> ::= <expr> "?" <selector-case> {":" <selector-case>} ["::" <default-selector-case>]
 	SymSelectorCase // <selector-case> ::= [<list>] "{" <multi-expr> "}"
@@ -101,9 +116,15 @@ const (
 	SymKwBut
 	SymKwFunc
 	SymKwBuiltin
+	SymKwPlugin
 	SymKwIn
 	SymKwInclude
+	SymKwMap
+	SymKwFilter
+	SymKwDigest
+	SymKwJoin
 	SymKwNil
+	SymKwUnset
 )
 
 var keywords map[string]Symbol
@@ -113,12 +134,18 @@ func init() {
 	keywords = map[string]Symbol{
 		"AND":     SymKwAnd,
 		"BUILTIN": SymKwBuiltin,
+		"PLUGIN":  SymKwPlugin,
 		"BUT":     SymKwBut,
 		"FUNC":    SymKwFunc,
 		"IN":      SymKwIn,
 		"INCLUDE": SymKwInclude,
+		"MAP":     SymKwMap,
+		"FILTER":  SymKwFilter,
 		"NOT":     SymKwNot,
 		"OR":      SymKwOr,
 		"NIL":     SymKwNil,
+		"UNSET":   SymKwUnset,
+		"DIGEST":  SymKwDigest,
+		"JOIN":    SymKwJoin,
 	}
 }