solved a number of problems highlighted by the syntax analyzer

Also, fixed and improved some parsing sections concerning collection indeces and ranges

ast.go

@@ -8,11 +8,6 @@ import (
 	"strings"
 )
 
-type Expr interface {
-	Eval(ctx ExprContext) (result any, err error)
-	String() string
-}
-
 //-------- ast
 
 type ast struct {
@@ -24,65 +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 {
@@ -97,20 +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) {
-	self.Finish()
+func (expr *ast) Eval(ctx ExprContext) (result any, err error) {
+	expr.Finish()
 
-	if self.root != nil {
+	if expr.root != nil {
 		// initDefaultVars(ctx)
-		if self.forest != nil {
-			for _, root := range self.forest {
+		if expr.forest != nil {
+			for _, root := range expr.forest {
 				if result, err = root.compute(ctx); err == nil {
 					ctx.UnsafeSetVar(ControlLastResult, result)
 				} else {
@@ -120,7 +119,7 @@ func (self *ast) Eval(ctx ExprContext) (result any, err error) {
 			}
 		}
 		if err == nil {
-			if result, err = self.root.compute(ctx); err == nil {
+			if result, err = expr.root.compute(ctx); err == nil {
 				ctx.UnsafeSetVar(ControlLastResult, result)
 			}
 		}

bind-expr-functions.go

@@ -12,47 +12,48 @@ type exprFunctor struct {
 	defCtx ExprContext
 }
 
-// func newExprFunctor(e Expr, params []string, ctx ExprContext) *exprFunctor {
-// 	return &exprFunctor{expr: e, params: params, defCtx: ctx}
-// }
-
-func newExprFunctor(e Expr, params []ExprFuncParam, ctx ExprContext) *exprFunctor {
-	return &exprFunctor{expr: e, params: params, defCtx: ctx}
+func (functor *exprFunctor) GetParams() (params []ExprFuncParam) {
+	return functor.params
 }
 
-func (functor *exprFunctor) Invoke(ctx ExprContext, name string, args []any) (result any, err error) {
-	if functor.defCtx != nil {
-		ctx.Merge(functor.defCtx)
+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}
+}
 
-	for i, p := range functor.params {
-		if i < len(args) {
-			arg := args[i]
+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 {
-				// ctx.RegisterFunc(p, functor, 0, -1)
 				paramSpecs := funcArg.GetParams()
 				ctx.RegisterFunc(p.Name(), funcArg, TypeAny, paramSpecs)
 			} else {
 				ctx.UnsafeSetVar(p.Name(), arg)
 			}
 		} else {
-			ctx.UnsafeSetVar(p.Name(), nil)
+			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
 }
-
-// func CallExprFunction(parentCtx ExprContext, funcName string, params ...any) (v any, err error) {
-// 	ctx := cloneContext(parentCtx)
-// 	ctx.SetParent(parentCtx)
-
-// 	if err == nil {
-// 		if err = checkFunctionCall(ctx, funcName, &params); err == nil {
-// 			if v, err = ctx.Call(funcName, params); err == nil {
-// 				exportObjects(parentCtx, ctx)
-// 			}
-// 		}
-// 	}
-// 	return
-// }

bind-go-functions.go

@@ -14,6 +14,10 @@ func NewGolangFunctor(f FuncTemplate) *golangFunctor {
 	return &golangFunctor{f: f}
 }
 
-func (functor *golangFunctor) Invoke(ctx ExprContext, name string, args []any) (result any, err error) {
+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

@@ -5,57 +5,63 @@
 package expr
 
 import (
+	"fmt"
 	"math"
 	"strconv"
+	"strings"
 )
 
-func isNilFunc(ctx ExprContext, name string, args []any) (result any, err error) {
-	result = args[0] == nil
+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 []any) (result any, err error) {
-	result = IsInteger(args[0])
+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 []any) (result any, err error) {
-	result = IsFloat(args[0])
+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 []any) (result any, err error) {
-	result = IsBool(args[0])
+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 []any) (result any, err error) {
-	result = IsString(args[0])
+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 []any) (result any, err error) {
-	result = IsFract(args[0])
+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 []any) (result any, err error) {
-	result = IsRational(args[0])
+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 []any) (result any, err error) {
-	result = IsList(args[0])
+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 []any) (result any, err error) {
-	result = IsDict(args[0])
+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 []any) (result any, err error) {
-	switch v := args[0].(type) {
+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:
@@ -72,8 +78,8 @@ func boolFunc(ctx ExprContext, name string, args []any) (result any, err error)
 	return
 }
 
-func intFunc(ctx ExprContext, name string, args []any) (result any, err error) {
-	switch v := args[0].(type) {
+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:
@@ -95,8 +101,8 @@ func intFunc(ctx ExprContext, name string, args []any) (result any, err error) {
 	return
 }
 
-func decFunc(ctx ExprContext, name string, args []any) (result any, err error) {
-	switch v := args[0].(type) {
+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:
@@ -120,18 +126,44 @@ func decFunc(ctx ExprContext, name string, args []any) (result any, err error) {
 	return
 }
 
-func fractFunc(ctx ExprContext, name string, args []any) (result any, err error) {
-	switch v := args[0].(type) {
+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
-		if len(args) > 1 {
+
 		var ok bool
-			if den, ok = args[1].(int64); !ok {
-				err = ErrExpectedGot(name, "integer", args[1])
+		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)
 		}
@@ -153,10 +185,34 @@ func fractFunc(ctx ExprContext, name string, args []any) (result any, err error)
 	return
 }
 
-func iteratorFunc(ctx ExprContext, name string, args []any) (result any, err error) {
+// 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
 }
 
+//// import
+
 func ImportBuiltinsFuncs(ctx ExprContext) {
 	anyParams := []ExprFuncParam{
 		NewFuncParam(ParamValue),
@@ -175,9 +231,14 @@ func ImportBuiltinsFuncs(ctx ExprContext) {
 	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("denominator", PfDefault, 1),
+		NewFuncParamFlagDef(ParamDenominator, PfDefault, int64(1)),
+	})
+
+	ctx.RegisterFunc("eval", NewGolangFunctor(evalFunc), TypeAny, []ExprFuncParam{
+		NewFuncParam(ParamSource),
 	})
 }
 

builtin-fmt.go

@@ -4,21 +4,42 @@
 // builtin-fmt.go
 package expr
 
-import "fmt"
+import (
+	"fmt"
+	"io"
+	"os"
+)
 
-func printFunc(ctx ExprContext, name string, args []any) (result any, err error) {
-	var n int
-	if n, err = fmt.Print(args...); err == nil {
-		result = int64(n)
+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 []any) (result any, err error) {
-	var n int
-	if n, err = fmt.Println(args...); err == nil {
-		result = int64(n)
+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
 }
 

builtin-import.go

@@ -9,18 +9,21 @@ import (
 	"os"
 )
 
-func importFunc(ctx ExprContext, name string, args []any) (result any, err error) {
+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 []any) (result any, err error) {
+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 []any) (result any, err error) {
+func importGeneral(ctx ExprContext, name string, args map[string]any) (result any, err error) {
 	dirList := buildSearchDirList("sources", ENV_EXPR_SOURCE_PATH)
-	result, err = doImport(ctx, name, dirList, NewArrayIterator(args))
+	if v, exists := args[ParamFilepath]; exists && v != nil {
+		argv := v.([]any)
+		result, err = doImport(ctx, name, dirList, NewArrayIterator(argv))
+	}
 	return
 }
 
@@ -41,7 +44,7 @@ func doImport(ctx ExprContext, name string, dirList []string, it Iterator) (resu
 			var expr *ast
 			scanner := NewScanner(file, DefaultTranslations())
 			parser := NewParser()
-			if expr, err = parser.parseGeneral(scanner, true, true); err == nil {
+			if expr, err = parser.parseGeneral(scanner, allowMultiExpr|allowVarRef, SymEos); err == nil {
 				result, err = expr.Eval(ctx)
 			}
 			if err != nil {

builtin-iterator.go

@@ -0,0 +1,104 @@
+// 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 op, ok = args[iterParamOperator].(Functor); !ok && args[iterParamOperator] != 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 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 {
+		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

@@ -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
 				}
 			}
@@ -161,17 +162,18 @@ 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{
+	ctx.RegisterFunc("add", NewGolangFunctor(addFunc), TypeNumber, []ExprFuncParam{
 		NewFuncParamFlagDef(ParamValue, PfDefault|PfRepeat, int64(0)),
 	})
 
-	ctx.RegisterFunc("mul", &golangFunctor{f: mulFunc}, TypeNumber, []ExprFuncParam{
+	ctx.RegisterFunc("mul", NewGolangFunctor(mulFunc), TypeNumber, []ExprFuncParam{
 		NewFuncParamFlagDef(ParamValue, PfDefault|PfRepeat, int64(1)),
 	})
 }

builtin-os-file.go

@@ -11,6 +11,10 @@ import (
 	"os"
 )
 
+const (
+	osLimitCh = "limitCh"
+)
+
 type osHandle interface {
 	getFile() *os.File
 }
@@ -61,8 +65,8 @@ func errInvalidFileHandle(funcName string, v any) error {
 	}
 }
 
-func createFileFunc(ctx ExprContext, name string, args []any) (result any, err error) {
-	if filePath, ok := args[0].(string); ok && len(filePath) > 0 {
+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)}
@@ -73,8 +77,8 @@ func createFileFunc(ctx ExprContext, name string, args []any) (result any, err e
 	return
 }
 
-func openFileFunc(ctx ExprContext, name string, args []any) (result any, err error) {
-	if filePath, ok := args[0].(string); ok && len(filePath) > 0 {
+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)}
@@ -85,8 +89,8 @@ func openFileFunc(ctx ExprContext, name string, args []any) (result any, err err
 	return
 }
 
-func appendFileFunc(ctx ExprContext, name string, args []any) (result any, err error) {
-	if filePath, ok := args[0].(string); ok && len(filePath) > 0 {
+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)}
@@ -97,13 +101,13 @@ func appendFileFunc(ctx ExprContext, name string, args []any) (result any, err e
 	return
 }
 
-func closeFileFunc(ctx ExprContext, name string, args []any) (result any, err error) {
+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[0].(osHandle); !ok {
-		invalidFileHandle = args[0]
+	if handle, ok = args[ParamHandle].(osHandle); !ok {
+		invalidFileHandle = args[ParamHandle]
 	}
 
 	if handle != nil {
@@ -124,18 +128,21 @@ func closeFileFunc(ctx ExprContext, name string, args []any) (result any, err er
 	return
 }
 
-func fileWriteTextFunc(ctx ExprContext, name string, args []any) (result any, err error) {
+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[0].(osHandle); !ok {
-		invalidFileHandle = args[0]
+	if handle, ok = args[ParamHandle].(osHandle); !ok {
+		invalidFileHandle = args[ParamHandle]
 	}
 
 	if handle != nil {
 		if w, ok := handle.(*osWriter); ok {
-			result, err = fmt.Fprint(w.writer, args[1:]...)
+			if v, exists := args[ParamItem]; exists {
+				argv := v.([]any)
+				result, err = fmt.Fprint(w.writer, argv...)
+			}
 		} else {
 			invalidFileHandle = handle
 		}
@@ -147,21 +154,21 @@ func fileWriteTextFunc(ctx ExprContext, name string, args []any) (result any, er
 	return
 }
 
-func fileReadTextFunc(ctx ExprContext, name string, args []any) (result any, err error) {
+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[0].(osHandle); !ok || args[0] == nil {
-		invalidFileHandle = args[0]
+	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[1].(string); ok && len(s) > 0 {
+			if s, ok := args[osLimitCh].(string); ok && len(s) > 0 {
 				limit = s[0]
 			}
 
@@ -187,14 +194,14 @@ func fileReadTextFunc(ctx ExprContext, name string, args []any) (result any, err
 	return
 }
 
-func fileReadTextAllFunc(ctx ExprContext, name string, args []any) (result any, err error) {
+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[0].(osHandle); !ok || args[0] == nil {
-		invalidFileHandle = args[0]
+	if handle, ok = args[ParamHandle].(osHandle); !ok || args[ParamHandle] == nil {
+		invalidFileHandle = args[ParamHandle]
 	}
 
 	if handle != nil {
@@ -214,34 +221,34 @@ func fileReadTextAllFunc(ctx ExprContext, name string, args []any) (result any,
 }
 
 func ImportOsFuncs(ctx ExprContext) {
-	ctx.RegisterFunc("fileOpen", NewGolangFunctor(openFileFunc), TypeHandle, []ExprFuncParam{
+	ctx.RegisterFunc("fileOpen", NewGolangFunctor(openFileFunc), TypeFileHandle, []ExprFuncParam{
 		NewFuncParam(ParamFilepath),
 	})
 
-	ctx.RegisterFunc("fileAppend", NewGolangFunctor(appendFileFunc), TypeHandle, []ExprFuncParam{
+	ctx.RegisterFunc("fileAppend", NewGolangFunctor(appendFileFunc), TypeFileHandle, []ExprFuncParam{
 		NewFuncParam(ParamFilepath),
 	})
 
-	ctx.RegisterFunc("fileCreate", NewGolangFunctor(createFileFunc), TypeHandle, []ExprFuncParam{
+	ctx.RegisterFunc("fileCreate", NewGolangFunctor(createFileFunc), TypeFileHandle, []ExprFuncParam{
 		NewFuncParam(ParamFilepath),
 	})
 
 	ctx.RegisterFunc("fileClose", NewGolangFunctor(closeFileFunc), TypeBoolean, []ExprFuncParam{
-		NewFuncParam(TypeHandle),
+		NewFuncParam(ParamHandle),
 	})
 
 	ctx.RegisterFunc("fileWriteText", NewGolangFunctor(fileWriteTextFunc), TypeInt, []ExprFuncParam{
-		NewFuncParam(TypeHandle),
-		NewFuncParamFlagDef(TypeItem, PfDefault|PfRepeat, ""),
+		NewFuncParam(ParamHandle),
+		NewFuncParamFlagDef(ParamItem, PfDefault|PfRepeat, ""),
 	})
 
 	ctx.RegisterFunc("fileReadText", NewGolangFunctor(fileReadTextFunc), TypeString, []ExprFuncParam{
-		NewFuncParam(TypeHandle),
-		NewFuncParamFlagDef("limitCh", PfDefault, "\n"),
+		NewFuncParam(ParamHandle),
+		NewFuncParamFlagDef(osLimitCh, PfDefault, "\n"),
 	})
 
 	ctx.RegisterFunc("fileReadTextAll", NewGolangFunctor(fileReadTextAllFunc), TypeString, []ExprFuncParam{
-		NewFuncParam(TypeHandle),
+		NewFuncParam(ParamHandle),
 	})
 }
 

builtin-string.go

@@ -10,6 +10,10 @@ import (
 	"strings"
 )
 
+const (
+	strParamOther = "other"
+)
+
 // --- Start of function definitions
 func doJoinStr(funcName string, sep string, it Iterator) (result any, err error) {
 	var sb strings.Builder
@@ -25,52 +29,52 @@ func doJoinStr(funcName string, sep string, it Iterator) (result any, err error)
 			return
 		}
 	}
-	if err == nil || err == io.EOF {
+	if 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 {
+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 := args[1].(Iterator); ok {
+				} 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, ParamParts, args[1])
+					err = ErrInvalidParameterValue(name, ParamItem, v)
 				}
 			} else {
-			result, err = doJoinStr(name, sep, NewArrayIterator(args[1:]))
+				result, err = doJoinStr(name, sep, NewArrayIterator(argv))
+			}
 		}
 	} else {
-		err = ErrWrongParamType(name, ParamSeparator, TypeString, args[0])
+		err = ErrWrongParamType(name, ParamSeparator, TypeString, args[ParamSeparator])
 	}
 	return
 }
 
-func subStrFunc(ctx ExprContext, name string, args []any) (result any, err error) {
+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[0].(string); !ok {
-		return nil, ErrWrongParamType(name, ParamSource, TypeString, args[0])
+	if source, ok = args[ParamSource].(string); !ok {
+		return nil, ErrWrongParamType(name, ParamSource, TypeString, args[ParamSource])
 	}
 
-	if start, err = ToInt(args[1], name+"()"); err != nil {
+	if start, err = ToGoInt(args[ParamStart], name+"()"); err != nil {
 		return
 	}
 
-	if count, err = ToInt(args[2], name+"()"); err != nil {
+	if count, err = ToGoInt(args[ParamCount], name+"()"); err != nil {
 		return
 	}
 
@@ -86,81 +90,99 @@ func subStrFunc(ctx ExprContext, name string, args []any) (result any, err error
 	return
 }
 
-func trimStrFunc(ctx ExprContext, name string, args []any) (result any, err error) {
+func trimStrFunc(ctx ExprContext, name string, args map[string]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])
+	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 []any) (result any, err error) {
-	var source string
+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[0].(string); !ok {
-		return result, ErrWrongParamType(name, ParamSource, TypeString, args[0])
+	if source, ok = args[ParamSource].(string); !ok {
+		return result, ErrWrongParamType(name, ParamSource, TypeString, args[ParamSource])
 	}
-	for i, targetSpec := range args[1:] {
+
+	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 %T, expected string", i+1, targetSpec)
+				err = fmt.Errorf("target item nr %d is %s, string expected", i+1, TypeName(targetSpec))
 				break
 			}
 		}
+	}
 	return
 }
 
-func endsWithStrFunc(ctx ExprContext, name string, args []any) (result any, err error) {
-	var source string
+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[0].(string); !ok {
-		return result, ErrWrongParamType(name, ParamSource, TypeString, args[0])
+	if source, ok = args[ParamSource].(string); !ok {
+		return result, ErrWrongParamType(name, ParamSource, TypeString, args[ParamSource])
 	}
-	for i, targetSpec := range args[1:] {
+
+	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 %T, expected string", i+1, targetSpec)
+				err = fmt.Errorf("target item nr %d is %s, string expected", i+1, TypeName(targetSpec))
 				break
 			}
 		}
+	}
 	return
 }
 
-func splitStrFunc(ctx ExprContext, name string, args []any) (result any, err error) {
+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[0].(string); !ok {
-		return result, ErrWrongParamType(name, ParamSource, TypeString, args[0])
+	if source, ok = args[ParamSource].(string); !ok {
+		return result, ErrWrongParamType(name, ParamSource, TypeString, args[ParamSource])
 	}
 
-	if sep, ok = args[1].(string); !ok {
-		return nil, fmt.Errorf("separator param must be string, got %T (%v)", args[1], args[1])
+	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[2].(int64); ok { // TODO replace type assertion with toInt()
+	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 %T (%v)", args[2], args[2])
+		return nil, fmt.Errorf("part count must be integer, got %s (%v)", TypeName(args[ParamCount]), args[ParamCount])
 	}
 
 	if count > 0 {
@@ -206,13 +228,13 @@ func ImportStringFuncs(ctx ExprContext) {
 	ctx.RegisterFunc("strStartsWith", NewGolangFunctor(startsWithStrFunc), TypeBoolean, []ExprFuncParam{
 		NewFuncParam(ParamSource),
 		NewFuncParam(ParamPrefix),
-		NewFuncParamFlag("other "+ParamPrefix, PfRepeat),
+		NewFuncParamFlag(strParamOther, PfRepeat),
 	})
 
 	ctx.RegisterFunc("strEndsWith", NewGolangFunctor(endsWithStrFunc), TypeBoolean, []ExprFuncParam{
 		NewFuncParam(ParamSource),
 		NewFuncParam(ParamSuffix),
-		NewFuncParamFlag("other "+ParamSuffix, PfRepeat),
+		NewFuncParamFlag(strParamOther, PfRepeat),
 	})
 }
 

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

@@ -6,8 +6,13 @@ package expr
 
 import (
 	"fmt"
+	"strings"
 )
 
+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("%s(): too few params -- expected %d or more, got %d", funcName, minArgs, argCount)
@@ -17,8 +22,8 @@ func ErrTooFewParams(funcName string, minArgs, maxArgs, argCount int) (err error
 	return
 }
 
-func ErrTooMuchParams(funcName string, maxArgs, argCount int) (err error) {
-	err = fmt.Errorf("%s(): too much params -- expected %d, got %d", funcName, 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
 }
 
@@ -36,20 +41,47 @@ func ErrFuncDivisionByZero(funcName string) error {
 	return fmt.Errorf("%s(): division by zero", funcName)
 }
 
-func ErrDivisionByZero() error {
-	return fmt.Errorf("division by zero")
-}
+// func ErrDivisionByZero() error {
+// 	return fmt.Errorf("division by zero")
+// }
 
 // --- Parameter errors
 
-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 undefArticle(s string) (article string) {
+	if len(s) > 0 && strings.Contains("aeiou", s[0:1]) {
+		article = "an"
+	} else {
+		article = "a"
+	}
+	return
+}
+
+func prependUndefArticle(s string) (result string) {
+	return undefArticle(s) + " " + s
+}
+
 func ErrWrongParamType(funcName, paramName, paramType string, paramValue any) error {
-	return fmt.Errorf("%s(): the %q parameter must be a %s, got a %s (%v)", funcName, paramName, paramType, TypeName(paramValue), paramValue)
+	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)
+}
+
+// --- Operator errors
+
+func ErrLeftOperandMustBeVariable(leftTerm, opTerm *term) error {
+	return leftTerm.Errorf("left operand of %q must be a variable", opTerm.source())
 }

common-params.go

@@ -5,8 +5,10 @@
 package expr
 
 const (
+	ParamArgs      = "args"
 	ParamCount     = "count"
 	ParamItem      = "item"
+	ParamIndex     = "index"
 	ParamParts     = "parts"
 	ParamSeparator = "separator"
 	ParamSource    = "source"
@@ -19,6 +21,9 @@ const (
 	ParamEllipsis  = "..."
 	ParamFilepath  = "filepath"
 	ParamDirpath   = "dirpath"
+	ParamHandle    = "handle"
+	ParamResource  = "resource"
+	ParamIterator  = "iterator"
 )
 
 // to be moved in its own source file

common-type-names.go

@@ -6,15 +6,17 @@ package expr
 
 const (
 	TypeAny           = "any"
+	TypeNil           = "nil"
 	TypeBoolean       = "boolean"
 	TypeFloat         = "float"
 	TypeFraction      = "fraction"
-	TypeHandle   = "handle"
+	TypeFileHandle    = "file-handle"
 	TypeInt           = "integer"
 	TypeItem          = "item"
 	TypeNumber        = "number"
 	TypePair          = "pair"
 	TypeString        = "string"
+	TypeDict          = "dict"
 	TypeListOf        = "list-of-"
 	TypeListOfStrings = "list-of-strings"
 )

context-helpers.go

@@ -29,7 +29,7 @@ func exportObjects(destCtx, sourceCtx ExprContext) {
 	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)

context.go

@@ -1,53 +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
-	GetParams() []ExprFuncParam
-}
-
-// ---- 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
-	ReturnType() string
-}
-
-// ----Expression Context
-type ExprContext interface {
-	Clone() ExprContext
-	Merge(ctx 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)
-	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

@@ -11,6 +11,7 @@ const (
 	ControlBoolShortcut  = "_bool_shortcut"
 	ControlSearchPath    = "_search_path"
 	ControlParentContext = "_parent_context"
+	ControlStdout        = "_stdout"
 )
 
 // Other control variables
@@ -23,11 +24,17 @@ const (
 	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) {
 	if _, exists := ctx.GetVar(ControlPreset); exists {
 		return
 	}
-	ctx.SetVar(ControlPreset, true)
-	ctx.SetVar(ControlBoolShortcut, true)
-	ctx.SetVar(ControlSearchPath, init_search_path)
+	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
+	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
-	currentFunc 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,
+		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{})
+		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
-			}
+		actualParams := bindActualParams(dc.resetFunc, []any{dc.resource})
+		_, err = dc.resetFunc.InvokeNamed(ctx, ResetName, actualParams)
 		exportObjects(dc.ctx, ctx)
-		} else {
-			err = errInvalidDataSource()
 	}
-	} else {
-		err = errNoOperation(resetName)
-	}
-	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
+		actualParams := bindActualParams(dc.cleanFunc, []any{dc.resource})
+		_, err = dc.cleanFunc.InvokeNamed(ctx, CleanName, actualParams)
 		exportObjects(dc.ctx, ctx)
-		} else {
-			err = errInvalidDataSource()
 	}
-	} else {
-		err = errors.New("no 'clean' function defined in the data-source")
-	}
-	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 {
+func (dc *dataCursor) checkFilter(filter Functor, item any) (accepted bool, err error) {
+	var v any
+	var ok bool
 	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++
+
+	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-type.go

@@ -18,7 +18,22 @@ func MakeDict() (dict *DictType) {
 	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 wi a call to NewDict()
 	var d DictType
 	if dictAny != nil {
 		d = make(DictType, len(dictAny))

doc/Expr.adoc

@@ -9,6 +9,7 @@ Expressions calculator
 :icons: font
 :icon-set: fi
 :numbered:
+:data-uri:
 //:table-caption: Tabella
 //:figure-caption: Diagramma
 :docinfo1:
@@ -19,10 +20,12 @@ Expressions calculator
 :rouge-style: gruvbox
 // :rouge-style: colorful
 //:rouge-style: monokay
+// Work around to manage double-column in back-tick quotes
+:2c: ::
 
 toc::[]
 
-#TODO: Work in progress (last update on 2024/06/17, 16:31 a.m.)#
+#TODO: Work in progress (last update on 2024/06/21, 05:40 a.m.)#
 
 == Expr
 _Expr_ is a GO package capable of analysing, interpreting and calculating expressions.
@@ -55,11 +58,13 @@ The expression context is analogous to the stack-frame of other programming lang
 
 Function contexts are created by cloning the calling context. More details on this topic are given later in this document.
 
-_Expr_ creates and keeps a inner _global context_ where it stores imported functions, either from builtin or plugin modules. To perform calculations, the calling program must provide its own context; this is the _main context_. All calculations take place in this context. As mentioned eralier, when a function is called, a new context is created by cloning the calling context. The createt context can be called _function context_.
+_Expr_ creates and keeps a inner _global context_ where it stores imported functions, either from builtin or plugin modules. To perform calculations, the user program must provide its own context; this is the _main context_. All calculations take place in this context. As mentioned eralier, when a function is called, a new context is created by cloning the calling context. The created context can be called _function context_.
 
 Imported functions are registerd in the _global context_. When an expression first calls an imported function, that function is linked to the current context; this can be the _main context_ or a _function context_.
 
 === `dev-expr` test tool
+Before we begin to describe the syntax of _Expr_, it is worth introducing _dev-expr_ because it will be used to show many examples of expressions.
+
 `dev-expr` is a simple program that can be used to evaluate expressions interactively. As its name suggests, it was created for testing purpose.  In fact, in additon to the automatic verification test suite based on the Go test framework, `dev-expr` provided an important aid for quickly testing of new features during their development.
 
 `dev-expr` can work as a _REPL_, _**R**ead-**E**xecute-**P**rint-**L**oop_, or it can process expression acquired from files or standard input.
@@ -74,20 +79,20 @@ Here are some examples of execution.
 # Type 'exit' or Ctrl+D to quit the program.
 
 [user]$ ./dev-expr
-dev-expr -- Expressions calculator v1.10.0(build 14),2024/06/17 (celestino.amoroso@portale-stac.it)
-	Based on the Expr package v0.19.0
+dev-expr -- Expressions calculator v1.12.0(build 1),2024/09/14 (celestino.amoroso@portale-stac.it)
+	Based on the Expr package v0.26.0
 	Type help to get the list of available commands
 	See also https://git.portale-stac.it/go-pkg/expr/src/branch/main/README.adoc
 >>> help
 --- REPL commands:
-      source -- Load a file as input
-         tty -- Enable/Disable ansi output <1>
         base -- Set the integer output base: 2, 8, 10, or 16
         exit -- Exit the program
         help -- Show command list
           ml -- Enable/Disable multi-line output
         mods -- List builtin modules
       output -- Enable/Disable printing expression results. Options 'on', 'off', 'status'
+      source -- Load a file as input
+         tty -- Enable/Disable ansi output <1>
 
 --- Command line options:
     -b <builtin>       Import builtin modules.
@@ -122,22 +127,22 @@ dev-expr -- Expressions calculator v1.10.0(build 14),2024/06/17 (celestino.amoro
 9.5
 >>> 0xFD + 0b1 + 0o1 <1>
 255
->>> 1|2 + 2|3 <2>
-7|6
+>>> 1:2 + 2:3 <2>
+7:6
 >>> ml <3>
->>> 1|2 + 2|3
+>>> 1:2 + 2:3
 7
 -
 6
->>> 4+2 but 5|2+0.5 <4>
+>>> 4+2 but 5:2+0.5 <4>
 3
->>> 4+2; 5|2+0.5 <5>
+>>> 4+2; 5:2+0.5 <5>
 3
 >>>
 ----
 
 <1> Number bases: 0x = _hexadecimal_, 0o = _octal_, 0b = _binary_.
-<2> Fractions: _numerator_ | _denominator_.
+<2> Fractions: _numerator_ : _denominator_.
 <3> Activate multi-line output of fractions.
 <4> But operator, see <<_but_operator>>.
 <5> Multi-expression: the same result of the previous single expression but this it is obtained with two separated calculations.
@@ -150,9 +155,9 @@ _Expr_ supports three type of numbers:
 
 . [blue]#Integers#
 . [blue]#Floats#
-. [blue]#Factions#
+. [blue]#Fractions#
 
-In mixed operations involving integers, fractions and floats, automatic type promotion to the largest type take place.
+In mixed operations involving integers, fractions and floats, automatic type promotion to the largest type is performed.
 
 ==== Integers
 __Expr__'s integers are a subset of the integer set. Internally they are stored as Golang _int64_ values.
@@ -178,11 +183,11 @@ Value range: *-9223372036854775808* to *9223372036854775807*
 [cols="^1,^2,6,4"]
 |===
 | Symbol    | Operation     | Description               | Examples
-| [blue]`+` | _sum_         | Add two values            | [blue]`-1 + 2` -> 1
-| [blue]`-` | _subtraction_ | Subtract the right value from the left one | [blue]`3 - 1` -> 2
-| [blue]`*` | _product_     | Multiply two values       | [blue]`-1 * 2` -> -2
-| [blue]`/` | _Division_    | Divide the left value by the right one^(*)^ | [blue]`-10 / 2` -> 5
-| [blue]`%` | _Modulo_      | Remainder of the integer division | [blue]`5 % 2` -> 1
+| [blue]`+` | _Sum_         | Add two values            | [blue]`-1 + 2` -> _1_
+| [blue]`-` | _Subtraction_ | Subtract the right value from the left one | [blue]`3 - 1` -> _2_
+| [blue]`*` | _Product_     | Multiply two values       | [blue]`-1 * 2` -> _-2_
+| [blue]`/` | _Integer division_    | Divide the left value by the right one^(*)^ | [blue]`-11 / 2` -> _-5_
+| [blue]`%` | _Modulo_      | Remainder of the integer division | [blue]`5 % 2` -> _1_
 |===
 
 ^(*)^ See also the _float division_ [blue]`./` below.
@@ -201,15 +206,20 @@ _dec-seq_ = _see-integer-literal-syntax_
 
 .Examples
 `>>>` [blue]`1.0` +
-[green]`1` +
+[green]`1`
+
 `>>>` [blue]`0.123` +
-[green]`0.123` +
+[green]`0.123`
+
 `>>>` [blue]`4.5e+3` +
-[green]`4500` +
+[green]`4500`
+
 `>>>` [blue]`4.5E-33` +
-[green]`4.5e-33` +
+[green]`4.5e-33`
+
 `>>>` [blue]`4.5E-3` +
-[green]`0.0045` +
+[green]`0.0045`
+
 `>>>` [blue]`4.5E10` +
 [green]`4.5e+10`
 
@@ -218,19 +228,19 @@ _dec-seq_ = _see-integer-literal-syntax_
 [cols="^1,^2,6,4"]
 |===
 | Symbol    | Operation     | Description               | Examples
-| [blue]`+` | _sum_         | Add two values            | [blue]`4 + 0.5` -> 4.5
-| [blue]`-` | _subtraction_ | Subtract the right value from the left one | [blue]`4 - 0.5` -> 3.5
-| [blue]`*` | _product_     | Multiply two values       | [blue]`4 * 0.5` -> 2.0
-| [blue]`/` | _Division_    | Divide the left value by the right one | [blue]`1.0 / 2` -> 0.5
-| [blue]`./`| _Float division_ | Force float division   | [blue]`-1 ./ 2` -> -0.5
+| [blue]`+` | _Sum_         | Add two values            | [blue]`4 + 0.5` -> 4.5
+| [blue]`-` | _Subtraction_ | Subtract the right value from the left one | [blue]`4 - 0.5` -> 3.5
+| [blue]`*` | _Product_     | Multiply two values       | [blue]`4 * 0.5` -> 2.0
+| [blue]`/` | _Float division_    | Divide the left value by the right one | [blue]`1.0 / 2` -> 0.5
+| [blue]`./`| _Forced float division_ | Force float division   | [blue]`-1 ./ 2` -> -0.5
 |===
 
 ==== Fractions
-_Expr_ also supports fractions. Fraction literals are made with two integers separated by a vertical bar `|`.
+_Expr_ also supports fractions. Fraction literals are made with two integers separated by a colon character `:`.
 
 .Fraction literal syntax
 ====
-*_fraction_* = [__sign__] (_num-den-spec_ | _float-spec_) +
+*_fraction_* = [__sign__] (_num-den-spec_ "**:**" _float-spec_) +
 _sign_ = "**+**" | "**-**" +
 _num-den-spec_ = _digit-seq_ "**|**" _digit-seq_ +
 _float-spec_ = _dec-seq_ "**.**" [_dec-seq_] "**(**" _dec-seq_ "**)**" +
@@ -239,36 +249,44 @@ _digit-seq_ = _see-integer-literal-syntax_
 ====
 
 .Examples
-// [source,go]
-// ----
-`>>>` [blue]`1 | 2` +
-[green]`1|2` +
-`>>>` [blue]`4|6`  [gray]_// Fractions are always reduced to their lowest terms_ +
-[green]`2|3` +
-`>>>` [blue]`1|2 + 2|3` +
-[green]`7|6` +
-`>>>` [blue]`1|2 * 2|3` +
-[green]`1|3` +
-`>>>` [blue]`1|2 / 1|3` +
-[green]`3|2` +
-`>>>` [blue]`1|2 ./ 1|3` [gray]_// Force decimal division_ +
-[green]`1.5` +
-`>>>` [blue]`-1|2` +
-[green]`-1|2` +
-`>>>` [blue]`1|-2` [gray]_// Invalid sign specification_ +
-[red]_Eval Error: [1:3] infix operator "|" requires two non-nil operands, got 1_ +
-`>>>` [blue]`1|(-2)` +
-[green]`-1|2`
-// ----
+`>>>` [blue]`1 : 2` +
+[green]`1:2`
+
+`>>>` [blue]`4:6`  [gray]_// Fractions are always reduced to their lowest terms_ +
+[green]`2:3`
+
+`>>>` [blue]`1:2 + 2:3` +
+[green]`7:6`
+
+`>>>` [blue]`1:2 * 2:3` +
+[green]`1:3`
+
+`>>>` [blue]`1:2 / 1:3` +
+[green]`3:2`
+
+`>>>` [blue]`1:2 ./ 1:3` [gray]_// Force decimal division_ +
+[green]`1.5`
+
+`>>>` [blue]`-1:2` +
+[green]`-1:2`
+
+`>>>` [blue]`1:-2` [gray]_// Invalid sign specification_ +
+[red]_Eval Error: [1:3] infix operator ":" requires two non-nil operands, got 1_
+
+`>>>` [blue]`1:(-2)` +
+[green]`-1:2`
+
 
 Fractions can be used together with integers and floats in expressions.
 
 .Examples
-`>>>` [blue]`1|2 + 5` +
-[green]`11|2` +
-`>>>` [blue]`4 - 1|2` +
-[green]`7|2` +
-`>>>` [blue]`1.0 + 1|2` +
+`>>>` [blue]`1:2 + 5` +
+[green]`11:2`
+
+`>>>` [blue]`4 - 1:2` +
+[green]`7:2`
+
+`>>>` [blue]`1.0 + 1:2` +
 [green]`1.5`
 
 
@@ -278,16 +296,19 @@ Strings are character sequences enclosed between two double quote [blue]`"`.
 
 .Examples
 `>>>` [blue]`"I'm a string"` +
-[green]`I'm a string` +
+[green]`I'm a string`
+
 `>>>` [blue]`"123abc?!"` +
-[green]`123abc?!` +
+[green]`123abc?!`
+
 `>>>` [blue]`"123\nabc"` +
 [green]`123` +
-[green]`abc` +
+[green]`abc`
+
 `>>>` [blue]`"123\tabc"` +
 [green]`123{nbsp}{nbsp}{nbsp}{nbsp}abc`
 
-Some arithmetic operators can also be used with strings.
+Some arithmetic operators also apply to strings.
 
 .String operators
 [cols="^1,^2,6,4"]
@@ -300,29 +321,34 @@ Some arithmetic operators can also be used with strings.
 | [blue]`*` | _repeat_ | Make _n_ copy of a string  | [blue]`"one" * 2` -> _"oneone"_
 |===
 
-The items of strings can be accessed using the square `[]` operator.
+The charanters in a string can be accessed using the square `[]` operator.
 
 .Item access syntax
 ====
-_item_ = _string-expr_ "**[**" _integer-expr_ "**]**" 
+*_item_* = _string-expr_ "**[**" _integer-expr_ "**]**"
 ====
 
-.Sub string syntax
+.Sub-string syntax
 ====
-_sub-string_ = _string-expr_ "**[**" _integer-expr_ "**:**" _integer-expr_ "**]**" 
+*_sub-string_* = _string-expr_ "**[**" _integer-expr_ "**:**" _integer-expr_ "**]**"
 ====
 
 .String examples
 `>>>` [blue]`s="abcd"`  [gray]_// assign the string to variable s_ +
-[green]`"abcd"` +
+[green]`"abcd"`
+
 `>>>` [blue]`s[1]`      [gray]_// char at position 1 (starting from 0)_ +
-[green]`"b"` +
-`>>>` [blue]`s.[-1]`    [gray]_// char at position -1, the rightmost one_ +
-[green]`"d"` +
-`>>>` [blue]`\#s`       [gray]_// number of chars_ +
-[gren]`4` +
+[green]`"b"`
+
+`>>>` [blue]`s[-1]`    [gray]_// char at position -1, the rightmost one_ +
+[green]`"d"`
+
+`>>>` [blue]`#s`       [gray]_// number of chars_ +
+[gren]`4`
+
 `>>>` [blue]`#"abc"`    [gray]_// number of chars_ +
-[green]`3` +
+[green]`3`
+
 `>>>` [blue]`s[1:3]`    [gray]_// chars from position 1 to position 3 excluded_ +
 [grean]`"bc"`
 
@@ -343,9 +369,9 @@ Boolean data type has two values only: [blue]_true_ and [blue]_false_. Relationa
 | [blue]`\<=` | _Less or Equal_ | True if the left value is less than or equal to the right one | [blue]`5 \<= 2` -> _false_ +
 [blue]`"b" \<= "b"` -> _true_
 | [blue]`>` | _Greater_ | True if the left value is greater than the right one | [blue]`5 > 2` -> _true_ +
-[blue]`"a" < "b"` -> _false_
+[blue]`"a" > "b"` -> _false_
 | [blue]`>=` | _Greater or Equal_ | True if the left value is greater than or equal to the right one | [blue]`5 >= 2` -> _true_ +
-[blue]`"b" \<= "b"` -> _true_
+[blue]`"b" >= "b"` -> _true_
 |===
 
 ^(*)^ See also the  [blue]`in` operator in the _list_ and _dictionary_ sections.
@@ -362,20 +388,22 @@ Boolean data type has two values only: [blue]_true_ and [blue]_false_. Relationa
 | [blue]`AND` / [blue]`&&` | _And_ | True if both left and right values are true  | [blue]`false && true` -> _false_ +
 [blue]`"a" < "b" AND NOT (2 < 1)` -> _true_
 
-| [blue]`OR` / [blue]`\|\|` | _Or_ | True if at least one of the left and right values integers true| [blue]`false or true` -> _true_ +
+| [blue]`OR` / [blue]`\|\|` | _Or_ | True if at least one of the left and right values integers is true| [blue]`false or true` -> _true_ +
 [blue]`"a" == "b" OR (2 == 1)` -> _false_
 |===
 
 [CAUTION]
 ====
-Currently, boolean operations are evaluated using _short cut evaluation_. This means that, if the left expression of the [blue]`and` and [blue]`or` operators is sufficient to establish the result of the whole operation, the right expression would not evaluated at all.
-
+Currently, boolean operations are evaluated using _short cut evaluation_. This means that, if the left expression of the [blue]`and` and [blue]`or` operators is sufficient to establish the result of the whole operation, the right expression would not be evaluated at all.
 .Example
 [source,go]
 ----
 2 > (a=1) or (a=8) > 0; a // <1>
 ----
 <1> This multi-expression returns _1_ because in the first expression the left value of [blue]`or` is _true_ and as a conseguence its right value is not computed. Therefore the _a_ variable only receives the integer _1_.
+
+
+TIP: `dev-expr` provides the _ctrl()_ function that allows to change this behaviour.
 ====
 
 === Lists
@@ -385,18 +413,22 @@ _Expr_ supports list of mixed-type values, also specified by normal expressions.
 ====
 *_list_* = _empty-list_ | _non-empty-list_ +
 _empty-list_ = "**[]**" +
-_non-empty-list_ = "**[**" _any-value_ {"**,**" _any-value} "**]**" +
+_non-empty-list_ = "**[**" _any-value_ {"**,**" _any-value_} "**]**" +
 ====
 
 .Examples
 `>>>` [blue]`[1,2,3]`                     [gray]_// List of integers_ +
-[green]`[1, 2, 3]` +
+[green]`[1, 2, 3]`
+
 `>>>` [blue]`["one", "two", "three"]`     [gray]_// List of strings_ +
-[green]`["one", "two", "three"]` +
+[green]`["one", "two", "three"]`
+
 `>>>` [blue]`["one", 2, false, 4.1]`      [gray]_// List of mixed-types_ +
-[green]`["one", 2, false, 4.1]` +
+[green]`["one", 2, false, 4.1]`
+
 `>>>` [blue]`["one"+1, 2.0*(9-2)]`        [gray]_// List of expressions_ +
-[green]`["one1", 14]` +
+[green]`["one1", 14]`
+
 `>>>` [blue]`[ [1,"one"], [2,"two"]]`     [gray]_// List of lists_ +
 [green]`[[1, "one"], [2, "two"]]`
 
@@ -409,40 +441,81 @@ _non-empty-list_ = "**[**" _any-value_ {"**,**" _any-value} "**]**" +
 | [blue]`-` | _Difference_ | Left list without elements in the right list  | [blue]`[1,2,3] - [2]` -> _[1,3]_
 | [blue]`>>` | _Front insertion_ | Insert an item in front | [blue]`0 >> [1,2]` -> _[0,1,2]_
 | [blue]`<<` | _Back insertion_ | Insert an item at end | [blue]`[1,2] << 3` -> _[1,2,3]_
-| [blue]`.` | _List item_ | Item at given position | [blue]`[1,2.3].1` -> _2_
+| [blue]`[]` | _Item at index_ | Item at given position | [blue]`[1,2,3][1]` -> _2_
 | [blue]`in` | _Item in list_ | True if item is in list | [blue]`2 in [1,2,3]` -> _true_ +
 [blue]`6 in [1,2,3]` -> _false_
+| [blue]`#` | _Size_ | Number of items in a list | [blue]`#[1,2,3]` -> _3_
 |===
 
-The items of array can be accessed using the dot `.` operator.
+Array's items can be accessed using the index `[]` operator.
 
 .Item access syntax
 ====
-_item_ = _list-expr_ "**.**" _integer-expr_
+*_item_* = _list-expr_ "**[**" _integer-expr_ "**]**"
 ====
 
-.Items of list
-`>>>` [blue]`[1,2,3].1` +
-[green]`2` +
-`>>>` [blue]`list=[1,2,3]; list.1` +
-[green]`2` +
-`>>>` [blue]`["one","two","three"].1` +
-[green]`two` +
-`>>>` [blue]`list=["one","two","three"]; list.(2-1)` +
-[green]`two` +
-`>>>` [blue]`list.(-1)` +
-[green]`three` +
-`>>>` [blue]`list.(10)` +
-[red]`Eval Error: [1:9] index 10 out of bounds` +
-`>>>` [blue]`#list` +
-[green]`3` +
-`>>>` [blue]`index=2; ["a", "b", "c", "d"].index` +
+.Sub-array (or slice of array) syntax
+====
+*_slice_* = _string-expr_ "**[**" _integer-expr_ "**:**" _integer-expr_ "**]**"
+====
+
+.Examples: Getting items from lists
+`>>>` [blue]`[1,2,3][1]` +
+[green]`2`
+
+`>>>` [blue]`index=2; ["a", "b", "c", "d"][index]` +
 [green]`c`
 
+`>>>` [blue]`["a", "b", "c", "d"][2:]` +
+[green]`["c", "d"]`
+
+`>>>` [blue]`list=[1,2,3]; list[1]` +
+[green]`2`
+
+`>>>` [blue]`["one","two","three"][1]` +
+[green]`two`
+
+`>>>` [blue]`list=["one","two","three"]; list[2-1]` +
+[green]`two`
+
+`>>>` [blue]`list[1]="six"; list` +
+[green]`["one", "six", "three"]`
+
+`>>>` [blue]`list[-1]` +
+[green]`three`
+
+`>>>` [blue]`list[10]` +
+[red]`Eval Error: [1:9] index 10 out of bounds`
+
+.Example: Number of elements in a list
+`>>>` [blue]`#list` +
+[green]`3`
+
+.Examples: Element insertion
+`>>>` [blue]`"first" >> list` +
+[green]`["first", "one", "six", "three"]`
+
+`>>>` [blue]`list << "last"` +
+[green]`["first", "one", "six", "three", "last"]`
+
+.Examples: Element in list
+`>>>` [blue]`"six" in list` +
+[green]`true`
+
+`>>>` [blue]`"ten" in list` +
+[green]`false`
+
+.Examples: Concatenation and filtering
+`>>>` [blue]`[1,2,3] + ["one", "two", "three"]` +
+[green]`[1, 2, 3, "one", "two", "three"]`
+
+`>>>` [blue]`[1,2,3,4] - [2,4]` +
+[green]`[1, 3]`
+
 
 
 === Dictionaries
-The _dictionary_, or _dict_, data-type is set of pairs _key/value_. It is also known as _map_ or _associative array_.
+The _dictionary_, or _dict_, data-type represents sets  of pairs _key/value_. It is also known as _map_ or _associative array_.
 
 Dictionary literals are sequences of pairs separated by comma [blue]`,` enclosed between brace brackets.
 
@@ -450,17 +523,14 @@ Dictionary literals are sequences of pairs separated by comma [blue]`,` enclosed
 ====
 *_dict_* = _empty-dict_ | _non-empty-dict_ +
 _empty-dict_ = "**{}**" +
-_non-empty-dict_ = "**{**" _key-scalar_ "**:**" _any-value_ {"**,**" _key-scalar_ "**:**" _any-value} "**}**" +
+_non-empty-dict_ = "**{**" _key-scalar_ "**:**" _any-value_ {"**,**" _key-scalar_ "**:**" _any-value_} "**}**" +
 ====
 
-.Examples
-`>>>` [blue]`{1:"one", 2:"two"}` +
-[green]`{1: "one", 2: "two"}` +
-`>>>` [blue]`{"one":1, "two": 2}` +
-[green]`{"one": 1, "two": 2}` +
-`>>>` [blue]`{"sum":1+2+3, "prod":1*2*3}` +
-[green]`{"sum": 6, "prod": 6}`
 
+.Item access syntax
+====
+*_item_* = _dict-expr_ "**[**" _key-expr_ "**]**"
+====
 
 .Dict operators
 [cols="^2,^2,4,5"]
@@ -468,11 +538,31 @@ _non-empty-dict_ = "**{**" _key-scalar_ "**:**" _any-value_ {"**,**" _key-scalar
 | Symbol    | Operation     | Description               | Examples
 
 | [blue]`+` | _Join_ | Joins two dicts | [blue]`{1:"one"}+{6:"six"}` -> _{1: "one", 6: "six"}_
-| [blue]`.` | _Dict item value_ | Item value of given key | [blue]`{"one":1, "two":2}."two"` -> _2_
+| [blue]`[]` | _Dict item value_ | Item value of given key | [blue]`{"one":1, "two":2}["two"]` -> _2_
 | [blue]`in` | _Key in dict_ | True if key is in dict | [blue]`"one" in {"one":1, "two":2}` -> _true_ +
 [blue]`"six" in {"one":1, "two":2}` -> _false_
+| [blue]`#` | _Size_ | Number of items in a dict | [blue]`#{1:"a",2:"b",3:"c"}` -> _3_
 |===
 
+.Examples
+`>>>` [blue]`{1:"one", 2:"two"}` +
+[green]`{1: "one", 2: "two"}`
+
+`>>>` [blue]`{"one":1, "two": 2}` +
+[green]`{"one": 1, "two": 2}`
+
+`>>>` [blue]`{"sum":1+2+3, "prod":1*2*3}` +
+[green]`{"sum": 6, "prod": 6}`
+
+`>>>` [blue]`{"one":1, "two":2}["two"]` +
+[green]`2`
+
+`>>>` [blue]`d={"one":1, "two":2}; d["six"]=6; d` +
+[green]`{"two": 2, "one": 1, "six": 6}`
+
+`>>>` [blue]`#d` +
+[green]`3`
+
 
 == Variables
 _Expr_, like most programming languages, supports variables. A variable is an identifier with an assigned value. Variables are stored in _contexts_.
@@ -488,17 +578,23 @@ NOTE: The assign operator [blue]`=` returns the value assigned to the variable.
 
 .Examples
 `>>>` [blue]`a=1` +
-[green]`1` +
+[green]`1`
+
 `>>>` [blue]`a_b=1+2` +
-[green]`1+2` +
+[green]`3`
+
 `>>>` [blue]`a_b` +
-[green]`3` +
-`>>>` [blue]`x = 5.2 * (9-3)`  [gray]_// The assigned value has the approximation error typical of the float data-type_ +
-[green]`31.200000000000003` +
+[green]`3`
+
+`>>>` [blue]`x = 5.2 * (9-3)`  [gray]_// The assigned value here has the typical approximation error of the float data-type_ +
+[green]`31.200000000000003`
+
 `>>>` [blue]`x = 1; y = 2*x` +
-[green]`2` +
-`>>>` [blue]`_a=2` +
-[red]`Parse Error: [1:2] unexpected token "_"` +
+[green]`2`
+
+`>>>` [blue]`\_a=2` +
+[red]`Parse Error: [1:2] unexpected token "_"`
+
 `>>>` [blue]`1=2` +
 [red]`Parse Error: assign operator ("=") must be preceded by a variable`
 
@@ -508,7 +604,12 @@ NOTE: The assign operator [blue]`=` returns the value assigned to the variable.
 === [blue]`;` operator
 The semicolon operator [blue]`;` is an infixed pseudo-operator. It evaluates the left expression first and then the right expression. The value of the latter is the final result.
 
-An expression that contains [blue]`;` is called a _multi-expression_ and each component expressione is called a _sub-expression_.
+.Multi-expression syntax
+====
+*_multi-expression_* = _expression_ {"**;**" _expression_ }
+====
+
+An expression that contains [blue]`;` is called a _multi-expression_ and each component expression is called a _sub-expression_.
 
 IMPORTANT: Technically [blue]`;` is not treated as a real operator. It acts as a separator in lists of expressions.
 
@@ -518,7 +619,7 @@ TIP: [blue]`;` can be used to set some variables before the final calculation.
 `>>>` [blue]`a=1; b=2; c=3; a+b+c` +
 [green]`6`
 
-The value of each sub-expression is stored in the automatica variable _last_.
+The value of each sub-expression is stored in the automatic variable _last_.
 
 .Example
 `>>>` [blue]`2+3; b=last+10; last` +
@@ -529,9 +630,10 @@ The value of each sub-expression is stored in the automatica variable _last_.
 [blue]`but` is an infixed operator. Its operands can be expressions of any type. It evaluates the left expression first, then the right expression. The value of the right expression is the final result.
 
 .Examples
-[blue]`5 but 2` +
-[green]`2` +
-[blue]`x=2*3 but x-1` +
+`>>>` [blue]`5 but 2` +
+[green]`2`
+
+`>>>` [blue]`x=2*3 but x-1` +
 [green]`5`.
 
 [blue]`but` behavior is very similar to [blue]`;`. The only difference is that [blue]`;` is not a true operator and can't be used inside parenthesis [blue]`(` and [blue]`)`.
@@ -539,17 +641,21 @@ The value of each sub-expression is stored in the automatica variable _last_.
 === Assignment operator [blue]`=`
 The assignment operator [blue]`=` is used to define variables or to change their value in the evaluation context (see _ExprContext_).
 
-The value on the left side of [blue]`=` must be an identifier. The value on the right side can be any expression and it becomes the result of the assignment operation.
+The value on the left side of [blue]`=` must be a variable identifier or an expression that evalutes to a variable. The value on the right side can be any expression and it becomes the result of the assignment operation.
 
-.Example
-`>>>` [blue]`a=15+1`
+.Examples
+`>>>` [blue]`a=15+1` +
 [green]`16`
 
+`>>>` [blue]`L=[1,2,3]; L[1]=5; L` +
+[green]`[1, 5, 3]`
+
 
 === Selector operator [blue]`? : ::`
 The _selector operator_ is very similar to the _switch/case/default_ statement available in many programming languages.
 
 .Selector literal Syntax
+====
 _selector-operator_ = _select-expression_ "*?*" _selector-case_ { "*:*" _selector-case_ } ["*::*" _default-multi-expression_] +
 _selector-case_ = [_match-list_] _case-value_ +
 _match-list_ = "*[*" _item_ {"*,*" _items_} "*]*" +
@@ -557,6 +663,7 @@ _item_ = _expression_ +
 _case-multi-expression_ = "*{*" _multi-expression_ "*}*" +
 _multi-expression_ = _expression_ { "*;*" _expression_ } +
 _default-multi-expression_ = _multi-expression_
+====
 
 In other words, the selector operator evaluates the _select-expression_ on the left-hand side of the [blue]`?` symbol; it then compares the result obtained with the values listed in the __match-list__'s, from left to right. If the comparision finds a match with a value in a _match-list_, the associated _case-multi-expression_ is evaluted, and its result will be the final result of the selection operation.
 
@@ -566,40 +673,62 @@ The [blue]`:` symbol (colon) is the separator of the selector-cases. Note that i
 
 .Examples
 `>>>` [blue]`1 ? {"a"} : {"b"}` +
-[green]`b` +
-`>>>` [blue]`10 ? {"a"} : {"b"} :: {"c"}` +
-[green]`c' +
-[green]`>>>` [blue]`10 ? {"a"} :[true, 2+8] {"b"} :: {"c"}` +
-[green]`b` +
-`>>>` [blue]`10 ? {"a"} :[true, 2+8] {"b"} ::[10] {"c"}` +
-[red]`Parse Error: [1:34] case list in default clause` +
-[green]`>>>` [blue]`10 ? {"a"} :[10] {x="b" but x} :: {"c"}` +
-[green]`b` +
-`>>>` [blue]`10 ? {"a"} :[10] {x="b"; x} :: {"c"}` +
-[green]`b` +
+[green]`b`
+
+`>>>` [blue]`10 ? {"a"} : {"b"} {2c} {"c"}` +
+[green]`c`
+
+`>>>` [blue]`10 ? {"a"} :[true, 2+8] {"b"} {2c} {"c"}` +
+[green]`b`
+
+`>>>` [blue]`10 ? {"a"} :[true, 2+8] {"b"} {2c} [10] {"c"}` +
+[red]`Parse Error: [1:34] case list in default clause`
+
+`>>>` [blue]`10 ? {"a"} :[10] {x="b" but x} {2c} {"c"}` +
+[green]`b`
+
+`>>>` [blue]`10 ? {"a"} :[10] {x="b"; x} {2c} {"c"}` +
+[green]`b`
+
 `>>>` [blue]`10 ? {"a"} : {"b"}` +
 [red]`Eval Error: [1:3] no case catches the value (10) of the selection expression`
 
 
-=== Variable default value [blue]`??` and [blue]`?=`
-The left operand of these two operators must be a variable. The right operator can be any expression. They return the value of the variable if this is define; otherwise they return the value of the right expression.
+=== Variable default value [blue]`??`, [blue]`?=`, and [blue]`?!`
+The left operand of first two operators, [blue]`??` and [blue]`?=`, must be a variable. The right operator can be any expression. They return the value of the variable if this is defined; otherwise they return the value of the right expression.
 
-IMPORTANT: If the left variable is defined, the right expression is not evuated at all.
+IMPORTANT: If the left variable is defined, the right expression is not evaluated at all.
 
-The [blue]`??` do not change the status of the left variable.
+The [blue]`??` operator do not change the status of the left variable.
 
 The [blue]`?=` assigns the calculated value of the right expression to the left variable.
 
+The third one, [blue]`?!`, is the alternate operator. If the variable on the left size is not defined, it returns [blue]_nil_. Otherwise it returns the result of the expressione on the right side.
+
+IMPORTANT: If the left variable is NOT defined, the right expression is not evaluated at all.
+
 .Examples
-`>>>` [blue]`var ?? (1+2)`'
-[green]`3` +
+`>>>` [blue]`var ?? (1+2)` +
+[green]`3`
+
 `>>>` [blue]`var` +
-[red]`Eval Error: undefined variable or function "var"` +
+[red]`Eval Error: undefined variable or function "var"`
+
 `>>>` [blue]`var ?= (1+2)` +
-[green]`3` +
+[green]`3`
+
 `>>>` [blue]`var` +
 [green]`3`
 
+`>>>` [blue]`x ?! 5` +
+[green]`nil`
+
+`>>>` [blue]`x=1; x ?! 5` +
+[green]`5`
+
+`>>>` [blue]`y ?! (c=5); c` +
+[red]`Eval Error: undefined variable or function "c"`
+
 NOTE: These operators have a high priority, in particular higher than the operator [blue]`=`.
 
 == Priorities of operators
@@ -610,57 +739,213 @@ The table below shows all supported operators by decreasing priorities.
 |===
 | Priority | Operators     | Position | Operation | Operands and results
 
-.2+|*ITEM*| [blue]`.` | _Infix_ | _List item_| _list_ `"."` _integer_ -> _any_
-| [blue]`.` | _Infix_ | _Dict item_ | _dict_ `"."` _any_ -> _any_
-.2+|*INC*| [blue]`++` | _Postfix_ | _Post increment_| _integer-variable_ `"++"` -> _integer_
-| [blue]`++` | _Postfix_ | _Next item_ | _iterator_ `"++"` -> _any_
-.1+|*FACT*| [blue]`!` | _Postfix_ | _Factorial_| _integer_ `"!"` -> _integer_
-.3+|*SIGN*| [blue]`+`, [blue]`-` | _Prefix_ | _Change-sign_| (`"+"`\|`"-"`) _number_ -> _number_
-| [blue]`#` | _Prefix_ | _Lenght-of_ | `"#"` _collection_ -> _integer_
-| [blue]`#` | _Prefix_ | _Size-of_ | `"#"` _iterator_ -> _integer_
-.5+|*PROD*| [blue]`*` | _Infix_ | _Product_ | _number_ `"*"` _number_ -> _number_
-| [blue]`*` | _Infix_ | _String-repeat_ | _string_ `"*"` _integer_ -> _string_
-| [blue]`/` | _Infix_ | _Division_ | _number_ `"/"` _number_ -> _number_
-| [blue]`./` | _Infix_ | _Float-division_ | __number__ `"./"` _number_ -> _float_
-| [blue]`%` | _Infix_ | _Integer-remainder_ | _integer_ `"%"` _integer_ -> _integer_
-.6+|*SUM*| [blue]`+` | _Infix_ | _Sum_ | _number_ `"+"` _number_ -> _number_
-| [blue]`+` | _Infix_ |  _String-concat_ | (_string_\|_number_) `"+"` (_string_\|_number_) -> _string_
-| [blue]`+` | _Infix_ |  _List-join_ | _list_ `"+"` _list_ -> _list_
-| [blue]`+` | _Infix_ |  _Dict-join_ | _dict_ `"+"` _dict_ -> _dict_
-| [blue]`-` | _Infix_ | _Subtraction_ | _number_ `"-"` _number_ -> _number_
-| [blue]`-` | _Infix_ | _List-difference_ | _list_ `"-"` _list_ -> _list_
-.8+|*RELATION*| [blue]`<` | _Infix_ | _less_ | _comparable_ `"<"` _comparable_ -> _boolean_
-| [blue]`\<=` | _Infix_ |  _less-equal_ | _comparable_ `"\<="` _comparable_ -> _boolean_
-| [blue]`>` | _Infix_ |  _greater_ | _comparable_ `">"` _comparable_ -> _boolean_
-| [blue]`>=` | _Infix_ |  _greater-equal_ | _comparable_ `">="` _comparable_ -> _boolean_
-| [blue]`==` | _Infix_ |  _equal_ | _comparable_ `"=="` _comparable_ -> _boolean_
-| [blue]`!=` | _Infix_ |  _not-equal_ | _comparable_ `"!="` _comparable_ -> _boolean_
-| [blue]`in` | _Infix_ |  _member-of-list_ | _any_ `"in"` _list_ -> _boolean_
-| [blue]`in` | _Infix_ |  _key-of-dict_ | _any_ `"in"` _dict_ -> _boolean_
-.1+|*NOT*| [blue]`not` | _Prefix_ | _not_ | `"not"` _boolean_ -> _boolean_
-.2+|*AND*| [blue]`and` | _Infix_ | _and_ | _boolean_ `"and"` _boolean_ -> _boolean_
-| [blue]`&&` | _Infix_ | _and_ | _boolean_ `"&&"` _boolean_ -> _boolean_
-.2+|*OR*| [blue]`or` | _Infix_ | _or_ | _boolean_ `"or"` _boolean_ -> _boolean_
-| [blue]`\|\|` | _Infix_ | _or_ | _boolean_ `"\|\|"` _boolean_ -> _boolean_
-.3+|*ASSIGN*| [blue]`=` | _Infix_ | _assignment_ | _identifier_ "=" _any_ -> _any_
-| [blue]`>>` | _Infix_ | _front-insert_ | _any_ ">>" _list_ -> _list_
-| [blue]`<<` | _Infix_ | _back-insert_ | _list_ "<<" _any_ -> _list_
- .1+|*BUT*| [blue]`but` | _Infix_ | _but_ | _any_ "but" _any_ -> _any_
+.2+|*ITEM*| [blue]`[`...`]` | _Postfix_ | _List item_| _list_ `[`  _integer_ `]` -> _any_
+| [blue]`[`...`]` | _Postfix_ | _Dict item_ | _dict_ `[` _any_ `]` -> _any_
+.2+|*INC*| [blue]`++` | _Postfix_ | _Post increment_| _integer-variable_ `++` -> _integer_
+| [blue]`++` | _Postfix_ | _Next item_ | _iterator_ `++` -> _any_
+.3+|*DEFAULT*| [blue]`??` | _Infix_ | _Default value_| _variable_ `??` _any-expr_ -> _any_
+| [blue]`?=` | _Infix_ | _Default/assign value_| _variable_ `?=` _any-expr_ -> _any_
+| [blue]`?!` | _Infix_ | _Alternate value_| _variable_ `?!` _any-expr_ -> _any_
+//.1+| *ITER*^1^| [blue]`()` | _Prefix_ | _Iterator value_ | `()` _iterator_ -> _any_
+.1+|*FACT*| [blue]`!` | _Postfix_ | _Factorial_| _integer_ `!` -> _integer_
+.3+|*SIGN*| [blue]`+`, [blue]`-` | _Prefix_ | _Change-sign_| (`+`\|`-`) _number_ -> _number_
+| [blue]`#` | _Prefix_ | _Lenght-of_ | `#` _collection_ -> _integer_
+| [blue]`#` | _Prefix_ | _Size-of_ | `#` _iterator_ -> _integer_
+.2+|*SELECT*| [blue]`? : ::` | _Multi-Infix_ | _Case-Selector_ | _any-expr_ `?` _case-list_ _case-expr_ `:` _case-list_ _case-expr_ ... `::` _default-expr_ -> _any_
+| [blue]`? : ::` | _Multi-Infix_ | _Index-Selector_ | _int-expr_ `?` _case-expr_ `:` _case-expr_ ... `::` _default-expr_ -> _any_
+.1+|*FRACT*| [blue]`:` | _Infix_ | _Fraction_ | _integer_ `:` _integer_ -> _fraction_
+.5+|*PROD*| [blue]`*` | _Infix_ | _Product_ | _number_ `*` _number_ -> _number_
+| [blue]`*` | _Infix_ | _String-repeat_ | _string_ `*` _integer_ -> _string_
+| [blue]`/` | _Infix_ | _Division_ | _number_ `/` _number_ -> _number_
+| [blue]`./` | _Infix_ | _Float-division_ | __number__ `./` _number_ -> _float_
+| [blue]`%` | _Infix_ | _Integer-remainder_ | _integer_ `%` _integer_ -> _integer_
+.6+|*SUM*| [blue]`+` | _Infix_ | _Sum_ | _number_ `+` _number_ -> _number_
+| [blue]`+` | _Infix_ |  _String-concat_ | (_string_\|_number_) `+` (_string_\|_number_) -> _string_
+| [blue]`+` | _Infix_ |  _List-join_ | _list_ `+` _list_ -> _list_
+| [blue]`+` | _Infix_ |  _Dict-join_ | _dict_ `+` _dict_ -> _dict_
+| [blue]`-` | _Infix_ | _Subtraction_ | _number_ `-` _number_ -> _number_
+| [blue]`-` | _Infix_ | _List-difference_ | _list_ `-` _list_ -> _list_
+.3+|*BINARY*| [blue]`&` | _Infix_ | _Binary And_ | _number_ `&` _number_ -> _number_
+| [blue]`\|` | _Infix_ | _Binary Or_ | _number_ `\|` _number_ -> _number_
+| [blue]`~` | _Prefix_ | _Binary Not_ | `~` _number_ -> _number_
+.8+|*RELATION*| [blue]`<` | _Infix_ | _Less_ | _comparable_ `<` _comparable_ -> _boolean_
+| [blue]`\<=` | _Infix_ |  _less-equal_ | _comparable_ `\<=` _comparable_ -> _boolean_
+| [blue]`>` | _Infix_ |  _Greater_ | _comparable_ `>` _comparable_ -> _boolean_
+| [blue]`>=` | _Infix_ |  _Greater-equal_ | _comparable_ `>=` _comparable_ -> _boolean_
+| [blue]`==` | _Infix_ |  _Equal_ | _comparable_ `==` _comparable_ -> _boolean_
+| [blue]`!=` | _Infix_ |  _Not-equal_ | _comparable_ `!=` _comparable_ -> _boolean_
+| [blue]`in` | _Infix_ |  _Member-of-list_ | _any_ `in` _list_ -> _boolean_
+| [blue]`in` | _Infix_ |  _Key-of-dict_ | _any_ `in` _dict_ -> _boolean_
+.1+|*NOT*| [blue]`not` | _Prefix_ | _Not_ | `not` _boolean_ -> _boolean_
+.2+|*AND*| [blue]`and` | _Infix_ | _And_ | _boolean_ `and` _boolean_ -> _boolean_
+| [blue]`&&` | _Infix_ | _And_ | _boolean_ `&&` _boolean_ -> _boolean_
+.2+|*OR*| [blue]`or` | _Infix_ | _Or_ | _boolean_ `or` _boolean_ -> _boolean_
+| [blue]`\|\|` | _Infix_ | _Or_ | _boolean_ `\|\|` _boolean_ -> _boolean_
+.3+|*ASSIGN*| [blue]`=` | _Infix_ | _Assignment_ | _identifier_ `=` _any_ -> _any_
+| [blue]`>>` | _Infix_ | _Front-insert_ | _any_ `>>` _list_ -> _list_
+| [blue]`<<` | _Infix_ | _Back-insert_ | _list_ `<<` _any_ -> _list_
+.1+|*BUT*| [blue]`but` | _Infix_ | _But_ | _any_ `but` _any_ -> _any_
+.1+|*RANGE*| [blue]`:` | _Infix_ | _Index-range_ | _integer_ `:` _integer_ -> _integer-pair_
 |===
 
+//^1^ Experimental
+
+
 == Functions
-Functions in _Expr_ are very similar to functions available in many programming languages. Actually, _Expr_ supports two types of function, _expr-functions_ and _go-functions_.
+Functions in _Expr_ are very similar to functions available in many programming languages. Currently, _Expr_ supports two types of function, _expr-functions_ and _go-functions_.
 
 * _expr-functions_ are defined using _Expr_'s syntax. They can be passed as arguments to other functions and can be returned from functions. Moreover, they bind themselves to the defining context, thus becoming closures.
-* _go-functions_ are regular Golang functions callable from _Expr_ expressions. They are defined in Golang source files called _modules_ and compiled within the _Expr_ package. To make Golang functions available in _Expr_ contextes, it is required to _import_ the module in which they are defined.
+* _go-functions_ are regular Golang functions callable from _Expr_ expressions. They are defined in Golang source files called _modules_ and compiled within the _Expr_ package. To make Golang functions available in _Expr_ contextes, it is required to activate the builtin module or to load the plugin module in which they are defined.
 
-In _Expr_ functions compute values in a local context (scope) that do not make effects on the calling context. This is the normal behavior. Using the reference operator [blue]`@` it is possibile to export local definition to the calling context.
+
+=== _Expr_ function definition
+A function is identified and referenced by its name. It can have zero or more parameter. _Expr_ functions also support optional parameters and passing paramters by name.
+
+.Expr's function definition syntax
+====
+*_function-definition_* = _identifier_ "**=**"  "**func(**" [_formal-param-list_] "**)**"  "**{**" _multi-expression_ "**}**" +
+_formal-param_list_ = _required-param-list_ [ "**,**" _optional-param-list_ ] +
+_required-param-list_ = _identifier_ { "**,**" _identifier_ } +
+_optional-param-list_ = _optional-parm_ { "**,**" _optional-param_ } +
+_optional-param_ = _param-name_ "**=**" _any-expr_ +
+_param-name_ = _identifier_
+====
+
+.Examples
+`>>>` [gray]_// A simple function: it takes two parameters and returns their "sum"_**^(*)^** +
+`>>>` [blue]`sum = func(a, b){ a + b }` +
+[green]`sum(a, b):any{}`
+
+^(\*)^ Since the plus, *+*, operator is defined for multiple data-types, the _sum()_ function can be used for any pair of that types.
+
+`>>>` [gray]_// A more complex example: recursive calculation of the n-th value of Fibonacci's sequence_ +
+`>>>` [blue]`fib = func(n){ n ? [0] {0}: [1] {1} :: {fib(n-1)+fib(n-2)} }` +
+[green]`fib(n):any{}`
+
+
+`>>>` [gray]_// Same function fib() but entered by splitting it over mulple text lines_ +
+`>>>` [blue]`fib = func(n){ \` +
+`\...` [blue]`{nbsp}{nbsp}n ? \` +
+`\...` [blue]`{nbsp}{nbsp}{nbsp}{nbsp}[0] {0} : \` +
+`\...` [blue]`{nbsp}{nbsp}{nbsp}{nbsp}[1] {1} :: \` +
+`\...` [blue]`{nbsp}{nbsp}{nbsp}{nbsp}{ \` +
+`\...` [blue]`{nbsp}{nbsp}{nbsp}{nbsp}{nbsp}{nbsp}fib(n-1) + fib(n-2) \` +
+`\...` [blue]`{nbsp}{nbsp}{nbsp}{nbsp}} \` +
+`\...` [blue]`}` +
+[green]`fib(n):any{}`
+
+`>>>` [gray]_// Required and optional parameters_ +
+`>>>` [blue]`measure = func(value, unit="meter"){ value + " " + unit + (value > 1) ? [true] {"s"} :: {""}}` +
+[green]`measure(value, unit="meter"):any{}`
+
+
+=== _Golang_ function definition
+Description of how to define Golan functions and how to bind them to _Expr_ are topics treated in another document that I'll write, one day, maybe.
 
 === Function calls
-#TODO: function calls operations#
+To call a function, either Expr or Golang type, it is necessary to specify its name and, at least, its required parameters.
 
-=== Function definitions
-#TODO: function definitions operations#
+.Function invocation syntax
+====
+*_function-call_* = _identifier_ "**(**" _actual-param-list_ "**)**" +
+_actual-param-list_ = [_positional-params_] [_named-parameters_] +
+_positional-params_ = _any-value_ { "*,*" _any-value_ } +
+_named-params_ = _param-name_ "**=**" _any-value_ { "*,*" _param-name_ "**=**" _any-value_ } +
+_param-name_ = _identifier_
+====
+
+.Examples of calling the `sum()` functions defined above
+`>>>` [gray]_// sum of two integers_ +
+`>>>` [blue]`sum(-6, 2)` +
+[green]`-4` +
+`>>>` [gray]_// same as above but passing the parameters by name_ +
+`>>>` [blue]`sum(a=-6, b=2)` +
+[green]`-4` +
+`>>>` [gray]_// again, but swapping parameter positions (see the diff() examples below)_ +
+`>>>` [blue]`sum(b=2, a=-6)` +
+[green]`-4` +
+`>>>` [gray]_// sum of a fraction and an integer_ +
+`>>>` [blue]`sum(3|2, 2)` +
+[green]`7|2` +
+`>>>` [gray]_// sum of two strings_ +
+`>>>` [blue]`sum("bye", "-bye")` +
+[green]`"bye-bye"` +
+`>>>` [gray]_// sum of two lists_ +
+`>>>` [blue]`sum(["one", 1], ["two", 2])` +
+[green]`["one", 1, "two", 2]`
+
+.Examples of calling a function with parameters passed by name
+`>>>` [gray]_// diff(a,b) calculates a-b_ +
+`>>>` [blue]`diff = func(a,b){a-b}` +
+[green]`diff(a, b):any{}` +
+`>>>` [gray]_// simple invocation_ +
+`>>>` [blue]`diff(10,8)` +
+[green]`2` +
+`>>>` [gray]_// swapped parameters passed by name_ +
+`>>>` [blue]`diff(b=8,a=10)` +
+[green]`2`
+
+.Examples of calling the `fib()` function defined above
+`>>>` [gray]_// Fibonacci sequence: 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, ..._ +
+`>>>` [blue]`fib(6)` +
+[green]`8` +
+`>>>` [blue]`fib(9)` +
+[green]`34`
+
+.Examples of calling the `measure()` functions defined above
+`>>>` [gray]_// simple call_ +
+`>>>` [blue]`measure(10,"litre")` +
+[green]`"10 litres"` +
+`>>>` [gray]_// accept the default unit_ +
+`>>>` [blue]`measure(8)` +
+[green]`"8 meters"` +
+`>>>` [gray]_// without the required parameter 'value'_ +
+`>>>` [blue]`measure(unit="degrees"))` +
+[red]`Eval Error: measure(): missing params -- value`
+
+.Examples of context binding (closures)
+`>>>` [blue]`factory = func(n=2){ func(x){x*n} }` +
+[green]`factory(n=2):any{}` +
+`>>>` [blue]`double = factory()` +
+[green]`double(x):any{}` +
+`>>>` [blue]`triple = factory(3)` +
+[green]`triple(x):any{}` +
+`>>>` [blue]`double(5)` +
+[green]`10` +
+`>>>` [blue]`triple(5)` +
+[green]`15`
+
+
+=== Function context
+Functions compute values in a local context (scope) that do not make effects on the calling context. This is the normal behavior. Using the _clone_ modifier [blue]`@` it is possibile to export local definition to the calling context. The clone modifier must be used as prefix to variable names and it is part of the name. E.g. [blue]`@x` is not the same as [blue]`x`; they are two different and un related variables.
+
+Clone variables are normal local variables. The only diffence will appear when the defining function terminate, just before the destruction of its local context. At that point, all local clone variables are cloned in the calling context with the same names but the [blue]`@` symbol.
+
+.Example
+`>>>` [blue]`f = func() { @x = 3; x = 5 }` [gray]_// f() declares two *different* local variables: ``@x`` and ``x``_ +
+[green]`f():any{}` +
+`>>>` [blue]`f()` [gray]_// The multi-expression (two) in f() is calculated and the last result is returned_ +
+[green]`5` +
+`>>>` [blue]`x` [gray]_// The `x` variable was not defined in the main context before the f() invocation. It appears in the main context by cloning the `@x` variable, local to f() after its termnation._ +
+[green]`3`
+
+NOTE: The clone modifier [blue]`@` does not make a variable a reference variable, as the ampersand character `&` does in languages such as C and C++. 
+
+[IMPORTANT]
+====
+The clone modifier can also be used to declare the formal parameters of functions, because they are local variables too.
+
+.Example
+`>>>` [blue]`g = func(@p) {2+@p}`
+g(@p):any{}`
+`>>>` [blue]`g(9)`
+11`
+`>>>` [blue]`p
+9
+====
+
+== Iterators
+#TODO: function calls operations#
 
 == Builtins
 #TODO: builtins#
@@ -671,4 +956,7 @@ In _Expr_ functions compute values in a local context (scope) that do not make e
 [blue]_import([grey]#<source-file>#)_ loads the multi-expression contained in the specified source and returns its value.
 
 
+== Plugins
+#TODO: plugins#
+
 

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
+}

fraction-type.go

@@ -50,9 +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
@@ -123,36 +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()
@@ -311,7 +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

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 {
@@ -21,7 +22,7 @@ func (functor *baseFunctor) ToString(opt FmtOpt) (s string) {
 	if functor.info != nil {
 		s = functor.info.ToString(opt)
 	} else {
-		s = "func() {}"
+		s = "func(){}"
 	}
 	return s
 }
@@ -42,6 +43,10 @@ func (functor *baseFunctor) GetFunc() ExprFunc {
 	return functor.info
 }
 
+func (functor *baseFunctor) GetDefinitionContext() ExprContext {
+	return nil
+}
+
 // ---- Function Parameters
 type paramFlags uint16
 
@@ -94,19 +99,20 @@ func (param *funcParamInfo) DefaultValue() any {
 }
 
 // --- Functions
+
+// funcInfo implements ExprFunc
 type funcInfo struct {
 	name         string
 	minArgs      int
 	maxArgs      int
 	functor      Functor
-	params     []ExprFuncParam
+	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())
@@ -124,20 +130,16 @@ func newFuncInfo(name string, functor Functor, returnType string, params []ExprF
 			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 {
@@ -152,8 +154,8 @@ 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(", ")
 			}
@@ -180,7 +182,7 @@ func (info *funcInfo) ToString(opt FmtOpt) string {
 	} else {
 		sb.WriteString(TypeAny)
 	}
-	sb.WriteString(" {}")
+	sb.WriteString("{}")
 	return sb.String()
 }
 
@@ -200,27 +202,129 @@ func (info *funcInfo) Functor() Functor {
 	return info.functor
 }
 
-// ----- Call a function ---
+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 checkFunctionCall(ctx ExprContext, name string, varParams *[]any) (err error) {
-	if info, exists, owner := GetFuncInfo(ctx, name); exists {
-		passedCount := len(*varParams)
+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
 	}
-		for i, p := range info.Params() {
-			if i >= passedCount {
+
+	if passedCount < len(info.formalParams) {
+		for _, p := range info.formalParams {
+			if _, exists := actualParams[p.Name()]; !exists {
 				if !p.IsDefault() {
 					break
 				}
-				*varParams = append(*varParams, p.DefaultValue())
+				if p.IsRepeat() {
+					varArgs := make([]any, 1)
+					varArgs[0] = p.DefaultValue()
+					actualParams[p.Name()] = varArgs
+				} else {
+					actualParams[p.Name()] = p.DefaultValue()
 				}
 			}
-		if err == nil && info.MaxArgs() >= 0 && info.MaxArgs() < len(*varParams) {
-			err = ErrTooMuchParams(name, info.MaxArgs(), len(*varParams))
 		}
-		if err == nil && owner != ctx {
-			ctx.RegisterFuncInfo(info)
+	}
+
+	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)
@@ -228,13 +332,55 @@ func checkFunctionCall(ctx ExprContext, name string, varParams *[]any) (err erro
 	return
 }
 
-func CallFunction(parentCtx ExprContext, name string, params []any) (result any, err error) {
-	ctx := cloneContext(parentCtx)
-	ctx.SetParent(parentCtx)
-
-	if err = checkFunctionCall(ctx, name, &params); err == nil {
-		result, err = ctx.Call(name, params)
+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

@@ -55,7 +55,20 @@ func GetLocalFuncInfo(ctx ExprContext, name string) (item ExprFunc, exists bool)
 	}
 	return
 }
-func GetFuncInfo(ctx ExprContext, name string) (item ExprFunc, exists bool, ownerCtx ExprContext) {
+
+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

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=

import-utils.go

@@ -25,13 +25,13 @@ func checkStringParamExpected(funcName string, paramValue any, paramPos int) (er
 	return
 }
 
-func addSourceEnvImportDirs(varName string, dirList []string) []string {
-	return addEnvImportDirs(ENV_EXPR_SOURCE_PATH, dirList)
-}
+// 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 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 {
@@ -75,7 +75,11 @@ func isFile(filePath string) bool {
 }
 
 func searchAmongPath(filename string, dirList []string) (filePath string) {
+	var err error
 	for _, dir := range dirList {
+		if dir, err = ExpandPath(dir); err != nil {
+			continue
+		}
 		if fullPath := path.Join(dir, filename); isFile(fullPath) {
 			filePath = fullPath
 			break
@@ -90,6 +94,10 @@ func isPathRelative(filePath string) bool {
 }
 
 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

iterator.go

@@ -5,38 +5,44 @@
 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"
 )
 
 type Iterator interface {
+	Typer
 	Next() (item any, err error) // must return io.EOF after the last item
 	Current() (item any, err error)
 	Index() int
+	Count() int
 }
 
 type ExtIterator interface {
 	Iterator
+	Reset() error
+	Clean() error
 	HasOperation(name string) bool
-	CallOperation(name string, args []any) (value any, err error)
+	CallOperation(name string, args map[string]any) (value any, err error)
 }
 
 func errNoOperation(name string) error {
 	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")
+// }

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
 					}
@@ -85,18 +85,28 @@ func (it *ListIterator) String() string {
 	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)
@@ -135,7 +145,16 @@ 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

@@ -26,9 +26,10 @@ func newList(listAny []any) (list *ListType) {
 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
@@ -105,16 +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) {

operand-dict.go

@@ -18,8 +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

@@ -21,20 +21,26 @@ func newFuncCallTerm(tk *Token, args []*term) *term {
 }
 
 // -------- eval func call
-func evalFuncCall(ctx ExprContext, self *term) (v any, err error) {
-	name, _ := self.tk.Value.(string)
-	params := make([]any, len(self.children), len(self.children)+5)
-	for i, tree := range self.children {
-		var param any
-		if param, err = tree.compute(ctx); err != nil {
-			break
-		}
-		params[i] = param
-	}
+// 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
+// 	}
 
-	if err == nil {
-		v, err = CallFunction(ctx, name, params)
-	}
+// 	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
 }
 
@@ -51,11 +57,11 @@ func newFuncDefTerm(tk *Token, args []*term) *term {
 }
 
 // -------- eval func def
-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([]ExprFuncParam, 0, len(self.children))
-		for _, param := range self.children {
+		paramList := make([]ExprFuncParam, 0, len(opTerm.children))
+		for _, param := range opTerm.children {
 			var defValue any
 			flags := paramFlags(0)
 			if len(param.children) > 0 {

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 {
@@ -91,57 +72,59 @@ 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 {
 		return
 	}
 
 	if ds != nil {
-		dc := newDataCursor(ctx, ds)
-		if initFunc, exists := ds[initName]; exists && initFunc != nil {
+		var dc *dataCursor
+		dcCtx := ctx.Clone()
+		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 {
+			var resource any
+			if len(opTerm.children) > 1 {
+				if args, err = evalTermArray(ctx, opTerm.children[1:]); err != nil {
 					return
 				}
 			} else {
 				args = []any{}
 			}
 
-			initCtx := dc.ctx.Clone()
-			if dc.resource, err = initFunc.Invoke(initCtx, initName, args); err != nil {
+			actualParams := bindActualParams(initFunc, args)
+
+			initCtx := ctx.Clone()
+			if resource, err = initFunc.InvokeNamed(initCtx, InitName, actualParams); err != nil {
 				return
 			}
-			exportObjects(dc.ctx, initCtx)
+			exportObjects(dcCtx, initCtx)
+			dc = NewDataCursor(dcCtx, ds, resource)
+		} else {
+			dc = NewDataCursor(dcCtx, ds, nil)
 		}
 
-		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)
 		}
 	}

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

@@ -21,11 +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

@@ -60,22 +60,23 @@ func assignValue(ctx ExprContext, leftTerm *term, v any) (err error) {
 	return
 }
 
-func evalAssign(ctx ExprContext, self *term) (v any, err error) {
-	if err = self.checkOperands(); err != nil {
+func evalAssign(ctx ExprContext, opTerm *term) (v any, err error) {
+	if err = opTerm.checkOperands(); err != nil {
 		return
 	}
 
-	leftTerm := self.children[0]
+	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", self.tk.source)
+		err = leftTerm.tk.Errorf("left operand of %q must be a variable or a collection's item", opTerm.tk.source)
 		return
 	}
 
-	rightChild := self.children[1]
+	rightChild := opTerm.children[1]
 
 	if v, err = rightChild.compute(ctx); err == nil {
 		if functor, ok := v.(Functor); ok {
+			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 {
@@ -83,7 +84,10 @@ func evalAssign(ctx ExprContext, self *term) (v any, err error) {
 
 					ctx.RegisterFunc(leftTerm.source(), functor, TypeAny, paramSpecs)
 				} else {
-				err = self.Errorf("unknown function %s()", rightChild.source())
+					err = opTerm.Errorf("unknown function %s()", rightChild.source())
+				}
+			} else {
+				err = assignValue(ctx, leftTerm, v)
 			}
 		} else {
 			err = assignValue(ctx, leftTerm, v)
@@ -95,7 +99,106 @@ func evalAssign(ctx ExprContext, self *term) (v any, err error) {
 	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)
+			default:
+				err = opTerm.Errorf("unsupported assign operator %q", opTerm.source())
+			}
+			if err == nil {
+				err = assignValue(ctx, leftTerm, v)
+			}
+		}
+	}
+	return
+}
+
 // init
 func init() {
 	registerTermConstructor(SymEqual, newAssignTerm)
+	registerTermConstructor(SymPlusEqual, newOpAssignTerm)
+	registerTermConstructor(SymMinusEqual, newOpAssignTerm)
+	registerTermConstructor(SymStarEqual, newOpAssignTerm)
+	registerTermConstructor(SymSlashEqual, newOpAssignTerm)
 }

operator-binary.go

@@ -0,0 +1,104 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// operator-binary.go
+package expr
+
+//-------- NOT term
+
+func newBinNotTerm(tk *Token) (inst *term) {
+	return &term{
+		tk:       *tk,
+		children: make([]*term, 0, 1),
+		position: posPrefix,
+		priority: priBinary,
+		evalFunc: evalBinaryNot,
+	}
+}
+
+func evalBinaryNot(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
+}
+
+//-------- Binary AND term
+
+func newBinAndTerm(tk *Token) (inst *term) {
+	return &term{
+		tk:       *tk,
+		children: make([]*term, 0, 2),
+		position: posInfix,
+		priority: priBinary,
+		evalFunc: evalBinaryAnd,
+	}
+}
+
+func evalBinaryAnd(ctx ExprContext, self *term) (v any, err error) {
+	var leftValue, rightValue any
+	var leftInt, rightInt int64
+	var lok, rok bool
+
+	if leftValue, rightValue, err = self.evalInfix(ctx); err != nil {
+		return
+	}
+
+	leftInt, lok = leftValue.(int64)
+	rightInt, rok = rightValue.(int64)
+
+	if lok && rok {
+		v = leftInt & rightInt
+	} else {
+		err = self.errIncompatibleTypes(leftValue, rightValue)
+	}
+	return
+}
+
+//-------- Binary OR term
+
+func newBinOrTerm(tk *Token) (inst *term) {
+	return &term{
+		tk:       *tk,
+		children: make([]*term, 0, 2),
+		position: posInfix,
+		priority: priBinary,
+		evalFunc: evalBinaryOr,
+	}
+}
+
+func evalBinaryOr(ctx ExprContext, self *term) (v any, err error) {
+	var leftValue, rightValue any
+	var leftInt, rightInt int64
+	var lok, rok bool
+
+	if leftValue, rightValue, err = self.evalInfix(ctx); err != nil {
+		return
+	}
+
+	leftInt, lok = leftValue.(int64)
+	rightInt, rok = rightValue.(int64)
+
+	if lok && rok {
+		v = leftInt | rightInt
+	} else {
+		err = self.errIncompatibleTypes(leftValue, rightValue)
+	}
+	return
+}
+
+// init
+func init() {
+	registerTermConstructor(SymTilde, newBinNotTerm)
+	registerTermConstructor(SymAmpersand, newBinAndTerm)
+	registerTermConstructor(SymVertBar, newBinOrTerm)
+}

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 {
 		v = !b
 	} else {
-		err = self.errIncompatibleType(rightValue)
+		err = opTerm.errIncompatibleType(rightValue)
 	}
 	return
 }
@@ -38,8 +38,6 @@ func evalNot(ctx ExprContext, self *term) (v any, err error) {
 func newAndTerm(tk *Token) (inst *term) {
 	return &term{
 		tk:       *tk,
-		// class:    classOperator,
-		// kind:     kindBool,
 		children: make([]*term, 0, 2),
 		position: posInfix,
 		priority: priAnd,
@@ -88,7 +86,7 @@ func evalAndWithShortcut(ctx ExprContext, self *term) (v any, err error) {
 	}
 
 	if leftBool, lok := ToBool(leftValue); !lok {
-		err = fmt.Errorf("got %T as left operand type of 'and' operator, it must be bool", leftBool)
+		err = fmt.Errorf("got %s as left operand type of 'AND' operator, it must be bool", TypeName(leftValue))
 		return
 	} else if !leftBool {
 		v = false
@@ -107,8 +105,6 @@ func evalAndWithShortcut(ctx ExprContext, self *term) (v any, err error) {
 func newOrTerm(tk *Token) (inst *term) {
 	return &term{
 		tk:       *tk,
-		// class:    classOperator,
-		// kind:     kindBool,
 		children: make([]*term, 0, 2),
 		position: posInfix,
 		priority: priOr,
@@ -157,7 +153,7 @@ func evalOrWithShortcut(ctx ExprContext, self *term) (v any, err error) {
 	}
 
 	if leftBool, lok := ToBool(leftValue); !lok {
-		err = fmt.Errorf("got %T as left operand type of 'or' operator, it must be bool", leftBool)
+		err = fmt.Errorf("got %s as left operand type of 'OR' operator, it must be bool", TypeName(leftValue))
 		return
 	} else if leftBool {
 		v = true

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
 	}
 
@@ -37,11 +37,11 @@ func evalBuiltin(ctx ExprContext, self *term) (v any, err error) {
 				if ImportInContext(module) {
 					count++
 				} else {
-					err = self.Errorf("unknown builtin module %q", module)
+					err = opTerm.Errorf("unknown builtin module %q", module)
 					break
 				}
 			} else {
-				err = self.Errorf("expected string at item nr %d, got %s", it.Index()+1, TypeName(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, PfDefault|PfRepeat),
-			})
-		} else {
-			v = rightValue
-			ctx.UnsafeSetVar(leftTerm.source(), rightValue)
-		}
-	}
-	return
-}
-
-// init
-func init() {
-	registerTermConstructor(SymDoubleQuestion, newNullCoalesceTerm)
-	registerTermConstructor(SymQuestionEqual, newCoalesceAssignTerm)
-}

operator-context.go

@@ -16,15 +16,15 @@ 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
 		}
@@ -49,7 +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

@@ -16,7 +16,7 @@ func newExportAllTerm(tk *Token) (inst *term) {
 	}
 }
 
-func evalExportAll(ctx ExprContext, self *term) (v any, err error) {
+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-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-fraction.go

@@ -24,12 +24,12 @@ 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 {
@@ -49,6 +49,7 @@ func evalFraction(ctx ExprContext, self *term) (v any, err error) {
 		den = -den
 		num = -num
 	}
+	if num != 0 {
 		g := gcd(num, den)
 		num = num / g
 		den = den / g
@@ -57,10 +58,14 @@ func evalFraction(ctx ExprContext, self *term) (v any, err error) {
 		} else {
 			v = &FractionType{num, den}
 		}
+	} else {
+		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)
-	} else {
-		err = self.errIncompatibleType(childValue)
+		if v, err = EvalFile(ctx, filePath); err == nil {
+			count++
 		}
-	if err == nil {
-		v = count
+	} else {
+		err = opTerm.errIncompatibleType(childValue)
+	}
+	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
 		}
@@ -59,18 +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")
@@ -90,16 +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) {
@@ -115,19 +108,14 @@ 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)
-
-		/* 		var ok bool
-		   		var indexValue any
-		   		if indexValue, err = verifyKey(indexTerm, indexList); err == nil {
-		   			if v, ok = (*d)[indexValue]; !ok {
-		   				err = indexTerm.Errorf("key %v does not belong to the dictionary", rightValue)
-		   			}
-		   		}*/
 		v, err = getDictItem(d, indexTerm, indexList, rightValue)
+	} else {
+		rightChild := opTerm.children[1]
+		err = rightChild.Errorf("invalid index type: %v", (*indexList)[0])
 	}
 	return
 }
@@ -136,7 +124,7 @@ func getDictItem(d *DictType, indexTerm *term, indexList *ListType, rightValue a
 	var ok bool
 	var indexValue any
 
-	if indexValue, err = verifyKey(indexTerm, indexList); err == nil {
+	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)
 		}

operator-insert.go

@@ -26,10 +26,10 @@ func newAppendTerm(tk *Token) (inst *term) {
 	}
 }
 
-func evalInsert(ctx ExprContext, self *term) (v any, err error) {
+func evalInsert(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 +37,23 @@ 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 if IsInteger(leftValue) && IsInteger(rightValue) {
+		leftInt := leftValue.(int64)
+		rightInt := rightValue.(int64)
+		v = leftInt >> rightInt
 	} 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 +61,15 @@ 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 if IsInteger(leftValue) && IsInteger(rightValue) {
+		leftInt := leftValue.(int64)
+		rightInt := rightValue.(int64)
+		v = leftInt << rightInt
 	} else {
-		err = self.errIncompatibleTypes(leftValue, rightValue)
+		err = opTerm.errIncompatibleTypes(leftValue, rightValue)
 	}
 	return
 }

operator-iter-value.go

@@ -16,22 +16,23 @@ func newIterValueTerm(tk *Token) (inst *term) {
 	}
 }
 
-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(SymCaret, newIterValueTerm)
 }

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, "")
+		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 {
-			v = int64(it.Index() + 1)
-		}
-	} else {
-		err = self.errIncompatibleType(childValue)
+		err = opTerm.errIncompatibleType(childValue)
 	}
 	return
 }

operator-plugin.go

@@ -4,10 +4,6 @@
 // operator-plugin.go
 package expr
 
-import (
-	"io"
-)
-
 //-------- plugin term
 
 func newPluginTerm(tk *Token) (inst *term) {
@@ -20,33 +16,15 @@ func newPluginTerm(tk *Token) (inst *term) {
 	}
 }
 
-func evalPlugin(ctx ExprContext, self *term) (v any, err error) {
+func evalPlugin(ctx ExprContext, opTerm *term) (v any, err error) {
 	var childValue any
-	var moduleSpec any
+	var count int
 
-	if childValue, err = self.evalPrefix(ctx); err != nil {
+	if childValue, err = opTerm.evalPrefix(ctx); err != nil {
 		return
 	}
 
-	dirList := buildSearchDirList("plugin", ENV_EXPR_PLUGIN_PATH)
-	count := 0
-	it := NewAnyIterator(childValue)
-	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 = self.Errorf("expected string as item nr %d, got %s", it.Index()+1, TypeName(moduleSpec))
-			break
-		}
-	}
-	if err == io.EOF {
-		err = nil
-	}
-
-	if err == nil {
+	if count, err = importPluginFromSearchPath(childValue); err == nil {
 		v = int64(count)
 	}
 	return

operator-post-inc.go

@@ -17,20 +17,51 @@ func newPostIncTerm(tk *Token) *term {
 	}
 }
 
-func evalPostInc(ctx ExprContext, self *term) (v any, err error) {
+func evalPostInc(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.Next()
-	} else if IsInteger(childValue) && self.children[0].symbol() == SymVariable {
+	} else if IsInteger(childValue) && opTerm.children[0].symbol() == SymVariable {
 		v = childValue
 		i, _ := childValue.(int64)
-		ctx.SetVar(self.children[0].source(), i+1)
+		ctx.SetVar(opTerm.children[0].source(), i+1)
 	} else {
-		err = self.errIncompatibleType(childValue)
+		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
 }
@@ -38,4 +69,5 @@ func evalPostInc(ctx ExprContext, self *term) (v any, err error) {
 // init
 func init() {
 	registerTermConstructor(SymDoublePlus, newPostIncTerm)
+	registerTermConstructor(SymDoubleMinus, newPostDecTerm)
 }

operator-prod.go

@@ -14,8 +14,6 @@ import (
 func newMultiplyTerm(tk *Token) (inst *term) {
 	return &term{
 		tk:       *tk,
-		// class:    classOperator,
-		// kind:     kindUnknown,
 		children: make([]*term, 0, 2),
 		position: posInfix,
 		priority: priProduct,
@@ -23,13 +21,7 @@ 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 +37,26 @@ 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,
 		children: make([]*term, 0, 2),
 		position: posInfix,
 		priority: priProduct,
@@ -64,13 +64,7 @@ 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)
@@ -90,11 +84,21 @@ func evalDivide(ctx ExprContext, self *term) (v any, err error) {
 			}
 		}
 	} 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) {
@@ -107,10 +111,10 @@ 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
 	}
 
@@ -122,32 +126,23 @@ func evalDivideAsFloat(ctx ExprContext, self *term) (v any, err error) {
 			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,
 		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 {
@@ -157,15 +152,25 @@ func evalReminder(ctx ExprContext, self *term) (v any, err error) {
 			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

@@ -34,25 +34,30 @@ func newRangeTerm(tk *Token) (inst *term) {
 	}
 }
 
-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(ConstLastIndex)
-	} else if leftValue, rightValue, err = self.evalInfix(ctx); err != nil {
+	} 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
 	}
 
@@ -68,8 +68,8 @@ func newNotEqualTerm(tk *Token) (inst *term) {
 	}
 }
 
-func evalNotEqual(ctx ExprContext, self *term) (v any, err error) {
-	if v, err = evalEqual(ctx, self); err == nil {
+func evalNotEqual(ctx ExprContext, opTerm *term) (v any, err error) {
+	if v, err = evalEqual(ctx, opTerm); err == nil {
 		b, _ := ToBool(v)
 		v = !b
 	}
@@ -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

@@ -22,9 +22,19 @@ func trySelectorCase(ctx ExprContext, exprValue, caseSel any, caseIndex int) (ma
 		selectedValue, err = caseData.caseExpr.Eval(ctx)
 		match = true
 	} else if filterList, ok := caseData.filterList.value().([]*term); ok {
-		if len(filterList) == 0 && exprValue == int64(caseIndex) {
+		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 {
@@ -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-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 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

@@ -6,10 +6,46 @@ package expr
 
 import (
 	"errors"
+
+	"golang.org/x/exp/constraints"
 )
 
 //-------- parser
 
+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 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 {
 }
 
@@ -18,13 +54,19 @@ func NewParser() (p *parser) {
 	return p
 }
 
-func (self *parser) parseFuncCall(scanner *scanner, allowVarRef bool, tk *Token) (tree *term, err error) {
+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, err = parser.parseItem(scanner, ctx, SymComma, SymClosedRound); err != nil {
 			break
 		}
 		prev := scanner.Previous()
@@ -48,7 +90,7 @@ func (self *parser) parseFuncCall(scanner *scanner, allowVarRef bool, tk *Token)
 	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)
@@ -57,15 +99,21 @@ func (self *parser) parseFuncDef(scanner *scanner) (tree *term, err error) {
 	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 = self.parseItem(scanner, false, SymComma, SymClosedRound); err != nil {
+				if paramExpr, err = parser.parseItem(scanner, parserNoFlags, SymComma, SymClosedRound); err != nil {
 					break
 				}
 				param.forceChild(paramExpr.root)
@@ -86,9 +134,9 @@ 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("{")
 		}
@@ -104,27 +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))
@@ -141,26 +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 {
@@ -184,8 +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
@@ -194,7 +260,7 @@ 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 {
@@ -206,14 +272,14 @@ func (self *parser) parseDictKey(scanner *scanner, allowVarRef bool) (key any, e
 	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()
@@ -223,10 +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
@@ -242,16 +308,16 @@ func (self *parser) parseDictionary(scanner *scanner, allowVarRef bool) (subtree
 			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 {
@@ -259,10 +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 {
@@ -270,7 +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 {
@@ -296,25 +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 {
@@ -325,28 +394,36 @@ func couldBeACollection(t *term) bool {
 	return sym == SymList || sym == SymString || sym == SymDict || sym == SymExpression || sym == SymVariable
 }
 
-// func areSymbolsOutOfCtx(tk *Token, ctxTerm *term, syms ...Symbol) bool {
-// 	var areOut = false
-// 	if ctxTerm != nil {
-// 		areOut = tk.IsOneOf(syms)
-// 	}
-// 	return areOut
-// }
+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 (self *parser) parseGeneral(scanner *scanner, allowForest bool, allowVarRef bool, termSymbols ...Symbol) (tree *ast, err error) {
+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); /*&& !areSymbolsOutOfCtx(tk, selectorTerm, SymColon, SymDoubleColon)*/ tk = scanner.Next() {
-		if tk.Sym == SymComment {
-			continue
-		}
+	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
@@ -364,6 +441,9 @@ func (self *parser) parseGeneral(scanner *scanner, allowForest bool, allowVarRef
 				tk.Sym = SymChangeSign
 			} else if tk.Sym == SymPlus {
 				tk.Sym = SymUnchangeSign
+			} else if tk.IsSymbol(SymExclamation) {
+				err = tk.Errorf("postfix opertor %q requires an operand on its left", tk)
+				break
 			}
 			firstToken = false
 		}
@@ -371,72 +451,63 @@ func (self *parser) parseGeneral(scanner *scanner, allowForest bool, allowVarRef
 		switch tk.Sym {
 		case SymOpenRound:
 			var subTree *ast
-			if subTree, err = self.parseGeneral(scanner, false, allowVarRef, SymClosedRound); err == nil {
+			if subTree, err = parser.parseGeneral(scanner, ctx, SymClosedRound); err == nil {
 				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:
+			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 {
@@ -444,31 +515,38 @@ func (self *parser) parseGeneral(scanner *scanner, allowForest bool, allowVarRef
 					}
 				}
 			} else {
-				currentTerm, err = tree.addToken2(tk)
+				// if hasFlag(ctx, allowIndex) {
+				// 	tk.Sym = SymRange
+				// }
+				currentTerm, err = tree.addToken(tk)
 			}
-			if tk.IsSymbol(SymColon) {
+			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
 	}
+
 	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
 }
-
-// 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)
-// 	}
-// 	return
-// }

plugins.go

@@ -6,6 +6,7 @@ package expr
 
 import (
 	"fmt"
+	"io"
 	"os"
 	"plugin"
 	"strings"
@@ -29,7 +30,7 @@ func pluginExists(name string) (exists bool) {
 
 func makePluginName(name string) (decorated string) {
 	var template string
-	if execName, err := os.Executable(); err != nil || strings.Index(execName, "debug") < 0 {
+	if execName, err := os.Executable(); err != nil || !strings.Contains(execName, "debug") {
 		template = "expr-%s-plugin.so"
 	} else {
 		template = "expr-%s-plugin.so.debug"
@@ -90,6 +91,29 @@ func importPlugin( /*ctx ExprContext,*/ dirList []string, name string) (err erro
 	return
 }
 
+func importPluginFromSearchPath(name any) (count int, err error) {
+	var moduleSpec any
+
+	dirList := buildSearchDirList("plugin", ENV_EXPR_PLUGIN_PATH)
+	count = 0
+	it := NewAnyIterator(name)
+	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 {

scanner.go

@@ -16,6 +16,7 @@ import (
 type scanner struct {
 	current      *Token
 	prev         *Token
+	stage        *Token
 	stream       *bufio.Reader
 	row          int
 	column       int
@@ -39,7 +40,7 @@ func DefaultTranslations() map[Symbol]Symbol {
 		SymKwAnd:           SymAnd,
 		SymDoubleVertBar:   SymOr,
 		SymKwOr:            SymOr,
-		SymTilde:           SymNot,
+		// SymTilde:           SymNot,
 		SymKwNot:       SymNot,
 		SymLessGreater: SymNotEqual,
 	}
@@ -49,255 +50,276 @@ 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 {
-				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 {
-				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)
+			tk = scanner.makeToken(SymCaret, ch)
 		case ':':
-			if next, _ := self.peek(); next == ':' {
-				tk = self.moveOn(SymDoubleColon, ch, next)
+			if next, _ := scanner.peek(); next == ':' {
+				tk = scanner.moveOn(SymDoubleColon, ch, next)
 			} else {
-				tk = self.makeToken(SymColon, ch)
+				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 '\'':
 			if escape {
-				tk = self.makeToken(SymQuote, ch)
+				tk = scanner.makeToken(SymQuote, ch)
 				escape = false
 			} else {
-				tk = self.fetchString(ch)
+				tk = scanner.fetchString(ch)
 			}
 		case '"':
 			if escape {
-				tk = self.makeToken(SymDoubleQuote, ch)
+				tk = scanner.makeToken(SymDoubleQuote, ch)
 				escape = false
 			} else {
-				tk = self.fetchString(ch)
+				tk = scanner.fetchString(ch)
 			}
 		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 {
-				tk = self.makeToken(SymAmpersand, ch)
+				tk = scanner.makeToken(SymAmpersand, ch)
 			}
 		case '%':
-			tk = self.makeToken(SymPercent, ch)
+			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)
+				tk = scanner.moveOn(SymAppend, ch, next)
 			} else if next == '>' {
-				tk = self.moveOn(SymLessGreater, ch, next)
+				tk = scanner.moveOn(SymLessGreater, 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)
+				tk = scanner.moveOn(SymInsert, 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 {
-				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 {
@@ -305,14 +327,14 @@ 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
 }
@@ -333,32 +355,32 @@ 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 {
@@ -372,7 +394,7 @@ 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
@@ -381,9 +403,9 @@ 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)
 	}
 
@@ -391,9 +413,9 @@ 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)
 				}
 			}
@@ -402,32 +424,32 @@ 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()
 					}
 				}
 			}
@@ -435,10 +457,10 @@ 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)
@@ -448,39 +470,39 @@ 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)
 		}
 	}
 
@@ -500,29 +522,29 @@ 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 {
@@ -531,18 +553,18 @@ 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(termCh byte) (tk *Token) {
+func (scanner *scanner) fetchString(termCh byte) (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 '"':
@@ -570,65 +592,65 @@ func (self *scanner) fetchString(termCh byte) (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)
+		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))
+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++ {
-		self.readChar()
+		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) makeToken(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) makeKeywordToken(sym Symbol, upperCaseKeyword string) (tk *Token) {
+	tk = NewToken(scanner.row, scanner.column, scanner.translate(sym), upperCaseKeyword)
 	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) makeValueToken(sym Symbol, source string, value any) (tk *Token) {
+	tk = NewValueToken(scanner.row, scanner.column, scanner.translate(sym), source, value)
 	return
 }
 
-func (self *scanner) makeErrorToken(err error) *Token {
-	return NewErrorToken(self.row, self.column, err)
+func (scanner *scanner) makeErrorToken(err error) *Token {
+	return NewErrorToken(scanner.row, scanner.column, err)
 }

simple-store.go

@@ -25,7 +25,7 @@ func NewSimpleStore() *SimpleStore {
 }
 
 func filterRefName(name string) bool  { return name[0] != '@' }
-func filterPrivName(name string) bool { return name[0] != '_' }
+//func filterPrivName(name string) bool { return name[0] != '_' }
 
 func (ctx *SimpleStore) SetParent(parentCtx ExprContext) {
 	ctx.parent = parentCtx
@@ -36,88 +36,21 @@ func (ctx *SimpleStore) GetParent() ExprContext {
 }
 
 func (ctx *SimpleStore) Clone() ExprContext {
-	return &SimpleStore{
+	clone := &SimpleStore{
 		varStore:  CloneFilteredMap(ctx.varStore, filterRefName),
 		funcStore: CloneFilteredMap(ctx.funcStore, filterRefName),
 	}
+	return clone
 }
 
-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 varsCtxToBuilder(sb *strings.Builder, ctx ExprContext, indent int) {
-	sb.WriteString("vars: {\n")
-	first := true
-	for _, name := range ctx.EnumVars(nil) {
-		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}")
-}
-
-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
-	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))
-		if formatter, ok := value.(Formatter); ok {
-			sb.WriteString(formatter.ToString(0))
-		} else {
-			sb.WriteString(fmt.Sprintf("%v", value))
-		}
-	}
-	sb.WriteString("\n}")
-}
-
-func (ctx *SimpleStore) ToString(opt FmtOpt) string {
-	var sb strings.Builder
-	varsCtxToBuilder(&sb, ctx, 0)
-	sb.WriteByte('\n')
-	funcsCtxToBuilder(&sb, ctx, 0)
-	return sb.String()
-}
-*/
+// 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()
@@ -199,6 +132,14 @@ 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
@@ -208,10 +149,11 @@ 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
 }
@@ -230,10 +172,18 @@ func (ctx *SimpleStore) EnumFuncs(acceptor func(name string) (accept bool)) (fun
 	return
 }
 
-func (ctx *SimpleStore) Call(name string, args []any) (result any, err error) {
+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.Invoke(ctx, name, args)
+		result, err = functor.InvokeNamed(ctx, name, args)
 	} else {
 		err = fmt.Errorf("unknown function %s()", name)
 	}

symbol-map.go

@@ -0,0 +1,181 @@
+// 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
+	symClassPostOp
+	symClassIdentifier
+	symClassDelimiter
+	symClassParenthesis
+	symClassDeclaration
+	symClassValue
+	symClassOther
+)
+
+type symbolSpec struct {
+	repr string
+	kind symbolClass
+}
+
+func init() {
+
+	symbolMap = map[Symbol]symbolSpec{
+		SymUnknown:         {"<unknown>", symClassOther}, //  -1: Unknown symbol
+		SymNone:            {"<null>", symClassOther},    //   0: Null value for variable of type symbol
+		SymError:           {"<error>", symClassOther},   //   1: Error reading from stream
+		SymEos:             {"<eos>", symClassOther},     //   2: End of stream
+		SymMinus:           {"-", symClassOperator},      //   3: '-'
+		SymMinusEqual:      {"-=", symClassOperator},     //   4: '-='
+		SymDoubleMinus:     {"--", symClassOperator},     //   5: '--'
+		SymPlus:            {"+", symClassOperator},      //   6: '+'
+		SymPlusEqual:       {"+=", symClassOperator},     //   7: '+='
+		SymDoublePlus:      {"++", symClassOperator},     //   8: '++'
+		SymStar:            {"*", symClassOperator},      //   9: '*'
+		SymDoubleStar:      {"**", symClassOperator},     //  10: '**'
+		SymSlash:           {"/", symClassOperator},      //  11: '/'
+		SymBackSlash:       {"\\", symClassOperator},     //  12: '\'
+		SymVertBar:         {"|", symClassOperator},      //  13: '|'
+		SymDoubleVertBar:   {"||", symClassOperator},     //  14: '||'
+		SymComma:           {",", symClassOperator},      //  15: ','
+		SymColon:           {":", symClassOperator},      //  16: ':'
+		SymSemiColon:       {";", symClassOperator},      //  17: ';'
+		SymDot:             {".", symClassOperator},      //  18: '.'
+		SymDotSlash:        {"./", symClassOperator},     //  19: './'
+		SymQuote:           {"'", symClassDelimiter},     //  20: '\''
+		SymDoubleQuote:     {"\"", symClassDelimiter},    //  21: '"'
+		SymBackTick:        {"`", symClassOperator},      //  22: '`'
+		SymExclamation:     {"!", symClassPostOp},        //  23: '!'
+		SymQuestion:        {"?", symClassOperator},      //  24: '?'
+		SymAmpersand:       {"&", symClassOperator},      //  25: '&'
+		SymDoubleAmpersand: {"&&", symClassOperator},     //  26: '&&'
+		SymPercent:         {"%", symClassOperator},      //  27: '%'
+		SymAt:              {"@", symClassOperator},      //  28: '@'
+		SymUndescore:       {"_", symClassOperator},      //  29: '_'
+		SymEqual:           {"=", symClassOperator},      //  30: '='
+		SymDoubleEqual:     {"==", symClassOperator},     //  31: '=='
+		SymLess:            {"<", symClassOperator},      //  32: '<'
+		SymLessOrEqual:     {"<=", symClassOperator},     //  33: '<='
+		SymGreater:         {">", symClassOperator},      //  34: '>'
+		SymGreaterOrEqual:  {">=", symClassOperator},     //  35: '>='
+		SymLessGreater:     {"<>", symClassOperator},     //  36: '<>'
+		SymNotEqual:        {"!=", symClassOperator},     //  37: '!='
+		SymDollar:          {"$", symClassOperator},      //  38: '$'
+		SymHash:            {"#", symClassOperator},      //  39: '#'
+		SymOpenRound:       {"(", symClassParenthesis},   //  40: '('
+		SymClosedRound:     {")", symClassParenthesis},   //  41: ')'
+		SymOpenSquare:      {"[", symClassParenthesis},   //  42: '['
+		SymClosedSquare:    {"]", symClassParenthesis},   //  43: ']'
+		SymOpenBrace:       {"{", symClassParenthesis},   //  44: '{'
+		SymClosedBrace:     {"}", symClassParenthesis},   //  45: '}'
+		SymTilde:           {"~", symClassOperator},      //  46: '~'
+		SymDoubleQuestion:  {"??", symClassOperator},     //  47: '??'
+		SymQuestionEqual:   {"?=", symClassOperator},     //  48: '?='
+		SymQuestionExclam:  {"?!", symClassOperator},     //  49: '?!'
+		SymDoubleAt:        {"@@", symClassOperator},     //  50: '@@'
+		SymDoubleColon:     {"::", symClassOperator},     //  51: '::'
+		SymInsert:          {">>", symClassOperator},     //  52: '>>'
+		SymAppend:          {"<<", symClassOperator},     //  53: '<<'
+		SymCaret:           {"^", symClassOperator},      //  54: '^'
+		SymDollarRound:     {"$(", symClassOperator},     //  55: '$('
+		SymOpenClosedRound: {"()", symClassPostOp},       //  56: '()'
+		SymDoubleDollar:    {"$$", symClassOperator},     //  57: '$$'
+		SymDoubleDot:       {"..", symClassOperator},     //  58: '..'
+		SymTripleDot:       {"...", symClassOperator},    //  59: '...'
+		SymStarEqual:       {"*=", symClassOperator},     //  60: '*='
+		SymSlashEqual:      {"/=", symClassOperator},     //  61: '/='
+		SymPercEqual:       {"%=", symClassOperator},     //  62: '%='
+		// 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},
+		SymKwNot:     {"not", symClassOperator},
+		SymKwOr:      {"or", symClassOperator},
+		SymKwBut:     {"but", symClassOperator},
+		SymKwFunc:    {"func(", symClassDeclaration},
+		SymKwBuiltin: {"builtin", symClassOperator},
+		SymKwPlugin:  {"plugin", symClassOperator},
+		SymKwIn:      {"in", symClassOperator},
+		SymKwInclude: {"include", symClassOperator},
+		SymKwNil:     {"nil", symClassValue},
+		SymKwUnset:   {"unset", symClassOperator},
+	}
+}
+
+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) {
+	sym = SymNone
+	lower := strings.ToLower(s)
+	for symbol, spec := range symbolMap {
+		if spec.kind == symClassOperator && strings.HasSuffix(lower, spec.repr) {
+			sym = symbol
+			break
+		}
+	}
+	return
+}

symbol.go

@@ -57,16 +57,20 @@ const (
 	SymTilde                             //  46: '~'
 	SymDoubleQuestion                    //  47: '??'
 	SymQuestionEqual                     //  48: '?='
-	SymDoubleAt                          //  49: '@@'
-	SymDoubleColon                       //  50: '::'
-	SymInsert                            //  51: '>>'
-	SymAppend                            //  52: '<<'
-	SymCaret                             //  53: '^'
-	SymDollarRound                       //  54: '$('
-	SymOpenClosedRound                   //  55: '()'
-	SymDoubleDollar                      //  56: '$$'
-	SymDoubleDot                         //  57: '..'
-	SymTripleDot                         //  58: '...'
+	SymQuestionExclam                    //  49: '?!'
+	SymDoubleAt                          //  50: '@@'
+	SymDoubleColon                       //  51: '::'
+	SymInsert                            //  52: '>>'
+	SymAppend                            //  53: '<<'
+	SymCaret                             //  54: '^'
+	SymDollarRound                       //  55: '$('
+	SymOpenClosedRound                   //  56: '()'
+	SymDoubleDollar                      //  57: '$$'
+	SymDoubleDot                         //  58: '..'
+	SymTripleDot                         //  59: '...'
+	SymStarEqual                         //  60: '*='
+	SymSlashEqual                        //  61: '/='
+	SymPercEqual                         //  62: '%='
 	SymChangeSign
 	SymUnchangeSign
 	SymIdentifier
@@ -86,6 +90,7 @@ const (
 	SymList
 	SymDict
 	SymIndex
+	SymRange // [index : index]
 	SymExpression
 	SymSelector     // <selector> ::= <expr> "?" <selector-case> {":" <selector-case>} ["::" <default-selector-case>]
 	SymSelectorCase // <selector-case> ::= [<list>] "{" <multi-expr> "}"
@@ -105,6 +110,7 @@ const (
 	SymKwIn
 	SymKwInclude
 	SymKwNil
+	SymKwUnset
 )
 
 var keywords map[string]Symbol
@@ -122,5 +128,6 @@ func init() {
 		"NOT":     SymKwNot,
 		"OR":      SymKwOr,
 		"NIL":     SymKwNil,
+		"UNSET":   SymKwUnset,
 	}
 }

t_ast_test.go

@@ -47,7 +47,7 @@ func TestAddUnknownTokens(t *testing.T) {
 	wantErr := errors.New(`unexpected token "%"`)
 
 	tree := NewAst()
-	if gotErr := tree.addToken(tk0); gotErr != nil && gotErr.Error() != wantErr.Error() {
+	if _, gotErr := tree.addToken(tk0); gotErr != nil && gotErr.Error() != wantErr.Error() {
 		t.Errorf("err: got <%v>, want <%v>", gotErr, wantErr)
 	}
 }

t_bool_test.go

@@ -0,0 +1,66 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// t_bool_test.go
+package expr
+
+import (
+	"errors"
+	"testing"
+)
+
+func TestBool(t *testing.T) {
+	section := "Bool"
+	inputs := []inputType{
+		/*   1 */ {`true`, true, nil},
+		/*   2 */ {`false`, false, nil},
+		/*   3 */ {`not false`, true, nil},
+		/*   4 */ {`not 1`, false, nil},
+		/*   5 */ {`not "true"`, false, nil},
+		/*   6 */ {`not "false"`, false, nil},
+		/*   7 */ {`not ""`, true, nil},
+		/*   8 */ {`not []`, nil, errors.New(`[1:4] prefix/postfix operator "NOT" do not support operand '[]' [list]`)},
+		/*   9 */ {`true and false`, false, nil},
+		/*  10 */ {`true and []`, nil, errors.New(`[1:9] left operand 'true' [bool] and right operand '[]' [list] are not compatible with operator "AND"`)},
+		/*  11 */ {`[] and false`, nil, errors.New(`got list as left operand type of 'AND' operator, it must be bool`)},
+		/*  12 */ {`true or false`, true, nil},
+		/*  13 */ {`true or []`, true, nil},
+		/*  14 */ {`[] or false`, nil, errors.New(`got list as left operand type of 'OR' operator, it must be bool`)},
+		/*  13 */ //{`true or []`, nil, errors.New(`[1:8] left operand 'true' [bool] and right operand '[]' [list] are not compatible with operator "OR"`)},
+	}
+
+	// t.Setenv("EXPR_PATH", ".")
+
+	// runTestSuiteSpec(t, section, inputs, 1)
+	runTestSuite(t, section, inputs)
+}
+
+func TestBoolNoShortcut(t *testing.T) {
+	section := "Bool-NoShortcut"
+	inputs := []inputType{
+		/*   1 */ {`true`, true, nil},
+		/*   2 */ {`false`, false, nil},
+		/*   3 */ {`not false`, true, nil},
+		/*   4 */ {`not 1`, false, nil},
+		/*   5 */ {`not "true"`, false, nil},
+		/*   6 */ {`not "false"`, false, nil},
+		/*   7 */ {`not ""`, true, nil},
+		/*   8 */ {`not []`, nil, `[1:4] prefix/postfix operator "NOT" do not support operand '[]' [list]`},
+		/*   9 */ {`true and false`, false, nil},
+		/*  10 */ {`true and []`, nil, `[1:9] left operand 'true' [bool] and right operand '[]' [list] are not compatible with operator "AND"`},
+		/*  11 */ {`[] and false`, nil, `[1:7] left operand '[]' [list] and right operand 'false' [bool] are not compatible with operator "AND"`},
+		/*  12 */ {`true or false`, true, nil},
+		/*  13 */ {`true or []`, nil, `[1:8] left operand 'true' [bool] and right operand '[]' [list] are not compatible with operator "OR"`},
+		/*  14 */ {`[] or false`, nil, `[1:6] left operand '[]' [list] and right operand 'false' [bool] are not compatible with operator "OR"`},
+	}
+
+	// t.Setenv("EXPR_PATH", ".")
+
+	ctx := NewSimpleStore()
+	current := SetCtrl(ctx, ControlBoolShortcut, false)
+
+	// runCtxTestSuiteSpec(t, ctx, section, inputs, 1)
+	runCtxTestSuite(t, ctx, section, inputs)
+
+	SetCtrl(ctx, ControlBoolShortcut, current)
+}

t_builtin-base_test.go

@@ -5,7 +5,6 @@
 package expr
 
 import (
-	"errors"
 	"testing"
 )
 
@@ -21,9 +20,9 @@ func TestFuncBase(t *testing.T) {
 		/*   6 */ {`int(3.1)`, int64(3), nil},
 		/*   7 */ {`int(3.9)`, int64(3), nil},
 		/*   8 */ {`int("432")`, int64(432), nil},
-		/*   9 */ {`int("1.5")`, nil, errors.New(`strconv.Atoi: parsing "1.5": invalid syntax`)},
-		/*  10 */ {`int("432", 4)`, nil, errors.New(`int(): too much params -- expected 1, got 2`)},
-		/*  11 */ {`int(nil)`, nil, errors.New(`int(): can't convert nil to int`)},
+		/*   9 */ {`int("1.5")`, nil, `strconv.Atoi: parsing "1.5": invalid syntax`},
+		/*  10 */ {`int("432", 4)`, nil, `int(): too many params -- expected 1, got 2`},
+		/*  11 */ {`int(nil)`, nil, `int(): can't convert nil to int`},
 		/*  12 */ {`isInt(2+1)`, true, nil},
 		/*  13 */ {`isInt(3.1)`, false, nil},
 		/*  14 */ {`isFloat(3.1)`, true, nil},
@@ -31,9 +30,9 @@ func TestFuncBase(t *testing.T) {
 		/*  16 */ {`isString("3" + 1)`, true, nil},
 		/*  17 */ {`isList(["3",  1])`, true, nil},
 		/*  18 */ {`isDict({"a":"3",  "b":1})`, true, nil},
-		/*  19 */ {`isFract(1|3)`, true, nil},
-		/*  20 */ {`isFract(3|1)`, false, nil},
-		/*  21 */ {`isRational(3|1)`, true, nil},
+		/*  19 */ {`isFract(1:3)`, true, nil},
+		/*  20 */ {`isFract(3:1)`, false, nil},
+		/*  21 */ {`isRational(3:1)`, true, nil},
 		/*  22 */ {`fract("2.2(3)")`, newFraction(67, 30), nil},
 		/*  23 */ {`fract("1.21(3)")`, newFraction(91, 75), nil},
 		/*  24 */ {`fract(1.21(3))`, newFraction(91, 75), nil},
@@ -42,26 +41,27 @@ func TestFuncBase(t *testing.T) {
 		/*  27 */ {`dec(2.0)`, float64(2), nil},
 		/*  28 */ {`dec("2.0")`, float64(2), nil},
 		/*  29 */ {`dec(true)`, float64(1), nil},
-		/*  30 */ {`dec(true")`, nil, errors.New("[1:11] missing string termination \"")},
-		/*  31 */ {`dec()`, nil, errors.New(`dec(): too few params -- expected 1, got 0`)},
-		/*  32 */ {`dec(1,2,3)`, nil, errors.New(`dec(): too much params -- expected 1, got 3`)},
+		/*  30 */ {`dec(true")`, nil, "[1:11] expected one of `,`, `)`, got `\"`"},
+		/*  31 */ {`dec()`, nil, `dec(): too few params -- expected 1, got 0`},
+		/*  32 */ {`dec(1,2,3)`, nil, `dec(): too many params -- expected 1, got 3`},
 		/*  33 */ {`isBool(false)`, true, nil},
-		/*  34 */ {`fract(1|2)`, newFraction(1, 2), nil},
+		/*  34 */ {`fract(1:2)`, newFraction(1, 2), nil},
 		/*  35 */ {`fract(12,2)`, newFraction(6, 1), nil},
 		/*  36 */ {`bool(2)`, true, nil},
-		/*  37 */ {`bool(1|2)`, true, nil},
+		/*  37 */ {`bool(1:2)`, true, nil},
 		/*  38 */ {`bool(1.0)`, true, nil},
 		/*  39 */ {`bool("1")`, true, nil},
 		/*  40 */ {`bool(false)`, false, nil},
-		/*  41 */ {`bool([1])`, nil, errors.New(`bool(): can't convert list to bool`)},
+		/*  41 */ {`bool([1])`, nil, `bool(): can't convert list to bool`},
 		/*  42 */ {`dec(false)`, float64(0), nil},
-		/*  43 */ {`dec(1|2)`, float64(0.5), nil},
-		/*  44 */ {`dec([1])`, nil, errors.New(`dec(): can't convert list to float`)},
-		// /*  45 */ {`string([1])`, nil, errors.New(`string(): can't convert list to string`)},
+		/*  43 */ {`dec(1:2)`, float64(0.5), nil},
+		/*  44 */ {`dec([1])`, nil, `dec(): can't convert list to float`},
+		/*  45 */ {`eval("a=3"); a`, int64(3), nil},
+		// /*  45 */ {`string([1])`, nil, `string(): can't convert list to string`},
 	}
 
 	t.Setenv("EXPR_PATH", ".")
 
-	// parserTestSpec(t, section, inputs, 2)
-	parserTest(t, section, inputs)
+	// runTestSuiteSpec(t, section, inputs, 45)
+	runTestSuite(t, section, inputs)
 }

t_builtin-fmt_test.go

@@ -0,0 +1,48 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// t_builtin-fmt.go
+package expr
+
+import (
+	// "errors"
+	"bytes"
+	"fmt"
+	"testing"
+)
+
+func TestFuncFmt(t *testing.T) {
+	section := "Builtin-Fmt"
+
+	inputs := []inputType{
+		/*   1 */ {`builtin "fmt"; print("ciao")`, int64(4), nil},
+		/*   2 */ {`builtin "fmt"; println(" ciao")`, int64(6), nil},
+	}
+
+	//t.Setenv("EXPR_PATH", ".")
+
+	// runTestSuiteSpec(t, section, inputs, 1)
+	runTestSuite(t, section, inputs)
+}
+
+func TestFmt(t *testing.T) {
+	section := "Builtin-Fmt"
+
+	text := "ciao mondo"
+	inputs := []inputType{
+		/*   1 */ {fmt.Sprintf(`builtin "fmt"; println("%s")`, text), int64(11), nil},
+	}
+
+	// t.Setenv("EXPR_PATH", ".")
+
+	var b bytes.Buffer
+	ctx := NewSimpleStore()
+	currentStdout := SetCtrl(ctx, ControlStdout, &b)
+
+	runCtxTestSuite(t, ctx, section, inputs)
+
+	SetCtrl(ctx, ControlStdout, currentStdout)
+	if b.String() != text+"\n" {
+		t.Errorf("println(): Got: %q, Want: %q", b.String(), text+"\n")
+	}
+}

t_builtin-import_test.go

@@ -19,6 +19,6 @@ func TestFuncImport(t *testing.T) {
 
 	t.Setenv("EXPR_PATH", "test-resources")
 
-	// parserTestSpec(t, section, inputs, 69)
-	parserTest(t, section, inputs)
+	//runTestSuiteSpec(t, section, inputs, 1)
+	runTestSuite(t, section, inputs)
 }

t_builtin-iterator_test.go

@@ -0,0 +1,30 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// t_builtin-iterator.go
+package expr
+
+import (
+	"testing"
+)
+
+func TestFuncRun(t *testing.T) {
+	section := "Builtin-Iterator"
+
+	inputs := []inputType{
+		/*   1 */ {`builtin "iterator"; it=$(1,2,3); run(it)`, nil, nil},
+		/*   2 */ {`builtin "iterator"; run($(1,2,3), func(index,item){item+10})`, nil, nil},
+		/*   3 */ {`builtin "iterator"; run($(1,2,3), func(index,item){status=status+item; true}, {"status":0})`, int64(6), nil},
+		/*   4 */ {`builtin ["iterator", "fmt"]; run($(1,2,3), func(index,item){println(item+10)})`, nil, nil},
+		/*   5 */ {`builtin "iterator"; run(nil)`, nil, `paramter "iterator" must be an iterator, passed <nil> [nil]`},
+		/*   6 */ {`builtin "iterator"; run($(1,2,3), nil)`, nil, nil},
+		/*   7 */ {`builtin "iterator"; run($(1,2,3), func(){1}, "prrr")`, nil, `paramter "vars" must be a dictionary, passed prrr [string]`},
+		/*   8 */ {`builtin "iterator"; run($(1,2,3), operator=nil)`, nil, nil},
+		/*   9 */ {`builtin "iterator"; run($(1,2,3), operatorx=nil)`, nil, `run(): unknown param "operatorx"`},
+	}
+
+	//t.Setenv("EXPR_PATH", ".")
+
+	//runTestSuiteSpec(t, section, inputs, 1)
+	runTestSuite(t, section, inputs)
+}

t_builtin-math-arith_test.go

@@ -5,7 +5,6 @@
 package expr
 
 import (
-	"errors"
 	"testing"
 )
 
@@ -14,16 +13,21 @@ func TestFuncMathArith(t *testing.T) {
 	inputs := []inputType{
 		/*   1 */ {`builtin "math.arith"; add(1,2)`, int64(3), nil},
 		/*   2 */ {`builtin "math.arith"; add(1,2,3)`, int64(6), nil},
-		/*   3 */ {`builtin "math.arith"; mulX(1,2,3)`, nil, errors.New(`unknown function mulX()`)},
+		/*   3 */ {`builtin "math.arith"; mulX(1,2,3)`, nil, `unknown function mulX()`},
 		/*   4 */ {`builtin "math.arith"; add(1+4,3+2,5*(3-2))`, int64(15), nil},
 		/*   5 */ {`builtin "math.arith"; add(add(1+4),3+2,5*(3-2))`, int64(15), nil},
 		/*   6 */ {`builtin "math.arith"; add(add(1,4),/*3+2,*/5*(3-2))`, int64(10), nil},
 		/*   7 */ {`builtin "math.arith"; a=5; b=2; add(a, b*3)`, int64(11), nil},
 		/*   8 */ {`builtin "math.arith"; var2="abc"; add(1,2) but var2`, "abc", nil},
+		/*   9 */ {`builtin "math.arith"; add()`, int64(0), nil},
+		/*  10 */ {`builtin "math.arith"; mul()`, int64(1), nil},
+		/*  11 */ {`builtin "math.arith"; add([1,2,3])`, int64(6), nil},
+		/*  12 */ {`builtin "math.arith"; mul([2,2,3])`, int64(12), nil},
+		/*  13 */ {`builtin "math.arith"; mul(2,2,3)`, int64(12), nil},
 	}
 
 	// t.Setenv("EXPR_PATH", ".")
 
-	// parserTestSpec(t, section, inputs, 69)
-	parserTest(t, section, inputs)
+	//runTestSuiteSpec(t, section, inputs, 10)
+	runTestSuite(t, section, inputs)
 }

t_builtin-os-file_test.go

@@ -5,7 +5,6 @@
 package expr
 
 import (
-	"errors"
 	"testing"
 )
 
@@ -14,16 +13,23 @@ func TestFuncOs(t *testing.T) {
 	inputs := []inputType{
 		/*   1 */ {`builtin "os.file"`, int64(1), nil},
 		/*   2 */ {`builtin "os.file"; handle=fileOpen("/etc/hosts"); fileClose(handle)`, true, nil},
-		/*   3 */ {`builtin "os.file"; handle=fileOpen("/etc/hostsX")`, nil, errors.New(`open /etc/hostsX: no such file or directory`)},
+		/*   3 */ {`builtin "os.file"; handle=fileOpen("/etc/hostsX")`, nil, `open /etc/hostsX: no such file or directory`},
 		/*   4 */ {`builtin "os.file"; handle=fileCreate("/tmp/dummy"); fileClose(handle)`, true, nil},
 		/*   5 */ {`builtin "os.file"; handle=fileAppend("/tmp/dummy"); fileWriteText(handle, "bye-bye"); fileClose(handle)`, true, nil},
 		/*   6 */ {`builtin "os.file"; handle=fileOpen("/tmp/dummy"); word=fileReadText(handle, "-"); fileClose(handle);word`, "bye", nil},
-		/*   7 */ {`builtin "os.file"; word=fileReadText(nil, "-")`, nil, errors.New(`fileReadText(): invalid file handle`)},
-		/*   7 */ {`builtin "os.file"; fileWriteText(nil, "bye")`, nil, errors.New(`fileWriteText(): invalid file handle`)},
+		/*   7 */ {`builtin "os.file"; word=fileReadText(nil, "-")`, nil, `fileReadText(): invalid file handle`},
+		/*   8 */ {`builtin "os.file"; fileWriteText(nil, "bye")`, nil, `fileWriteText(): invalid file handle`},
+		/*   9 */ {`builtin "os.file"; handle=fileOpen()`, nil, `fileOpen(): too few params -- expected 1, got 0`},
+		/*  10 */ {`builtin "os.file"; handle=fileOpen(123)`, nil, `fileOpen(): missing or invalid file path`},
+		/*  11 */ {`builtin "os.file"; handle=fileCreate(123)`, nil, `fileCreate(): missing or invalid file path`},
+		/*  12 */ {`builtin "os.file"; handle=fileAppend(123)`, nil, `fileAppend(): missing or invalid file path`},
+		/*  13 */ {`builtin "os.file"; handle=fileClose(123)`, nil, `fileClose(): invalid file handle`},
+		/*  14 */ {`builtin "os.file"; handle=fileOpen("/tmp/dummy"); c=fileReadTextAll(handle); fileClose(handle); c`, "bye-bye", nil},
+		/*  15 */ {`builtin "os.file"; c=fileReadTextAll(123)`, nil, `fileReadTextAll(): invalid file handle 123 [int64]`},
 	}
 
 	// t.Setenv("EXPR_PATH", ".")
 
-	// parserTestSpec(t, section, inputs, 69)
-	parserTest(t, section, inputs)
+	//runTestSuiteSpec(t, section, inputs, 2)
+	runTestSuite(t, section, inputs)
 }

t_builtin-string_test.go

@@ -5,7 +5,6 @@
 package expr
 
 import (
-	"errors"
 	"testing"
 )
 
@@ -16,8 +15,8 @@ func TestFuncString(t *testing.T) {
 		/*   1 */ {`builtin "string"; strJoin("-", "one", "two", "three")`, "one-two-three", nil},
 		/*   2 */ {`builtin "string"; strJoin("-", ["one", "two", "three"])`, "one-two-three", nil},
 		/*   3 */ {`builtin "string"; ls= ["one", "two", "three"]; strJoin("-", ls)`, "one-two-three", nil},
-		/*   4 */ {`builtin "string"; ls= ["one", "two", "three"]; strJoin(1, ls)`, nil, errors.New(`strJoin(): the "separator" parameter must be a string, got a integer (1)`)},
-		/*   5 */ {`builtin "string"; ls= ["one", 2, "three"]; strJoin("-", ls)`, nil, errors.New(`strJoin(): expected string, got integer (2)`)},
+		/*   4 */ {`builtin "string"; ls= ["one", "two", "three"]; strJoin(1, ls)`, nil, `strJoin(): the "separator" parameter must be a string, got an integer (1)`},
+		/*   5 */ {`builtin "string"; ls= ["one", 2, "three"]; strJoin("-", ls)`, nil, `strJoin(): expected string, got integer (2)`},
 		/*   6 */ {`builtin "string"; "<"+strTrim("  bye bye  ")+">"`, "<bye bye>", nil},
 		/*   7 */ {`builtin "string"; strSub("0123456789", 1,2)`, "12", nil},
 		/*   8 */ {`builtin "string"; strSub("0123456789", -3,2)`, "78", nil},
@@ -25,13 +24,13 @@ func TestFuncString(t *testing.T) {
 		/*  10 */ {`builtin "string"; strSub("0123456789")`, "0123456789", nil},
 		/*  11 */ {`builtin "string"; strStartsWith("0123456789", "xyz", "012")`, true, nil},
 		/*  12 */ {`builtin "string"; strStartsWith("0123456789", "xyz", "0125")`, false, nil},
-		/*  13 */ {`builtin "string"; strStartsWith("0123456789")`, nil, errors.New(`strStartsWith(): too few params -- expected 2 or more, got 1`)},
+		/*  13 */ {`builtin "string"; strStartsWith("0123456789")`, nil, `strStartsWith(): too few params -- expected 2 or more, got 1`},
 		/*  14 */ {`builtin "string"; strEndsWith("0123456789", "xyz", "789")`, true, nil},
 		/*  15 */ {`builtin "string"; strEndsWith("0123456789", "xyz", "0125")`, false, nil},
-		/*  16 */ {`builtin "string"; strEndsWith("0123456789")`, nil, errors.New(`strEndsWith(): too few params -- expected 2 or more, got 1`)},
+		/*  16 */ {`builtin "string"; strEndsWith("0123456789")`, nil, `strEndsWith(): too few params -- expected 2 or more, got 1`},
 		/*  17 */ {`builtin "string"; strSplit("one-two-three", "-")`, newListA("one", "two", "three"), nil},
-		/*  18 */ {`builtin "string"; strJoin("-", [1, "two", "three"])`, nil, errors.New(`strJoin(): expected string, got integer (1)`)},
-		/*  19 */ {`builtin "string"; strJoin()`, nil, errors.New(`strJoin(): too few params -- expected 1 or more, got 0`)},
+		/*  18 */ {`builtin "string"; strJoin("-", [1, "two", "three"])`, nil, `strJoin(): expected string, got integer (1)`},
+		/*  19 */ {`builtin "string"; strJoin()`, nil, `strJoin(): too few params -- expected 1 or more, got 0`},
 
 		/*  69 */ /*{`builtin "string"; $$global`, `vars: {
 		}
@@ -64,6 +63,6 @@ func TestFuncString(t *testing.T) {
 
 	//t.Setenv("EXPR_PATH", ".")
 
-	// parserTestSpec(t, section, inputs, 19)
-	parserTest(t, section, inputs)
+	// runTestSuiteSpec(t, section, inputs, 19)
+	runTestSuite(t, section, inputs)
 }

t_common_test.go

@@ -0,0 +1,115 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// t_common_test.go
+package expr
+
+import (
+	"errors"
+	"reflect"
+	"strings"
+	"testing"
+)
+
+type inputType struct {
+	source     string
+	wantResult any
+	wantErr    any
+}
+
+func runCtxTestSuiteSpec(t *testing.T, ctx ExprContext, section string, inputs []inputType, spec ...int) {
+	succeeded := 0
+	failed := 0
+	for _, count := range spec {
+		good := doTest(t, ctx, section, &inputs[count-1], count)
+
+		if good {
+			succeeded++
+		} else {
+			failed++
+		}
+	}
+	t.Logf("%s -- test count: %d, succeeded: %d, failed: %d", section, len(spec), succeeded, failed)
+}
+
+func runTestSuiteSpec(t *testing.T, section string, inputs []inputType, spec ...int) {
+	runCtxTestSuiteSpec(t, nil, section, inputs, spec...)
+}
+
+func runCtxTestSuite(t *testing.T, ctx ExprContext, section string, inputs []inputType) {
+
+	succeeded := 0
+	failed := 0
+
+	for i, input := range inputs {
+		// fmt.Printf("%3d: %s\n", i+1, input.source)
+
+		good := doTest(t, ctx, section, &input, i+1)
+		if good {
+			succeeded++
+		} else {
+			failed++
+		}
+	}
+	t.Logf("%s -- test count: %d, succeeded: %d, failed: %d", section, len(inputs), succeeded, failed)
+}
+func runTestSuite(t *testing.T, section string, inputs []inputType) {
+	runCtxTestSuite(t, nil, section, inputs)
+}
+
+func getWantedError(input *inputType) error {
+	var wantErr error
+	var ok bool
+	if wantErr, ok = input.wantErr.(error); !ok {
+		if msg, ok := input.wantErr.(string); ok {
+			wantErr = errors.New(msg)
+		}
+	}
+	return wantErr
+}
+
+func doTest(t *testing.T, ctx ExprContext, section string, input *inputType, count int) (good bool) {
+	var expr Expr
+	var gotResult any
+	var gotErr error
+
+	wantErr := getWantedError(input)
+
+	parser := NewParser()
+	if ctx == nil {
+		ctx = NewSimpleStore()
+	}
+
+	logTest(t, count, section, input.source, input.wantResult, wantErr)
+
+	r := strings.NewReader(input.source)
+	scanner := NewScanner(r, DefaultTranslations())
+
+	good = true
+	if expr, gotErr = parser.Parse(scanner); gotErr == nil {
+		gotResult, gotErr = expr.Eval(ctx)
+	}
+
+	eq := reflect.DeepEqual(gotResult, input.wantResult)
+
+	if !eq /*gotResult != input.wantResult*/ {
+		t.Errorf("%d: `%s` -> result = %v [%s], want = %v [%s]", count, input.source, gotResult, TypeName(gotResult), input.wantResult, TypeName(input.wantResult))
+		good = false
+	}
+
+	if gotErr != wantErr {
+		if wantErr == nil || gotErr == nil || (gotErr.Error() != wantErr.Error()) {
+			t.Errorf("%d: %s -> got-err = <%v>, expected-err = <%v>", count, input.source, gotErr, wantErr)
+			good = false
+		}
+	}
+	return
+}
+
+func logTest(t *testing.T, n int, section, source string, wantResult any, wantErr error) {
+	if wantErr == nil {
+		t.Logf("[+]%s nr %3d -- `%s`  --> %v", section, n, source, wantResult)
+	} else {
+		t.Logf("[-]%s nr %3d -- `%s`  --> %v", section, n, source, wantErr)
+	}
+}

t_dict_test.go

@@ -22,7 +22,7 @@ func TestDictParser(t *testing.T) {
 
 	inputs := []inputType{
 		/*  1 */ {`{}`, map[any]any{}, nil},
-		/*  2 */ {`{123}`, nil, errors.New(`[1:6] expected ":", got "}"`)},
+		/*  2 */ {`{123}`, nil, errors.New("[1:6] expected `:`, got `}`")},
 		/*  3 */ {`{1:"one",2:"two",3:"three"}`, map[int64]any{int64(1): "one", int64(2): "two", int64(3): "three"}, nil},
 		/*  4 */ {`{1:"one",2:"two",3:"three"}[3]`, "three", nil},
 		/*  5 */ {`#{1:"one",2:"two",3:"three"}`, int64(3), nil},
@@ -32,6 +32,11 @@ func TestDictParser(t *testing.T) {
 		/*  9 */ {`D={"a":1, "b":2}; D["z"]=9; D`, map[any]any{"z": 9, "a": 1, "b": 2}, nil},
 		/* 10 */ {`D={"a":1, "b":2}; D[nil]=9`, nil, errors.New(`[1:21] index/key is nil`)},
 		/* 11 */ {`D={"a":1, "b":2}; D["a"]`, int64(1), nil},
+		/* 12 */ {`m={
+			"a":1,
+			//"b":2,
+			"c":3
+			}`, map[any]any{"a": 1, "c": 3}, nil},
 		}
 
 	succeeded := 0

t_expr_test.go

@@ -17,10 +17,22 @@ func TestExpr(t *testing.T) {
 		/*   3 */ {`builtin "os.file"; f=fileOpen("test-file.txt"); line=fileReadText(f); fileClose(f); line`, "uno", nil},
 		/*   4 */ {`mynot=func(v){int(v)?{true}::{false}}; mynot(0)`, true, nil},
 		/*   5 */ {`1 ? {1} : [1+0] {3*(1+1)}`, int64(6), nil},
-		/*   6 */ {`
+		/*   6 */ {`a=3; a+=1; a`, int64(4), nil},
+		/*   7 */ {`a=3; a-=1; a`, int64(2), nil},
+		/*   8 */ {`a=3; a*=2; a`, int64(6), nil},
+		/*   9 */ {`v=[10,20,30]; v[0]+=1; v[0]`, int64(11), nil},
+		/*  10 */ {`r={"a":10}; r["a"]+=1; r["a"]`, int64(11), nil},
+		/*  11 */ {`a=3; a/=2`, int64(1), nil},
+		/*  12 */ {`*=2`, nil, `[1:2] infix operator "*=" requires two non-nil operands, got 1`},
+		/*  13 */ {`a=3; a*=2+1; a`, int64(9), nil},
+		/*  14 */ {`a=3; (a*=2)+1; a`, int64(6), nil},
+		/*  15 */ {`a=3; a*=2)+1; a`, nil, `[1:11] unexpected token ")"`},
+		/*  16 */ {`v=[2]; a=1; v[a-=1]=5; v[0]`, int64(5), nil},
+		/*  17 */ {`true ? {"a"} :: {"b"}`, "a", nil},
+		/*  18 */ {`
 		ds={
-			"init":func(end){@end=end; @current=0 but true},
-			"current":func(){current},
+			"init":func(@end){@current=0 but true},
+			//"current":func(){current},
 			"next":func(){
 				((next=current+1) <= end) ? [true] {@current=next but current} :: {nil}
 			}
@@ -32,6 +44,6 @@ func TestExpr(t *testing.T) {
 	}
 	// t.Setenv("EXPR_PATH", ".")
 
-	// parserTestSpec(t, section, inputs, 3)
-	parserTest(t, section, inputs)
+	// runTestSuiteSpec(t, section, inputs, 6, 7, 8, 9)
+	runTestSuite(t, section, inputs)
 }

t_fractions_test.go

@@ -5,41 +5,45 @@
 package expr
 
 import (
-	"errors"
 	"testing"
 )
 
 func TestFractionsParser(t *testing.T) {
 	section := "Fraction"
 	inputs := []inputType{
-		/*   1 */ {`1|2`, newFraction(1, 2), nil},
-		/*   2 */ {`1|2 + 1`, newFraction(3, 2), nil},
-		/*   3 */ {`1|2 - 1`, newFraction(-1, 2), nil},
-		/*   4 */ {`1|2 * 1`, newFraction(1, 2), nil},
-		/*   5 */ {`1|2 * 2|3`, newFraction(2, 6), nil},
-		/*   6 */ {`1|2 / 2|3`, newFraction(3, 4), nil},
-		/*   7 */ {`1|"5"`, nil, errors.New(`denominator must be integer, got string (5)`)},
-		/*   8 */ {`"1"|5`, nil, errors.New(`numerator must be integer, got string (1)`)},
-		/*   9 */ {`1|+5`, nil, errors.New(`[1:3] infix operator "|" requires two non-nil operands, got 1`)},
-		/*  10 */ {`1|(-2)`, newFraction(-1, 2), nil},
-		/*  11 */ {`builtin "math.arith"; add(1|2, 2|3)`, newFraction(7, 6), nil},
-		/*  12 */ {`builtin "math.arith"; add(1|2, 1.0, 2)`, float64(3.5), nil},
-		/*  13 */ {`builtin "math.arith"; mul(1|2, 2|3)`, newFraction(2, 6), nil},
-		/*  14 */ {`builtin "math.arith"; mul(1|2, 1.0, 2)`, float64(1.0), nil},
-		/*  15 */ {`1|0`, nil, errors.New(`division by zero`)},
+		/*   1 */ {`1:2`, newFraction(1, 2), nil},
+		/*   2 */ {`1:2 + 1`, newFraction(3, 2), nil},
+		/*   3 */ {`1:2 - 1`, newFraction(-1, 2), nil},
+		/*   4 */ {`1:2 * 1`, newFraction(1, 2), nil},
+		/*   5 */ {`1:2 * 2:3`, newFraction(2, 6), nil},
+		/*   6 */ {`1:2 / 2:3`, newFraction(3, 4), nil},
+		/*   7 */ {`1:"5"`, nil, `denominator must be integer, got string (5)`},
+		/*   8 */ {`"1":5`, nil, `numerator must be integer, got string (1)`},
+		/*   9 */ {`1:+5`, newFraction(1, 5), nil},
+		/*  10 */ {`1:(-2)`, newFraction(-1, 2), nil},
+		/*  11 */ {`builtin "math.arith"; add(1:2, 2:3)`, newFraction(7, 6), nil},
+		/*  12 */ {`builtin "math.arith"; add(1:2, 1.0, 2)`, float64(3.5), nil},
+		/*  13 */ {`builtin "math.arith"; mul(1:2, 2:3)`, newFraction(2, 6), nil},
+		/*  14 */ {`builtin "math.arith"; mul(1:2, 1.0, 2)`, float64(1.0), nil},
+		/*  15 */ {`1:0`, nil, `division by zero`},
 		/*  16 */ {`fract(-0.5)`, newFraction(-1, 2), nil},
-		/*  17 */ {`fract("")`, (*FractionType)(nil), errors.New(`bad syntax`)},
+		/*  17 */ {`fract("")`, (*FractionType)(nil), `bad syntax`},
 		/*  18 */ {`fract("-1")`, newFraction(-1, 1), nil},
 		/*  19 */ {`fract("+1")`, newFraction(1, 1), nil},
-		/*  20 */ {`fract("1a")`, (*FractionType)(nil), errors.New(`strconv.ParseInt: parsing "1a": invalid syntax`)},
-		/*  21 */ {`fract(1,0)`, nil, errors.New(`fract(): division by zero`)},
+		/*  20 */ {`fract("1a")`, (*FractionType)(nil), `strconv.ParseInt: parsing "1a": invalid syntax`},
+		/*  21 */ {`fract(1,0)`, nil, `fract(): division by zero`},
+		/*  22 */ {`string(1:2)`, "1:2", nil},
+		/*  23 */ {`1+1:2+0.5`, float64(2), nil},
+		/*  24 */ {`1:(2-2)`, nil, `division by zero`},
+		/*  25 */ {`[0,1][1-1]:1`, newFraction(0, 1), nil},
 	}
-	parserTest(t, section, inputs)
+	// runTestSuiteSpec(t, section, inputs, 25)
+	runTestSuite(t, section, inputs)
 }
 
 func TestFractionToStringSimple(t *testing.T) {
 	source := newFraction(1, 2)
-	want := "1|2"
+	want := "1:2"
 	got := source.ToString(0)
 	if got != want {
 		t.Errorf(`(1,2) -> result = %v [%T], want = %v [%T]`, got, got, want, want)
@@ -55,10 +59,9 @@ func TestFractionToStringMultiline(t *testing.T) {
 	}
 }
 
-// TODO Check this test: the output string ends with a space
-func _TestToStringMultilineTty(t *testing.T) {
+func TestToStringMultilineTty(t *testing.T) {
 	source := newFraction(-1, 2)
-	want := "\x1b[4m-1\x1b[0m\n2"
+	want := "\x1b[4m-1\x1b[0m\n 2"
 	got := source.ToString(MultiLine | TTY)
 	if got != want {
 		t.Errorf(`(1,2) -> result = %#v [%T], want = %#v [%T]`, got, got, want, want)

t_funcs_test.go

@@ -5,7 +5,6 @@
 package expr
 
 import (
-	"errors"
 	"testing"
 )
 
@@ -17,34 +16,44 @@ func TestFuncs(t *testing.T) {
 		/*   3 */ {`double=func(x){2*x}; double(3)`, int64(6), nil},
 		/*   4 */ {`double=func(x){2*x}; a=5; double(3+a) + 1`, int64(17), nil},
 		/*   5 */ {`double=func(x){2*x}; a=5; two=func() {2}; (double(3+a) + 1) * two()`, int64(34), nil},
-		/*   6 */ {`@x="hello"; @x`, nil, errors.New(`[1:3] variable references are not allowed in top level expressions: "@x"`)},
+		/*   6 */ {`@x="hello"; @x`, nil, `[1:3] variable references are not allowed in top level expressions: "@x"`},
 		/*   7 */ {`f=func(){@x="hello"}; f(); x`, "hello", nil},
 		/*   8 */ {`f=func(@y){@y=@y+1}; f(2); y`, int64(3), nil},
-		/*   9 */ {`f=func(@y){g=func(){@x=5}; @y=@y+g()}; f(2); y+x`, nil, errors.New(`undefined variable or function "x"`)},
+		/*   9 */ {`f=func(@y){g=func(){@x=5}; @y=@y+g()}; f(2); y+x`, nil, `undefined variable or function "x"`},
 		/*  10 */ {`f=func(@y){g=func(){@x=5}; @z=g(); @y=@y+@z}; f(2); y+z`, int64(12), nil},
 		/*  11 */ {`f=func(@y){g=func(){@x=5}; g(); @z=x; @y=@y+@z}; f(2); y+z`, int64(12), nil},
 		/*  12 */ {`f=func(@y){g=func(){@x=5}; g(); @z=x; @x=@y+@z}; f(2); y+x`, int64(9), nil},
 		/*  13 */ {`two=func(){2}; four=func(f){f()+f()}; four(two)`, int64(4), nil},
-		/*  14 */ {`two=func(){2}; two(123)`, nil, errors.New(`two(): too much params -- expected 0, got 1`)},
+		/*  14 */ {`two=func(){2}; two(123)`, nil, `two(): too many params -- expected 0, got 1`},
 		/*  15 */ {`f=func(x,n=2){x+n}; f(3)`, int64(5), nil},
-		/*  16 */ {`f=func(x,n=2,y){x+n}`, nil, errors.New(`[1:16] can't mix default and non-default parameters`)},
-		/*  17 */ {`f=func(x,n){1}; f(3,4,)`, nil, errors.New(`[1:24] expected "function-param-value", got ")"`)},
+		/*  16 */ {`f=func(x,n=2,y){x+n}`, nil, `[1:16] can't mix default and non-default parameters`},
+		/*  17 */ {`f=func(x,n){1}; f(3,4,)`, nil, "[1:24] expected `function-param-value`, got `)`"},
+		/*  18 */ {`factory=func(base){func(){@base=base+1}}; inc10=factory(10); inc5=factory(5); inc10(); inc5(); inc10()`, int64(12), nil},
+		/*  19 */ {`f=func(a,y=1,z="sos"){}; string(f)`, `f(a, y=1, z="sos"):any{}`, nil},
+		/*  20 */ {`f=func(a,b){a*2+b}; f(1,10)`, int64(12), nil},
+		/*  21 */ {`f=func(a,b){a*2+b}; f(a=2,b=1)`, int64(5), nil},
+		/*  22 */ {`f=func(a,b){a*2+b}; f(b=2,a=1)`, int64(4), nil},
+		/*  23 */ {`f=func(a=10,b=10){a*2+b}; f(b=1)`, int64(21), nil},
+		/*  24 */ {`f=func(a,b){a*2+b}; f(a=1,2)`, nil, `f(): positional param nr 2 not allowed after named params`},
+		/*  25 */ {`f=func(x,x){x}`, nil, `[1:11] parameter "x" at position 2 already defined at position 1`},
+		//		/*  20 */ {`a=[func(){3}]; a[0]()`, int64(3), nil},
+		//		/*  20 */ {`m={}; m["f"]=func(){3}; m["f"]()`, int64(3), nil},
 		// /*  18 */ {`f=func(a){a*2}`, nil, errors.New(`[1:24] expected "function-param-value", got ")"`)},
 	}
 
 	// t.Setenv("EXPR_PATH", ".")
 
-	// parserTestSpec(t, section, inputs, 17)
-	parserTest(t, section, inputs)
+	//runTestSuiteSpec(t, section, inputs, 19)
+	runTestSuite(t, section, inputs)
 }
 
-func dummy(ctx ExprContext, name string, args []any) (result any, err error) {
+func dummy(ctx ExprContext, name string, args map[string]any) (result any, err error) {
 	return
 }
 
 func TestFunctionToStringSimple(t *testing.T) {
 	source := NewGolangFunctor(dummy)
-	want := "func() {}"
+	want := "func(){}"
 	got := source.ToString(0)
 	if got != want {
 		t.Errorf(`(func() -> result = %v [%T], want = %v [%T]`, got, got, want, want)

t_helpers_test.go

@@ -5,50 +5,51 @@
 package expr
 
 import (
-	"fmt"
 	"testing"
 )
 
-func subtract(ctx ExprContext, name string, args []any) (result any, err error) {
-	if len(args) != 2 {
-		err = fmt.Errorf("%s(): requires exactly two arguments", name)
-		return
-	}
-	x, xok := args[0].(int64)
-	y, yok := args[1].(int64)
-	if xok && yok {
-		result = x - y
-	} else {
-		err = fmt.Errorf("expected integer (int64) arguments, got %T and %T values", x, y)
-	}
-	return
-}
+// TODO The new function param model does not allow this kind of test
+// ------------------------------------------------------------------
+// func subtract(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+// 	if len(args) != 2 {
+// 		err = fmt.Errorf("%s(): requires exactly two arguments", name)
+// 		return
+// 	}
+// 	x, xok := args[0].(int64)
+// 	y, yok := args[1].(int64)
+// 	if xok && yok {
+// 		result = x - y
+// 	} else {
+// 		err = fmt.Errorf("expected integer (int64) arguments, got %T and %T values", x, y)
+// 	}
+// 	return
+// }
 
-func TestEvalStringA(t *testing.T) {
+// func TestEvalStringA(t *testing.T) {
 
-	source := `a + b * subtract(4,2)`
-	args := []Arg{
-		{"a", uint8(1)},
-		{"b", int8(2)},
-		{"subtract", FuncTemplate(subtract)},
-		// force coverage
-		{"a16", uint16(1)},
-		{"b16", int16(2)},
-		{"a32", uint32(1)},
-		{"b32", int32(2)},
-		{"a64", uint64(1)},
-		{"b64", int64(2)},
-		{"f32", float32(1.0)},
-		{"f64", float64(1.0)},
-	}
+// 	source := `a + b * subtract(4,2)`
+// 	args := []Arg{
+// 		{"a", uint8(1)},
+// 		{"b", int8(2)},
+// 		{"subtract", FuncTemplate2(subtract)},
+// 		// force coverage
+// 		{"a16", uint16(1)},
+// 		{"b16", int16(2)},
+// 		{"a32", uint32(1)},
+// 		{"b32", int32(2)},
+// 		{"a64", uint64(1)},
+// 		{"b64", int64(2)},
+// 		{"f32", float32(1.0)},
+// 		{"f64", float64(1.0)},
+// 	}
 
-	wantResult := int64(5)
-	gotResult, gotErr := EvalStringA(source, args...)
-	if value, ok := gotResult.(int64); ok && value != wantResult {
-		t.Errorf("Source %q got %v, want %v", source, gotResult, wantResult)
-		t.Errorf("Error: %v", gotErr)
-	}
-}
+// 	wantResult := int64(5)
+// 	gotResult, gotErr := EvalStringA(source, args...)
+// 	if value, ok := gotResult.(int64); ok && value != wantResult {
+// 		t.Errorf("Source %q got %v, want %v", source, gotResult, wantResult)
+// 		t.Errorf("Error: %v", gotErr)
+// 	}
+// }
 
 func TestEvalString(t *testing.T) {
 
@@ -68,7 +69,7 @@ func TestEvalString(t *testing.T) {
 
 	// force coverage
 	ctx.GetFuncInfo("dummy")
-	ctx.Call("dummy", []any{})
+	ctx.Call("dummy", map[string]any{})
 
 	source := `a + b * f`
 

t_index_test.go

@@ -5,7 +5,6 @@
 package expr
 
 import (
-	"errors"
 	"testing"
 )
 
@@ -17,11 +16,13 @@ func TestCollections(t *testing.T) {
 		/*   3 */ {`"abcdef"[1:]`, "bcdef", nil},
 		/*   4 */ {`"abcdef"[:]`, "abcdef", nil},
 		// /*   5 */ {`[0,1,2,3,4][:]`, ListType{int64(0), int64(1), int64(2), int64(3), int64(4)}, nil},
-		/*   5 */ {`"abcdef"[1:2:3]`, nil, errors.New(`[1:14] left operand '(1, 2)' [pair] and right operand '3' [integer] are not compatible with operator ":"`)},
+		/*   5 */ {`"abcdef"[1:2:3]`, nil, `[1:14] invalid range specification`},
+		/*   6 */ {`"abcdef"[((1>0)?{1}:{0}):3]`, "bc", nil},
+		/*   7 */ {`"abcdef"[[0,1][0]:1]`, "a", nil},
 	}
 
 	t.Setenv("EXPR_PATH", ".")
 
-	// parserTestSpec(t, section, inputs, 5)
-	parserTest(t, section, inputs)
+	// runTestSuiteSpec(t, section, inputs, 5)
+	runTestSuite(t, section, inputs)
 }

t_iter-list_test.go

@@ -15,7 +15,7 @@ func TestNewListIterator(t *testing.T) {
 	if item, err := it.Next(); err != nil {
 		t.Errorf("error: %v", err)
 	} else if item != "b" {
-		t.Errorf("expcted %q, got %q", "b", item)
+		t.Errorf("expected %q, got %q", "b", item)
 	} else {
 		t.Logf("Next: %v", item)
 	}
@@ -27,7 +27,7 @@ func TestNewListIterator2(t *testing.T) {
 	if item, err := it.Next(); err != nil {
 		t.Errorf("error: %v", err)
 	} else if item != "d" {
-		t.Errorf("expcted %q, got %q", "d", item)
+		t.Errorf("expected %q, got %q", "d", item)
 	} else {
 		t.Logf("Next: %v", item)
 	}
@@ -39,7 +39,7 @@ func TestNewListIterator3(t *testing.T) {
 	if item, err := it.Next(); err != nil {
 		t.Errorf("error: %v", err)
 	} else if item != "b" {
-		t.Errorf("expcted %q, got %q", "b", item)
+		t.Errorf("expected %q, got %q", "b", item)
 	} else {
 		t.Logf("Next: %v", item)
 	}
@@ -51,7 +51,7 @@ func TestNewIterList2(t *testing.T) {
 	if item, err := it.Next(); err != nil {
 		t.Errorf("error: %v", err)
 	} else if item != "a" {
-		t.Errorf("expcted %q, got %q", "a", item)
+		t.Errorf("expected %q, got %q", "a", item)
 	} else {
 		t.Logf("Next: %v", item)
 	}
@@ -63,7 +63,7 @@ func TestNewIterList3(t *testing.T) {
 	if item, err := it.Next(); err != nil {
 		t.Errorf("error: %v", err)
 	} else if item != "a" {
-		t.Errorf("expcted %q, got %q", "a", item)
+		t.Errorf("expected %q, got %q", "a", item)
 	} else {
 		t.Logf("Next: %v", item)
 	}
@@ -83,7 +83,7 @@ func TestNewIterList5(t *testing.T) {
 	if item, err := it.Next(); err != nil {
 		t.Errorf("error: %v", err)
 	} else if item != "123" {
-		t.Errorf("expcted %q, got %q", "123", item)
+		t.Errorf("expected %q, got %q", "123", item)
 	} else {
 		t.Logf("Next: %v", item)
 	}
@@ -96,7 +96,7 @@ func TestNewIterList6(t *testing.T) {
 	if item, err := it.Next(); err != nil {
 		t.Errorf("error: %v", err)
 	} else if item != "a" {
-		t.Errorf("expcted %q, got %q", "a", item)
+		t.Errorf("expected %q, got %q", "a", item)
 	} else {
 		t.Logf("Next: %v", item)
 	}

t_iterator_test.go

@@ -7,20 +7,28 @@ package expr
 import "testing"
 
 func TestIteratorParser(t *testing.T) {
+	section := "Iterator"
 	inputs := []inputType{
-		/*   1 */ {`include "test-resources/iterator.expr"; it=$(ds,3); ()it`, int64(0), nil},
+		/*   1 */ {`include "test-resources/iterator.expr"; it=$(ds,3); ^it`, int64(0), nil},
 		/*   2 */ {`include "test-resources/iterator.expr"; it=$(ds,3); it++; it++`, int64(1), nil},
-		/*   3 */ {`include "test-resources/iterator.expr"; it=$(ds,3); it++; it++; #it`, int64(2), nil},
-		/*   4 */ {`include "test-resources/iterator.expr"; it=$(ds,3); it++; it++; it.reset; ()it`, int64(0), nil},
+		/*   3 */ {`include "test-resources/iterator.expr"; it=$(ds,3); it++; it++; #it`, int64(3), nil},
+		/*   4 */ {`include "test-resources/iterator.expr"; it=$(ds,3); it++; it++; it.reset; ^it`, int64(0), nil},
 		/*   5 */ {`builtin "math.arith"; include "test-resources/iterator.expr"; it=$(ds,3); add(it)`, int64(6), nil},
 		/*   6 */ {`builtin "math.arith"; include "test-resources/iterator.expr"; it=$(ds,3); mul(it)`, int64(0), nil},
 		/*   7 */ {`builtin "math.arith"; include "test-resources/file-reader.expr"; it=$(ds,"test-resources/int.list"); mul(it)`, int64(12000), nil},
 		/*   8 */ {`include "test-resources/file-reader.expr"; it=$(ds,"test-resources/int.list"); it++; it.index`, int64(0), nil},
-		/*  10 */ {`include "test-resources/file-reader.expr"; it=$(ds,"test-resources/int.list"); it.clean`, true, nil},
-		/*  11 */ {`it=$(1,2,3); it++`, int64(1), nil},
+		/*   9 */ {`include "test-resources/file-reader.expr"; it=$(ds,"test-resources/int.list"); it.clean`, nil, nil},
+		/*  10 */ {`it=$(1,2,3); it++`, int64(1), nil},
+		/*  11 */ {`it=$(1,2,3); it++; it.reset; it++`, int64(1), nil},
+		/*  12 */ {`it=$([1,2,3,4],1); it++`, int64(2), nil},
+		/*  13 */ {`it=$([1,2,3,4],1,3); it++; it++;`, int64(3), nil},
+		/*  14 */ {`it=$([1,2,3,4],1,3,2); it++; it++;`, int64(4), nil},
+		/*  15 */ {`it=$([1,2,3,4],1,2,2); it++; it++;`, nil, `EOF`},
+		/*  16 */ {`include "test-resources/filter.expr"; it=$(ds,10); it++`, int64(2), nil},
+		/*  17 */ {`it=$({"next":func(){5}}); it++`, int64(5), nil},
+		/*  18 */ {`it=$({"next":func(){5}}); it.clean`, nil, nil},
 	}
-	// inputs1 := []inputType{
-	// 	/*   1 */ {`0?{}`, nil, nil},
-	// }
-	parserTest(t, "Iterator", inputs)
+
+	//runTestSuiteSpec(t, section, inputs, 18)
+	runTestSuite(t, section, inputs)
 }

t_list_test.go

@@ -5,7 +5,6 @@
 package expr
 
 import (
-	"errors"
 	"testing"
 )
 
@@ -22,14 +21,14 @@ func TestListParser(t *testing.T) {
 		/*   7 */ {`add([1,4,3,2])`, int64(10), nil},
 		/*   8 */ {`add([1,[2,2],3,2])`, int64(10), nil},
 		/*   9 */ {`mul([1,4,3.0,2])`, float64(24.0), nil},
-		/*  10 */ {`add([1,"hello"])`, nil, errors.New(`add(): param nr 2 (2 in 1) has wrong type string, number expected`)},
+		/*  10 */ {`add([1,"hello"])`, nil, `add(): param nr 2 (2 in 1) has wrong type string, number expected`},
 		/*  11 */ {`[a=1,b=2,c=3] but a+b+c`, int64(6), nil},
 		/*  12 */ {`[1,2,3] << 2+2`, newListA(int64(1), int64(2), int64(3), int64(4)), nil},
 		/*  13 */ {`2-1 >> [2,3]`, newListA(int64(1), int64(2), int64(3)), nil},
 		/*  14 */ {`[1,2,3][1]`, int64(2), nil},
 		/*  15 */ {`ls=[1,2,3] but ls[1]`, int64(2), nil},
 		/*  16 */ {`ls=[1,2,3] but ls[-1]`, int64(3), nil},
-		/*  17 */ {`list=["one","two","three"]; list[10]`, nil, errors.New(`[1:34] index 10 out of bounds`)},
+		/*  17 */ {`list=["one","two","three"]; list[10]`, nil, `[1:34] index 10 out of bounds`},
 		/*  18 */ {`["a", "b", "c"]`, newListA("a", "b", "c"), nil},
 		/*  19 */ {`["a", "b", "c"]`, newList([]any{"a", "b", "c"}), nil},
 		/*  20 */ {`#["a", "b", "c"]`, int64(3), nil},
@@ -37,18 +36,18 @@ func TestListParser(t *testing.T) {
 		/*  22 */ {`a=[1,2]; (a)<<3`, newListA(int64(1), int64(2), int64(3)), nil},
 		/*  23 */ {`a=[1,2]; (a)<<3; a`, newListA(int64(1), int64(2)), nil},
 		/*  24 */ {`["a","b","c","d"][1]`, "b", nil},
-		/*  25 */ {`["a","b","c","d"][1,1]`, nil, errors.New(`[1:19] one index only is allowed`)},
+		/*  25 */ {`["a","b","c","d"][1,1]`, nil, `[1:19] one index only is allowed`},
 		/*  26 */ {`[0,1,2,3,4][:]`, newListA(int64(0), int64(1), int64(2), int64(3), int64(4)), nil},
-		/*  27 */ {`["a", "b", "c"] << ;`, nil, errors.New(`[1:18] infix operator "<<" requires two non-nil operands, got 1`)},
-		/*  28 */ {`2 << 3;`, nil, errors.New(`[1:4] left operand '2' [integer] and right operand '3' [integer] are not compatible with operator "<<"`)},
-		/*  29 */ {`but >> ["a", "b", "c"]`, nil, errors.New(`[1:6] infix operator ">>" requires two non-nil operands, got 0`)},
-		/*  30 */ {`2 >> 3;`, nil, errors.New(`[1:4] left operand '2' [integer] and right operand '3' [integer] are not compatible with operator ">>"`)},
+		/*  27 */ {`["a", "b", "c"] << ;`, nil, `[1:18] infix operator "<<" requires two non-nil operands, got 1`},
+		/*  28 */ {`2 << 3;`, int64(16), nil},
+		/*  29 */ {`but >> ["a", "b", "c"]`, nil, `[1:6] infix operator ">>" requires two non-nil operands, got 0`},
+		/*  30 */ {`2 >> 3;`, int64(0), nil},
 		/*  31 */ {`a=[1,2]; a<<3`, newListA(int64(1), int64(2), int64(3)), nil},
 		/*  33 */ {`a=[1,2]; 5>>a`, newListA(int64(5), int64(1), int64(2)), nil},
 		/*  34 */ {`L=[1,2]; L[0]=9; L`, newListA(int64(9), int64(2)), nil},
-		/*  35 */ {`L=[1,2]; L[5]=9; L`, nil, errors.New(`index 5 out of bounds (0, 1)`)},
-		/*  36 */ {`L=[1,2]; L[]=9; L`, nil, errors.New(`[1:12] index/key specification expected, got [] [list]`)},
-		/*  37 */ {`L=[1,2]; L[nil]=9;`, nil, errors.New(`[1:12] index/key is nil`)},
+		/*  35 */ {`L=[1,2]; L[5]=9; L`, nil, `index 5 out of bounds (0, 1)`},
+		/*  36 */ {`L=[1,2]; L[]=9; L`, nil, `[1:12] index/key specification expected, got [] [list]`},
+		/*  37 */ {`L=[1,2]; L[nil]=9;`, nil, `[1:12] index/key is nil`},
 		/*  38 */ {`[0,1,2,3,4][2:3]`, newListA(int64(2)), nil},
 		/*  39 */ {`[0,1,2,3,4][3:-1]`, newListA(int64(3)), nil},
 		/*  40 */ {`[0,1,2,3,4][-3:-1]`, newListA(int64(2), int64(3)), nil},
@@ -57,6 +56,6 @@ func TestListParser(t *testing.T) {
 
 	// t.Setenv("EXPR_PATH", ".")
 
-	// parserTestSpec(t, section, inputs, 17)
-	parserTest(t, section, inputs)
+	// runTestSuiteSpec(t, section, inputs, 1)
+	runTestSuite(t, section, inputs)
 }

t_operator_test.go

@@ -0,0 +1,23 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// t_operator_test.go
+package expr
+
+import (
+	"testing"
+)
+
+func TestOperator(t *testing.T) {
+	section := "Operator"
+	inputs := []inputType{
+		/*   1 */ {`a=1; unset "a"; a`, nil, `undefined variable or function "a"`},
+		/*   2 */ {`a=1; unset ["a", "b"]`, int64(1), nil},
+		/*   3 */ {`f=func(){3}; unset "f()"`, int64(1), nil},
+	}
+
+	// t.Setenv("EXPR_PATH", ".")
+
+	//runTestSuiteSpec(t, section, inputs, 3)
+	runTestSuite(t, section, inputs)
+}

t_parser_test.go

@@ -5,18 +5,9 @@
 package expr
 
 import (
-	"errors"
-	"reflect"
-	"strings"
 	"testing"
 )
 
-type inputType struct {
-	source     string
-	wantResult any
-	wantErr    error
-}
-
 func TestGeneralParser(t *testing.T) {
 	section := "Parser"
 
@@ -57,13 +48,13 @@ func TestGeneralParser(t *testing.T) {
 		/*  34 */ {`(((1)))`, int64(1), nil},
 		/*  35 */ {`var2="abc"; "uno_" + var2`, `uno_abc`, nil},
 		/*  36 */ {`0 || 0.0 && "hello"`, false, nil},
-		/*  37 */ {`"s" + true`, nil, errors.New(`[1:6] left operand 's' [string] and right operand 'true' [bool] are not compatible with operator "+"`)},
-		/*  38 */ {`+false`, nil, errors.New(`[1:2] prefix/postfix operator "+" do not support operand 'false' [bool]`)},
+		/*  37 */ {`"s" + true`, nil, `[1:6] left operand 's' [string] and right operand 'true' [bool] are not compatible with operator "+"`},
+		/*  38 */ {`+false`, nil, `[1:2] prefix/postfix operator "+" do not support operand 'false' [bool]`},
 		/*  39 */ {`false // very simple expression`, false, nil},
-		/*  40 */ {`1 + // Missing right operator`, nil, errors.New(`[1:4] infix operator "+" requires two non-nil operands, got 1`)},
+		/*  40 */ {`1 + // Missing right operator`, nil, `[1:4] infix operator "+" requires two non-nil operands, got 1`},
 		/*  41 */ {"", nil, nil},
 		/*  42 */ {"4!", int64(24), nil},
-		/*  43 */ {"(-4)!", nil, errors.New(`factorial of a negative integer (-4) is not allowed`)},
+		/*  43 */ {"(-4)!", nil, `factorial of a negative integer (-4) is not allowed`},
 		/*  44 */ {"-4!", int64(-24), nil},
 		/*  45 */ {"1.5 < 7", true, nil},
 		/*  46 */ {"1.5 > 7", false, nil},
@@ -75,20 +66,20 @@ func TestGeneralParser(t *testing.T) {
 		/*  52 */ {`"1.5" > "7"`, false, nil},
 		/*  53 */ {`"1.5" == "7"`, false, nil},
 		/*  54 */ {`"1.5" != "7"`, true, nil},
-		/*  55 */ {"1.5 < ", nil, errors.New(`[1:6] infix operator "<" requires two non-nil operands, got 1`)},
-		/*  56 */ {"1.5 > ", nil, errors.New(`[1:6] infix operator ">" requires two non-nil operands, got 1`)},
-		/*  57 */ {"1.5 <= ", nil, errors.New(`[1:6] infix operator "<=" requires two non-nil operands, got 1`)},
-		/*  58 */ {"1.5 >= ", nil, errors.New(`[1:6] infix operator ">=" requires two non-nil operands, got 1`)},
-		/*  59 */ {"1.5 != ", nil, errors.New(`[1:6] infix operator "!=" requires two non-nil operands, got 1`)},
-		/*  60 */ {"1.5 == ", nil, errors.New(`[1:6] infix operator "==" requires two non-nil operands, got 1`)},
-		/*  61 */ {`"1.5" < `, nil, errors.New(`[1:8] infix operator "<" requires two non-nil operands, got 1`)},
-		/*  62 */ {`"1.5" > `, nil, errors.New(`[1:8] infix operator ">" requires two non-nil operands, got 1`)},
-		/*  63 */ {`"1.5" == `, nil, errors.New(`[1:8] infix operator "==" requires two non-nil operands, got 1`)},
-		/*  64 */ {`"1.5" != `, nil, errors.New(`[1:8] infix operator "!=" requires two non-nil operands, got 1`)},
+		/*  55 */ {"1.5 < ", nil, `[1:6] infix operator "<" requires two non-nil operands, got 1`},
+		/*  56 */ {"1.5 > ", nil, `[1:6] infix operator ">" requires two non-nil operands, got 1`},
+		/*  57 */ {"1.5 <= ", nil, `[1:6] infix operator "<=" requires two non-nil operands, got 1`},
+		/*  58 */ {"1.5 >= ", nil, `[1:6] infix operator ">=" requires two non-nil operands, got 1`},
+		/*  59 */ {"1.5 != ", nil, `[1:6] infix operator "!=" requires two non-nil operands, got 1`},
+		/*  60 */ {"1.5 == ", nil, `[1:6] infix operator "==" requires two non-nil operands, got 1`},
+		/*  61 */ {`"1.5" < `, nil, `[1:8] infix operator "<" requires two non-nil operands, got 1`},
+		/*  62 */ {`"1.5" > `, nil, `[1:8] infix operator ">" requires two non-nil operands, got 1`},
+		/*  63 */ {`"1.5" == `, nil, `[1:8] infix operator "==" requires two non-nil operands, got 1`},
+		/*  64 */ {`"1.5" != `, nil, `[1:8] infix operator "!=" requires two non-nil operands, got 1`},
 		/*  65 */ {"+1.5", float64(1.5), nil},
-		/*  66 */ {"+", nil, errors.New(`[1:2] prefix operator "+" requires one not nil operand`)},
-		/*  67 */ {"4 / 0", nil, errors.New(`division by zero`)},
-		/*  68 */ {"4.0 / 0", nil, errors.New(`division by zero`)},
+		/*  66 */ {"+", nil, `[1:2] prefix operator "+" requires one non-nil operand`},
+		/*  67 */ {"4 / 0", nil, `division by zero`},
+		/*  68 */ {"4.0 / 0", nil, `division by zero`},
 		/*  69 */ {"4.0 / \n2", float64(2.0), nil},
 		/*  70 */ {`123`, int64(123), nil},
 		/*  71 */ {`1.`, float64(1.0), nil},
@@ -100,25 +91,25 @@ func TestGeneralParser(t *testing.T) {
 		/*  77 */ {`5 % 2`, int64(1), nil},
 		/*  78 */ {`5 % (-2)`, int64(1), nil},
 		/*  79 */ {`-5 % 2`, int64(-1), nil},
-		/*  80 */ {`5 % 2.0`, nil, errors.New(`[1:4] left operand '5' [integer] and right operand '2' [float] are not compatible with operator "%"`)},
+		/*  80 */ {`5 % 2.0`, nil, `[1:4] left operand '5' [integer] and right operand '2' [float] are not compatible with operator "%"`},
 		/*  81 */ {`"a" < "b" AND NOT (2 < 1)`, true, nil},
 		/*  82 */ {`"a" < "b" AND NOT (2 == 1)`, true, nil},
-		/*  83 */ {`"a" < "b" AND ~ 2 == 1`, true, nil},
-		/*  84 */ {`~ 2 > 1`, false, nil},
-		/*  85 */ {`~ true && true`, false, nil},
-		/*  86 */ {`~ false || true`, true, nil},
+		/*  83 */ {`"a" < "b" AND NOT 2 == 1`, true, nil},
+		/*  84 */ {`NOT 2 > 1`, false, nil},
+		/*  85 */ {`nOT true && true`, false, nil},
+		/*  86 */ {`NOT false || true`, true, nil},
 		/*  87 */ {`false but true`, true, nil},
 		/*  88 */ {`2+3 but 5*2`, int64(10), nil},
 		/*  89 */ {`x=2`, int64(2), nil},
 		/*  90 */ {`x=2 but x*10`, int64(20), nil},
 		/*  91 */ {`false and true`, false, nil},
 		/*  92 */ {`false and (x==2)`, false, nil},
-		/*  93 */ {`false and (x=2 but x==2) or x==2`, nil, errors.New(`undefined variable or function "x"`)},
+		/*  93 */ {`false and (x=2 but x==2) or x==2`, nil, `undefined variable or function "x"`},
 		/*  94 */ {`false or true`, true, nil},
-		/*  95 */ {`false or (x==2)`, nil, errors.New(`undefined variable or function "x"`)},
+		/*  95 */ {`false or (x==2)`, nil, `undefined variable or function "x"`},
 		/*  96 */ {`a=5; a`, int64(5), nil},
-		/*  97 */ {`2=5`, nil, errors.New(`[1:2] left operand of "=" must be a variable or a collection's item`)},
-		/*  98 */ {`2+a=5`, nil, errors.New(`[1:3] left operand of "=" must be a variable or a collection's item`)},
+		/*  97 */ {`2=5`, nil, `[1:2] left operand of "=" must be a variable or a collection's item`},
+		/*  98 */ {`2+a=5`, nil, `[1:3] left operand of "=" must be a variable or a collection's item`},
 		/*  99 */ {`2+(a=5)`, int64(7), nil},
 		/* 100 */ {`x ?? "default"`, "default", nil},
 		/* 101 */ {`x="hello"; x ?? "default"`, "hello", nil},
@@ -128,98 +119,29 @@ func TestGeneralParser(t *testing.T) {
 		/* 105 */ {`1 ? {"a"} : {"b"}`, "b", nil},
 		/* 106 */ {`10 ? {"a"} : {"b"} :: {"c"}`, "c", nil},
 		/* 107 */ {`10 ? {"a"} :[true, 2+8] {"b"} :: {"c"}`, "b", nil},
-		/* 108 */ {`10 ? {"a"} :[true, 2+8] {"b"} ::[10] {"c"}`, nil, errors.New(`[1:34] case list in default clause`)},
+		/* 108 */ {`10 ? {"a"} :[true, 2+8] {"b"} ::[10] {"c"}`, nil, `[1:34] case list in default clause`},
 		/* 109 */ {`10 ? {"a"} :[10] {x="b" but x} :: {"c"}`, "b", nil},
 		/* 110 */ {`10 ? {"a"} :[10] {x="b"; x} :: {"c"}`, "b", nil},
-		/* 111 */ {`10 ? {"a"} : {"b"}`, nil, errors.New(`[1:3] no case catches the value (10) of the selection expression`)},
-		/* 112 */ {`10 ? {"a"} :: {"b"} : {"c"}`, nil, errors.New(`[1:22] selector-case outside of a selector context`)},
+		/* 111 */ {`10 ? {"a"} : {"b"}`, nil, `[1:3] no case catches the value (10) of the selection expression`},
+		/* 112 */ {`10 ? {"a"} :: {"b"} : {"c"}`, nil, `[1:22] selector-case outside of a selector context`},
 		/* 113 */ {`1 ? {"a"} : {"b"} ? ["a"] {"A"} :["b"] {"B"}`, "B", nil},
 		/* 114 */ {`2 + 1 ? {"a"} : {"b"} * 3`, "2bbb", nil},
 		/* 115 */ {`nil`, nil, nil},
-		/* 116 */ {`null`, nil, errors.New(`undefined variable or function "null"`)},
-		/* 117 */ {`{"key"}`, nil, errors.New(`[1:8] expected ":", got "}"`)},
-		/* 118 */ {`{"key":}`, nil, errors.New(`[1:9] expected "dictionary-value", got "}"`)},
+		/* 116 */ {`null`, nil, `undefined variable or function "null"`},
+		/* 117 */ {`{"key"}`, nil, "[1:8] expected `:`, got `}`"},
+		/* 118 */ {`{"key":}`, nil, "[1:9] expected `dictionary-value`, got `}`"},
 		/* 119 */ {`{}`, &DictType{}, nil},
 		/* 120 */ {`v=10; v++; v`, int64(11), nil},
-		/* 121 */ {`1+1|2+0.5`, float64(2), nil},
-		/* 122 */ {`1.2()`, newFraction(6, 5), nil},
-		/* 123 */ {`1|(2-2)`, nil, errors.New(`division by zero`)},
+		/* 121 */ {`1.2()`, newFraction(6, 5), nil},
+		/* 122 */ {`x="abc"; x ?! #x`, int64(3), nil},
+		/* 123 */ {`x ?! #x`, nil, `[1:7] prefix/postfix operator "#" do not support operand '<nil>' [nil]`},
+		/* 124 */ {`x ?! (x+1)`, nil, nil},
+		/* 125 */ {`"abx" ?! (x+1)`, nil, `[1:6] left operand of "?!" must be a variable`},
+		/* 126 */ {`"abx" ?? "pqr"`, nil, `[1:6] left operand of "??" must be a variable`},
+		/* 127 */ {`"abx" ?= "pqr"`, nil, `[1:6] left operand of "?=" must be a variable`},
 	}
 
 	// t.Setenv("EXPR_PATH", ".")
-	// parserTestSpec(t, section, inputs, 102)
-	parserTest(t, section, inputs)
-}
-
-func parserTestSpec(t *testing.T, section string, inputs []inputType, spec ...int) {
-	succeeded := 0
-	failed := 0
-	for _, count := range spec {
-		good := doTest(t, section, &inputs[count-1], count)
-
-		if good {
-			succeeded++
-		} else {
-			failed++
-		}
-	}
-	t.Logf("%s -- test count: %d, succeeded: %d, failed: %d", section, len(spec), succeeded, failed)
-}
-
-func parserTest(t *testing.T, section string, inputs []inputType) {
-
-	succeeded := 0
-	failed := 0
-
-	for i, input := range inputs {
-		good := doTest(t, section, &input, i+1)
-		if good {
-			succeeded++
-		} else {
-			failed++
-		}
-	}
-	t.Logf("%s -- test count: %d, succeeded: %d, failed: %d", section, len(inputs), succeeded, failed)
-}
-
-func doTest(t *testing.T, section string, input *inputType, count int) (good bool) {
-	var expr Expr
-	var gotResult any
-	var gotErr error
-
-	ctx := NewSimpleStore()
-	parser := NewParser()
-
-	logTest(t, count, section, input.source, input.wantResult, input.wantErr)
-
-	r := strings.NewReader(input.source)
-	scanner := NewScanner(r, DefaultTranslations())
-
-	good = true
-	if expr, gotErr = parser.Parse(scanner); gotErr == nil {
-		gotResult, gotErr = expr.Eval(ctx)
-	}
-
-	eq := reflect.DeepEqual(gotResult, input.wantResult)
-
-	if !eq /*gotResult != input.wantResult*/ {
-		t.Errorf("%d: %q -> result = %v [%s], want = %v [%s]", count, input.source, gotResult, TypeName(gotResult), input.wantResult, TypeName(input.wantResult))
-		good = false
-	}
-
-	if gotErr != input.wantErr {
-		if input.wantErr == nil || gotErr == nil || (gotErr.Error() != input.wantErr.Error()) {
-			t.Errorf("%d: %q -> got-err = <%v>, expected-err = <%v>", count, input.source, gotErr, input.wantErr)
-			good = false
-		}
-	}
-	return
-}
-
-func logTest(t *testing.T, n int, section, source string, wantResult any, wantErr error) {
-	if wantErr == nil {
-		t.Logf("[+]%s nr %3d -- %q  --> %v", section, n, source, wantResult)
-	} else {
-		t.Logf("[-]%s nr %3d -- %q  --> %v", section, n, source, wantErr)
-	}
+	//runTestSuiteSpec(t, section, inputs, 130)
+	runTestSuite(t, section, inputs)
 }

t_plugin_test.go

@@ -0,0 +1,38 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// t_plugin_test.go
+package expr
+
+import (
+	"testing"
+)
+
+// func TestImportPlugin(t *testing.T) {
+// 	t.Setenv("PLUGINS", "${HOME}/go/src/git.portale-stac.it/go")
+// 	t.Setenv("EXPR_PLUGIN_PATH","${PLUGINS}/expr-json-plugin:${PLUGINS}/expr-csv-plugin")
+
+// 	gotCount, gotErr := importPluginFromSearchPath("json")
+// 	if gotCount != 1 {
+// 		t.Errorf("Import count: got=%d, want=1", gotCount)
+// 	}
+// 	if gotErr != nil {
+// 		t.Errorf("importPlugin() failed: %v", gotErr)
+// 	}
+// }
+
+func TestPluginExists(t *testing.T) {
+	name := "json"
+	exists := pluginExists(name)
+	t.Logf("pluginExists(%v): %v", name, exists)
+
+}
+
+func TestMakePluginName(t *testing.T) {
+	name := "json"
+	want := "expr-" + name + "-plugin.so"
+
+	if got := makePluginName(name); got != want {
+		t.Errorf("makePluginName(%q) failed: Got: %q, Want: %q", name, got, want)
+	}
+}

t_relational_test.go

@@ -21,9 +21,9 @@ func TestRelational(t *testing.T) {
 		/*   8 */ {`true != false`, true, nil},
 		/*   9 */ {`1.0 != 3.0-2`, false, nil},
 		/*  10 */ {`[1,2] != [2,1]`, true, nil},
-		/*  11 */ {`1|2 == 1|3`, false, nil},
-		/*  12 */ {`1|2 != 1|3`, true, nil},
-		/*  13 */ {`1|2 == 4|8`, true, nil},
+		/*  11 */ {`1:2 == 1:3`, false, nil},
+		/*  12 */ {`1:2 != 1:3`, true, nil},
+		/*  13 */ {`1:2 == 4:8`, true, nil},
 		/*  14 */ {`1 < 8`, true, nil},
 		/*  15 */ {`1 <= 8`, true, nil},
 		/*  16 */ {`"a" < "b"`, true, nil},
@@ -32,10 +32,10 @@ func TestRelational(t *testing.T) {
 		/*  19 */ {`1.0 <= 8`, true, nil},
 		/*  20 */ {`1.0 <= 1.0`, true, nil},
 		/*  21 */ {`1.0 == 1`, true, nil},
-		/*  22 */ {`1|2 < 1|3`, false, nil},
-		/*  23 */ {`1|2 <= 1|3`, false, nil},
-		/*  24 */ {`1|2 > 1|3`, true, nil},
-		/*  25 */ {`1|2 >= 1|3`, true, nil},
+		/*  22 */ {`1:2 < 1:3`, false, nil},
+		/*  23 */ {`1:2 <= 1:3`, false, nil},
+		/*  24 */ {`1:2 > 1:3`, true, nil},
+		/*  25 */ {`1:2 >= 1:3`, true, nil},
 		/*  26 */ {`[1,2,3] > [2]`, true, nil},
 		/*  27 */ {`[1,2,3] > [9]`, false, nil},
 		/*  28 */ {`[1,2,3] >= [6]`, false, nil},
@@ -48,5 +48,5 @@ func TestRelational(t *testing.T) {
 	// t.Setenv("EXPR_PATH", ".")
 
 	// parserTestSpec(t, section, inputs, 31)
-	parserTest(t, section, inputs)
+	runTestSuite(t, section, inputs)
 }

t_scanner_test.go

@@ -6,7 +6,6 @@ package expr
 
 import (
 	"errors"
-	"fmt"
 	"reflect"
 	"strings"
 	"testing"
@@ -69,9 +68,9 @@ func TestScanner(t *testing.T) {
 		// 	continue
 		// }
 		if input.wantErr == nil {
-			t.Log(fmt.Sprintf("[+]Test nr %2d -- %q", i+1, input.source))
+			t.Logf("[+]Test nr %2d -- %q", i+1, input.source)
 		} else {
-			t.Log(fmt.Sprintf("[-]Test nr %2d -- %q", i+1, input.source))
+			t.Logf("[-]Test nr %2d -- %q", i+1, input.source)
 		}
 
 		r := strings.NewReader(input.source)

t_strings_test.go

@@ -17,5 +17,5 @@ func TestStringsParser(t *testing.T) {
 		/*  5 */ {`"abc"[1]`, `b`, nil},
 		/*  6 */ {`#"abc"`, int64(3), nil},
 	}
-	parserTest(t, "String", inputs)
+	runTestSuite(t, "String", inputs)
 }

t_template_test.go

@@ -16,6 +16,6 @@ func TestSomething(t *testing.T) {
 
 	// t.Setenv("EXPR_PATH", ".")
 
-	// parserTestSpec(t, section, inputs, 1)
-	parserTest(t, section, inputs)
+	// runTestSuiteSpec(t, section, inputs, 1)
+	runTestSuite(t, section, inputs)
 }