graph.go: conditioned compilation by 'graph' tag

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

README.adoc

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

ast.go

@@ -5,13 +5,11 @@
 package expr
 
 import (
+	"errors"
 	"strings"
-)
 
-type Expr interface {
+	"git.portale-stac.it/go-pkg/expr/kern"
-	Eval(ctx ExprContext) (result any, err error)
+)
-	String() string
-}
 
 //-------- ast
 
@@ -24,65 +22,69 @@ func NewAst() *ast {
 	return &ast{}
 }
 
-func (self *ast) ToForest() {
+func (ast *ast) TypeName() string {
-	if self.root != nil {
+	return "Expression"
-		if self.forest == nil {
+}
-			self.forest = make([]*term, 0)
+
+func (ast *ast) ToForest() {
+	if ast.root != nil {
+		if ast.forest == nil {
+			ast.forest = make([]*term, 0)
 		}
-		self.forest = append(self.forest, self.root)
+		ast.forest = append(ast.forest, ast.root)
-		self.root = nil
+		ast.root = nil
 	}
 }
 
-func (self *ast) String() string {
+func (ast *ast) String() string {
 	var sb strings.Builder
-	if self.root == nil {
+	if ast.root == nil {
 		sb.WriteString("(nil)")
 	} else {
-		self.root.toString(&sb)
+		ast.root.toString(&sb)
 	}
 	return sb.String()
 }
 
-func (self *ast) addTokens(tokens ...*Token) (err error) {
+func (ast *ast) addTokens(tokens ...*Token) (err error) {
 	for _, tk := range tokens {
-		if err = self.addToken(tk); err != nil {
+		if _, err = ast.addToken(tk); err != nil {
 			break
 		}
 	}
 	return
 }
 
-func (self *ast) addToken(tk *Token) (err error) {
+// func (expr *ast) addToken(tk *Token) (err error) {
-	_, err = self.addToken2(tk)
+// 	_, err = expr.addToken2(tk)
-	return
+// 	return
-}
+// }
 
-func (self *ast) addToken2(tk *Token) (t *term, err error) {
+func (ast *ast) addToken(tk *Token) (t *term, err error) {
 	if t = newTerm(tk); t != nil {
-		err = self.addTerm(t)
+		err = ast.addTerm(t)
 	} else {
 		err = tk.Errorf("unexpected token %q", tk.String())
 	}
 	return
 }
 
-func (self *ast) addTerm(node *term) (err error) {
+func (ast *ast) addTerm(node *term) (err error) {
-	if self.root == nil {
+	if ast.root == nil {
-		self.root = node
+		ast.root = node
 	} else {
-		self.root, err = self.insert(self.root, node)
+		ast.root, err = ast.insert(ast.root, node)
 	}
 	return
 }
 
-func (self *ast) insert(tree, node *term) (root *term, err error) {
+func (ast *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 = ast.insert(last, node); err == nil {
 				subRoot.setParent(tree)
 			}
 		} else {
@@ -97,22 +99,32 @@ func (self *ast) insert(tree, node *term) (root *term, err error) {
 	return
 }
 
-func (self *ast) Finish() {
+func (ast *ast) Finish() {
-	if self.root == nil && self.forest != nil && len(self.forest) >= 1 {
+	if ast.root == nil && ast.forest != nil && len(ast.forest) >= 1 {
-		self.root = self.forest[len(self.forest)-1]
+		ast.root = ast.forest[len(ast.forest)-1]
-		self.forest = self.forest[0 : len(self.forest)-1]
+		ast.forest = ast.forest[0 : len(ast.forest)-1]
 	}
 }
 
-func (self *ast) Eval(ctx ExprContext) (result any, err error) {
+func (ast *ast) Eval(ctx kern.ExprContext) (result any, err error) {
-	self.Finish()
+	defer func() {
+		if r := recover(); r != nil {
+			if errVal, ok := r.(error); ok {
+				err = errVal
+			} else {
+				err = errors.New("unexpected error while evaluating the expression")
+			}
+		}
+	}()
 
-	if self.root != nil {
+	ast.Finish()
+
+	if ast.root != nil {
 		// initDefaultVars(ctx)
-		if self.forest != nil {
+		if ast.forest != nil {
-			for _, root := range self.forest {
+			for _, tree := range ast.forest {
-				if result, err = root.compute(ctx); err == nil {
+				if result, err = tree.Compute(ctx); err == nil {
-					ctx.UnsafeSetVar(ControlLastResult, result)
+					ctx.UnsafeSetVar(kern.ControlLastResult, result)
 				} else {
 					//err = fmt.Errorf("error in expression nr %d: %v", i+1, err)
 					break
@@ -120,8 +132,8 @@ 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 = ast.root.Compute(ctx); err == nil {
-				ctx.UnsafeSetVar(ControlLastResult, result)
+				ctx.UnsafeSetVar(kern.ControlLastResult, result)
 			}
 		}
 		// } else {

bind-expr-functions.go

@@ -4,55 +4,60 @@
 // function.go
 package expr
 
+import (
+	"git.portale-stac.it/go-pkg/expr/kern"
+)
+
 // ---- Linking with Expr functions
 type exprFunctor struct {
-	baseFunctor
+	kern.BaseFunctor
-	params []ExprFuncParam
+	params []kern.ExprFuncParam
 	expr   Expr
-	defCtx ExprContext
+	defCtx kern.ExprContext
 }
 
-// func newExprFunctor(e Expr, params []string, ctx ExprContext) *exprFunctor {
+func (functor *exprFunctor) GetParams() (params []kern.ExprFuncParam) {
-// 	return &exprFunctor{expr: e, params: params, defCtx: ctx}
+	return functor.params
-// }
-
-func newExprFunctor(e Expr, params []ExprFuncParam, ctx ExprContext) *exprFunctor {
-	return &exprFunctor{expr: e, params: params, defCtx: ctx}
 }
 
-func (functor *exprFunctor) Invoke(ctx ExprContext, name string, args []any) (result any, err error) {
+func newExprFunctor(e Expr, params []kern.ExprFuncParam, ctx kern.ExprContext) *exprFunctor {
-	if functor.defCtx != nil {
+	var defCtx kern.ExprContext
-		ctx.Merge(functor.defCtx)
+	if ctx != nil {
+		defCtx = ctx
 	}
+	return &exprFunctor{expr: e, params: params, defCtx: defCtx}
+}
 
-	for i, p := range functor.params {
+func (functor *exprFunctor) TypeName() string {
-		if i < len(args) {
+	return "ExprFunctor"
-			arg := args[i]
+}
-			if funcArg, ok := arg.(Functor); ok {
+
-				// ctx.RegisterFunc(p, functor, 0, -1)
+func (functor *exprFunctor) GetDefinitionContext() kern.ExprContext {
+	return functor.defCtx
+}
+
+func (functor *exprFunctor) InvokeNamed(ctx kern.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.(kern.Functor); ok {
 				paramSpecs := funcArg.GetParams()
-				ctx.RegisterFunc(p.Name(), funcArg, TypeAny, paramSpecs)
+				ctx.RegisterFunc(p.Name(), funcArg, kern.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)
 		}
 	}
-	result, err = functor.expr.Eval(ctx)
+	if missing != nil {
+		err = kern.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
-// }

builtin-base.go

@@ -5,75 +5,87 @@
 package expr
 
 import (
+	"fmt"
 	"math"
 	"strconv"
+	"strings"
+
+	"git.portale-stac.it/go-pkg/expr/kern"
 )
 
-func isNilFunc(ctx ExprContext, name string, args []any) (result any, err error) {
+const (
-	result = args[0] == nil
+	ParamDenominator = "denominator"
+)
+
+func isNilFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
+	result = args[kern.ParamValue] == nil
 	return
 }
 
-func isIntFunc(ctx ExprContext, name string, args []any) (result any, err error) {
+func isIntFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
-	result = IsInteger(args[0])
+	result = kern.IsInteger(args[kern.ParamValue])
 	return
 }
 
-func isFloatFunc(ctx ExprContext, name string, args []any) (result any, err error) {
+func isFloatFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
-	result = IsFloat(args[0])
+	result = kern.IsFloat(args[kern.ParamValue])
 	return
 }
 
-func isBoolFunc(ctx ExprContext, name string, args []any) (result any, err error) {
+func isBoolFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
-	result = IsBool(args[0])
+	result = kern.IsBool(args[kern.ParamValue])
 	return
 }
 
-func isStringFunc(ctx ExprContext, name string, args []any) (result any, err error) {
+func isStringFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
-	result = IsString(args[0])
+	result = kern.IsString(args[kern.ParamValue])
 	return
 }
 
-func isFractionFunc(ctx ExprContext, name string, args []any) (result any, err error) {
+func isFractionFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
-	result = IsFract(args[0])
+	result = kern.IsFraction(args[kern.ParamValue])
 	return
 }
 
-func isRationalFunc(ctx ExprContext, name string, args []any) (result any, err error) {
+func isRationalFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
-	result = IsRational(args[0])
+	result = kern.IsRational(args[kern.ParamValue])
 	return
 }
 
-func isListFunc(ctx ExprContext, name string, args []any) (result any, err error) {
+func isListFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
-	result = IsList(args[0])
+	result = kern.IsList(args[kern.ParamValue])
 	return
 }
 
-func isDictionaryFunc(ctx ExprContext, name string, args []any) (result any, err error) {
+func isDictionaryFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
-	result = IsDict(args[0])
+	result = kern.IsDict(args[kern.ParamValue])
 	return
 }
 
-func boolFunc(ctx ExprContext, name string, args []any) (result any, err error) {
+func boolFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
-	switch v := args[0].(type) {
+	switch v := args[kern.ParamValue].(type) {
 	case int64:
 		result = (v != 0)
-	case *FractionType:
+	case *kern.FractionType:
-		result = v.num != 0
+		result = v.N() != 0
 	case float64:
 		result = v != 0.0
 	case bool:
 		result = v
 	case string:
 		result = len(v) > 0
+	case *kern.ListType:
+		result = len(*v) > 0
+	case *kern.DictType:
+		result = len(*v) > 0
 	default:
-		err = ErrCantConvert(name, v, "bool")
+		err = kern.ErrCantConvert(name, v, "bool")
 	}
 	return
 }
 
-func intFunc(ctx ExprContext, name string, args []any) (result any, err error) {
+func intFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
-	switch v := args[0].(type) {
+	switch v := args[kern.ParamValue].(type) {
 	case int64:
 		result = v
 	case float64:
@@ -89,14 +101,16 @@ func intFunc(ctx ExprContext, name string, args []any) (result any, err error) {
 		if i, err = strconv.Atoi(v); err == nil {
 			result = int64(i)
 		}
+	case *kern.FractionType:
+		result = int64(v.N() / v.D())
 	default:
-		err = ErrCantConvert(name, v, "int")
+		err = kern.ErrCantConvert(name, v, "int")
 	}
 	return
 }
 
-func decFunc(ctx ExprContext, name string, args []any) (result any, err error) {
+func decFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
-	switch v := args[0].(type) {
+	switch v := args[kern.ParamValue].(type) {
 	case int64:
 		result = float64(v)
 	case float64:
@@ -112,73 +126,191 @@ func decFunc(ctx ExprContext, name string, args []any) (result any, err error) {
 		if f, err = strconv.ParseFloat(v, 64); err == nil {
 			result = f
 		}
-	case *FractionType:
+	case *kern.FractionType:
-		result = v.toFloat()
+		result = v.ToFloat()
 	default:
-		err = ErrCantConvert(name, v, "float")
+		err = kern.ErrCantConvert(name, v, "float")
 	}
 	return
 }
 
-func fractFunc(ctx ExprContext, name string, args []any) (result any, err error) {
+func stringFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
-	switch v := args[0].(type) {
+	switch v := args[kern.ParamValue].(type) {
 	case int64:
-		var den int64 = 1
+		result = strconv.FormatInt(v, 10)
-		if len(args) > 1 {
-			var ok bool
-			if den, ok = args[1].(int64); !ok {
-				err = ErrExpectedGot(name, "integer", args[1])
-			} else if den == 0 {
-				err = ErrFuncDivisionByZero(name)
-			}
-		}
-		if err == nil {
-			result = newFraction(v, den)
-		}
 	case float64:
-		result, err = float64ToFraction(v)
+		result = strconv.FormatFloat(v, 'g', -1, 64)
 	case bool:
 		if v {
-			result = newFraction(1, 1)
+			result = "true"
 		} else {
-			result = newFraction(0, 1)
+			result = "false"
 		}
 	case string:
-		result, err = makeGeneratingFraction(v)
+		result = v
-	case *FractionType:
+	case *kern.FractionType:
+		result = v.ToString(0)
+	case kern.Formatter:
+		result = v.ToString(0)
+	case fmt.Stringer:
+		result = v.String()
+	default:
+		err = kern.ErrCantConvert(name, v, "string")
+	}
+	return
+}
+
+func fractFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
+	switch v := args[kern.ParamValue].(type) {
+	case int64:
+		var den int64 = 1
+
+		var ok bool
+		if den, ok = args[ParamDenominator].(int64); !ok {
+			err = kern.ErrExpectedGot(name, "integer", args[ParamDenominator])
+		} else if den == 0 {
+			err = kern.ErrFuncDivisionByZero(name)
+		}
+
+		if err == nil {
+			result = kern.NewFraction(v, den)
+		}
+	case float64:
+		result, err = kern.Float64ToFraction(v)
+	case bool:
+		if v {
+			result = kern.NewFraction(1, 1)
+		} else {
+			result = kern.NewFraction(0, 1)
+		}
+	case string:
+		result, err = kern.MakeGeneratingFraction(v)
+	case *kern.FractionType:
 		result = v
 	default:
-		err = ErrCantConvert(name, v, "float")
+		err = kern.ErrCantConvert(name, v, "float")
 	}
 	return
 }
 
-func iteratorFunc(ctx ExprContext, name string, args []any) (result any, err error) {
+// func iteratorFunc(ctx expr.ExprContext, name string, args []any) (result any, err error) {
+// 	return
+// }
+
+func evalFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
+	if source, ok := args[kern.ParamSource].(string); ok {
+		var ast Expr
+
+		parser := NewParser()
+		if ctx == nil {
+			ctx = NewSimpleStoreWithoutGlobalContext()
+		}
+
+		r := strings.NewReader(source)
+		scanner := NewScanner(r, DefaultTranslations())
+
+		if ast, err = parser.Parse(scanner); err == nil {
+			CtrlEnable(ctx, kern.ControlExportAll)
+			result, err = ast.Eval(ctx)
+		}
+	} else {
+		err = kern.ErrWrongParamType(name, kern.ParamSource, kern.TypeString, args[kern.ParamSource])
+	}
 	return
 }
 
-func ImportBuiltinsFuncs(ctx ExprContext) {
+func varFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
-	anyParams := []ExprFuncParam{
+	var varName string
-		NewFuncParam(ParamValue),
+	var ok bool
+
+	if varName, ok = args[kern.ParamName].(string); !ok {
+		return nil, kern.ErrWrongParamType(name, kern.ParamName, kern.TypeString, args[kern.ParamName])
 	}
 
-	ctx.RegisterFunc("isNil", NewGolangFunctor(isNilFunc), TypeBoolean, anyParams)
+	if result, ok = args[kern.ParamValue]; ok && result != nil {
-	ctx.RegisterFunc("isInt", NewGolangFunctor(isIntFunc), TypeBoolean, anyParams)
+		ctx.GetParent().UnsafeSetVar(varName, result)
-	ctx.RegisterFunc("isFloat", NewGolangFunctor(isFloatFunc), TypeBoolean, anyParams)
+		// } else {
-	ctx.RegisterFunc("isBool", NewGolangFunctor(isBoolFunc), TypeBoolean, anyParams)
+		// 	err = expr.ErrWrongParamType(name, expr.ParamSource, expr.TypeString, args[expr.ParamSource])
-	ctx.RegisterFunc("isString", NewGolangFunctor(isStringFunc), TypeBoolean, anyParams)
+		// }
-	ctx.RegisterFunc("isFract", NewGolangFunctor(isFractionFunc), TypeBoolean, anyParams)
+	} else if result, ok = ctx.GetVar(varName); !ok {
-	ctx.RegisterFunc("isRational", NewGolangFunctor(isRationalFunc), TypeBoolean, anyParams)
+		err = kern.ErrUnknownVar(name, varName)
-	ctx.RegisterFunc("isList", NewGolangFunctor(isListFunc), TypeBoolean, anyParams)
+	}
-	ctx.RegisterFunc("isDict", NewGolangFunctor(isDictionaryFunc), TypeBoolean, anyParams)
+	return
+}
 
-	ctx.RegisterFunc("bool", NewGolangFunctor(boolFunc), TypeBoolean, anyParams)
+func setFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
-	ctx.RegisterFunc("int", NewGolangFunctor(intFunc), TypeInt, anyParams)
+	var varName string
-	ctx.RegisterFunc("dec", NewGolangFunctor(decFunc), TypeFloat, anyParams)
+	var ok bool
-	ctx.RegisterFunc("fract", NewGolangFunctor(fractFunc), TypeFraction, []ExprFuncParam{
+
-		NewFuncParam(ParamValue),
+	if varName, ok = args[kern.ParamName].(string); !ok {
-		NewFuncParamFlagDef("denominator", PfDefault, 1),
+		return nil, kern.ErrWrongParamType(name, kern.ParamName, kern.TypeString, args[kern.ParamName])
+	}
+
+	if result, ok = args[kern.ParamValue]; ok {
+		ctx.GetParent().UnsafeSetVar(varName, result)
+	} else {
+		err = kern.ErrWrongParamType(name, kern.ParamValue, kern.TypeAny, args[kern.ParamValue])
+	}
+	return
+}
+
+// func unsetFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
+// 	var varName string
+// 	var ok bool
+
+// 	if varName, ok = args[kern.ParamName].(string); !ok {
+// 		return nil, kern.ErrWrongParamType(name, kern.ParamName, kern.TypeString, args[kern.ParamName])
+// 	} else {
+// 		ctx.GetParent().DeleteVar(varName)
+// 		result = nil
+// 	}
+// 	return
+// }
+
+//// import
+
+func ImportBuiltinsFuncs(ctx kern.ExprContext) {
+	anyParams := []kern.ExprFuncParam{
+		NewFuncParam(kern.ParamValue),
+	}
+
+	ctx.RegisterFunc("isNil", kern.NewGolangFunctor(isNilFunc), kern.TypeBoolean, anyParams)
+	ctx.RegisterFunc("isInt", kern.NewGolangFunctor(isIntFunc), kern.TypeBoolean, anyParams)
+	ctx.RegisterFunc("isFloat", kern.NewGolangFunctor(isFloatFunc), kern.TypeBoolean, anyParams)
+	ctx.RegisterFunc("isBool", kern.NewGolangFunctor(isBoolFunc), kern.TypeBoolean, anyParams)
+	ctx.RegisterFunc("isString", kern.NewGolangFunctor(isStringFunc), kern.TypeBoolean, anyParams)
+	ctx.RegisterFunc("isFract", kern.NewGolangFunctor(isFractionFunc), kern.TypeBoolean, anyParams)
+	ctx.RegisterFunc("isRational", kern.NewGolangFunctor(isRationalFunc), kern.TypeBoolean, anyParams)
+	ctx.RegisterFunc("isList", kern.NewGolangFunctor(isListFunc), kern.TypeBoolean, anyParams)
+	ctx.RegisterFunc("isDict", kern.NewGolangFunctor(isDictionaryFunc), kern.TypeBoolean, anyParams)
+
+	ctx.RegisterFunc("bool", kern.NewGolangFunctor(boolFunc), kern.TypeBoolean, anyParams)
+	ctx.RegisterFunc("int", kern.NewGolangFunctor(intFunc), kern.TypeInt, anyParams)
+	ctx.RegisterFunc("dec", kern.NewGolangFunctor(decFunc), kern.TypeFloat, anyParams)
+	ctx.RegisterFunc("string", kern.NewGolangFunctor(stringFunc), kern.TypeString, anyParams)
+	ctx.RegisterFunc("fract", kern.NewGolangFunctor(fractFunc), kern.TypeFraction, []kern.ExprFuncParam{
+		NewFuncParam(kern.ParamValue),
+		NewFuncParamFlagDef(ParamDenominator, PfDefault, int64(1)),
 	})
+
+	ctx.RegisterFunc("eval", kern.NewGolangFunctor(evalFunc), kern.TypeAny, []kern.ExprFuncParam{
+		NewFuncParam(kern.ParamSource),
+	})
+
+	ctx.RegisterFunc("var", kern.NewGolangFunctor(varFunc), kern.TypeAny, []kern.ExprFuncParam{
+		NewFuncParam(kern.ParamName),
+		NewFuncParamFlagDef(kern.ParamValue, PfDefault, nil),
+	})
+
+	ctx.RegisterFunc("set", kern.NewGolangFunctor(setFunc), kern.TypeAny, []kern.ExprFuncParam{
+		NewFuncParam(kern.ParamName),
+		NewFuncParam(kern.ParamValue),
+	})
+
+	// ctx.RegisterFunc("unset", kern.NewGolangFunctor(unsetFunc), kern.TypeAny, []kern.ExprFuncParam{
+	// 	NewFuncParam(kern.ParamName),
+	// 	NewFuncParam(kern.ParamValue),
+	// })
 }
 
 func init() {

builtin-fmt.go

@@ -4,30 +4,53 @@
 // builtin-fmt.go
 package expr
 
-import "fmt"
+import (
+	"fmt"
+	"io"
+	"os"
 
-func printFunc(ctx ExprContext, name string, args []any) (result any, err error) {
+	"git.portale-stac.it/go-pkg/expr/kern"
-	var n int
+)
-	if n, err = fmt.Print(args...); err == nil {
+
-		result = int64(n)
+func getStdout(ctx kern.ExprContext) io.Writer {
+	var w io.Writer
+	if wany, exists := ctx.GetVar(kern.ControlStdout); exists && wany != nil {
+		w, _ = wany.(io.Writer)
 	}
+	if w == nil {
+		w = os.Stdout
+	}
+	return w
+}
+
+func printFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
+	var n int = 0
+	if v, exists := args[kern.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) {
+func printLnFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
-	var n int
+	var n int = 0
-	if n, err = fmt.Println(args...); err == nil {
+	if v, exists := args[kern.ParamItem]; exists && v != nil {
-		result = int64(n)
+		argv := v.([]any)
+		n, err = fmt.Fprintln(getStdout(ctx), argv...)
+	} else {
+		n, err = fmt.Fprintln(getStdout(ctx))
 	}
+	result = int64(n)
 	return
 }
 
-func ImportFmtFuncs(ctx ExprContext) {
+func ImportFmtFuncs(ctx kern.ExprContext) {
-	ctx.RegisterFunc("print", NewGolangFunctor(printFunc), TypeInt, []ExprFuncParam{
+	ctx.RegisterFunc("print", kern.NewGolangFunctor(printFunc), kern.TypeInt, []kern.ExprFuncParam{
-		NewFuncParamFlag(ParamItem, PfRepeat),
+		NewFuncParamFlag(kern.ParamItem, PfRepeat),
 	})
-	ctx.RegisterFunc("println", NewGolangFunctor(printLnFunc), TypeInt, []ExprFuncParam{
+	ctx.RegisterFunc("println", kern.NewGolangFunctor(printLnFunc), kern.TypeInt, []kern.ExprFuncParam{
-		NewFuncParamFlag(ParamItem, PfRepeat),
+		NewFuncParamFlag(kern.ParamItem, PfRepeat),
 	})
 }
 

builtin-import.go

@@ -7,29 +7,34 @@ package expr
 import (
 	"io"
 	"os"
+
+	"git.portale-stac.it/go-pkg/expr/kern"
 )
 
-func importFunc(ctx ExprContext, name string, args []any) (result any, err error) {
+func importFunc(ctx kern.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 kern.ExprContext, name string, args map[string]any) (result any, err error) {
-	CtrlEnable(ctx, control_export_all)
+	CtrlEnable(ctx, kern.ControlExportAll)
 	return importGeneral(ctx, name, args)
 }
 
-func importGeneral(ctx ExprContext, name string, args []any) (result any, err error) {
+func importGeneral(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
-	dirList := buildSearchDirList("sources", ENV_EXPR_SOURCE_PATH)
+	dirList := buildSearchDirList(ctx, "sources", ENV_EXPR_SOURCE_PATH)
-	result, err = doImport(ctx, name, dirList, NewArrayIterator(args))
+	if v, exists := args[kern.ParamFilepath]; exists && v != nil {
+		argv := v.([]any)
+		result, err = doImport(ctx, name, dirList, NewArrayIterator(argv))
+	}
 	return
 }
 
-func doImport(ctx ExprContext, name string, dirList []string, it Iterator) (result any, err error) {
+func doImport(ctx kern.ExprContext, name string, dirList []string, it kern.Iterator) (result any, err error) {
 	var v any
 	var sourceFilepath string
 
 	for v, err = it.Next(); err == nil; v, err = it.Next() {
-		if err = checkStringParamExpected(name, v, it.Index()); err != nil {
+		if err = checkStringParamExpected(name, v, int(it.Index())); err != nil {
 			break
 		}
 		if sourceFilepath, err = makeFilepath(v.(string), dirList); err != nil {
@@ -41,7 +46,7 @@ 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 {
@@ -61,12 +66,12 @@ func doImport(ctx ExprContext, name string, dirList []string, it Iterator) (resu
 	return
 }
 
-func ImportImportFuncs(ctx ExprContext) {
+func ImportImportFuncs(ctx kern.ExprContext) {
-	ctx.RegisterFunc("import", NewGolangFunctor(importFunc), TypeAny, []ExprFuncParam{
+	ctx.RegisterFunc("import", kern.NewGolangFunctor(importFunc), kern.TypeAny, []kern.ExprFuncParam{
-		NewFuncParamFlag(ParamFilepath, PfRepeat),
+		NewFuncParamFlag(kern.ParamFilepath, PfRepeat),
 	})
-	ctx.RegisterFunc("importAll", NewGolangFunctor(importAllFunc), TypeAny, []ExprFuncParam{
+	ctx.RegisterFunc("importAll", kern.NewGolangFunctor(importAllFunc), kern.TypeAny, []kern.ExprFuncParam{
-		NewFuncParamFlag(ParamFilepath, PfRepeat),
+		NewFuncParamFlag(kern.ParamFilepath, PfRepeat),
 	})
 }
 

builtin-iterator.go

@@ -0,0 +1,105 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// builtin-iterator.go
+package expr
+
+import (
+	"fmt"
+	"io"
+
+	"git.portale-stac.it/go-pkg/expr/kern"
+)
+
+const (
+	iterParamOperator = "operator"
+	iterParamVars     = "vars"
+	iterVarStatus     = "status"
+)
+
+func parseRunArgs(localCtx kern.ExprContext, args map[string]any) (it kern.Iterator, op kern.Functor, err error) {
+	var ok bool
+
+	if it, ok = args[kern.ParamIterator].(kern.Iterator); !ok {
+		err = fmt.Errorf("paramter %q must be an iterator, passed %v [%s]", kern.ParamIterator, args[kern.ParamIterator], kern.TypeName(args[kern.ParamIterator]))
+		return
+	}
+
+	if args[iterParamOperator] != nil {
+		if op, ok = args[iterParamOperator].(kern.Functor); !ok || op == nil {
+			err = fmt.Errorf("paramter %q must be a function, passed %v [%s]", iterParamOperator, args[iterParamOperator], kern.TypeName(args[iterParamOperator]))
+			return
+		}
+	}
+
+	var vars *kern.DictType
+	if vars, ok = args[iterParamVars].(*kern.DictType); !ok && args[iterParamVars] != nil {
+		err = fmt.Errorf("paramter %q must be a dictionary, passed %v [%s]", iterParamVars, args[iterParamVars], kern.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 kern.ExprContext, name string, args map[string]any) (result any, err error) {
+	var it kern.Iterator
+	var ok bool
+	var op kern.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
+	}
+
+	for item, err = it.Next(); err == nil; item, err = it.Next() {
+		if op != nil {
+			params = map[string]any{kern.ParamIndex: it.Index(), kern.ParamItem: item}
+			if v, err = op.InvokeNamed(localCtx, iterParamOperator, params); err != nil {
+				break
+			} else {
+				var success bool
+				if success, ok = kern.ToBool(v); !success || !ok {
+					break
+				}
+			}
+		}
+	}
+
+	if err == io.EOF {
+		err = nil
+	}
+	if err == nil {
+		if op == nil {
+			ctx.UnsafeSetVar(iterVarStatus, it.Count())
+		}
+		result, _ = localCtx.GetVar(iterVarStatus)
+	}
+	return
+}
+
+func ImportIterFuncs(ctx kern.ExprContext) {
+	ctx.RegisterFunc("run", kern.NewGolangFunctor(runFunc), kern.TypeAny, []kern.ExprFuncParam{
+		NewFuncParam(kern.ParamIterator),
+		NewFuncParamFlag(iterParamOperator, PfOptional),
+		NewFuncParamFlag(iterParamVars, PfOptional),
+	})
+}
+
+func init() {
+	RegisterBuiltinModule("iterator", ImportIterFuncs, "Iterator helper functions")
+}

builtin-math-arith.go

@@ -7,67 +7,69 @@ package expr
 import (
 	"fmt"
 	"io"
+
+	"git.portale-stac.it/go-pkg/expr/kern"
 )
 
 func checkNumberParamExpected(funcName string, paramValue any, paramPos, level, subPos int) (err error) {
-	if !(IsNumber(paramValue) || isFraction(paramValue)) /*|| isList(paramValue)*/ {
+	if !(kern.IsNumber(paramValue) || kern.IsFraction(paramValue)) /*|| isList(paramValue)*/ {
 		err = fmt.Errorf("%s(): param nr %d (%d in %d) has wrong type %T, number expected",
 			funcName, paramPos+1, subPos+1, level, paramValue)
 	}
 	return
 }
 
-func doAdd(ctx ExprContext, name string, it Iterator, count, level int) (result any, err error) {
+func doAdd(ctx kern.ExprContext, name string, it kern.Iterator, count, level int) (result any, err error) {
 	var sumAsFloat, sumAsFract bool
 	var floatSum float64 = 0.0
 	var intSum int64 = 0
-	var fractSum *FractionType
+	var fractSum *kern.FractionType
 	var v any
 
 	level++
 
 	for v, err = it.Next(); err == nil; v, err = it.Next() {
-		if list, ok := v.(*ListType); ok {
+		if list, ok := v.(*kern.ListType); ok {
 			v = NewListIterator(list, nil)
 		}
-		if subIter, ok := v.(Iterator); ok {
+		if subIter, ok := v.(kern.Iterator); ok {
 			if v, err = doAdd(ctx, name, subIter, count, level); err != nil {
 				break
 			}
-			if extIter, ok := v.(ExtIterator); ok && extIter.HasOperation(cleanName) {
+			if extIter, ok := v.(kern.ExtIterator); ok && extIter.HasOperation(kern.CleanName) {
-				if _, err = extIter.CallOperation(cleanName, nil); err != nil {
+				if _, err = extIter.CallOperation(kern.CleanName, nil); err != nil {
 					return
 				}
 			}
-		} else if err = checkNumberParamExpected(name, v, count, level, it.Index()); err != nil {
+		} else if err = checkNumberParamExpected(name, v, count, level, int(it.Index())); err != nil {
 			break
 		}
 		count++
 
 		if !sumAsFloat {
-			if IsFloat(v) {
+			if kern.IsFloat(v) {
 				sumAsFloat = true
 				if sumAsFract {
-					floatSum = fractSum.toFloat()
+					floatSum = fractSum.ToFloat()
 				} else {
 					floatSum = float64(intSum)
 				}
-			} else if !sumAsFract && isFraction(v) {
+			} else if !sumAsFract && kern.IsFraction(v) {
-				fractSum = newFraction(intSum, 1)
+				fractSum = kern.NewFraction(intSum, 1)
 				sumAsFract = true
 			}
 		}
 
 		if sumAsFloat {
-			floatSum += numAsFloat(v)
+			floatSum += kern.NumAsFloat(v)
 		} else if sumAsFract {
-			var item *FractionType
+			var item *kern.FractionType
 			var ok bool
-			if item, ok = v.(*FractionType); !ok {
+			if item, ok = v.(*kern.FractionType); !ok {
 				iv, _ := v.(int64)
-				item = newFraction(iv, 1)
+				item = kern.NewFraction(iv, 1)
 			}
-			fractSum = sumFract(fractSum, item)
+			fractSum = kern.SumFract(fractSum, item)
 		} else {
 			iv, _ := v.(int64)
 			intSum += iv
@@ -86,63 +88,64 @@ 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) {
+func addFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
-	result, err = doAdd(ctx, name, NewArrayIterator(args), 0, -1)
+	argv := args[kern.ParamValue].([]any)
+	result, err = doAdd(ctx, name, NewArrayIterator(argv), 0, -1)
 	return
 }
 
-func doMul(ctx ExprContext, name string, it Iterator, count, level int) (result any, err error) {
+func doMul(ctx kern.ExprContext, name string, it kern.Iterator, count, level int) (result any, err error) {
 	var mulAsFloat, mulAsFract bool
 	var floatProd float64 = 1.0
 	var intProd int64 = 1
-	var fractProd *FractionType
+	var fractProd *kern.FractionType
 	var v any
 
 	level++
 	for v, err = it.Next(); err == nil; v, err = it.Next() {
-		if list, ok := v.(*ListType); ok {
+		if list, ok := v.(*kern.ListType); ok {
 			v = NewListIterator(list, nil)
 		}
-		if subIter, ok := v.(Iterator); ok {
+		if subIter, ok := v.(kern.Iterator); ok {
 			if v, err = doMul(ctx, name, subIter, count, level); err != nil {
 				break
 			}
-			if extIter, ok := v.(ExtIterator); ok && extIter.HasOperation(cleanName) {
+			if extIter, ok := v.(kern.ExtIterator); ok && extIter.HasOperation(kern.CleanName) {
-				if _, err = extIter.CallOperation(cleanName, nil); err != nil {
+				if _, err = extIter.CallOperation(kern.CleanName, nil); err != nil {
 					return
 				}
 			}
 		} else {
-			if err = checkNumberParamExpected(name, v, count, level, it.Index()); err != nil {
+			if err = checkNumberParamExpected(name, v, count, level, int(it.Index())); err != nil {
 				break
 			}
 		}
 		count++
 
 		if !mulAsFloat {
-			if IsFloat(v) {
+			if kern.IsFloat(v) {
 				mulAsFloat = true
 				if mulAsFract {
-					floatProd = fractProd.toFloat()
+					floatProd = fractProd.ToFloat()
 				} else {
 					floatProd = float64(intProd)
 				}
-			} else if !mulAsFract && isFraction(v) {
+			} else if !mulAsFract && kern.IsFraction(v) {
-				fractProd = newFraction(intProd, 1)
+				fractProd = kern.NewFraction(intProd, 1)
 				mulAsFract = true
 			}
 		}
 
 		if mulAsFloat {
-			floatProd *= numAsFloat(v)
+			floatProd *= kern.NumAsFloat(v)
 		} else if mulAsFract {
-			var item *FractionType
+			var item *kern.FractionType
 			var ok bool
-			if item, ok = v.(*FractionType); !ok {
+			if item, ok = v.(*kern.FractionType); !ok {
 				iv, _ := v.(int64)
-				item = newFraction(iv, 1)
+				item = kern.NewFraction(iv, 1)
 			}
-			fractProd = mulFract(fractProd, item)
+			fractProd = kern.MulFract(fractProd, item)
 		} else {
 			iv, _ := v.(int64)
 			intProd *= iv
@@ -161,18 +164,19 @@ 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) {
+func mulFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
-	result, err = doMul(ctx, name, NewArrayIterator(args), 0, -1)
+	argv := args[kern.ParamValue].([]any)
+	result, err = doMul(ctx, name, NewArrayIterator(argv), 0, -1)
 	return
 }
 
-func ImportMathFuncs(ctx ExprContext) {
+func ImportMathFuncs(ctx kern.ExprContext) {
-	ctx.RegisterFunc("add", &golangFunctor{f: addFunc}, TypeNumber, []ExprFuncParam{
+	ctx.RegisterFunc("add", kern.NewGolangFunctor(addFunc), kern.TypeNumber, []kern.ExprFuncParam{
-		NewFuncParamFlagDef(ParamValue, PfDefault|PfRepeat, int64(0)),
+		NewFuncParamFlagDef(kern.ParamValue, PfDefault|PfRepeat, int64(0)),
 	})
 
-	ctx.RegisterFunc("mul", &golangFunctor{f: mulFunc}, TypeNumber, []ExprFuncParam{
+	ctx.RegisterFunc("mul", kern.NewGolangFunctor(mulFunc), kern.TypeNumber, []kern.ExprFuncParam{
-		NewFuncParamFlagDef(ParamValue, PfDefault|PfRepeat, int64(1)),
+		NewFuncParamFlagDef(kern.ParamValue, PfDefault|PfRepeat, int64(1)),
 	})
 }
 

builtin-os-file-iter.go

@@ -0,0 +1,151 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// builtin-os-file.go
+package expr
+
+import (
+	"fmt"
+	"io"
+	"slices"
+
+	"git.portale-stac.it/go-pkg/expr/kern"
+)
+
+const paramHandleOrPath = "handle-or-path"
+const fileReadTextIteratorType = "fileReadTextIterator"
+
+type fileReadTextIterator struct {
+	osReader  *osReader
+	index     int64
+	count     int64
+	line      string
+	autoClose bool
+}
+
+func newReadTextIterator(r *osReader, autoClose bool) *fileReadTextIterator {
+	return &fileReadTextIterator{osReader: r, index: -1, autoClose: autoClose}
+}
+
+func (it *fileReadTextIterator) TypeName() string {
+	return fileReadTextIteratorType
+}
+
+func (it *fileReadTextIterator) String() string {
+	if it.osReader != nil && it.osReader.fh != nil {
+		return fmt.Sprintf("$(%s@%q)", fileReadTextIteratorType, it.osReader.fh.Name())
+	}
+	return fmt.Sprintf("$(%s@<nil>)", fileReadTextIteratorType)
+}
+
+func (it *fileReadTextIterator) Count() int64 {
+	return it.count
+}
+
+func (it *fileReadTextIterator) Next() (item any, err error) { // must return io.EOF after the last item
+	if it.osReader.fh != nil {
+		if it.line, err = it.osReader.reader.ReadString('\n'); err == nil {
+			it.index++
+			it.count++
+			item = it.line[0 : len(it.line)-1]
+		} else if it.autoClose {
+			it.Clean()
+		}
+	}
+	return
+}
+
+func (it *fileReadTextIterator) Current() (item any, err error) {
+	if len(it.line) > 0 {
+		item = it.line[0 : len(it.line)-1]
+	}
+	return
+}
+
+func (it *fileReadTextIterator) Index() int64 {
+	return it.index
+}
+
+func (it *fileReadTextIterator) Reset() (err error) {
+	if _, err = it.osReader.fh.Seek(0, io.SeekStart); err == nil {
+		it.index = -1
+		it.count = 0
+		it.line = ""
+	}
+	return
+}
+
+func (it *fileReadTextIterator) HasOperation(name string) bool {
+	return slices.Contains([]string{kern.NextName, kern.ResetName, kern.IndexName, kern.CountName, kern.CurrentName, kern.CleanName}, name)
+}
+
+func (it *fileReadTextIterator) Clean() (err error) {
+	if it.osReader.fh != nil {
+		if err = it.osReader.fh.Close(); err == nil {
+			it.osReader = nil
+		}
+	}
+	return nil
+}
+
+func (it *fileReadTextIterator) CallOperation(name string, args map[string]any) (v any, err error) {
+	switch name {
+	case kern.NextName:
+		v, err = it.Next()
+	case kern.ResetName:
+		err = it.Reset()
+	case kern.CleanName:
+		err = it.Clean()
+	case kern.IndexName:
+		v = int64(it.Index())
+	case kern.CurrentName:
+		v, err = it.Current()
+	case kern.CountName:
+		v = it.count
+	default:
+		err = kern.ErrNoOperation(name)
+	}
+	return
+}
+
+func fileReadIteratorFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
+	var handle *osReader
+	var invalidFileHandle any
+	var ok, autoClose bool
+
+	result = nil
+	if handle, ok = args[paramHandleOrPath].(*osReader); !ok {
+		if fileName, ok := args[paramHandleOrPath].(string); ok && len(fileName) > 0 {
+			var handleAny any
+			if handleAny, err = openFileFunc(ctx, name, map[string]any{kern.ParamFilepath: fileName}); err != nil {
+				return
+			}
+			if handleAny != nil {
+				handle = handleAny.(*osReader)
+				autoClose = true
+			}
+		} else {
+			invalidFileHandle = args[paramHandleOrPath]
+		}
+	}
+
+	if handle != nil {
+		result = newReadTextIterator(handle, autoClose)
+
+	}
+
+	if err == nil && (handle == nil || invalidFileHandle != nil) {
+		err = errInvalidFileHandle(name, invalidFileHandle)
+	}
+	return
+}
+
+// func ImportOsIterFuncs(ctx ExprContext) {
+// 	ctx.RegisterFunc("fileReadIterator", NewGolangFunctor(fileReadIteratorFunc), TypeIterator, []ExprFuncParam{
+// 		NewFuncParam(paramHandleOrPath),
+// 	})
+// }
+
+// func init() {
+// 	RegisterBuiltinModule("os.file", ImportOsIterFuncs, "Operating system file iterator functions")
+// }

builtin-os-file.go

@@ -9,6 +9,12 @@ import (
 	"fmt"
 	"io"
 	"os"
+
+	"git.portale-stac.it/go-pkg/expr/kern"
+)
+
+const (
+	osLimitCh = "limitCh"
 )
 
 type osHandle interface {
@@ -61,8 +67,8 @@ func errInvalidFileHandle(funcName string, v any) error {
 	}
 }
 
-func createFileFunc(ctx ExprContext, name string, args []any) (result any, err error) {
+func createFileFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
-	if filePath, ok := args[0].(string); ok && len(filePath) > 0 {
+	if filePath, ok := args[kern.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 +79,8 @@ 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) {
+func openFileFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
-	if filePath, ok := args[0].(string); ok && len(filePath) > 0 {
+	if filePath, ok := args[kern.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 +91,8 @@ 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) {
+func appendFileFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
-	if filePath, ok := args[0].(string); ok && len(filePath) > 0 {
+	if filePath, ok := args[kern.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 +103,13 @@ 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 kern.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 {
+	if handle, ok = args[kern.ParamHandle].(osHandle); !ok {
-		invalidFileHandle = args[0]
+		invalidFileHandle = args[kern.ParamHandle]
 	}
 
 	if handle != nil {
@@ -124,18 +130,21 @@ 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 kern.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 {
+	if handle, ok = args[kern.ParamHandle].(osHandle); !ok {
-		invalidFileHandle = args[0]
+		invalidFileHandle = args[kern.ParamHandle]
 	}
 
 	if handle != nil {
 		if w, ok := handle.(*osWriter); ok {
-			result, err = fmt.Fprint(w.writer, args[1:]...)
+			if v, exists := args[kern.ParamItem]; exists {
+				argv := v.([]any)
+				result, err = fmt.Fprint(w.writer, argv...)
+			}
 		} else {
 			invalidFileHandle = handle
 		}
@@ -147,21 +156,21 @@ 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 kern.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 {
+	if handle, ok = args[kern.ParamHandle].(osHandle); !ok || args[kern.ParamHandle] == nil {
-		invalidFileHandle = args[0]
+		invalidFileHandle = args[kern.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 +196,14 @@ 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 kern.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 {
+	if handle, ok = args[kern.ParamHandle].(osHandle); !ok || args[kern.ParamHandle] == nil {
-		invalidFileHandle = args[0]
+		invalidFileHandle = args[kern.ParamHandle]
 	}
 
 	if handle != nil {
@@ -213,35 +222,39 @@ func fileReadTextAllFunc(ctx ExprContext, name string, args []any) (result any,
 	return
 }
 
-func ImportOsFuncs(ctx ExprContext) {
+func ImportOsFuncs(ctx kern.ExprContext) {
-	ctx.RegisterFunc("fileOpen", NewGolangFunctor(openFileFunc), TypeHandle, []ExprFuncParam{
+	ctx.RegisterFunc("fileOpen", kern.NewGolangFunctor(openFileFunc), kern.TypeFileHandle, []kern.ExprFuncParam{
-		NewFuncParam(ParamFilepath),
+		NewFuncParam(kern.ParamFilepath),
 	})
 
-	ctx.RegisterFunc("fileAppend", NewGolangFunctor(appendFileFunc), TypeHandle, []ExprFuncParam{
+	ctx.RegisterFunc("fileAppend", kern.NewGolangFunctor(appendFileFunc), kern.TypeFileHandle, []kern.ExprFuncParam{
-		NewFuncParam(ParamFilepath),
+		NewFuncParam(kern.ParamFilepath),
 	})
 
-	ctx.RegisterFunc("fileCreate", NewGolangFunctor(createFileFunc), TypeHandle, []ExprFuncParam{
+	ctx.RegisterFunc("fileCreate", kern.NewGolangFunctor(createFileFunc), kern.TypeFileHandle, []kern.ExprFuncParam{
-		NewFuncParam(ParamFilepath),
+		NewFuncParam(kern.ParamFilepath),
 	})
 
-	ctx.RegisterFunc("fileClose", NewGolangFunctor(closeFileFunc), TypeBoolean, []ExprFuncParam{
+	ctx.RegisterFunc("fileClose", kern.NewGolangFunctor(closeFileFunc), kern.TypeBoolean, []kern.ExprFuncParam{
-		NewFuncParam(TypeHandle),
+		NewFuncParam(kern.ParamHandle),
 	})
 
-	ctx.RegisterFunc("fileWriteText", NewGolangFunctor(fileWriteTextFunc), TypeInt, []ExprFuncParam{
+	ctx.RegisterFunc("fileWriteText", kern.NewGolangFunctor(fileWriteTextFunc), kern.TypeInt, []kern.ExprFuncParam{
-		NewFuncParam(TypeHandle),
+		NewFuncParam(kern.ParamHandle),
-		NewFuncParamFlagDef(TypeItem, PfDefault|PfRepeat, ""),
+		NewFuncParamFlagDef(kern.ParamItem, PfDefault|PfRepeat, ""),
 	})
 
-	ctx.RegisterFunc("fileReadText", NewGolangFunctor(fileReadTextFunc), TypeString, []ExprFuncParam{
+	ctx.RegisterFunc("fileReadText", kern.NewGolangFunctor(fileReadTextFunc), kern.TypeString, []kern.ExprFuncParam{
-		NewFuncParam(TypeHandle),
+		NewFuncParam(kern.ParamHandle),
-		NewFuncParamFlagDef("limitCh", PfDefault, "\n"),
+		NewFuncParamFlagDef(osLimitCh, PfDefault, "\n"),
 	})
 
-	ctx.RegisterFunc("fileReadTextAll", NewGolangFunctor(fileReadTextAllFunc), TypeString, []ExprFuncParam{
+	ctx.RegisterFunc("fileReadTextAll", kern.NewGolangFunctor(fileReadTextAllFunc), kern.TypeString, []kern.ExprFuncParam{
-		NewFuncParam(TypeHandle),
+		NewFuncParam(kern.ParamHandle),
+	})
+
+	ctx.RegisterFunc("fileReadIterator", kern.NewGolangFunctor(fileReadIteratorFunc), kern.TypeIterator, []kern.ExprFuncParam{
+		NewFuncParam(paramHandleOrPath),
 	})
 }
 

builtin-string.go

@@ -8,10 +8,16 @@ import (
 	"fmt"
 	"io"
 	"strings"
+
+	"git.portale-stac.it/go-pkg/expr/kern"
+)
+
+const (
+	strParamOther = "other"
 )
 
 // --- Start of function definitions
-func doJoinStr(funcName string, sep string, it Iterator) (result any, err error) {
+func doJoinStr(funcName string, sep string, it kern.Iterator) (result any, err error) {
 	var sb strings.Builder
 	var v any
 	for v, err = it.Next(); err == nil; v, err = it.Next() {
@@ -21,56 +27,56 @@ func doJoinStr(funcName string, sep string, it Iterator) (result any, err error)
 		if s, ok := v.(string); ok {
 			sb.WriteString(s)
 		} else {
-			err = ErrExpectedGot(funcName, TypeString, v)
+			err = kern.ErrExpectedGot(funcName, kern.TypeString, v)
 			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) {
+func joinStrFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
-	//	if len(args) < 1 {
+	if sep, ok := args[kern.ParamSeparator].(string); ok {
-	//		return nil, errMissingRequiredParameter(name, paramSeparator)
+		if v, exists := args[kern.ParamItem]; exists {
-	//	}
+			argv := v.([]any)
-	if sep, ok := args[0].(string); ok {
+			if len(argv) == 1 {
-		if len(args) == 1 {
+				if ls, ok := argv[0].(*kern.ListType); ok {
-			result = ""
+					result, err = doJoinStr(name, sep, NewListIterator(ls, nil))
-		} else if len(args) == 2 {
+				} else if it, ok := argv[0].(kern.Iterator); ok {
-			if ls, ok := args[1].(*ListType); ok {
+					result, err = doJoinStr(name, sep, it)
-				result, err = doJoinStr(name, sep, NewListIterator(ls, nil))
+				} else if s, ok := argv[0].(string); ok {
-			} else if it, ok := args[1].(Iterator); ok {
+					result = s
-				result, err = doJoinStr(name, sep, it)
+				} else {
+					err = kern.ErrInvalidParameterValue(name, kern.ParamItem, v)
+				}
 			} else {
-				err = ErrInvalidParameterValue(name, ParamParts, args[1])
+				result, err = doJoinStr(name, sep, NewArrayIterator(argv))
 			}
-		} else {
-			result, err = doJoinStr(name, sep, NewArrayIterator(args[1:]))
 		}
 	} else {
-		err = ErrWrongParamType(name, ParamSeparator, TypeString, args[0])
+		err = kern.ErrWrongParamType(name, kern.ParamSeparator, kern.TypeString, args[kern.ParamSeparator])
 	}
 	return
 }
 
-func subStrFunc(ctx ExprContext, name string, args []any) (result any, err error) {
+func subStrFunc(ctx kern.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 {
+	if source, ok = args[kern.ParamSource].(string); !ok {
-		return nil, ErrWrongParamType(name, ParamSource, TypeString, args[0])
+		return nil, kern.ErrWrongParamType(name, kern.ParamSource, kern.TypeString, args[kern.ParamSource])
 	}
 
-	if start, err = ToInt(args[1], name+"()"); err != nil {
+	if start, err = kern.ToGoInt(args[kern.ParamStart], name+"()"); err != nil {
 		return
 	}
 
-	if count, err = ToInt(args[2], name+"()"); err != nil {
+	if count, err = kern.ToGoInt(args[kern.ParamCount], name+"()"); err != nil {
 		return
 	}
 
@@ -86,81 +92,99 @@ 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 kern.ExprContext, name string, args map[string]any) (result any, err error) {
 	var source string
 	var ok bool
 
-	if source, ok = args[0].(string); !ok {
+	if source, ok = args[kern.ParamSource].(string); !ok {
-		return nil, ErrWrongParamType(name, ParamSource, TypeString, args[0])
+		return nil, kern.ErrWrongParamType(name, kern.ParamSource, kern.TypeString, args[kern.ParamSource])
 	}
 	result = strings.TrimSpace(source)
 	return
 }
 
-func startsWithStrFunc(ctx ExprContext, name string, args []any) (result any, err error) {
+func startsWithStrFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
-	var source string
+	var source, prefix string
 	var ok bool
 
 	result = false
 
-	if source, ok = args[0].(string); !ok {
+	if source, ok = args[kern.ParamSource].(string); !ok {
-		return result, ErrWrongParamType(name, ParamSource, TypeString, args[0])
+		return result, kern.ErrWrongParamType(name, kern.ParamSource, kern.TypeString, args[kern.ParamSource])
 	}
-	for i, targetSpec := range args[1:] {
+
-		if target, ok := targetSpec.(string); ok {
+	if prefix, ok = args[kern.ParamPrefix].(string); !ok {
-			if strings.HasPrefix(source, target) {
+		return result, kern.ErrWrongParamType(name, kern.ParamPrefix, kern.TypeString, args[kern.ParamPrefix])
-				result = true
+	}
+	if strings.HasPrefix(source, prefix) {
+		result = true
+	} else if v, exists := args[strParamOther]; exists {
+		argv := v.([]any)
+		for i, targetSpec := range argv {
+			if target, ok := targetSpec.(string); ok {
+				if strings.HasPrefix(source, target) {
+					result = true
+					break
+				}
+			} else {
+				err = fmt.Errorf("target item nr %d is %s, string expected", i+1, kern.TypeName(targetSpec))
 				break
 			}
-		} else {
-			err = fmt.Errorf("target item nr %d is %T, expected string", i+1, targetSpec)
-			break
 		}
 	}
 	return
 }
 
-func endsWithStrFunc(ctx ExprContext, name string, args []any) (result any, err error) {
+func endsWithStrFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
-	var source string
+	var source, suffix string
 	var ok bool
 
 	result = false
 
-	if source, ok = args[0].(string); !ok {
+	if source, ok = args[kern.ParamSource].(string); !ok {
-		return result, ErrWrongParamType(name, ParamSource, TypeString, args[0])
+		return result, kern.ErrWrongParamType(name, kern.ParamSource, kern.TypeString, args[kern.ParamSource])
 	}
-	for i, targetSpec := range args[1:] {
+
-		if target, ok := targetSpec.(string); ok {
+	if suffix, ok = args[kern.ParamSuffix].(string); !ok {
-			if strings.HasSuffix(source, target) {
+		return result, kern.ErrWrongParamType(name, kern.ParamSuffix, kern.TypeString, args[kern.ParamSuffix])
-				result = true
+	}
+	if strings.HasPrefix(source, suffix) {
+		result = true
+	} else if v, exists := args[strParamOther]; exists {
+		argv := v.([]any)
+		for i, targetSpec := range argv {
+			if target, ok := targetSpec.(string); ok {
+				if strings.HasSuffix(source, target) {
+					result = true
+					break
+				}
+			} else {
+				err = fmt.Errorf("target item nr %d is %s, string expected", i+1, kern.TypeName(targetSpec))
 				break
 			}
-		} else {
-			err = fmt.Errorf("target item nr %d is %T, expected string", i+1, targetSpec)
-			break
 		}
 	}
 	return
 }
 
-func splitStrFunc(ctx ExprContext, name string, args []any) (result any, err error) {
+func splitStrFunc(ctx kern.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 {
+	if source, ok = args[kern.ParamSource].(string); !ok {
-		return result, ErrWrongParamType(name, ParamSource, TypeString, args[0])
+		return result, kern.ErrWrongParamType(name, kern.ParamSource, kern.TypeString, args[kern.ParamSource])
 	}
 
-	if sep, ok = args[1].(string); !ok {
+	if sep, ok = args[kern.ParamSeparator].(string); !ok {
-		return nil, fmt.Errorf("separator param must be string, got %T (%v)", args[1], args[1])
+		return nil, fmt.Errorf("separator param must be string, got %s (%v)", kern.TypeName(args[kern.ParamSeparator]), args[kern.ParamSeparator])
 	}
 
-	if count64, ok := args[2].(int64); ok { // TODO replace type assertion with toInt()
+	if count64, ok := args[kern.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)", kern.TypeName(args[kern.ParamCount]), args[kern.ParamCount])
 	}
 
 	if count > 0 {
@@ -170,7 +194,7 @@ func splitStrFunc(ctx ExprContext, name string, args []any) (result any, err err
 	} else {
 		parts = []string{}
 	}
-	list := make(ListType, len(parts))
+	list := make(kern.ListType, len(parts))
 	for i, part := range parts {
 		list[i] = part
 	}
@@ -178,41 +202,67 @@ func splitStrFunc(ctx ExprContext, name string, args []any) (result any, err err
 	return
 }
 
+func upperStrFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
+	if source, ok := args[kern.ParamSource].(string); ok {
+		result = strings.ToUpper(source)
+	} else {
+		err = kern.ErrWrongParamType(name, kern.ParamSource, kern.TypeString, args[kern.ParamSource])
+	}
+	return
+}
+
+func lowerStrFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
+	if source, ok := args[kern.ParamSource].(string); ok {
+		result = strings.ToLower(source)
+	} else {
+		err = kern.ErrWrongParamType(name, kern.ParamSource, kern.TypeString, args[kern.ParamSource])
+	}
+	return
+}
+
 // --- End of function definitions
 
 // Import above functions in the context
-func ImportStringFuncs(ctx ExprContext) {
+func ImportStringFuncs(ctx kern.ExprContext) {
-	ctx.RegisterFunc("strJoin", NewGolangFunctor(joinStrFunc), TypeString, []ExprFuncParam{
+	ctx.RegisterFunc("strJoin", kern.NewGolangFunctor(joinStrFunc), kern.TypeString, []kern.ExprFuncParam{
-		NewFuncParam(ParamSeparator),
+		NewFuncParam(kern.ParamSeparator),
-		NewFuncParamFlag(ParamItem, PfRepeat),
+		NewFuncParamFlag(kern.ParamItem, PfRepeat),
 	})
 
-	ctx.RegisterFunc("strSub", NewGolangFunctor(subStrFunc), TypeString, []ExprFuncParam{
+	ctx.RegisterFunc("strSub", kern.NewGolangFunctor(subStrFunc), kern.TypeString, []kern.ExprFuncParam{
-		NewFuncParam(ParamSource),
+		NewFuncParam(kern.ParamSource),
-		NewFuncParamFlagDef(ParamStart, PfDefault, int64(0)),
+		NewFuncParamFlagDef(kern.ParamStart, PfDefault, int64(0)),
-		NewFuncParamFlagDef(ParamCount, PfDefault, int64(-1)),
+		NewFuncParamFlagDef(kern.ParamCount, PfDefault, int64(-1)),
 	})
 
-	ctx.RegisterFunc("strSplit", NewGolangFunctor(splitStrFunc), "list of "+TypeString, []ExprFuncParam{
+	ctx.RegisterFunc("strSplit", kern.NewGolangFunctor(splitStrFunc), "list of "+kern.TypeString, []kern.ExprFuncParam{
-		NewFuncParam(ParamSource),
+		NewFuncParam(kern.ParamSource),
-		NewFuncParamFlagDef(ParamSeparator, PfDefault, ""),
+		NewFuncParamFlagDef(kern.ParamSeparator, PfDefault, ""),
-		NewFuncParamFlagDef(ParamCount, PfDefault, int64(-1)),
+		NewFuncParamFlagDef(kern.ParamCount, PfDefault, int64(-1)),
 	})
 
-	ctx.RegisterFunc("strTrim", NewGolangFunctor(trimStrFunc), TypeString, []ExprFuncParam{
+	ctx.RegisterFunc("strTrim", kern.NewGolangFunctor(trimStrFunc), kern.TypeString, []kern.ExprFuncParam{
-		NewFuncParam(ParamSource),
+		NewFuncParam(kern.ParamSource),
 	})
 
-	ctx.RegisterFunc("strStartsWith", NewGolangFunctor(startsWithStrFunc), TypeBoolean, []ExprFuncParam{
+	ctx.RegisterFunc("strStartsWith", kern.NewGolangFunctor(startsWithStrFunc), kern.TypeBoolean, []kern.ExprFuncParam{
-		NewFuncParam(ParamSource),
+		NewFuncParam(kern.ParamSource),
-		NewFuncParam(ParamPrefix),
+		NewFuncParam(kern.ParamPrefix),
-		NewFuncParamFlag("other "+ParamPrefix, PfRepeat),
+		NewFuncParamFlag(strParamOther, PfRepeat),
 	})
 
-	ctx.RegisterFunc("strEndsWith", NewGolangFunctor(endsWithStrFunc), TypeBoolean, []ExprFuncParam{
+	ctx.RegisterFunc("strEndsWith", kern.NewGolangFunctor(endsWithStrFunc), kern.TypeBoolean, []kern.ExprFuncParam{
-		NewFuncParam(ParamSource),
+		NewFuncParam(kern.ParamSource),
-		NewFuncParam(ParamSuffix),
+		NewFuncParam(kern.ParamSuffix),
-		NewFuncParamFlag("other "+ParamSuffix, PfRepeat),
+		NewFuncParamFlag(strParamOther, PfRepeat),
+	})
+
+	ctx.RegisterFunc("strUpper", kern.NewGolangFunctor(upperStrFunc), kern.TypeString, []kern.ExprFuncParam{
+		NewFuncParam(kern.ParamSource),
+	})
+
+	ctx.RegisterFunc("strLower", kern.NewGolangFunctor(lowerStrFunc), kern.TypeString, []kern.ExprFuncParam{
+		NewFuncParam(kern.ParamSource),
 	})
 }
 

builtins-register.go

@@ -6,21 +6,23 @@ package expr
 
 import (
 	"fmt"
+
+	"git.portale-stac.it/go-pkg/expr/kern"
 )
 
 type builtinModule struct {
-	importFunc  func(ExprContext)
+	importFunc  func(kern.ExprContext)
 	description string
 	imported    bool
 }
 
-func newBuiltinModule(importFunc func(ExprContext), description string) *builtinModule {
+func newBuiltinModule(importFunc func(kern.ExprContext), description string) *builtinModule {
 	return &builtinModule{importFunc, description, false}
 }
 
 var builtinModuleRegister map[string]*builtinModule
 
-func RegisterBuiltinModule(name string, importFunc func(ExprContext), description string) {
+func RegisterBuiltinModule(name string, importFunc func(kern.ExprContext), description string) {
 	if builtinModuleRegister == nil {
 		builtinModuleRegister = make(map[string]*builtinModule)
 	}

byte-slider.go

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

common-errors.go

@@ -1,55 +0,0 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
-// All rights reserved.
-
-// common-errors.go
-package expr
-
-import (
-	"fmt"
-)
-
-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)
-	} else {
-		err = fmt.Errorf("%s(): too few params -- expected %d, got %d", funcName, minArgs, argCount)
-	}
-	return
-}
-
-func ErrTooMuchParams(funcName string, maxArgs, argCount int) (err error) {
-	err = fmt.Errorf("%s(): too much params -- expected %d, got %d", funcName, maxArgs, argCount)
-	return
-}
-
-// --- General errors
-
-func ErrCantConvert(funcName string, value any, kind string) error {
-	return fmt.Errorf("%s(): can't convert %s to %s", funcName, TypeName(value), kind)
-}
-
-func ErrExpectedGot(funcName string, kind string, value any) error {
-	return fmt.Errorf("%s(): expected %s, got %s (%v)", funcName, kind, TypeName(value), value)
-}
-
-func ErrFuncDivisionByZero(funcName string) error {
-	return fmt.Errorf("%s(): division by zero", funcName)
-}
-
-func ErrDivisionByZero() error {
-	return fmt.Errorf("division by zero")
-}
-
-// --- Parameter errors
-
-func 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 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)
-}

common-type-names.go

@@ -1,20 +0,0 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
-// All rights reserved.
-
-// common-type-names.go
-package expr
-
-const (
-	TypeAny      = "any"
-	TypeBoolean  = "boolean"
-	TypeFloat    = "float"
-	TypeFraction = "fraction"
-	TypeHandle   = "handle"
-	TypeInt      = "integer"
-	TypeItem     = "item"
-	TypeNumber   = "number"
-	TypePair     = "pair"
-	TypeString   = "string"
-	TypeListOf = "list-of-"
-	TypeListOfStrings = "list-of-strings"
-)

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

@@ -1,33 +0,0 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
-// All rights reserved.
-
-// control.go
-package expr
-
-// Preset control variables
-const (
-	ControlPreset        = "_preset"
-	ControlLastResult    = "last"
-	ControlBoolShortcut  = "_bool_shortcut"
-	ControlSearchPath    = "_search_path"
-	ControlParentContext = "_parent_context"
-)
-
-// Other control variables
-const (
-	control_export_all = "_export_all"
-)
-
-// Initial values
-const (
-	init_search_path = "~/.local/lib/go-pkg/expr:/usr/local/lib/go-pkg/expr:/usr/lib/go-pkg/expr"
-)
-
-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)
-}

data-cursor.go

@@ -5,30 +5,53 @@
 package expr
 
 import (
-	"errors"
 	"io"
+	"slices"
+
+	"git.portale-stac.it/go-pkg/expr/kern"
 )
 
 type dataCursor struct {
-	ds          map[string]Functor
+	ds        map[string]kern.Functor
-	ctx         ExprContext
+	ctx       kern.ExprContext
-	index       int
+	initState bool // true if no item has produced yet (this replace di initial Next() call in the contructor)
-	resource    any
+	// cursorValid bool // true if resource is nil or if clean has not yet been called
-	nextFunc    Functor
+	index     int64
-	cleanFunc   Functor
+	count     int64
-	resetFunc   Functor
+	current   any
-	currentFunc Functor
+	lastErr   error
+	resource  any
+	nextFunc  kern.Functor
+	cleanFunc kern.Functor
+	resetFunc kern.Functor
 }
 
-func newDataCursor(ctx ExprContext, ds map[string]Functor) (dc *dataCursor) {
+func NewDataCursor(ctx kern.ExprContext, ds map[string]kern.Functor, resource any) (dc *dataCursor) {
 	dc = &dataCursor{
-		ds:    ds,
+		ds:        ds,
-		index: -1,
+		initState: true,
-		ctx:   ctx.Clone(),
+		// cursorValid: true,
+		index:     -1,
+		count:     0,
+		current:   nil,
+		lastErr:   nil,
+		resource:  resource,
+		ctx:       ctx.Clone(),
+		nextFunc:  ds[kern.NextName],
+		cleanFunc: ds[kern.CleanName],
+		resetFunc: ds[kern.ResetName],
 	}
 	return
 }
 
+func (dc *dataCursor) Context() kern.ExprContext {
+	return dc.ctx
+}
+
+func (dc *dataCursor) TypeName() string {
+	return "DataCursor"
+}
+
 // func mapToString(m map[string]Functor) string {
 // 	var sb strings.Builder
 // 	sb.WriteByte('{')
@@ -58,97 +81,227 @@ func (dc *dataCursor) String() string {
 }
 
 func (dc *dataCursor) HasOperation(name string) (exists bool) {
-	exists = name == indexName
+	exists = slices.Contains([]string{kern.CleanName, kern.ResetName, kern.CurrentName, kern.IndexName}, name)
 	if !exists {
 		f, ok := dc.ds[name]
-		exists = ok && isFunctor(f)
+		exists = ok && kern.IsFunctor(f)
 	}
 	return
 }
 
-func (dc *dataCursor) CallOperation(name string, args []any) (value any, err error) {
+func (dc *dataCursor) CallOperation(name string, args map[string]any) (value any, err error) {
-	if name == indexName {
+	if name == kern.IndexName {
 		value = int64(dc.Index())
-	} else if functor, ok := dc.ds[name]; ok && isFunctor(functor) {
+	} else if name == kern.CleanName {
-		if functor == dc.cleanFunc {
+		err = dc.Clean()
-			value, err = dc.Clean()
+	} else if name == kern.ResetName {
-		} else if functor == dc.resetFunc {
+		err = dc.Reset()
-			value, err = dc.Reset()
+	} else if functor, ok := dc.ds[name]; ok && kern.IsFunctor(functor) {
-		} else {
+		ctx := kern.CloneContext(dc.ctx)
-			ctx := cloneContext(dc.ctx)
+		value, err = functor.InvokeNamed(ctx, name, args)
-			value, err = functor.Invoke(ctx, name, []any{})
+		kern.ExportObjects(dc.ctx, ctx)
-			exportObjects(dc.ctx, ctx)
-		}
 	} else {
-		err = errNoOperation(name)
+		err = kern.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 := kern.CloneContext(dc.ctx)
-			ctx := cloneContext(dc.ctx)
+		actualParams := kern.BindActualParams(dc.resetFunc, []any{dc.resource})
-			if _, err = dc.resetFunc.Invoke(ctx, resetName, []any{dc.resource}); err == nil {
+		_, err = dc.resetFunc.InvokeNamed(ctx, kern.ResetName, actualParams)
-				dc.index = -1
+		kern.ExportObjects(dc.ctx, ctx)
-			}
-			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 := kern.CloneContext(dc.ctx)
-			ctx := cloneContext(dc.ctx)
+		actualParams := kern.BindActualParams(dc.cleanFunc, []any{dc.resource})
-			_, err = dc.cleanFunc.Invoke(ctx, cleanName, []any{dc.resource})
+		_, err = dc.cleanFunc.InvokeNamed(ctx, kern.CleanName, actualParams)
-			dc.resource = nil
+		kern.ExportObjects(dc.ctx, ctx)
-			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)
+	dc.init()
-	if item, err = dc.currentFunc.Invoke(ctx, currentName, []any{}); err == nil && item == nil {
+
+	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
+func (dc *dataCursor) checkFilter(filter kern.Functor, item any) (accepted bool, err error) {
-	if dc.resource != nil {
+	var v any
-		ctx := cloneContext(dc.ctx)
+	var ok bool
-		// fmt.Printf("Entering Inner-Ctx [%p]: %s\n", ctx, CtxToString(ctx, 0))
+	ctx := kern.CloneContext(dc.ctx)
-		if item, err = dc.nextFunc.Invoke(ctx, nextName, []any{dc.resource}); err == nil {
+
-			if item == nil {
+	actualParams := kern.BindActualParams(filter, []any{item, dc.index})
-				err = io.EOF
+	if v, err = filter.InvokeNamed(ctx, kern.FilterName, actualParams); err == nil && v != nil {
-			} else {
+		if accepted, ok = v.(bool); !ok {
-				dc.index++
+			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) Index() int {
+func (dc *dataCursor) mapItem(mapper kern.Functor, item any) (mappedItem any, err error) {
-	return dc.index
+	ctx := kern.CloneContext(dc.ctx)
+	actualParams := kern.BindActualParams(mapper, []any{item, dc.index})
+	mappedItem, err = mapper.InvokeNamed(ctx, kern.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[kern.FilterName]
+	mapper := dc.ds[kern.MapName]
+	var item any
+	for item == nil && dc.lastErr == nil {
+		ctx := kern.CloneContext(dc.ctx)
+		dc.index++
+
+		actualParams := kern.BindActualParams(dc.nextFunc, []any{dc.resource, dc.index})
+		if item, dc.lastErr = dc.nextFunc.InvokeNamed(ctx, kern.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)
+				}
+			}
+		}
+		kern.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() int64 {
+	return dc.index - 1
+}
+
+func (dc *dataCursor) Count() int64 {
+	return dc.count
 }

dict-iterator.go

@@ -0,0 +1,223 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// dict-iterator.go
+package expr
+
+import (
+	"fmt"
+	"io"
+	"slices"
+	"strings"
+
+	"git.portale-stac.it/go-pkg/expr/kern"
+)
+
+type dictIterMode int
+
+const (
+	dictIterModeKeys dictIterMode = iota
+	dictIterModeValues
+	dictIterModeItems
+)
+
+type DictIterator struct {
+	a        *kern.DictType
+	count    int64
+	index    int64
+	keys     []any
+	iterMode dictIterMode
+}
+
+type sortType int
+
+const (
+	sortTypeNone sortType = iota
+	sortTypeAsc
+	sortTypeDesc
+	sortTypeDefault = sortTypeAsc
+)
+
+func (it *DictIterator) makeKeys(m map[any]any, sort sortType) {
+	it.keys = make([]any, 0, len(m))
+
+	if sort == sortTypeNone {
+		for keyAny := range m {
+			it.keys = append(it.keys, keyAny)
+		}
+	} else {
+		scalarMap := make(map[string]any, len(m))
+		scalerKeys := make([]string, 0, len(m))
+		for keyAny := range m {
+			keyStr := fmt.Sprint(keyAny)
+			scalarMap[keyStr] = keyAny
+			scalerKeys = append(scalerKeys, keyStr)
+		}
+
+		switch sort {
+		case sortTypeAsc:
+			slices.Sort(scalerKeys)
+		case sortTypeDesc:
+			slices.Sort(scalerKeys)
+			slices.Reverse(scalerKeys)
+		}
+		for _, keyStr := range scalerKeys {
+			it.keys = append(it.keys, scalarMap[keyStr])
+		}
+	}
+}
+
+func NewDictIterator(dict *kern.DictType, args []any) (it *DictIterator, err error) {
+	var sortType = sortTypeNone
+	var s string
+	var argAny any
+
+	dictIt := &DictIterator{a: dict, count: 0, index: -1, keys: nil, iterMode: dictIterModeKeys}
+	if len(args) > 0 {
+		argAny = args[0]
+	} else {
+		argAny = "default"
+	}
+	if s, err = kern.ToGoString(argAny, "sort type"); err == nil {
+		switch strings.ToLower(s) {
+		case "a", "asc":
+			sortType = sortTypeAsc
+		case "d", "desc":
+			sortType = sortTypeDesc
+		case "n", "none", "nosort", "no-sort":
+			sortType = sortTypeNone
+		case "", "default":
+			sortType = sortTypeDefault
+		default:
+			err = fmt.Errorf("invalid sort type %q", s)
+		}
+
+		if err == nil {
+			if len(args) > 1 {
+				argAny = args[1]
+			} else {
+				argAny = "default"
+			}
+
+			if s, err = kern.ToGoString(argAny, "iteration mode"); err == nil {
+				switch strings.ToLower(s) {
+				case "k", "key", "keys":
+					dictIt.iterMode = dictIterModeKeys
+				case "v", "value", "values":
+					dictIt.iterMode = dictIterModeValues
+				case "i", "item", "items":
+					dictIt.iterMode = dictIterModeItems
+				case "", "default":
+					dictIt.iterMode = dictIterModeKeys
+				default:
+					err = fmt.Errorf("invalid iteration mode %q", s)
+				}
+			}
+		}
+	}
+
+	dictIt.makeKeys(*dict, sortType)
+	return dictIt, err
+}
+
+func NewMapIterator(m map[any]any) (it *DictIterator) {
+	it = &DictIterator{a: (*kern.DictType)(&m), count: 0, index: -1, keys: nil}
+	it.makeKeys(m, sortTypeNone)
+	return
+}
+
+func (it *DictIterator) String() string {
+	var l = int64(0)
+	if it.a != nil {
+		l = int64(len(*it.a))
+	}
+	return fmt.Sprintf("$({#%d})", l)
+}
+
+func (it *DictIterator) TypeName() string {
+	return "DictIterator"
+}
+
+func (it *DictIterator) HasOperation(name string) bool {
+	// yes := name == NextName || name == ResetName || name == IndexName || name == CountName || name == CurrentName
+	yes := slices.Contains([]string{kern.NextName, kern.ResetName, kern.IndexName, kern.CountName, kern.CurrentName, kern.CleanName, kern.KeyName, kern.ValueName}, name)
+	return yes
+}
+
+func (it *DictIterator) CallOperation(name string, args map[string]any) (v any, err error) {
+	switch name {
+	case kern.NextName:
+		v, err = it.Next()
+	case kern.ResetName:
+		err = it.Reset()
+	case kern.CleanName:
+		err = it.Clean()
+	case kern.IndexName:
+		v = int64(it.Index())
+	case kern.CurrentName:
+		v, err = it.Current()
+	case kern.CountName:
+		v = it.count
+	case kern.KeyName:
+		if it.index >= 0 && it.index < int64(len(it.keys)) {
+			v = it.keys[it.index]
+		} else {
+			err = io.EOF
+		}
+	case kern.ValueName:
+		if it.index >= 0 && it.index < int64(len(it.keys)) {
+			a := *(it.a)
+			v = a[it.keys[it.index]]
+		} else {
+			err = io.EOF
+		}
+	default:
+		err = kern.ErrNoOperation(name)
+	}
+	return
+}
+
+func (it *DictIterator) Current() (item any, err error) {
+	if it.index >= 0 && it.index < int64(len(it.keys)) {
+		switch it.iterMode {
+		case dictIterModeKeys:
+			item = it.keys[it.index]
+		case dictIterModeValues:
+			a := *(it.a)
+			item = a[it.keys[it.index]]
+		case dictIterModeItems:
+			a := *(it.a)
+			pair := []any{it.keys[it.index], a[it.keys[it.index]]}
+			item = kern.NewList(pair)
+		}
+	} else {
+		err = io.EOF
+	}
+	return
+}
+
+func (it *DictIterator) Next() (item any, err error) {
+	it.index++
+	if item, err = it.Current(); err != io.EOF {
+		it.count++
+	}
+	return
+}
+
+func (it *DictIterator) Index() int64 {
+	return it.index
+}
+
+func (it *DictIterator) Count() int64 {
+	return it.count
+}
+
+func (it *DictIterator) Reset() error {
+	it.index = -1
+	it.count = 0
+	return nil
+}
+
+func (it *DictIterator) Clean() error {
+	return nil
+}

expr.go

@@ -0,0 +1,16 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// expr.go
+package expr
+
+import (
+	kern "git.portale-stac.it/go-pkg/expr/kern"
+)
+
+// ----Expression interface
+type Expr interface {
+	kern.Typer
+	Eval(ctx kern.ExprContext) (result any, err error)
+	String() string
+}

function.go

@@ -7,41 +7,47 @@ package expr
 import (
 	"fmt"
 	"strings"
+
+	"git.portale-stac.it/go-pkg/expr/kern"
 )
 
 // ---- Function template
-type FuncTemplate func(ctx ExprContext, name string, args []any) (result any, err error)
+// type FuncTemplate func(ctx expr.ExprContext, name string, args map[string]any) (result any, err error)
 
 // ---- Common functor definition
-type baseFunctor struct {
+type BaseFunctor struct {
-	info ExprFunc
+	info kern.ExprFunc
 }
 
-func (functor *baseFunctor) ToString(opt FmtOpt) (s string) {
+func (functor *BaseFunctor) ToString(opt kern.FmtOpt) (s string) {
 	if functor.info != nil {
 		s = functor.info.ToString(opt)
 	} else {
-		s = "func() {}"
+		s = "func(){}"
 	}
 	return s
 }
 
-func (functor *baseFunctor) GetParams() (params []ExprFuncParam) {
+func (functor *BaseFunctor) GetParams() (params []kern.ExprFuncParam) {
 	if functor.info != nil {
 		return functor.info.Params()
 	} else {
-		return []ExprFuncParam{}
+		return []kern.ExprFuncParam{}
 	}
 }
 
-func (functor *baseFunctor) SetFunc(info ExprFunc) {
+func (functor *BaseFunctor) SetFunc(info kern.ExprFunc) {
 	functor.info = info
 }
 
-func (functor *baseFunctor) GetFunc() ExprFunc {
+func (functor *BaseFunctor) GetFunc() kern.ExprFunc {
 	return functor.info
 }
 
+func (functor *BaseFunctor) GetDefinitionContext() kern.ExprContext {
+	return nil
+}
+
 // ---- Function Parameters
 type paramFlags uint16
 
@@ -57,11 +63,11 @@ type funcParamInfo struct {
 	defaultValue any
 }
 
-func NewFuncParam(name string) ExprFuncParam {
+func NewFuncParam(name string) kern.ExprFuncParam {
 	return &funcParamInfo{name: name}
 }
 
-func NewFuncParamFlag(name string, flags paramFlags) ExprFuncParam {
+func NewFuncParamFlag(name string, flags paramFlags) kern.ExprFuncParam {
 	return &funcParamInfo{name: name, flags: flags}
 }
 
@@ -74,7 +80,7 @@ func (param *funcParamInfo) Name() string {
 }
 
 func (param *funcParamInfo) Type() string {
-	return TypeAny
+	return kern.TypeAny
 }
 
 func (param *funcParamInfo) IsDefault() bool {
@@ -94,57 +100,54 @@ func (param *funcParamInfo) DefaultValue() any {
 }
 
 // --- Functions
+
+// funcInfo implements expr.ExprFunc
 type funcInfo struct {
-	name       string
+	name         string
-	minArgs    int
+	minArgs      int
-	maxArgs    int
+	maxArgs      int
-	functor    Functor
+	functor      kern.Functor
-	params     []ExprFuncParam
+	formalParams []kern.ExprFuncParam
-	returnType string
+	returnType   string
 }
 
-func newFuncInfo(name string, functor Functor, returnType string, params []ExprFuncParam) (info *funcInfo, err error) {
+func newFuncInfo(name string, functor kern.Functor, returnType string, params []kern.ExprFuncParam) (info *funcInfo, err error) {
 	var minArgs = 0
 	var maxArgs = 0
-	if params != nil {
+	for _, p := range params {
-		for _, p := range params {
+		if maxArgs == -1 {
-			if maxArgs == -1 {
+			return nil, fmt.Errorf("no more params can be specified after the ellipsis symbol: %q", p.Name())
-				return nil, fmt.Errorf("no more params can be specified after the ellipsis symbol: %q", p.Name())
+		}
-			}
+		if p.IsDefault() || p.IsOptional() {
-			if p.IsDefault() || p.IsOptional() {
+			maxArgs++
-				maxArgs++
+		} else if maxArgs == minArgs {
-			} else if maxArgs == minArgs {
+			minArgs++
-				minArgs++
+			maxArgs++
-				maxArgs++
+		} else {
-			} else {
+			return nil, fmt.Errorf("can't specify non-optional param after optional ones: %q", p.Name())
-				return nil, fmt.Errorf("can't specify non-optional param after optional ones: %q", p.Name())
+		}
-			}
+		if p.IsRepeat() {
-			if p.IsRepeat() {
+			minArgs--
-				minArgs--
+			maxArgs = -1
-				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) {
+func (info *funcInfo) Params() []kern.ExprFuncParam {
-	return newFuncInfo("unnamed", functor, returnType, params)
+	return info.formalParams
-}
-
-func (info *funcInfo) Params() []ExprFuncParam {
-	return info.params
 }
 
 func (info *funcInfo) ReturnType() string {
 	return info.returnType
 }
 
-func (info *funcInfo) ToString(opt FmtOpt) string {
+func (info *funcInfo) ToString(opt kern.FmtOpt) string {
 	var sb strings.Builder
 	if len(info.Name()) == 0 {
 		sb.WriteString("func")
@@ -152,8 +155,8 @@ func (info *funcInfo) ToString(opt FmtOpt) string {
 		sb.WriteString(info.Name())
 	}
 	sb.WriteByte('(')
-	if info.params != nil {
+	if info.formalParams != nil {
-		for i, p := range info.params {
+		for i, p := range info.formalParams {
 			if i > 0 {
 				sb.WriteString(", ")
 			}
@@ -178,9 +181,9 @@ func (info *funcInfo) ToString(opt FmtOpt) string {
 	if len(info.returnType) > 0 {
 		sb.WriteString(info.returnType)
 	} else {
-		sb.WriteString(TypeAny)
+		sb.WriteString(kern.TypeAny)
 	}
-	sb.WriteString(" {}")
+	sb.WriteString("{}")
 	return sb.String()
 }
 
@@ -196,45 +199,189 @@ func (info *funcInfo) MaxArgs() int {
 	return info.maxArgs
 }
 
-func (info *funcInfo) Functor() Functor {
+func (info *funcInfo) Functor() kern.Functor {
 	return info.functor
 }
 
+func (info *funcInfo) AllocContext(parentCtx kern.ExprContext) (ctx kern.ExprContext) {
+	if defCtx := info.functor.GetDefinitionContext(); defCtx != nil {
+		ctx = defCtx.Clone()
+		ctx.SetParent(defCtx)
+	} else {
+		ctx = parentCtx.Clone()
+		ctx.SetParent(parentCtx)
+	}
+	return
+}
+
+func (info *funcInfo) ParamSpec(paramName string) kern.ExprFuncParam {
+	for _, spec := range info.formalParams {
+		if spec.Name() == paramName {
+			return spec
+		}
+	}
+	return nil
+}
+
+func initActualParams(ctx kern.ExprContext, info kern.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 := kern.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 = kern.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 = kern.ErrTooFewParams(name, info.MinArgs(), info.MaxArgs(), passedCount)
+		return
+	}
+
+	if passedCount < len(info.formalParams) {
+		for _, p := range info.formalParams {
+			if _, exists := actualParams[p.Name()]; !exists {
+				if !p.IsDefault() {
+					break
+				}
+				if p.IsRepeat() {
+					varArgs := make([]any, 1)
+					varArgs[0] = p.DefaultValue()
+					actualParams[p.Name()] = varArgs
+				} else {
+					actualParams[p.Name()] = p.DefaultValue()
+				}
+			}
+		}
+	}
+
+	if info.MaxArgs() >= 0 && info.MaxArgs() < len(actualParams) {
+		err = kern.ErrTooManyParams(name, info.MaxArgs(), len(actualParams))
+	}
+	return
+}
+
 // ----- Call a function ---
 
-func checkFunctionCall(ctx ExprContext, name string, varParams *[]any) (err error) {
+// func getAssignVarName(t *term) (name string, ok bool) {
-	if info, exists, owner := GetFuncInfo(ctx, name); exists {
+// 	if ok = t.symbol() == SymEqual; ok {
-		passedCount := len(*varParams)
+// 		name = t.children[0].source()
-		if info.MinArgs() > passedCount {
+// 	}
-			err = ErrTooFewParams(name, info.MinArgs(), info.MaxArgs(), passedCount)
+// 	return
-		}
+// }
-		for i, p := range info.Params() {
-			if i >= passedCount {
-				if !p.IsDefault() {
-					break
-				}
-				*varParams = append(*varParams, 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)
-		}
-	} else {
-		err = fmt.Errorf("unknown function %s()", name)
-	}
-	return
-}
 
-func CallFunction(parentCtx ExprContext, name string, params []any) (result any, err error) {
+// func CallFunctionByTerm(parentCtx expr.ExprContext, name string, callTerm *term) (result any, err error) {
-	ctx := cloneContext(parentCtx)
+// 	var actualParams map[string]any
-	ctx.SetParent(parentCtx)
+// 	if info, exists := GetFuncInfo(parentCtx, name); exists {
+// 		if actualParams, err = initActualParams(parentCtx, info, callTerm); err == nil {
+// 			ctx := info.AllocContext(parentCtx)
+// 			if err = info.PrepareCall(name, actualParams); err == nil {
+// 				functor := info.Functor()
+// 				result, err = functor.InvokeNamed(ctx, name, actualParams)
+// 				exportObjectsToParent(ctx)
+// 			}
+// 		}
+// 	} else {
+// 		err = fmt.Errorf("unknown function %s()", name)
+// 	}
+// 	return
+// }
 
-	if err = checkFunctionCall(ctx, name, &params); err == nil {
+// func CallFunctionByArgs(parentCtx expr.ExprContext, name string, args []any) (result any, err error) {
-		result, err = ctx.Call(name, params)
+// 	var actualParams map[string]any
-		exportObjectsToParent(ctx)
+// 	if info, exists := GetFuncInfo(parentCtx, name); exists {
-	}
+// 		functor := info.Functor()
-	return
+// 		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 expr.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

@@ -7,88 +7,68 @@ package expr
 import (
 	"path/filepath"
 	"strings"
+
+	"git.portale-stac.it/go-pkg/expr/kern"
 )
 
-var globalCtx *SimpleStore
+//var globalCtx *SimpleStore
 
-func ImportInContext(name string) (exists bool) {
+func ImportInContext(ctx kern.ExprContext, name string) (exists bool) {
-	var mod *builtinModule
+	if globalCtx := ctx.GetGlobal(); globalCtx != nil {
-	if mod, exists = builtinModuleRegister[name]; exists {
+		var mod *builtinModule
-		mod.importFunc(globalCtx)
+		if mod, exists = builtinModuleRegister[name]; exists {
-		mod.imported = true
+			mod.importFunc(globalCtx)
+			mod.imported = true
+		}
 	}
 	return
 }
 
-func ImportInContextByGlobPattern(pattern string) (count int, err error) {
+func ImportInContextByGlobPattern(ctx kern.ExprContext, pattern string) (count int, err error) {
-	var matched bool
+	if globalCtx := ctx.GetGlobal(); globalCtx != nil {
-	for name, mod := range builtinModuleRegister {
+		var matched bool
-		if matched, err = filepath.Match(pattern, name); err == nil {
+		for name, mod := range builtinModuleRegister {
-			if matched {
+			if matched, err = filepath.Match(pattern, name); err == nil {
-				count++
+				if matched {
-				mod.importFunc(globalCtx)
+					count++
-				mod.imported = true
+					mod.importFunc(globalCtx)
+					mod.imported = true
+				}
+			} else {
+				break
 			}
-		} else {
-			break
 		}
 	}
 	return
 }
 
-func GetVar(ctx ExprContext, name string) (value any, exists bool) {
+func GlobalCtrlSet(ctx kern.ExprContext, name string, newValue any) (currentValue any) {
-	if value, exists = ctx.GetVar(name); !exists {
+	if globalCtx := ctx.GetGlobal(); globalCtx != nil {
-		value, exists = globalCtx.GetVar(name)
+		if !strings.HasPrefix(name, "_") {
-	}
+			name = "_" + name
-	return
-}
-
-func GetLocalFuncInfo(ctx ExprContext, name string) (item ExprFunc, exists bool) {
-	var v any
-	if len(name) > 0 {
-		if v, exists = ctx.GetVar(name); exists && isFunctor(v) {
-			f, _ := v.(Functor)
-			item = f.GetFunc()
-		} else {
-			item, exists = ctx.GetFuncInfo(name)
 		}
-	}
-	return
-}
-func GetFuncInfo(ctx ExprContext, name string) (item ExprFunc, exists bool, ownerCtx ExprContext) {
-	if len(name) > 0 {
-		if item, exists = GetLocalFuncInfo(ctx, name); exists {
-			ownerCtx = ctx
-		} else if item, exists = globalCtx.GetFuncInfo(name); exists {
-			ownerCtx = globalCtx
-		}
-	}
-	return
-}
 
-func GlobalCtrlSet(name string, newValue any) (currentValue any) {
+		currentValue, _ = globalCtx.GetVar(name)
-	if !strings.HasPrefix(name, "_") {
+		globalCtx.SetVar(name, newValue)
-		name = "_" + name
 	}
-	currentValue, _ = globalCtx.GetVar(name)
-
-	globalCtx.SetVar(name, newValue)
 	return currentValue
 }
 
-func GlobalCtrlGet(name string) (currentValue any) {
+func GlobalCtrlGet(ctx kern.ExprContext, name string) (currentValue any) {
-	if !strings.HasPrefix(name, "_") {
+	if globalCtx := ctx.GetGlobal(); globalCtx != nil {
-		name = "_" + name
+		if !strings.HasPrefix(name, "_") {
+			name = "_" + name
+		}
+		currentValue, _ = globalCtx.GetVar(name)
 	}
-	currentValue, _ = globalCtx.GetVar(name)
 	return currentValue
 }
 
-func CtrlEnable(ctx ExprContext, name string) (currentStatus bool) {
+func CtrlEnable(ctx kern.ExprContext, name string) (currentStatus bool) {
 	if !strings.HasPrefix(name, "_") {
 		name = "_" + name
 	}
-	if v, exists := ctx.GetVar(name); exists && IsBool(v) {
+	if v, exists := ctx.GetVar(name); exists && kern.IsBool(v) {
 		currentStatus, _ = v.(bool)
 	}
 
@@ -96,11 +76,11 @@ func CtrlEnable(ctx ExprContext, name string) (currentStatus bool) {
 	return currentStatus
 }
 
-func CtrlDisable(ctx ExprContext, name string) (currentStatus bool) {
+func CtrlDisable(ctx kern.ExprContext, name string) (currentStatus bool) {
 	if !strings.HasPrefix(name, "_") {
 		name = "_" + name
 	}
-	if v, exists := ctx.GetVar(name); exists && IsBool(v) {
+	if v, exists := ctx.GetVar(name); exists && kern.IsBool(v) {
 		currentStatus, _ = v.(bool)
 	}
 
@@ -108,36 +88,39 @@ func CtrlDisable(ctx ExprContext, name string) (currentStatus bool) {
 	return currentStatus
 }
 
-func CtrlIsEnabled(ctx ExprContext, name string) (status bool) {
+// func CtrlIsEnabled(ctx ExprContext, name string) (status bool) {
-	var v any
+// 	var v any
-	var exists bool
+// 	var exists bool
 
-	if !strings.HasPrefix(name, "_") {
+// 	if !strings.HasPrefix(name, "_") {
-		name = "_" + name
+// 		name = "_" + name
-	}
+// 	}
 
-	if v, exists = ctx.GetVar(name); !exists {
+// 	if v, exists = ctx.GetVar(name); !exists {
-		v, exists = globalCtx.GetVar(name)
+// 		v, exists = globalCtx.GetVar(name)
-	}
+// 	}
 
-	if exists {
+// 	if exists {
-		if b, ok := v.(bool); ok {
+// 		if b, ok := v.(bool); ok {
-			status = b
+// 			status = b
+// 		}
+// 	}
+// 	return
+// }
+
+func getControlString(ctx kern.ExprContext, name string) (s string, exists bool) {
+	if globalCtx := ctx.GetGlobal(); globalCtx != nil {
+		var v any
+		if v, exists = globalCtx.GetVar(name); exists {
+			s, exists = v.(string)
 		}
 	}
 	return
 }
 
-func getControlString(name string) (s string, exists bool) {
+func InitGlobal() (ctx kern.ExprContext) {
-	var v any
+	ctx = NewSimpleStoreWithoutGlobalContext()
-	if v, exists = globalCtx.GetVar(name); exists {
+	kern.InitDefaultVars(ctx)
-		s, exists = v.(string)
+	ImportBuiltinsFuncs(ctx)
-	}
 	return
 }
-
-func init() {
-	globalCtx = NewSimpleStore()
-	initDefaultVars(globalCtx)
-	ImportBuiltinsFuncs(globalCtx)
-}

go.mod

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

go.sum

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

graph.go

@@ -1,6 +1,8 @@
 // Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
 // All rights reserved.
 
+//go:build graph
+
 // graph.go
 package expr
 
@@ -53,7 +55,7 @@ func (r *Reticle) computeCharWidth() {
 			if v := ref.node.value(); v != nil {
 				ref.label = fmt.Sprintf("%v", v)
 			} else {
-				ref.label = ref.node.source()
+				ref.label = ref.node.Source()
 			}
 			r.colsWidth[c] = max(r.colsWidth[c], len(ref.label)+2) // +2 to make room for brakets
 		}

helpers.go

@@ -9,9 +9,12 @@ import (
 	"io"
 	"os"
 	"strings"
+
+	"git.portale-stac.it/go-pkg/expr/kern"
+	"git.portale-stac.it/go-pkg/expr/util"
 )
 
-func EvalString(ctx ExprContext, source string) (result any, err error) {
+func EvalString(ctx kern.ExprContext, source string) (result any, err error) {
 	var tree *ast
 
 	r := strings.NewReader(source)
@@ -34,21 +37,21 @@ func EvalStringA(source string, args ...Arg) (result any, err error) {
 }
 
 func EvalStringV(source string, args []Arg) (result any, err error) {
-	ctx := NewSimpleStore()
+	ctx := NewSimpleStoreWithoutGlobalContext()
 	for _, arg := range args {
-		if isFunc(arg.Value) {
+		if util.IsFunc(arg.Value) {
-			if f, ok := arg.Value.(FuncTemplate); ok {
+			if f, ok := arg.Value.(kern.FuncTemplate); ok {
-				functor := NewGolangFunctor(f)
+				functor := kern.NewGolangFunctor(f)
 				// ctx.RegisterFunc(arg.Name, functor, 0, -1)
-				ctx.RegisterFunc(arg.Name, functor, TypeAny, []ExprFuncParam{
+				ctx.RegisterFunc(arg.Name, functor, kern.TypeAny, []kern.ExprFuncParam{
-					NewFuncParamFlagDef(ParamValue, PfDefault|PfRepeat, 0),
+					NewFuncParamFlagDef(kern.ParamValue, PfDefault|PfRepeat, 0),
 				})
 			} else {
 				err = fmt.Errorf("invalid function specification: %q", arg.Name)
 			}
-		} else if integer, ok := anyInteger(arg.Value); ok {
+		} else if integer, ok := kern.AnyInteger(arg.Value); ok {
 			ctx.SetVar(arg.Name, integer)
-		} else if float, ok := anyFloat(arg.Value); ok {
+		} else if float, ok := kern.AnyFloat(arg.Value); ok {
 			ctx.SetVar(arg.Name, float)
 		} else if _, ok := arg.Value.(string); ok {
 			ctx.SetVar(arg.Name, arg.Value)
@@ -65,7 +68,7 @@ func EvalStringV(source string, args []Arg) (result any, err error) {
 	return
 }
 
-func EvalStream(ctx ExprContext, r io.Reader) (result any, err error) {
+func EvalStream(ctx kern.ExprContext, r io.Reader) (result any, err error) {
 	var tree *ast
 	scanner := NewScanner(r, DefaultTranslations())
 	parser := NewParser()
@@ -76,7 +79,7 @@ func EvalStream(ctx ExprContext, r io.Reader) (result any, err error) {
 	return
 }
 
-func EvalFile(ctx ExprContext, filePath string) (result any, err error) {
+func EvalFile(ctx kern.ExprContext, filePath string) (result any, err error) {
 	var fh *os.File
 	if fh, err = os.Open(filePath); err != nil {
 		return nil, err

import-utils.go

@@ -11,6 +11,9 @@ import (
 	"path"
 	"path/filepath"
 	"strings"
+
+	"git.portale-stac.it/go-pkg/expr/kern"
+	"git.portale-stac.it/go-pkg/expr/util"
 )
 
 const (
@@ -19,19 +22,19 @@ const (
 )
 
 func checkStringParamExpected(funcName string, paramValue any, paramPos int) (err error) {
-	if !(IsString(paramValue) /*|| isList(paramValue)*/) {
+	if !(kern.IsString(paramValue) /*|| isList(paramValue)*/) {
-		err = fmt.Errorf("%s(): param nr %d has wrong type %s, string expected", funcName, paramPos+1, TypeName(paramValue))
+		err = fmt.Errorf("%s(): param nr %d has wrong type %s, string expected", funcName, paramPos+1, kern.TypeName(paramValue))
 	}
 	return
 }
 
-func addSourceEnvImportDirs(varName string, dirList []string) []string {
+// func addSourceEnvImportDirs(varName string, dirList []string) []string {
-	return addEnvImportDirs(ENV_EXPR_SOURCE_PATH, dirList)
+// 	return addEnvImportDirs(ENV_EXPR_SOURCE_PATH, dirList)
-}
+// }
 
-func addPluginEnvImportDirs(varName string, dirList []string) []string {
+// func addPluginEnvImportDirs(varName string, dirList []string) []string {
-	return addEnvImportDirs(ENV_EXPR_PLUGIN_PATH, dirList)
+// 	return addEnvImportDirs(ENV_EXPR_PLUGIN_PATH, dirList)
-}
+// }
 
 func addEnvImportDirs(envVarName string, dirList []string) []string {
 	if dirSpec, exists := os.LookupEnv(envVarName); exists {
@@ -45,8 +48,8 @@ func addEnvImportDirs(envVarName string, dirList []string) []string {
 	return dirList
 }
 
-func addSearchDirs(endingPath string, dirList []string) []string {
+func addSearchDirs(ctx kern.ExprContext, endingPath string, dirList []string) []string {
-	if dirSpec, exists := getControlString(ControlSearchPath); exists {
+	if dirSpec, exists := getControlString(ctx, kern.ControlSearchPath); exists {
 		dirs := strings.Split(dirSpec, ":")
 		if dirList == nil {
 			dirList = dirs
@@ -63,9 +66,9 @@ func addSearchDirs(endingPath string, dirList []string) []string {
 	return dirList
 }
 
-func buildSearchDirList(endingPath, envVarName string) (dirList []string) {
+func buildSearchDirList(ctx kern.ExprContext, endingPath, envVarName string) (dirList []string) {
 	dirList = addEnvImportDirs(envVarName, dirList)
-	dirList = addSearchDirs(endingPath, dirList)
+	dirList = addSearchDirs(ctx, endingPath, dirList)
 	return
 }
 
@@ -75,11 +78,27 @@ func isFile(filePath string) bool {
 }
 
 func searchAmongPath(filename string, dirList []string) (filePath string) {
+	var err error
+
+	suffix := SHAREDLIBRARY_EXTENSION
+	if strings.HasSuffix(filename, ".debug") {
+		suffix += ".debug"
+	}
+
 	for _, dir := range dirList {
+		if dir, err = util.ExpandPath(dir); err != nil {
+			continue
+		}
 		if fullPath := path.Join(dir, filename); isFile(fullPath) {
 			filePath = fullPath
 			break
 		}
+
+		subdir := strings.TrimSuffix(filename, suffix)
+		if fullPath := path.Join(dir, subdir, filename); isFile(fullPath) {
+			filePath = fullPath
+			break
+		}
 	}
 	return
 }
@@ -90,6 +109,10 @@ func isPathRelative(filePath string) bool {
 }
 
 func makeFilepath(filename string, dirList []string) (filePath string, err error) {
+	if filename, err = util.ExpandPath(filename); err != nil {
+		return
+	}
+
 	if path.IsAbs(filename) || isPathRelative(filename) {
 		if isFile(filename) {
 			filePath = filename

int-iterator.go

@@ -0,0 +1,137 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// int-iterator.go
+package expr
+
+import (
+	"fmt"
+	"io"
+	"slices"
+
+	"git.portale-stac.it/go-pkg/expr/kern"
+)
+
+type IntIterator struct {
+	count int64
+	index int64
+	start int64
+	stop  int64
+	step  int64
+}
+
+func NewIntIterator(args []any) (it *IntIterator, err error) {
+	var argc int = 0
+	if args != nil {
+		argc = len(args)
+	}
+	it = &IntIterator{count: 0, index: -1, start: 0, stop: 0, step: 1}
+	if argc >= 1 {
+		if it.stop, err = kern.ToGoInt64(args[0], "start index"); err != nil {
+			return
+		}
+		if argc >= 2 {
+			it.start = it.stop
+			if it.stop, err = kern.ToGoInt64(args[1], "stop index"); err != nil {
+				return
+			}
+			if argc >= 3 {
+				if it.step, err = kern.ToGoInt64(args[2], "step"); err != nil {
+					return
+				}
+			} else if it.start > it.stop {
+				it.step = -1
+			}
+		}
+	}
+	if it.step == 0 {
+		err = fmt.Errorf("step cannot be zero")
+		return
+	}
+	if it.start < it.stop && it.step < 0 {
+		err = fmt.Errorf("step cannot be negative when start < stop")
+		return
+	}
+	if it.start > it.stop && it.step > 0 {
+		err = fmt.Errorf("step cannot be positive when start > stop")
+		return
+	}
+	it.Reset()
+	return
+}
+
+func (it *IntIterator) String() string {
+	return fmt.Sprintf("$(%d..%d..%d)", it.start, it.stop, it.step)
+}
+
+func (it *IntIterator) TypeName() string {
+	return "IntIterator"
+}
+
+func (it *IntIterator) HasOperation(name string) bool {
+	yes := slices.Contains([]string{kern.NextName, kern.ResetName, kern.IndexName, kern.CountName, kern.CurrentName}, name)
+	return yes
+}
+
+func (it *IntIterator) CallOperation(name string, args map[string]any) (v any, err error) {
+	switch name {
+	case kern.NextName:
+		v, err = it.Next()
+	case kern.ResetName:
+		err = it.Reset()
+	case kern.CleanName:
+		err = it.Clean()
+	case kern.IndexName:
+		v = int64(it.Index())
+	case kern.CurrentName:
+		v, err = it.Current()
+	case kern.CountName:
+		v = it.count
+	default:
+		err = kern.ErrNoOperation(name)
+	}
+	return
+}
+
+func (it *IntIterator) Current() (item any, err error) {
+	if it.start <= it.stop {
+		if it.index >= it.start && it.index < it.stop {
+			item = it.index
+		} else {
+			err = io.EOF
+		}
+	} else {
+		if it.index > it.stop && it.index <= it.start {
+			item = it.index
+		} else {
+			err = io.EOF
+		}
+	}
+	return
+}
+
+func (it *IntIterator) Next() (item any, err error) {
+	it.index += it.step
+	if item, err = it.Current(); err != io.EOF {
+		it.count++
+	}
+	return
+}
+
+func (it *IntIterator) Index() int64 {
+	return it.index
+}
+
+func (it *IntIterator) Count() int64 {
+	return it.count
+}
+
+func (it *IntIterator) Reset() error {
+	it.index = it.start - it.step
+	it.count = 0
+	return nil
+}
+
+func (it *IntIterator) Clean() error {
+	return nil
+}

iter-factory.go

@@ -0,0 +1,29 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// iter-factory.go
+package expr
+
+import (
+	"git.portale-stac.it/go-pkg/expr/kern"
+)
+
+func NewIterator(value any) (it kern.Iterator, err error) {
+	if value == nil {
+		return NewArrayIterator([]any{}), nil
+	}
+
+	switch v := value.(type) {
+	case *kern.ListType:
+		it = NewListIterator(v, nil)
+	case *kern.DictType:
+		it, err = NewDictIterator(v, nil)
+	case []any:
+		it = NewArrayIterator(v)
+	case kern.Iterator:
+		it = v
+	default:
+		it = NewArrayIterator([]any{value})
+	}
+	return
+}

iter-list.go

@@ -1,141 +0,0 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
-// All rights reserved.
-
-// iter-list.go
-package expr
-
-import (
-	"fmt"
-	"io"
-)
-
-type ListIterator struct {
-	a     *ListType
-	count int
-	index int
-	start int
-	stop  int
-	step  int
-}
-
-func NewListIterator(list *ListType, args []any) (it *ListIterator) {
-	var argc int = 0
-	listLen := len(([]any)(*list))
-	if args != nil {
-		argc = len(args)
-	}
-	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 < 0 {
-				i = listLen + i
-			}
-			it.start = i
-		}
-		if argc >= 2 {
-			if i, err := ToInt(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 < 0 {
-						i = -i
-					}
-					if it.start > it.stop {
-						it.step = -i
-					} else {
-						it.step = i
-					}
-				}
-			}
-		}
-	}
-	it.index = it.start - it.step
-	return
-}
-
-func NewArrayIterator(array []any) (it *ListIterator) {
-	it = &ListIterator{a: (*ListType)(&array), count: 0, index: -1, start: 0, stop: len(array) - 1, step: 1}
-	return
-}
-
-func NewAnyIterator(value any) (it *ListIterator) {
-	if value == nil {
-		it = NewArrayIterator([]any{})
-	} else if list, ok := value.(*ListType); ok {
-		it = NewListIterator(list, nil)
-	} else if array, ok := value.([]any); ok {
-		it = NewArrayIterator(array)
-	} else if it1, ok := value.(*ListIterator); ok {
-		it = it1
-	} else {
-		it = NewArrayIterator([]any{value})
-	}
-	return
-}
-
-func (it *ListIterator) String() string {
-	var l = 0
-	if it.a != nil {
-		l = len(*it.a)
-	}
-	return fmt.Sprintf("$(#%d)", l)
-}
-
-func (it *ListIterator) HasOperation(name string) bool {
-	yes := name == resetName || name == indexName || name == countName
-	return yes
-}
-
-func (it *ListIterator) CallOperation(name string, args []any) (v any, err error) {
-	switch name {
-	case resetName:
-		v, err = it.Reset()
-	case indexName:
-		v = int64(it.Index())
-	case countName:
-		v = it.count
-	default:
-		err = errNoOperation(name)
-	}
-	return
-}
-
-func (it *ListIterator) Current() (item any, err error) {
-	a := *(it.a)
-	if it.start <= it.stop {
-		if it.stop < len(a) && it.index >= it.start && it.index <= it.stop {
-			item = a[it.index]
-		} else {
-			err = io.EOF
-		}
-	} else {
-		if it.start < len(a) && it.index >= it.stop && it.index <= it.start {
-			item = a[it.index]
-		} else {
-			err = io.EOF
-		}
-
-	}
-	return
-}
-
-func (it *ListIterator) Next() (item any, err error) {
-	it.index += it.step
-	if item, err = it.Current(); err != io.EOF {
-		it.count++
-	}
-	return
-}
-
-func (it *ListIterator) Index() int {
-	return it.index
-}
-
-func (it *ListIterator) Reset() (bool, error) {
-	it.index = it.start
-	return true, nil
-}

iterator.go

@@ -1,42 +0,0 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
-// All rights reserved.
-
-// iterator.go
-package expr
-
-import (
-	"errors"
-	"fmt"
-)
-
-// Operator names
-
-const (
-	initName    = "init"
-	cleanName   = "clean"
-	resetName   = "reset"
-	nextName    = "next"
-	currentName = "current"
-	indexName   = "index"
-	countName   = "count"
-)
-
-type Iterator interface {
-	Next() (item any, err error) // must return io.EOF after the last item
-	Current() (item any, err error)
-	Index() int
-}
-
-type ExtIterator interface {
-	Iterator
-	HasOperation(name string) bool
-	CallOperation(name string, args []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")
-}

kern/bind-go-functions.go

@@ -2,11 +2,11 @@
 // All rights reserved.
 
 // bind-go-function.go
-package expr
+package kern
 
 // ---- Linking with Go functions
 type golangFunctor struct {
-	baseFunctor
+	BaseFunctor
 	f FuncTemplate
 }
 
@@ -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)
 }

kern/bool.go

@@ -0,0 +1,27 @@
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// string.go
+package kern
+
+func IsBool(v any) (ok bool) {
+	_, ok = v.(bool)
+	return ok
+}
+
+func ToBool(v any) (b bool, ok bool) {
+	ok = true
+	switch x := v.(type) {
+	case string:
+		b = len(x) > 0
+	case float64:
+		b = x != 0.0
+	case int64:
+		b = x != 0
+	case bool:
+		b = x
+	default:
+		ok = false
+	}
+	return
+}

kern/common-errors.go

@@ -0,0 +1,91 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// common-errors.go
+package kern
+
+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)
+	} else {
+		err = fmt.Errorf("%s(): too few params -- expected %d, got %d", funcName, minArgs, argCount)
+	}
+	return
+}
+
+func ErrTooManyParams(funcName string, maxArgs, argCount int) (err error) {
+	err = fmt.Errorf("%s(): too many params -- expected %d, got %d", funcName, maxArgs, argCount)
+	return
+}
+
+// --- General errors
+
+func ErrCantConvert(funcName string, value any, kind string) error {
+	return fmt.Errorf("%s(): can't convert %s to %s", funcName, TypeName(value), kind)
+}
+
+func ErrExpectedGot(funcName string, kind string, value any) error {
+	return fmt.Errorf("%s(): expected %s, got %s (%#v)", funcName, kind, TypeName(value), value)
+}
+
+func ErrFuncDivisionByZero(funcName string) error {
+	return fmt.Errorf("%s(): division by zero", funcName)
+}
+
+// func ErrDivisionByZero() error {
+// 	return fmt.Errorf("division by zero")
+// }
+
+// --- Parameter errors
+
+// func 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 {
+	var artWantType, artGotType string
+	gotType := TypeName(paramValue)
+	artGotType = prependUndefArticle(gotType)
+	artWantType = prependUndefArticle(paramType)
+	return fmt.Errorf("%s(): the %q parameter must be %s, got %s (%v)", funcName, paramName, artWantType, artGotType, paramValue)
+}
+
+func ErrUnknownParam(funcName, paramName string) error {
+	return fmt.Errorf("%s(): unknown parameter %q", funcName, paramName)
+}
+
+func ErrUnknownVar(funcName, varName string) error {
+	return fmt.Errorf("%s(): unknown variable %q", funcName, varName)
+}
+
+// --- Operator errors
+
+func ErrLeftOperandMustBeVariable(leftTerm, opTerm Term) error {
+	return leftTerm.Errorf("left operand of %q must be a variable", opTerm.Source())
+}

kern/common-params.go

@@ -2,11 +2,13 @@
 // All rights reserved.
 
 // common-params.go
-package expr
+package kern
 
 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

kern/common-type-names.go

@@ -0,0 +1,23 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// common-type-names.go
+package kern
+
+const (
+	TypeAny           = "any"
+	TypeNil           = "nil"
+	TypeBoolean       = "boolean"
+	TypeFloat         = "float"
+	TypeFraction      = "fraction"
+	TypeFileHandle    = "file-handle"
+	TypeInt           = "integer"
+	TypeItem          = "item"
+	TypeIterator      = "iterator"
+	TypeNumber        = "number"
+	TypePair          = "pair"
+	TypeString        = "string"
+	TypeDict          = "dict"
+	TypeListOf        = "list-of-"
+	TypeListOfStrings = "list-of-strings"
+)

kern/compare.go

@@ -0,0 +1,37 @@
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+package kern
+
+import "reflect"
+
+func Equal(value1, value2 any) (equal bool) {
+	if value1 == nil && value2 == nil {
+		equal = true
+	} else if value1 == nil || value2 == nil {
+		equal = false
+	} else if IsBool(value1) && IsBool(value2) {
+		equal = value1.(bool) == value2.(bool)
+	} else if IsList(value1) && IsList(value2) {
+		ls1 := value1.(*ListType)
+		ls2 := value2.(*ListType)
+		equal = ls1.Equals(*ls2)
+	} else if IsDict(value1) && IsDict(value2) {
+		d1 := value1.(*DictType)
+		d2 := value2.(*DictType)
+		equal = d1.Equals(*d2)
+	} else if IsInteger(value1) && IsInteger(value2) {
+		equal = value1.(int64) == value2.(int64)
+	} else if IsString(value1) && IsString(value2) {
+		equal = value1.(string) == value2.(string)
+	} else if IsFloat(value1) && IsFloat(value2) {
+		equal = value1.(float64) == value2.(float64)
+	} else if IsNumOrFract(value1) && IsNumOrFract(value2) {
+		if eq, err := CmpAnyFract(value1, value2); err == nil {
+			equal = eq == 0
+		}
+	} else if !reflect.DeepEqual(value1, value2) {
+		equal = false
+	}
+	return
+}

kern/context-helpers.go

@@ -2,9 +2,9 @@
 // All rights reserved.
 
 // context-helpers.go
-package expr
+package kern
 
-func cloneContext(sourceCtx ExprContext) (clonedCtx ExprContext) {
+func CloneContext(sourceCtx ExprContext) (clonedCtx ExprContext) {
 	if sourceCtx != nil {
 		clonedCtx = sourceCtx.Clone()
 	}
@@ -25,11 +25,11 @@ func exportFunc(ctx ExprContext, name string, info ExprFunc) {
 	ctx.RegisterFunc(name, info.Functor(), info.ReturnType(), info.Params())
 }
 
-func exportObjects(destCtx, sourceCtx ExprContext) {
+func ExportObjects(destCtx, sourceCtx ExprContext) {
-	exportAll := CtrlIsEnabled(sourceCtx, control_export_all)
+	exportAll := CtrlIsEnabled(sourceCtx, ControlExportAll)
 	// 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)
@@ -44,6 +44,6 @@ func exportObjects(destCtx, sourceCtx ExprContext) {
 
 func exportObjectsToParent(sourceCtx ExprContext) {
 	if parentCtx := sourceCtx.GetParent(); parentCtx != nil {
-		exportObjects(parentCtx, sourceCtx)
+		ExportObjects(parentCtx, sourceCtx)
 	}
 }

kern/control.go

@@ -0,0 +1,63 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// control.go
+package kern
+
+import "strings"
+
+// Preset control variables
+const (
+	ControlPreset        = "_preset"
+	ControlLastResult    = "last"
+	ControlBoolShortcut  = "_bool_shortcut"
+	ControlSearchPath    = "_search_path"
+	ControlParentContext = "_parent_context"
+	ControlStdout        = "_stdout"
+)
+
+// Other control variables
+const (
+	ControlExportAll = "_export_all"
+)
+
+// Initial values
+const (
+	init_search_path = "~/.local/lib/go-pkg/expr:/usr/local/lib/go-pkg/expr:/usr/lib/go-pkg/expr"
+)
+
+func CtrlIsEnabled(ctx ExprContext, name string) (status bool) {
+	var v any
+	var exists bool
+
+	if !strings.HasPrefix(name, "_") {
+		name = "_" + name
+	}
+
+	if v, exists = ctx.GetVar(name); !exists {
+		if globalCtx := ctx.GetGlobal(); globalCtx != nil {
+			v, exists = globalCtx.GetVar(name)
+		}
+	}
+
+	if exists {
+		if b, ok := v.(bool); ok {
+			status = b
+		}
+	}
+	return
+}
+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.UnsafeSetVar(ControlPreset, true)
+	ctx.UnsafeSetVar(ControlBoolShortcut, true)
+	ctx.UnsafeSetVar(ControlSearchPath, init_search_path)
+}

kern/dict-type.go

@@ -2,7 +2,7 @@
 // All rights reserved.
 
 // dict-type.go
-package expr
+package kern
 
 import (
 	"fmt"
@@ -12,13 +12,33 @@ import (
 
 type DictType map[any]any
 
+func IsDict(v any) (ok bool) {
+	_, ok = v.(*DictType)
+	return ok
+}
+
 func MakeDict() (dict *DictType) {
 	d := make(DictType)
 	dict = &d
 	return
 }
 
-func newDict(dictAny map[any]*term) (dict *DictType) {
+func NewDict(dictAny map[any]any) (dict *DictType) {
+	var d DictType
+	if dictAny != nil {
+		d = make(DictType, len(dictAny))
+		for i, item := range dictAny {
+			d[i] = item
+		}
+	} else {
+		d = make(DictType)
+	}
+	dict = &d
+	return
+}
+
+func newDict(dictAny map[any]Term) (dict *DictType) {
+	// TODO Change with a call to NewDict()
 	var d DictType
 	if dictAny != nil {
 		d = make(DictType, len(dictAny))
@@ -95,7 +115,7 @@ func (dict *DictType) ToString(opt FmtOpt) string {
 			sb.WriteString(": ")
 			if formatter, ok := value.(Formatter); ok {
 				sb.WriteString(formatter.ToString(opt))
-			} else if t, ok := value.(*term); ok {
+			} else if t, ok := value.(Term); ok {
 				sb.WriteString(t.String())
 			} else {
 				sb.WriteString(fmt.Sprintf("%#v", value))
@@ -114,7 +134,7 @@ func (dict *DictType) TypeName() string {
 	return "dict"
 }
 
-func (dict *DictType) hasKey(target any) (ok bool) {
+func (dict *DictType) HasKey(target any) (ok bool) {
 	for key := range *dict {
 		if ok = reflect.DeepEqual(key, target); ok {
 			break
@@ -123,7 +143,16 @@ func (dict *DictType) hasKey(target any) (ok bool) {
 	return
 }
 
-func (dict *DictType) clone() (c *DictType) {
+func (dict *DictType) SetItem(key any, value any) {
+	(*dict)[key] = value
+}
+
+func (dict *DictType) GetItem(key any) (value any, exists bool) {
+	value, exists = (*dict)[key]
+	return
+}
+
+func (dict *DictType) Clone() (c *DictType) {
 	c = newDict(nil)
 	for k, v := range *dict {
 		(*c)[k] = v
@@ -131,7 +160,7 @@ func (dict *DictType) clone() (c *DictType) {
 	return
 }
 
-func (dict *DictType) merge(second *DictType) {
+func (dict *DictType) Merge(second *DictType) {
 	if second != nil {
 		for k, v := range *second {
 			(*dict)[k] = v
@@ -139,8 +168,21 @@ func (dict *DictType) merge(second *DictType) {
 	}
 }
 
-func (dict *DictType) setItem(key any, value any) (err error) {
+func (dict *DictType) Equals(dict2 DictType) (answer bool) {
-	(*dict)[key] = value
+	if dict2 != nil && len(*dict) == len(dict2) {
+		answer = true
+		for key, value1 := range *dict {
+			if value2, exists := dict2.GetItem(key); exists {
+				if !Equal(value1, value2) {
+					answer = false
+					break
+				}
+			} else {
+				answer = false
+				break
+			}
+		}
+	}
 	return
 }
 

kern/expr-context.go

@@ -0,0 +1,31 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// expr-context.go
+package kern
+
+// ----Expression Context
+type ExprContext interface {
+	Clone() ExprContext
+	SetParent(ctx ExprContext)
+	GetParent() (ctx ExprContext)
+	GetGlobal() (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)
+
+	GetLocalFuncInfo(name string) (info ExprFunc, exists bool)
+	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)
+}

kern/expr-function.go

@@ -0,0 +1,39 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// expr-function.go
+package kern
+
+// ---- 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)
+}

kern/float.go

@@ -0,0 +1,23 @@
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// float.go
+package kern
+
+func IsFloat(v any) (ok bool) {
+	_, ok = v.(float64)
+	return ok
+}
+
+func AnyFloat(v any) (float float64, ok bool) {
+	ok = true
+	switch floatval := v.(type) {
+	case float32:
+		float = float64(floatval)
+	case float64:
+		float = floatval
+	default:
+		ok = false
+	}
+	return
+}

kern/formatter.go

@@ -2,7 +2,7 @@
 // All rights reserved.
 
 // formatter.go
-package expr
+package kern
 
 import "fmt"
 
@@ -46,7 +46,7 @@ type Formatter interface {
 	ToString(options FmtOpt) string
 }
 
-func getFormatted(v any, opt FmtOpt) (text string) {
+func GetFormatted(v any, opt FmtOpt) (text string) {
 	if v == nil {
 		text = "(nil)"
 	} else if s, ok := v.(string); ok {

kern/fraction-type.go

@@ -2,7 +2,7 @@
 // All rights reserved.
 
 // fraction-type.go
-package expr
+package kern
 
 //https://www.youmath.it/lezioni/algebra-elementare/lezioni-di-algebra-e-aritmetica-per-scuole-medie/553-dalle-frazioni-a-numeri-decimali.html
 
@@ -18,12 +18,12 @@ type FractionType struct {
 	num, den int64
 }
 
-func newFraction(num, den int64) *FractionType {
+func NewFraction(num, den int64) *FractionType {
 	num, den = simplifyIntegers(num, den)
 	return &FractionType{num, den}
 }
 
-func float64ToFraction(f float64) (fract *FractionType, err error) {
+func Float64ToFraction(f float64) (fract *FractionType, err error) {
 	var sign string
 	intPart, decPart := math.Modf(f)
 	if decPart < 0.0 {
@@ -33,11 +33,11 @@ func float64ToFraction(f float64) (fract *FractionType, err error) {
 	}
 	dec := fmt.Sprintf("%.12f", decPart)
 	s := fmt.Sprintf("%s%.f%s", sign, intPart, dec[1:])
-	return makeGeneratingFraction(s)
+	return MakeGeneratingFraction(s)
 }
 
 // Based on https://cs.opensource.google/go/go/+/refs/tags/go1.22.3:src/math/big/rat.go;l=39
-func makeGeneratingFraction(s string) (f *FractionType, err error) {
+func MakeGeneratingFraction(s string) (f *FractionType, err error) {
 	var num, den int64
 	var sign int64 = 1
 	var parts []string
@@ -50,15 +50,16 @@ func makeGeneratingFraction(s string) (f *FractionType, err error) {
 	} else if s[0] == '+' {
 		s = s[1:]
 	}
-	if strings.HasSuffix(s, "()") {
+	//	if strings.HasSuffix(s, "()") {
-		s = s[0 : len(s)-2]
+	//		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
 	}
 	if len(parts) == 1 {
-		f = newFraction(sign*num, 1)
+		f = NewFraction(sign*num, 1)
 	} else if len(parts) == 2 {
 		subParts := strings.SplitN(parts[1], "(", 2)
 		if len(subParts) == 1 {
@@ -75,7 +76,7 @@ func makeGeneratingFraction(s string) (f *FractionType, err error) {
 				num = num*10 + int64(c-'0')
 				den = den * 10
 			}
-			f = newFraction(sign*num, den)
+			f = NewFraction(sign*num, den)
 		} else if len(subParts) == 2 {
 			sub := num
 			mul := int64(1)
@@ -102,7 +103,7 @@ func makeGeneratingFraction(s string) (f *FractionType, err error) {
 				den *= mul
 			}
 			num -= sub
-			f = newFraction(sign*num, den)
+			f = NewFraction(sign*num, den)
 		}
 	}
 exit:
@@ -112,7 +113,15 @@ exit:
 	return
 }
 
-func (f *FractionType) toFloat() float64 {
+func (f *FractionType) N() int64 {
+	return f.num
+}
+
+func (f *FractionType) D() int64 {
+	return f.den
+}
+
+func (f *FractionType) ToFloat() float64 {
 	return float64(f.num) / float64(f.den)
 }
 
@@ -123,36 +132,38 @@ 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 {
+			if len(sign) > 0 {
-				sb.WriteString(s)
+				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()
@@ -165,7 +176,7 @@ func (f *FractionType) TypeName() string {
 // -------- fraction utility functions
 
 // greatest common divider
-func gcd(a, b int64) (g int64) {
+func Gcd(a, b int64) (g int64) {
 	if a < 0 {
 		a = -a
 	}
@@ -186,21 +197,21 @@ func gcd(a, b int64) (g int64) {
 
 // lower common multiple
 func lcm(a, b int64) (l int64) {
-	g := gcd(a, b)
+	g := Gcd(a, b)
 	l = a * b / g
 	return
 }
 
 // Sum two fractions
-func sumFract(f1, f2 *FractionType) (sum *FractionType) {
+func SumFract(f1, f2 *FractionType) (sum *FractionType) {
 	m := lcm(f1.den, f2.den)
-	sum = newFraction(f1.num*(m/f1.den)+f2.num*(m/f2.den), m)
+	sum = NewFraction(f1.num*(m/f1.den)+f2.num*(m/f2.den), m)
 	return
 }
 
 // Multiply two fractions
-func mulFract(f1, f2 *FractionType) (prod *FractionType) {
+func MulFract(f1, f2 *FractionType) (prod *FractionType) {
-	prod = newFraction(f1.num*f2.num, f1.den*f2.den)
+	prod = NewFraction(f1.num*f2.num, f1.den*f2.den)
 	return
 }
 
@@ -209,11 +220,12 @@ func anyToFract(v any) (f *FractionType, err error) {
 	if f, ok = v.(*FractionType); !ok {
 		if n, ok := v.(int64); ok {
 			f = intToFraction(n)
+		} else if dec, ok := v.(float64); ok {
+			f, err = Float64ToFraction(dec)
+		} else {
+			err = ErrExpectedGot("fract", TypeFraction, v)
 		}
 	}
-	if f == nil {
-		err = ErrExpectedGot("fract", TypeFraction, v)
-	}
 	return
 }
 
@@ -227,12 +239,12 @@ func anyPairToFract(v1, v2 any) (f1, f2 *FractionType, err error) {
 	return
 }
 
-func sumAnyFract(af1, af2 any) (sum any, err error) {
+func SumAnyFract(af1, af2 any) (sum any, err error) {
 	var f1, f2 *FractionType
 	if f1, f2, err = anyPairToFract(af1, af2); err != nil {
 		return
 	}
-	f := sumFract(f1, f2)
+	f := SumFract(f1, f2)
 	if f.num == 0 {
 		sum = 0
 	} else {
@@ -247,7 +259,7 @@ func sumAnyFract(af1, af2 any) (sum any, err error) {
 //		 =0 if af1 == af2
 //		 >0 if af1 > af2
 //	 err if af1 or af2 is not convertible to fraction
-func cmpAnyFract(af1, af2 any) (result int, err error) {
+func CmpAnyFract(af1, af2 any) (result int, err error) {
 	var f1, f2 *FractionType
 	if f1, f2, err = anyPairToFract(af1, af2); err != nil {
 		return
@@ -262,25 +274,27 @@ func cmpAnyFract(af1, af2 any) (result int, err error) {
 //	=0 if af1 == af2
 //	>0 if af1 > af2
 func cmpFract(f1, f2 *FractionType) (result int) {
-	f2.num = -f2.num
+	if f1 != nil && f2 != nil {
-	f := sumFract(f1, f2)
+		f2.num = -f2.num
-	if f.num < 0 {
+		f := SumFract(f1, f2)
-		result = -1
+		if f.num < 0 {
-	} else if f.num > 0 {
+			result = -1
-		result = 1
+		} else if f.num > 0 {
-	} else {
+			result = 1
-		result = 0
+		} else {
+			result = 0
+		}
 	}
 	return
 }
 
-func subAnyFract(af1, af2 any) (sum any, err error) {
+func SubAnyFract(af1, af2 any) (sum any, err error) {
 	var f1, f2 *FractionType
 	if f1, f2, err = anyPairToFract(af1, af2); err != nil {
 		return
 	}
 	f2.num = -f2.num
-	f := sumFract(f1, f2)
+	f := SumFract(f1, f2)
 	if f.num == 0 {
 		sum = 0
 	} else {
@@ -289,7 +303,7 @@ func subAnyFract(af1, af2 any) (sum any, err error) {
 	return
 }
 
-func mulAnyFract(af1, af2 any) (prod any, err error) {
+func MulAnyFract(af1, af2 any) (prod any, err error) {
 	var f1, f2 *FractionType
 	if f1, f2, err = anyPairToFract(af1, af2); err != nil {
 		return
@@ -303,7 +317,7 @@ func mulAnyFract(af1, af2 any) (prod any, err error) {
 	return
 }
 
-func divAnyFract(af1, af2 any) (quot any, err error) {
+func DivAnyFract(af1, af2 any) (quot any, err error) {
 	var f1, f2 *FractionType
 	if f1, f2, err = anyPairToFract(af1, af2); err != nil {
 		return
@@ -311,7 +325,6 @@ 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
@@ -343,7 +356,7 @@ func simplifyIntegers(num, den int64) (a, b int64) {
 		den = -den
 		num = -num
 	}
-	g := gcd(num, den)
+	g := Gcd(num, den)
 	a = num / g
 	b = den / g
 	return
@@ -353,7 +366,19 @@ func intToFraction(n int64) *FractionType {
 	return &FractionType{n, 1}
 }
 
-func isFraction(v any) (ok bool) {
+func IsFraction(v any) (ok bool) {
 	_, ok = v.(*FractionType)
 	return ok
 }
+
+// func IsFract(v any) (ok bool) {
+// 	_, ok = v.(*FractionType)
+// 	return ok
+// }
+
+func IsRational(v any) (ok bool) {
+	if _, ok = v.(*FractionType); !ok {
+		_, ok = v.(int64)
+	}
+	return ok
+}

kern/function.go

@@ -0,0 +1,278 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// function.go
+package kern
+
+import (
+	"fmt"
+	"strconv"
+)
+
+// ---- Function templates
+type FuncTemplate func(ctx ExprContext, name string, args map[string]any) (result any, err error)
+
+type DeepFuncTemplate func(a, b any) (eq bool, err error)
+
+func IsFunctor(v any) (ok bool) {
+	_, ok = v.(Functor)
+	return
+}
+
+// ---- Common functor definition
+type BaseFunctor struct {
+	info ExprFunc
+}
+
+func (functor *BaseFunctor) ToString(opt FmtOpt) (s string) {
+	if functor.info != nil {
+		s = functor.info.ToString(opt)
+	} else {
+		s = "func(){}"
+	}
+	return s
+}
+
+func (functor *BaseFunctor) GetParams() (params []ExprFuncParam) {
+	if functor.info != nil {
+		return functor.info.Params()
+	} else {
+		return []ExprFuncParam{}
+	}
+}
+
+func (functor *BaseFunctor) SetFunc(info ExprFunc) {
+	functor.info = info
+}
+
+func (functor *BaseFunctor) GetFunc() ExprFunc {
+	return functor.info
+}
+
+func (functor *BaseFunctor) GetDefinitionContext() ExprContext {
+	return nil
+}
+
+// ---- Function Parameters
+type paramFlags uint16
+
+const (
+	PfDefault paramFlags = 1 << iota
+	PfOptional
+	PfRepeat
+)
+
+type funcParamInfo struct {
+	name         string
+	flags        paramFlags
+	defaultValue any
+}
+
+func NewFuncParam(name string) ExprFuncParam {
+	return &funcParamInfo{name: name}
+}
+
+func NewFuncParamFlag(name string, flags paramFlags) ExprFuncParam {
+	return &funcParamInfo{name: name, flags: flags}
+}
+
+func NewFuncParamFlagDef(name string, flags paramFlags, defValue any) *funcParamInfo {
+	return &funcParamInfo{name: name, flags: flags, defaultValue: defValue}
+}
+
+func (param *funcParamInfo) Name() string {
+	return param.name
+}
+
+func (param *funcParamInfo) Type() string {
+	return TypeAny
+}
+
+func (param *funcParamInfo) IsDefault() bool {
+	return (param.flags & PfDefault) != 0
+}
+
+func (param *funcParamInfo) IsOptional() bool {
+	return (param.flags & PfOptional) != 0
+}
+
+func (param *funcParamInfo) IsRepeat() bool {
+	return (param.flags & PfRepeat) != 0
+}
+
+func (param *funcParamInfo) DefaultValue() any {
+	return param.defaultValue
+}
+
+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
+	}
+
+	childCount := callTerm.GetChildCount()
+	for i := range childCount {
+		tree := callTerm.GetChild(i)
+		// 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, childCount-i)
+					varArgs = append(varArgs, paramValue)
+					varName = spec.Name()
+				} else {
+					actualParams[spec.Name()] = paramValue
+				}
+			} else {
+				err = ErrTooManyParams(info.Name(), len(formalParams), childCount)
+				break
+			}
+		} else {
+			err = fmt.Errorf("%s(): positional param nr %d not allowed after named params", info.Name(), i+1)
+			break
+		}
+	}
+	if err == nil {
+		if varArgs != nil {
+			actualParams[varName] = varArgs
+		}
+	}
+	return
+}
+
+// func (info *funcInfo) PrepareCall(name string, actualParams map[string]any) (err error) {
+// 	passedCount := len(actualParams)
+// 	if info.MinArgs() > passedCount {
+// 		err = ErrTooFewParams(name, info.MinArgs(), info.MaxArgs(), passedCount)
+// 		return
+// 	}
+
+// 	if passedCount < len(info.formalParams) {
+// 		for _, p := range info.formalParams {
+// 			if _, exists := actualParams[p.Name()]; !exists {
+// 				if !p.IsDefault() {
+// 					break
+// 				}
+// 				if p.IsRepeat() {
+// 					varArgs := make([]any, 1)
+// 					varArgs[0] = p.DefaultValue()
+// 					actualParams[p.Name()] = varArgs
+// 				} else {
+// 					actualParams[p.Name()] = p.DefaultValue()
+// 				}
+// 			}
+// 		}
+// 	}
+
+// 	if info.MaxArgs() >= 0 && info.MaxArgs() < len(actualParams) {
+// 		err = ErrTooManyParams(name, info.MaxArgs(), len(actualParams))
+// 	}
+// 	return
+// }
+
+// ----- Call a function ---
+
+// func getAssignVarName(t *term) (name string, ok bool) {
+// 	if ok = t.symbol() == SymEqual; ok {
+// 		name = t.children[0].source()
+// 	}
+// 	return
+// }
+
+func GetAssignVarName(t Term) (name string, ok bool) {
+	if ok = t.IsAssign(); ok {
+		name = t.GetChildSource(0)
+	}
+	return
+}
+
+func CallFunctionByTerm(parentCtx ExprContext, name string, callTerm Term) (result any, err error) {
+	var actualParams map[string]any
+	if info, exists := parentCtx.GetFuncInfo(name); exists {
+		if actualParams, err = initActualParams(parentCtx, info, callTerm); err == nil {
+			ctx := info.AllocContext(parentCtx)
+			if err = info.PrepareCall(name, actualParams); err == nil {
+				functor := info.Functor()
+				result, err = functor.InvokeNamed(ctx, name, actualParams)
+				exportObjectsToParent(ctx)
+			}
+		}
+	} else {
+		err = fmt.Errorf("unknown function %s()", name)
+	}
+	return
+}
+
+func CallFunctionByArgs(parentCtx ExprContext, name string, args []any) (result any, err error) {
+	var actualParams map[string]any
+	if info, exists := parentCtx.GetFuncInfo(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 := parentCtx.GetFuncInfo(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
+}

kern/iterator.go

@@ -0,0 +1,52 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// iterator.go
+package kern
+
+import (
+	// "errors"
+	"fmt"
+)
+
+// Operator names
+
+const (
+	InitName    = "init"
+	CleanName   = "clean"
+	ResetName   = "reset"
+	NextName    = "next"
+	CurrentName = "current"
+	IndexName   = "index"
+	CountName   = "count"
+	FilterName  = "filter"
+	MapName     = "map"
+	KeyName     = "key"
+	ValueName   = "value"
+)
+
+type Iterator interface {
+	Typer
+	fmt.Stringer
+	Next() (item any, err error) // must return io.EOF after the last item
+	Current() (item any, err error)
+	Index() int64
+	Count() int64
+	HasOperation(name string) bool
+	CallOperation(name string, args map[string]any) (value any, err error)
+}
+
+type ExtIterator interface {
+	Iterator
+	Reset() error
+	Clean() error
+}
+
+func ErrNoOperation(name string) error {
+	return fmt.Errorf("no %s() function defined in the data-source", name)
+}
+
+func IsIterator(v any) (ok bool) {
+	_, ok = v.(Iterator)
+	return
+}

kern/list-type.go

@@ -2,7 +2,7 @@
 // All rights reserved.
 
 // list-type.go
-package expr
+package kern
 
 import (
 	"fmt"
@@ -12,23 +12,22 @@ import (
 
 type ListType []any
 
-func newListA(listAny ...any) (list *ListType) {
+func IsList(v any) (ok bool) {
+	_, ok = v.(*ListType)
+	return ok
+}
+
+func NewListA(listAny ...any) (list *ListType) {
 	if listAny == nil {
 		listAny = []any{}
 	}
-	return newList(listAny)
-}
-
-func newList(listAny []any) (list *ListType) {
 	return NewList(listAny)
 }
 
 func NewList(listAny []any) (list *ListType) {
 	if listAny != nil {
 		ls := make(ListType, len(listAny))
-		for i, item := range listAny {
+		copy(ls, listAny)
-			ls[i] = item
-		}
 		list = &ls
 	}
 	return
@@ -51,21 +50,21 @@ func ListFromStrings(stringList []string) (list *ListType) {
 	return
 }
 
-func (ls *ListType) ToString(opt FmtOpt) (s string) {
+func (dict *ListType) ToString(opt FmtOpt) (s string) {
-        indent := GetFormatIndent(opt)
+	indent := GetFormatIndent(opt)
-        flags := GetFormatFlags(opt)
+	flags := GetFormatFlags(opt)
 
 	var sb strings.Builder
 	sb.WriteByte('[')
-	if len(*ls) > 0 {
+	if len(*dict) > 0 {
-                innerOpt := MakeFormatOptions(flags, indent+1)
+		innerOpt := MakeFormatOptions(flags, indent+1)
-                nest := strings.Repeat("  ", indent+1)
+		nest := strings.Repeat("  ", indent+1)
 
 		if flags&MultiLine != 0 {
 			sb.WriteByte('\n')
 			sb.WriteString(nest)
 		}
-		for i, item := range []any(*ls) {
+		for i, item := range []any(*dict) {
 			if i > 0 {
 				if flags&MultiLine != 0 {
 					sb.WriteString(",\n")
@@ -97,30 +96,19 @@ func (ls *ListType) ToString(opt FmtOpt) (s string) {
 	return
 }
 
-func (ls *ListType) String() string {
+func (dict *ListType) String() string {
-	return ls.ToString(0)
+	return dict.ToString(0)
 }
 
-func (ls *ListType) TypeName() string {
+func (dict *ListType) TypeName() string {
 	return "list"
 }
 
-func (list *ListType) indexDeepCmp(target any) (index int) {
+func (dict *ListType) Contains(t *ListType) (answer bool) {
-	index = -1
+	if len(*dict) >= len(*t) {
-	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) {
 		answer = true
 		for _, item := range *t {
-			if answer = ls.indexDeepSameCmp(item) >= 0; !answer {
+			if answer = dict.IndexDeepSameCmp(item) >= 0; !answer {
 				break
 			}
 		}
@@ -128,12 +116,29 @@ func (ls *ListType) contains(t *ListType) (answer bool) {
 	return
 }
 
-func (list *ListType) indexDeepSameCmp(target any) (index int) {
+func (ls1 *ListType) Equals(ls2 ListType) (answer bool) {
+	if ls2 != nil && len(*ls1) == len(ls2) {
+		answer = true
+		for index, i1 := range *ls1 {
+			// if !reflect.DeepEqual(i1, ls2[index]) {
+			// 	answer = false
+			// 	break
+			// }
+			if !Equal(i1, ls2[index]) {
+				answer = false
+				break
+			}
+		}
+	}
+	return
+}
+
+func (dict *ListType) IndexDeepSameCmp(target any) (index int) {
 	var eq bool
 	var err error
 	index = -1
-	for i, item := range *list {
+	for i, item := range *dict {
-		if eq, err = deepSame(item, target, sameContent); err != nil {
+		if eq, err = deepSame(item, target, SameContent); err != nil {
 			break
 		} else if eq {
 			index = i
@@ -143,13 +148,13 @@ func (list *ListType) indexDeepSameCmp(target any) (index int) {
 	return
 }
 
-func sameContent(a, b any) (same bool, err error) {
+func SameContent(a, b any) (same bool, err error) {
 	la, _ := a.(*ListType)
 	lb, _ := b.(*ListType)
 	if len(*la) == len(*lb) {
 		same = true
 		for _, item := range *la {
-			if pos := lb.indexDeepSameCmp(item); pos < 0 {
+			if pos := lb.IndexDeepSameCmp(item); pos < 0 {
 				same = false
 				break
 			}
@@ -158,19 +163,19 @@ func sameContent(a, b any) (same bool, err error) {
 	return
 }
 
-func deepSame(a, b any, deepCmp deepFuncTemplate) (eq bool, err error) {
+func deepSame(a, b any, deepCmp DeepFuncTemplate) (eq bool, err error) {
-	if isNumOrFract(a) && isNumOrFract(b) {
+	if IsNumOrFract(a) && IsNumOrFract(b) {
 		if IsNumber(a) && IsNumber(b) {
 			if IsInteger(a) && IsInteger(b) {
 				li, _ := a.(int64)
 				ri, _ := b.(int64)
 				eq = li == ri
 			} else {
-				eq = numAsFloat(a) == numAsFloat(b)
+				eq = NumAsFloat(a) == NumAsFloat(b)
 			}
 		} else {
 			var cmp int
-			if cmp, err = cmpAnyFract(a, b); err == nil {
+			if cmp, err = CmpAnyFract(a, b); err == nil {
 				eq = cmp == 0
 			}
 		}
@@ -183,12 +188,15 @@ func deepSame(a, b any, deepCmp deepFuncTemplate) (eq bool, err error) {
 	return
 }
 
-func (list *ListType) setItem(index int64, value any) (err error) {
+func (dict *ListType) SetItem(index int64, value any) (err error) {
-	if index >= 0 && index < int64(len(*list)) {
+	if index >= 0 && index < int64(len(*dict)) {
-		(*list)[index] = value
+		(*dict)[index] = value
 	} else {
-		err = fmt.Errorf("index %d out of bounds (0, %d)", index, len(*list)-1)
+		err = fmt.Errorf("index %d out of bounds (0, %d)", index, len(*dict)-1)
 	}
 	return
 }
 
+func (dict *ListType) AppendItem(value any) {
+	*dict = append(*dict, value)
+}

kern/number.go

@@ -0,0 +1,88 @@
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// number.go
+package kern
+
+import (
+	"fmt"
+)
+
+func IsInteger(v any) (ok bool) {
+	_, ok = v.(int64)
+	return ok
+}
+
+func IsNumber(v any) (ok bool) {
+	return IsFloat(v) || IsInteger(v)
+}
+
+func IsNumOrFract(v any) (ok bool) {
+	return IsFloat(v) || IsInteger(v) || IsFraction(v)
+}
+
+func IsNumberString(v any) (ok bool) {
+	return IsString(v) || IsNumber(v)
+}
+
+func NumAsFloat(v any) (f float64) {
+	var ok bool
+	if f, ok = v.(float64); !ok {
+		if fract, ok := v.(*FractionType); ok {
+			f = fract.ToFloat()
+		} else {
+			i, _ := v.(int64)
+			f = float64(i)
+		}
+	}
+	return
+}
+
+func AnyInteger(v any) (i int64, ok bool) {
+	ok = true
+	switch intval := v.(type) {
+	case int:
+		i = int64(intval)
+	case uint8:
+		i = int64(intval)
+	case uint16:
+		i = int64(intval)
+	case uint64:
+		i = int64(intval)
+	case uint32:
+		i = int64(intval)
+	case int8:
+		i = int64(intval)
+	case int16:
+		i = int64(intval)
+	case int32:
+		i = int64(intval)
+	case int64:
+		i = intval
+	default:
+		ok = false
+	}
+	return
+}
+
+func ToGoInt(value any, description string) (i int, err error) {
+	if valueInt64, ok := value.(int64); ok {
+		i = int(valueInt64)
+	} else if valueInt, ok := value.(int); ok {
+		i = valueInt
+	} else {
+		err = fmt.Errorf("%s expected integer, got %s (%v)", description, TypeName(value), value)
+	}
+	return
+}
+
+func ToGoInt64(value any, description string) (i int64, err error) {
+	if valueInt64, ok := value.(int64); ok {
+		i = valueInt64
+	} else if valueInt, ok := value.(int); ok {
+		i = int64(valueInt)
+	} else {
+		err = fmt.Errorf("%s expected integer, got %s (%v)", description, TypeName(value), value)
+	}
+	return
+}

kern/string.go

@@ -0,0 +1,23 @@
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// string.go
+package kern
+
+import (
+	"fmt"
+)
+
+func IsString(v any) (ok bool) {
+	_, ok = v.(string)
+	return ok
+}
+
+func ToGoString(value any, description string) (s string, err error) {
+	if s, ok := value.(string); ok {
+		return s, nil
+	} else {
+		err = fmt.Errorf("%s expected string, got %s (%v)", description, TypeName(value), value)
+	}
+	return
+}

kern/term.go

@@ -0,0 +1,21 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// term.go
+package kern
+
+import (
+	"fmt"
+)
+
+type Term interface {
+	fmt.Stringer
+	// Children() []Term
+	Source() string
+	GetChildCount() (count int)
+	GetChild(index int) Term
+	GetChildSource(index int) string
+	Compute(ctx ExprContext) (result any, err error)
+	IsAssign() bool
+	Errorf(template string, args ...any) (err error)
+}

lib-ext-darwin.go

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

lib-ext-linux.go

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

lib-ext-windows.go

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

list-iterator.go

@@ -0,0 +1,149 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// list-iterator.go
+package expr
+
+import (
+	"fmt"
+	"io"
+	"slices"
+
+	"git.portale-stac.it/go-pkg/expr/kern"
+)
+
+type ListIterator struct {
+	a     *kern.ListType
+	count int64
+	index int64
+	start int64
+	stop  int64
+	step  int64
+}
+
+func NewListIterator(list *kern.ListType, args []any) (it *ListIterator) {
+	var argc int = 0
+	listLen := int64(len(([]any)(*list)))
+	if args != nil {
+		argc = len(args)
+	}
+	it = &ListIterator{a: list, count: 0, index: -1, start: 0, stop: listLen - 1, step: 1}
+	if argc >= 1 {
+		if i, err := kern.ToGoInt64(args[0], "start index"); err == nil {
+			if i < 0 {
+				i = listLen + i
+			}
+			it.start = i
+		}
+		if argc >= 2 {
+			if i, err := kern.ToGoInt64(args[1], "stop index"); err == nil {
+				if i < 0 {
+					i = listLen + i
+				}
+				it.stop = i
+			}
+			if argc >= 3 {
+				if i, err := kern.ToGoInt64(args[2], "step"); err == nil {
+					if i < 0 {
+						i = -i
+					}
+					if it.start > it.stop {
+						it.step = -i
+					} else {
+						it.step = i
+					}
+				}
+			}
+		}
+	}
+	it.index = it.start - it.step
+	return
+}
+
+func NewArrayIterator(array []any) (it *ListIterator) {
+	it = &ListIterator{a: (*kern.ListType)(&array), count: 0, index: -1, start: 0, stop: int64(len(array)) - 1, step: 1}
+	return
+}
+
+func (it *ListIterator) String() string {
+	var l = int64(0)
+	if it.a != nil {
+		l = int64(len(*it.a))
+	}
+	return fmt.Sprintf("$([#%d])", l)
+}
+
+func (it *ListIterator) TypeName() string {
+	return "ListIterator"
+}
+
+func (it *ListIterator) HasOperation(name string) bool {
+	//yes := name == expr.NextName || name == expr.ResetName || name == expr.IndexName || name == expr.CountName || name == expr.CurrentName
+	yes := slices.Contains([]string{kern.NextName, kern.ResetName, kern.IndexName, kern.CountName, kern.CurrentName}, name)
+	return yes
+}
+
+func (it *ListIterator) CallOperation(name string, args map[string]any) (v any, err error) {
+	switch name {
+	case kern.NextName:
+		v, err = it.Next()
+	case kern.ResetName:
+		err = it.Reset()
+	case kern.CleanName:
+		err = it.Clean()
+	case kern.IndexName:
+		v = int64(it.Index())
+	case kern.CurrentName:
+		v, err = it.Current()
+	case kern.CountName:
+		v = it.count
+	default:
+		err = kern.ErrNoOperation(name)
+	}
+	return
+}
+
+func (it *ListIterator) Current() (item any, err error) {
+	a := *(it.a)
+	if it.start <= it.stop {
+		if it.stop < int64(len(a)) && it.index >= it.start && it.index <= it.stop {
+			item = a[it.index]
+		} else {
+			err = io.EOF
+		}
+	} else {
+		if it.start < int64(len(a)) && it.index >= it.stop && it.index <= it.start {
+			item = a[it.index]
+		} else {
+			err = io.EOF
+		}
+
+	}
+	return
+}
+
+func (it *ListIterator) Next() (item any, err error) {
+	it.index += it.step
+	if item, err = it.Current(); err != io.EOF {
+		it.count++
+	}
+	return
+}
+
+func (it *ListIterator) Index() int64 {
+	return it.index
+}
+
+func (it *ListIterator) Count() int64 {
+	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
+}

operand-dict.go

@@ -4,6 +4,9 @@
 // operand-dict.go
 package expr
 
+import (
+	"git.portale-stac.it/go-pkg/expr/kern"
+)
 
 // -------- dict term
 func newDictTerm(args map[any]*term) *term {
@@ -18,12 +21,12 @@ func newDictTerm(args map[any]*term) *term {
 }
 
 // -------- dict func
-func evalDict(ctx ExprContext, self *term) (v any, err error) {
+func evalDict(ctx kern.ExprContext, opTerm *term) (v any, err error) {
-	dict, _ := self.value().(map[any]*term)
+	dict, _ := opTerm.value().(map[any]*term)
-	items := make(DictType, len(dict))
+	items := make(kern.DictType, len(dict))
 	for key, tree := range dict {
 		var param any
-		if param, err = tree.compute(ctx); err != nil {
+		if param, err = tree.Compute(ctx); err != nil {
 			break
 		}
 		items[key] = param

operand-expr.go

@@ -4,11 +4,15 @@
 // operand-expr.go
 package expr
 
-import "fmt"
+import (
+	"fmt"
+
+	"git.portale-stac.it/go-pkg/expr/kern"
+)
 
 // -------- expr term
 func newExprTerm(root *term) *term {
-	tk := NewValueToken(root.tk.row, root.tk.col, SymExpression, root.source(), root)
+	tk := NewValueToken(root.tk.row, root.tk.col, SymExpression, root.Source(), root)
 	return &term{
 		tk:       *tk,
 		parent:   nil,
@@ -20,11 +24,11 @@ func newExprTerm(root *term) *term {
 }
 
 // -------- eval expr
-func evalExpr(ctx ExprContext, self *term) (v any, err error) {
+func evalExpr(ctx kern.ExprContext, opTerm *term) (v any, err error) {
-	if expr, ok := self.value().(*term); ok {
+	if ast, ok := opTerm.value().(*term); ok {
-		v, err = expr.compute(ctx)
+		v, err = ast.Compute(ctx)
 	} else {
-		err = fmt.Errorf("expression expected, got %T", self.value())
+		err = fmt.Errorf("expression expected, got %T", opTerm.value())
 	}
 	return
 }

operand-func.go

@@ -6,35 +6,47 @@ package expr
 
 import (
 	"errors"
+
+	"git.portale-stac.it/go-pkg/expr/kern"
 )
 
 // -------- function call term
 func newFuncCallTerm(tk *Token, args []*term) *term {
+	var pos termPosition = posLeaf
+	if len(args) > 0 {
+		pos = posMultifix
+	}
 	return &term{
 		tk:       *tk,
 		parent:   nil,
 		children: args,
-		position: posLeaf,
+		position: pos,
 		priority: priValue,
 		evalFunc: evalFuncCall,
 	}
 }
 
 // -------- eval func call
-func evalFuncCall(ctx ExprContext, self *term) (v any, err error) {
+// func _evalFuncCall(ctx ExprContext, opTerm *term) (v any, err error) {
-	name, _ := self.tk.Value.(string)
+// 	name, _ := opTerm.tk.Value.(string)
-	params := make([]any, len(self.children), len(self.children)+5)
+// 	params := make([]any, len(opTerm.children), len(opTerm.children)+5)
-	for i, tree := range self.children {
+// 	for i, tree := range opTerm.children {
-		var param any
+// 		var param any
-		if param, err = tree.compute(ctx); err != nil {
+// 		if param, err = tree.compute(ctx); err != nil {
-			break
+// 			break
-		}
+// 		}
-		params[i] = param
+// 		params[i] = param
-	}
+// 	}
 
-	if err == nil {
+// 	if err == nil {
-		v, err = CallFunction(ctx, name, params)
+// 		v, err = CallFunction(ctx, name, params)
-	}
+// 	}
+// 	return
+// }
+
+func evalFuncCall(ctx kern.ExprContext, opTerm *term) (v any, err error) {
+	name, _ := opTerm.tk.Value.(string)
+	v, err = kern.CallFunctionByTerm(ctx, name, opTerm)
 	return
 }
 
@@ -51,23 +63,23 @@ func newFuncDefTerm(tk *Token, args []*term) *term {
 }
 
 // -------- eval func def
-func evalFuncDef(ctx ExprContext, self *term) (v any, err error) {
+func evalFuncDef(ctx kern.ExprContext, opTerm *term) (v any, err error) {
-	bodySpec := self.value()
+	bodySpec := opTerm.value()
-	if expr, ok := bodySpec.(*ast); ok {
+	if ast, ok := bodySpec.(*ast); ok {
-		paramList := make([]ExprFuncParam, 0, len(self.children))
+		paramList := make([]kern.ExprFuncParam, 0, len(opTerm.children))
-		for _, param := range self.children {
+		for _, param := range opTerm.children {
 			var defValue any
 			flags := paramFlags(0)
 			if len(param.children) > 0 {
 				flags |= PfDefault
-				if defValue, err = param.children[0].compute(ctx); err != nil {
+				if defValue, err = param.children[0].Compute(ctx); err != nil {
 					return
 				}
 			}
-			info := NewFuncParamFlagDef(param.source(), flags, defValue)
+			info := NewFuncParamFlagDef(param.Source(), flags, defValue)
 			paramList = append(paramList, info)
 		}
-		v = newExprFunctor(expr, paramList, ctx)
+		v = newExprFunctor(ast, paramList, ctx)
 	} else {
 		err = errors.New("invalid function definition: the body specification must be an expression")
 	}

operand-iterator.go

@@ -5,29 +5,14 @@
 package expr
 
 import (
-	"fmt"
 	"slices"
 	"strings"
+
+	"git.portale-stac.it/go-pkg/expr/kern"
 )
 
 // -------- 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{
@@ -42,11 +27,11 @@ func newIteratorTerm(tk *Token, args []*term) *term {
 
 // -------- eval iterator
 
-func evalTermArray(ctx ExprContext, a []*term) (values []any, err error) {
+func evalTermArray(ctx kern.ExprContext, terms []*term) (values []any, err error) {
-	values = make([]any, len(a))
+	values = make([]any, len(terms))
-	for i, t := range a {
+	for i, t := range terms {
 		var value any
-		if value, err = t.compute(ctx); err == nil {
+		if value, err = t.Compute(ctx); err == nil {
 			values[i] = value
 		} else {
 			break
@@ -55,27 +40,25 @@ func evalTermArray(ctx ExprContext, a []*term) (values []any, err error) {
 	return
 }
 
-func evalFirstChild(ctx ExprContext, self *term) (value any, err error) {
+func evalFirstChild(ctx kern.ExprContext, iteratorTerm *term) (value any, err error) {
-	if len(self.children) < 1 || self.children[0] == nil {
+	if len(iteratorTerm.children) < 1 || iteratorTerm.children[0] == nil {
-		err = self.Errorf("missing the data-source parameter")
+		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) {
+func getDataSourceDict(iteratorTerm *term, firstChildValue any) (ds map[string]kern.Functor, err error) {
-	// if dictAny, ok := firstChildValue.(map[any]any); ok {
+	if dictAny, ok := firstChildValue.(*kern.DictType); ok {
-	if dictAny, ok := firstChildValue.(*DictType); ok {
+		requiredFields := []string{kern.NextName}
-		requiredFields := []string{currentName, nextName}
+		fieldsMask := 0b1
-		fieldsMask := 0b11
 		foundFields := 0
-		ds = make(map[string]Functor)
+		ds = make(map[string]kern.Functor)
 		for keyAny, item := range *dictAny {
 			if key, ok := keyAny.(string); ok {
-				//if functor, ok := item.(*funcDefFunctor); ok {
+				if functor, ok := item.(kern.Functor); ok {
-				if functor, ok := item.(Functor); ok {
 					ds[key] = functor
 					if index := slices.Index(requiredFields, key); index >= 0 {
 						foundFields |= 1 << index
@@ -91,64 +74,83 @@ 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 kern.ExprContext, opTerm *term) (v any, err error) {
 	var firstChildValue any
-	var ds map[string]Functor
+	var ds map[string]kern.Functor
 
-	if firstChildValue, err = evalFirstChild(ctx, self); err != nil {
+	if firstChildValue, err = evalFirstChild(ctx, opTerm); err != nil {
 		return
 	}
 
-	if ds, err = getDataSourceDict(ctx, self, firstChildValue); err != nil {
+	if ds, err = getDataSourceDict(opTerm, firstChildValue); err != nil && ds == nil {
 		return
 	}
+	err = nil
 
 	if ds != nil {
-		dc := newDataCursor(ctx, ds)
+		if len(ds) > 0 {
-		if initFunc, exists := ds[initName]; exists && initFunc != nil {
+			var dc *dataCursor
-			var args []any
+			dcCtx := ctx.Clone()
-			if len(self.children) > 1 {
+			if initFunc, exists := ds[kern.InitName]; exists && initFunc != nil {
-				if args, err = evalTermArray(ctx, self.children[1:]); err != nil {
+				var args []any
+				var resource any
+				if len(opTerm.children) > 1 {
+					if args, err = evalTermArray(ctx, opTerm.children[1:]); err != nil {
+						return
+					}
+				} else {
+					args = []any{}
+				}
+
+				actualParams := kern.BindActualParams(initFunc, args)
+
+				initCtx := ctx.Clone()
+				if resource, err = initFunc.InvokeNamed(initCtx, kern.InitName, actualParams); err != nil {
 					return
 				}
+				kern.ExportObjects(dcCtx, initCtx)
+				dc = NewDataCursor(dcCtx, ds, resource)
 			} else {
-				args = []any{}
+				dc = NewDataCursor(dcCtx, ds, nil)
 			}
 
-			initCtx := dc.ctx.Clone()
+			v = dc
-			if dc.resource, err = initFunc.Invoke(initCtx, initName, args); err != nil {
+		} else {
-				return
+			if dictIt, ok := firstChildValue.(*kern.DictType); ok {
+				var args []any
+				if args, err = evalSibling(ctx, opTerm.children, nil); err == nil {
+					v, err = NewDictIterator(dictIt, args)
+				}
+			} else {
+				err = opTerm.children[0].Errorf("the data-source must be a dictionary")
 			}
-			exportObjects(dc.ctx, initCtx)
 		}
-
+	} else if list, ok := firstChildValue.(*kern.ListType); ok {
-		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 if intVal, ok := firstChildValue.(int64); ok {
+		var args []any
+		if args, err = evalSibling(ctx, opTerm.children, intVal); err == nil {
+			v, err = NewIntIterator(args)
+		}
 	} else {
 		var list []any
-		if list, err = evalSibling(ctx, self.children, firstChildValue); err == nil {
+		if list, err = evalSibling(ctx, opTerm.children, firstChildValue); err == nil {
 			v = NewArrayIterator(list)
 		}
 	}
 	return
 }
 
-func evalSibling(ctx ExprContext, terms []*term, firstChildValue any) (list []any, err error) {
+func evalSibling(ctx kern.ExprContext, terms []*term, firstChildValue any) (list []any, err error) {
 	items := make([]any, 0, len(terms))
 	for i, tree := range terms {
 		var param any
@@ -157,7 +159,7 @@ func evalSibling(ctx ExprContext, terms []*term, firstChildValue any) (list []an
 				continue
 			}
 			param = firstChildValue
-		} else if param, err = tree.compute(ctx); err != nil {
+		} else if param, err = tree.Compute(ctx); err != nil {
 			break
 		}
 		items = append(items, param)

operand-list.go

@@ -4,6 +4,10 @@
 // operand-list.go
 package expr
 
+import (
+	"git.portale-stac.it/go-pkg/expr/kern"
+)
+
 // -------- list term
 func newListTermA(args ...*term) *term {
 	return newListTerm(0, 0, args)
@@ -21,12 +25,12 @@ func newListTerm(row, col int, args []*term) *term {
 }
 
 // -------- list func
-func evalList(ctx ExprContext, self *term) (v any, err error) {
+func evalList(ctx kern.ExprContext, opTerm *term) (v any, err error) {
-	list, _ := self.value().([]*term)
+	list, _ := opTerm.value().([]*term)
-	items := make(ListType, len(list))
+	items := make(kern.ListType, len(list))
 	for i, tree := range list {
 		var param any
-		if param, err = tree.compute(ctx); err != nil {
+		if param, err = tree.Compute(ctx); err != nil {
 			break
 		}
 		items[i] = param

operand-literal.go

@@ -4,6 +4,10 @@
 // operand-literal.go
 package expr
 
+import (
+	"git.portale-stac.it/go-pkg/expr/kern"
+)
+
 // -------- literal term
 func newLiteralTerm(tk *Token) *term {
 	return &term{
@@ -17,8 +21,8 @@ func newLiteralTerm(tk *Token) *term {
 }
 
 // -------- eval func
-func evalLiteral(ctx ExprContext, self *term) (v any, err error) {
+func evalLiteral(ctx kern.ExprContext, opTerm *term) (v any, err error) {
-	v = self.tk.Value
+	v = opTerm.tk.Value
 	return
 }
 

operand-selector-case.go

@@ -7,6 +7,8 @@ package expr
 import (
 	"fmt"
 	"strings"
+
+	"git.portale-stac.it/go-pkg/expr/kern"
 )
 
 // -------- selector case term
@@ -41,10 +43,10 @@ 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 kern.ExprContext, opTerm *term) (v any, err error) {
 	var ok bool
-	if v, ok = self.value().(*selectorCase); !ok {
+	if v, ok = opTerm.value().(*selectorCase); !ok {
-		err = fmt.Errorf("selector-case expected, got %T", self.value())
+		err = fmt.Errorf("selector-case expected, got %T", opTerm.value())
 	}
 	return
 }

operand-var.go

@@ -4,7 +4,11 @@
 // operand-var.go
 package expr
 
-import "fmt"
+import (
+	"fmt"
+
+	"git.portale-stac.it/go-pkg/expr/kern"
+)
 
 // -------- variable term
 func newVarTerm(tk *Token) *term {
@@ -21,11 +25,11 @@ func newVarTerm(tk *Token) *term {
 }
 
 // -------- eval func
-func evalVar(ctx ExprContext, self *term) (v any, err error) {
+func evalVar(ctx kern.ExprContext, opTerm *term) (v any, err error) {
 	var exists bool
-	name := self.source()
+	name := opTerm.Source()
-	if v, exists = GetVar(ctx, name); !exists {
+	if v, exists = ctx.GetVar(name); !exists {
-		if info, exists, _ := GetFuncInfo(ctx, name); exists {
+		if info, exists := ctx.GetFuncInfo(name); exists {
 			v = info.Functor()
 		} else {
 			err = fmt.Errorf("undefined variable or function %q", name)

operator-assign.go

@@ -4,6 +4,11 @@
 // operator-assign.go
 package expr
 
+import (
+	"git.portale-stac.it/go-pkg/expr/kern"
+	"git.portale-stac.it/go-pkg/expr/util"
+)
+
 //-------- assign term
 
 func newAssignTerm(tk *Token) (inst *term) {
@@ -16,19 +21,19 @@ func newAssignTerm(tk *Token) (inst *term) {
 	}
 }
 
-func assignCollectionItem(ctx ExprContext, collectionTerm, keyListTerm *term, value any) (err error) {
+func assignCollectionItem(ctx kern.ExprContext, collectionTerm, keyListTerm *term, value any) (err error) {
 	var collectionValue, keyListValue, keyValue any
-	var keyList *ListType
+	var keyList *kern.ListType
 	var ok bool
 
-	if collectionValue, err = collectionTerm.compute(ctx); err != nil {
+	if collectionValue, err = collectionTerm.Compute(ctx); err != nil {
 		return
 	}
 
-	if keyListValue, err = keyListTerm.compute(ctx); err != nil {
+	if keyListValue, err = keyListTerm.Compute(ctx); err != nil {
 		return
-	} else if keyList, ok = keyListValue.(*ListType); !ok || len(*keyList) != 1 {
+	} else if keyList, ok = keyListValue.(*kern.ListType); !ok || len(*keyList) != 1 {
-		err = keyListTerm.Errorf("index/key specification expected, got %v [%s]", keyListValue, TypeName(keyListValue))
+		err = keyListTerm.Errorf("index/key specification expected, got %v [%s]", keyListValue, kern.TypeName(keyListValue))
 		return
 	}
 	if keyValue = (*keyList)[0]; keyValue == nil {
@@ -37,53 +42,57 @@ func assignCollectionItem(ctx ExprContext, collectionTerm, keyListTerm *term, va
 	}
 
 	switch collection := collectionValue.(type) {
-	case *ListType:
+	case *kern.ListType:
 		if index, ok := keyValue.(int64); ok {
-			err = collection.setItem(index, value)
+			err = collection.SetItem(index, value)
 		} else {
-			err = keyListTerm.Errorf("integer expected, got %v [%s]", keyValue, TypeName(keyValue))
+			err = keyListTerm.Errorf("integer expected, got %v [%s]", keyValue, kern.TypeName(keyValue))
 		}
-	case *DictType:
+	case *kern.DictType:
-		err = collection.setItem(keyValue, value)
+		collection.SetItem(keyValue, value)
 	default:
 		err = collectionTerm.Errorf("collection expected")
 	}
 	return
 }
 
-func assignValue(ctx ExprContext, leftTerm *term, v any) (err error) {
+func assignValue(ctx kern.ExprContext, leftTerm *term, v any) (err error) {
 	if leftTerm.symbol() == SymIndex {
 		err = assignCollectionItem(ctx, leftTerm.children[0], leftTerm.children[1], v)
 	} else {
-		ctx.UnsafeSetVar(leftTerm.source(), v)
+		ctx.UnsafeSetVar(leftTerm.Source(), v)
 	}
 	return
 }
 
-func evalAssign(ctx ExprContext, self *term) (v any, err error) {
+func evalAssign(ctx kern.ExprContext, opTerm *term) (v any, err error) {
-	if err = self.checkOperands(); err != nil {
+	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 v, err = rightChild.Compute(ctx); err == nil {
-		if functor, ok := v.(Functor); ok {
+		if functor, ok := v.(kern.Functor); ok {
-			if info := functor.GetFunc(); info != nil {
+			if leftSym == SymVariable {
-				ctx.RegisterFunc(leftTerm.source(), info.Functor(), info.ReturnType(), info.Params())
+				if info := functor.GetFunc(); info != nil {
-			} else if funcDef, ok := functor.(*exprFunctor); ok {
+					ctx.RegisterFunc(leftTerm.Source(), info.Functor(), info.ReturnType(), info.Params())
-				paramSpecs := ForAll(funcDef.params, func(p ExprFuncParam) ExprFuncParam { return p })
+				} else if funcDef, ok := functor.(*exprFunctor); ok {
+					paramSpecs := util.ForAll(funcDef.params, func(p kern.ExprFuncParam) kern.ExprFuncParam { return p })
 
-				ctx.RegisterFunc(leftTerm.source(), functor, TypeAny, paramSpecs)
+					ctx.RegisterFunc(leftTerm.Source(), functor, kern.TypeAny, paramSpecs)
+				} else {
+					err = opTerm.Errorf("unknown function %s()", rightChild.Source())
+				}
 			} else {
-				err = self.Errorf("unknown function %s()", rightChild.source())
+				err = assignValue(ctx, leftTerm, v)
 			}
 		} else {
 			err = assignValue(ctx, leftTerm, v)
@@ -95,7 +104,122 @@ 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 kern.ExprContext, collectionTerm, keyListTerm *term) (value any, err error) {
+	var collectionValue, keyListValue, keyValue any
+	var keyList *kern.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.(*kern.ListType); !ok || len(*keyList) != 1 {
+		err = keyListTerm.Errorf("index/key specification expected, got %v [%s]", keyListValue, kern.TypeName(keyListValue))
+		return
+	}
+	if keyValue = (*keyList)[0]; keyValue == nil {
+		err = keyListTerm.Errorf("index/key is nil")
+		return
+	}
+
+	switch collection := collectionValue.(type) {
+	case *kern.ListType:
+		if index, ok := keyValue.(int64); ok {
+			value = (*collection)[index]
+		} else {
+			err = keyListTerm.Errorf("integer expected, got %v [%s]", keyValue, kern.TypeName(keyValue))
+		}
+	case *kern.DictType:
+		value = (*collection)[keyValue]
+	default:
+		err = collectionTerm.Errorf("collection expected")
+	}
+	return
+}
+
+func getAssignValue(ctx kern.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 kern.ExprContext, opTerm *term) (v any, err error) {
+	var rightValue, leftValue any
+	if err = opTerm.checkOperands(); err != nil {
+		return
+	}
+
+	leftTerm := opTerm.children[0]
+	leftSym := leftTerm.symbol()
+	if leftSym != SymVariable && leftSym != SymIndex {
+		err = leftTerm.tk.Errorf("left operand of %q must be a variable or a collection's item", opTerm.tk.source)
+		return
+	}
+
+	rightChild := opTerm.children[1]
+
+	if rightValue, err = rightChild.Compute(ctx); err == nil {
+		if leftValue, err = getAssignValue(ctx, leftTerm); err == nil {
+			switch opTerm.symbol() {
+			case SymPlusEqual:
+				v, err = sumValues(opTerm, leftValue, rightValue)
+			case SymMinusEqual:
+				v, err = diffValues(opTerm, leftValue, rightValue)
+			case SymStarEqual:
+				v, err = mulValues(opTerm, leftValue, rightValue)
+			case SymSlashEqual:
+				v, err = divValues(opTerm, leftValue, rightValue)
+			case SymPercEqual:
+				v, err = remainderValues(opTerm, leftValue, rightValue)
+			case SymAmpersandEqual:
+				v, err = bitwiseAnd(opTerm, leftValue, rightValue)
+			case SymVertBarEqual:
+				v, err = bitwiseOr(opTerm, leftValue, rightValue)
+			case SymCaretEqual:
+				v, err = bitwiseXor(opTerm, leftValue, rightValue)
+			case SymDoubleLessEqual:
+				v, err = bitLeftShift(opTerm, leftValue, rightValue)
+			case SymDoubleGreaterEqual:
+				v, err = bitRightShift(opTerm, leftValue, rightValue)
+			default:
+				err = opTerm.Errorf("unsupported assign operator %q", opTerm.Source())
+			}
+			if err == nil {
+				err = assignValue(ctx, leftTerm, v)
+			}
+		}
+	}
+	return
+}
+
 // init
 func init() {
 	registerTermConstructor(SymEqual, newAssignTerm)
+	registerTermConstructor(SymPlusEqual, newOpAssignTerm)
+	registerTermConstructor(SymMinusEqual, newOpAssignTerm)
+	registerTermConstructor(SymStarEqual, newOpAssignTerm)
+	registerTermConstructor(SymSlashEqual, newOpAssignTerm)
+	registerTermConstructor(SymPercEqual, newOpAssignTerm)
+	registerTermConstructor(SymDoubleLessEqual, newOpAssignTerm)
+	registerTermConstructor(SymDoubleGreaterEqual, newOpAssignTerm)
+	registerTermConstructor(SymAmpersandEqual, newOpAssignTerm)
+	registerTermConstructor(SymVertBarEqual, newOpAssignTerm)
+	registerTermConstructor(SymCaretEqual, newOpAssignTerm)
 }

operator-bitwise.go

@@ -0,0 +1,158 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// operator-bitwise.go
+package expr
+
+import (
+	"git.portale-stac.it/go-pkg/expr/kern"
+)
+
+//-------- Bitwise NOT term
+
+func newBitwiseNotTerm(tk *Token) (inst *term) {
+	return &term{
+		tk:       *tk,
+		children: make([]*term, 0, 1),
+		position: posPrefix,
+		priority: priBitwiseNot,
+		evalFunc: evalBitwiseNot,
+	}
+}
+
+func evalBitwiseNot(ctx kern.ExprContext, opTerm *term) (v any, err error) {
+	var value any
+
+	if value, err = opTerm.evalPrefix(ctx); err != nil {
+		return
+	}
+
+	if kern.IsInteger(value) {
+		i, _ := value.(int64)
+		v = ^i
+	} else {
+		err = opTerm.errIncompatiblePrefixPostfixType(value)
+	}
+	return
+}
+
+//-------- Bitwise AND term
+
+func newBitwiseAndTerm(tk *Token) (inst *term) {
+	return &term{
+		tk:       *tk,
+		children: make([]*term, 0, 2),
+		position: posInfix,
+		priority: priBitwiseAnd,
+		evalFunc: evalBitwiseAnd,
+	}
+}
+
+func bitwiseAnd(opTerm *term, leftValue, rightValue any) (v any, err error) {
+	var leftInt, rightInt int64
+	var lok, rok bool
+
+	leftInt, lok = leftValue.(int64)
+	rightInt, rok = rightValue.(int64)
+
+	if lok && rok {
+		v = leftInt & rightInt
+	} else {
+		err = opTerm.errIncompatibleTypes(leftValue, rightValue)
+	}
+	return
+}
+
+func evalBitwiseAnd(ctx kern.ExprContext, opTerm *term) (v any, err error) {
+	var leftValue, rightValue any
+
+	if leftValue, rightValue, err = opTerm.evalInfix(ctx); err != nil {
+		return
+	}
+	v, err = bitwiseAnd(opTerm, leftValue, rightValue)
+	return
+}
+
+//-------- Bitwise OR term
+
+func newBitwiseOrTerm(tk *Token) (inst *term) {
+	return &term{
+		tk:       *tk,
+		children: make([]*term, 0, 2),
+		position: posInfix,
+		priority: priBitwiseOr,
+		evalFunc: evalBitwiseOr,
+	}
+}
+
+func bitwiseOr(opTerm *term, leftValue, rightValue any) (v any, err error) {
+	var leftInt, rightInt int64
+	var lok, rok bool
+
+	leftInt, lok = leftValue.(int64)
+	rightInt, rok = rightValue.(int64)
+
+	if lok && rok {
+		v = leftInt | rightInt
+	} else {
+		err = opTerm.errIncompatibleTypes(leftValue, rightValue)
+	}
+	return
+}
+
+func evalBitwiseOr(ctx kern.ExprContext, opTerm *term) (v any, err error) {
+	var leftValue, rightValue any
+
+	if leftValue, rightValue, err = opTerm.evalInfix(ctx); err != nil {
+		return
+	}
+
+	v, err = bitwiseOr(opTerm, leftValue, rightValue)
+	return
+}
+
+//-------- Bitwise XOR term
+
+func newBitwiseXorTerm(tk *Token) (inst *term) {
+	return &term{
+		tk:       *tk,
+		children: make([]*term, 0, 2),
+		position: posInfix,
+		priority: priBitwiseOr,
+		evalFunc: evalBitwiseXor,
+	}
+}
+
+func bitwiseXor(opTerm *term, leftValue, rightValue any) (v any, err error) {
+	var leftInt, rightInt int64
+	var lok, rok bool
+
+	leftInt, lok = leftValue.(int64)
+	rightInt, rok = rightValue.(int64)
+
+	if lok && rok {
+		v = leftInt ^ rightInt
+	} else {
+		err = opTerm.errIncompatibleTypes(leftValue, rightValue)
+	}
+	return
+}
+
+func evalBitwiseXor(ctx kern.ExprContext, opTerm *term) (v any, err error) {
+	var leftValue, rightValue any
+
+	if leftValue, rightValue, err = opTerm.evalInfix(ctx); err != nil {
+		return
+	}
+
+	v, err = bitwiseXor(opTerm, leftValue, rightValue)
+	return
+}
+
+// init
+func init() {
+	registerTermConstructor(SymTilde, newBitwiseNotTerm)
+	registerTermConstructor(SymAmpersand, newBitwiseAndTerm)
+	registerTermConstructor(SymVertBar, newBitwiseOrTerm)
+	registerTermConstructor(SymCaret, newBitwiseXorTerm)
+}

operator-bool.go

@@ -4,7 +4,11 @@
 // operator-bool.go
 package expr
 
-import "fmt"
+import (
+	"fmt"
+
+	"git.portale-stac.it/go-pkg/expr/kern"
+)
 
 //-------- NOT term
 
@@ -18,17 +22,17 @@ func newNotTerm(tk *Token) (inst *term) {
 	}
 }
 
-func evalNot(ctx ExprContext, self *term) (v any, err error) {
+func evalNot(ctx kern.ExprContext, opTerm *term) (v any, err error) {
 	var rightValue any
 
-	if rightValue, err = self.evalPrefix(ctx); err != nil {
+	if rightValue, err = opTerm.evalPrefix(ctx); err != nil {
 		return
 	}
 
-	if b, ok := ToBool(rightValue); ok {
+	if b, ok := kern.ToBool(rightValue); ok {
 		v = !b
 	} else {
-		err = self.errIncompatibleType(rightValue)
+		err = opTerm.errIncompatiblePrefixPostfixType(rightValue)
 	}
 	return
 }
@@ -37,9 +41,7 @@ func evalNot(ctx ExprContext, self *term) (v any, err error) {
 
 func newAndTerm(tk *Token) (inst *term) {
 	return &term{
-		tk: *tk,
+		tk:       *tk,
-		// class:    classOperator,
-		// kind:     kindBool,
 		children: make([]*term, 0, 2),
 		position: posInfix,
 		priority: priAnd,
@@ -47,8 +49,8 @@ func newAndTerm(tk *Token) (inst *term) {
 	}
 }
 
-func evalAnd(ctx ExprContext, self *term) (v any, err error) {
+func evalAnd(ctx kern.ExprContext, self *term) (v any, err error) {
-	if CtrlIsEnabled(ctx, ControlBoolShortcut) {
+	if kern.CtrlIsEnabled(ctx, kern.ControlBoolShortcut) {
 		v, err = evalAndWithShortcut(ctx, self)
 	} else {
 		v, err = evalAndWithoutShortcut(ctx, self)
@@ -56,7 +58,7 @@ func evalAnd(ctx ExprContext, self *term) (v any, err error) {
 	return
 }
 
-func evalAndWithoutShortcut(ctx ExprContext, self *term) (v any, err error) {
+func evalAndWithoutShortcut(ctx kern.ExprContext, self *term) (v any, err error) {
 	var leftValue, rightValue any
 	var leftBool, rightBool bool
 	var lok, rok bool
@@ -65,8 +67,8 @@ func evalAndWithoutShortcut(ctx ExprContext, self *term) (v any, err error) {
 		return
 	}
 
-	leftBool, lok = ToBool(leftValue)
+	leftBool, lok = kern.ToBool(leftValue)
-	rightBool, rok = ToBool(rightValue)
+	rightBool, rok = kern.ToBool(rightValue)
 
 	if lok && rok {
 		v = leftBool && rightBool
@@ -76,24 +78,25 @@ func evalAndWithoutShortcut(ctx ExprContext, self *term) (v any, err error) {
 	return
 }
 
-func evalAndWithShortcut(ctx ExprContext, self *term) (v any, err error) {
+func evalAndWithShortcut(ctx kern.ExprContext, self *term) (v any, err error) {
 	var leftValue, rightValue any
 
 	if err = self.checkOperands(); err != nil {
 		return
 	}
 
-	if leftValue, err = self.children[0].compute(ctx); err != nil {
+	if leftValue, err = self.children[0].Compute(ctx); err != nil {
 		return
 	}
 
-	if leftBool, lok := ToBool(leftValue); !lok {
+	if leftBool, lok := kern.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", expr.TypeName(leftValue))
-		return
+		// return
+		err = self.errIncompatibleType(leftValue, "left")
 	} else if !leftBool {
 		v = false
-	} else if rightValue, err = self.children[1].compute(ctx); err == nil {
+	} else if rightValue, err = self.children[1].Compute(ctx); err == nil {
-		if rightBool, rok := ToBool(rightValue); rok {
+		if rightBool, rok := kern.ToBool(rightValue); rok {
 			v = rightBool
 		} else {
 			err = self.errIncompatibleTypes(leftValue, rightValue)
@@ -106,9 +109,7 @@ func evalAndWithShortcut(ctx ExprContext, self *term) (v any, err error) {
 
 func newOrTerm(tk *Token) (inst *term) {
 	return &term{
-		tk: *tk,
+		tk:       *tk,
-		// class:    classOperator,
-		// kind:     kindBool,
 		children: make([]*term, 0, 2),
 		position: posInfix,
 		priority: priOr,
@@ -116,8 +117,8 @@ func newOrTerm(tk *Token) (inst *term) {
 	}
 }
 
-func evalOr(ctx ExprContext, self *term) (v any, err error) {
+func evalOr(ctx kern.ExprContext, self *term) (v any, err error) {
-	if CtrlIsEnabled(ctx, ControlBoolShortcut) {
+	if kern.CtrlIsEnabled(ctx, kern.ControlBoolShortcut) {
 		v, err = evalOrWithShortcut(ctx, self)
 	} else {
 		v, err = evalOrWithoutShortcut(ctx, self)
@@ -125,7 +126,7 @@ func evalOr(ctx ExprContext, self *term) (v any, err error) {
 	return
 }
 
-func evalOrWithoutShortcut(ctx ExprContext, self *term) (v any, err error) {
+func evalOrWithoutShortcut(ctx kern.ExprContext, self *term) (v any, err error) {
 	var leftValue, rightValue any
 	var leftBool, rightBool bool
 	var lok, rok bool
@@ -134,8 +135,8 @@ func evalOrWithoutShortcut(ctx ExprContext, self *term) (v any, err error) {
 		return
 	}
 
-	leftBool, lok = ToBool(leftValue)
+	leftBool, lok = kern.ToBool(leftValue)
-	rightBool, rok = ToBool(rightValue)
+	rightBool, rok = kern.ToBool(rightValue)
 
 	if lok && rok {
 		v = leftBool || rightBool
@@ -145,24 +146,24 @@ func evalOrWithoutShortcut(ctx ExprContext, self *term) (v any, err error) {
 	return
 }
 
-func evalOrWithShortcut(ctx ExprContext, self *term) (v any, err error) {
+func evalOrWithShortcut(ctx kern.ExprContext, self *term) (v any, err error) {
 	var leftValue, rightValue any
 
 	if err = self.checkOperands(); err != nil {
 		return
 	}
 
-	if leftValue, err = self.children[0].compute(ctx); err != nil {
+	if leftValue, err = self.children[0].Compute(ctx); err != nil {
 		return
 	}
 
-	if leftBool, lok := ToBool(leftValue); !lok {
+	if leftBool, lok := kern.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", kern.TypeName(leftValue))
 		return
 	} else if leftBool {
 		v = true
-	} else if rightValue, err = self.children[1].compute(ctx); err == nil {
+	} else if rightValue, err = self.children[1].Compute(ctx); err == nil {
-		if rightBool, rok := ToBool(rightValue); rok {
+		if rightBool, rok := kern.ToBool(rightValue); rok {
 			v = rightBool
 		} else {
 			err = self.errIncompatibleTypes(leftValue, rightValue)

operator-builtin.go

@@ -4,7 +4,11 @@
 // operator-builtin.go
 package expr
 
-import "io"
+import (
+	"io"
+
+	"git.portale-stac.it/go-pkg/expr/kern"
+)
 
 //-------- builtin term
 
@@ -18,30 +22,33 @@ func newBuiltinTerm(tk *Token) (inst *term) {
 	}
 }
 
-func evalBuiltin(ctx ExprContext, self *term) (v any, err error) {
+func evalBuiltin(ctx kern.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 IsString(childValue) {
+	if kern.IsString(childValue) {
 		module, _ := childValue.(string)
-		count, err = ImportInContextByGlobPattern(module)
+		count, err = ImportInContextByGlobPattern(ctx, module)
 	} else {
 		var moduleSpec any
-		it := NewAnyIterator(childValue)
+		var it kern.Iterator
+		if it, err = NewIterator(childValue); err != nil {
+			return
+		}
 		for moduleSpec, err = it.Next(); err == nil; moduleSpec, err = it.Next() {
 			if module, ok := moduleSpec.(string); ok {
-				if ImportInContext(module) {
+				if ImportInContext(ctx, 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, kern.TypeName(moduleSpec))
 				break
 			}
 		}

operator-but.go

@@ -4,6 +4,10 @@
 // operator-but.go
 package expr
 
+import (
+	"git.portale-stac.it/go-pkg/expr/kern"
+)
+
 //-------- but term
 
 func newButTerm(tk *Token) (inst *term) {
@@ -16,8 +20,8 @@ func newButTerm(tk *Token) (inst *term) {
 	}
 }
 
-func evalBut(ctx ExprContext, self *term) (v any, err error) {
+func evalBut(ctx kern.ExprContext, opTerm *term) (v any, err error) {
-	_, v, err = self.evalInfix(ctx)
+	_, 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

@@ -4,6 +4,10 @@
 // operator-context-value.go
 package expr
 
+import (
+	"git.portale-stac.it/go-pkg/expr/kern"
+)
+
 //-------- context term
 
 func newContextTerm(tk *Token) (inst *term) {
@@ -16,24 +20,24 @@ func newContextTerm(tk *Token) (inst *term) {
 	}
 }
 
-func evalContextValue(ctx ExprContext, self *term) (v any, err error) {
+func evalContextValue(ctx kern.ExprContext, opTerm *term) (v any, err error) {
 	var childValue any
 
-	var sourceCtx ExprContext
+	var sourceCtx kern.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
+		sourceCtx = ctx.GetGlobal()
-	} else if childValue, err = self.evalPrefix(ctx); err == nil {
+	} else if childValue, err = opTerm.evalPrefix(ctx); err == nil {
 		if dc, ok := childValue.(*dataCursor); ok {
 			sourceCtx = dc.ctx
 		}
 	}
 
 	if sourceCtx != nil {
-		if formatter, ok := sourceCtx.(DictFormat); ok {
+		if formatter, ok := sourceCtx.(kern.DictFormat); ok {
 			v = formatter.ToDict()
-		} else if formatter, ok := sourceCtx.(Formatter); ok {
+		} else if formatter, ok := sourceCtx.(kern.Formatter); ok {
 			v = formatter.ToString(0)
 		} else {
 			// keys := sourceCtx.EnumVars(func(name string) bool { return name[0] != '_' })
@@ -49,7 +53,7 @@ func evalContextValue(ctx ExprContext, self *term) (v any, err error) {
 			v = d
 		}
 	} else {
-		err = self.errIncompatibleType(childValue)
+		err = opTerm.errIncompatiblePrefixPostfixType(childValue)
 	}
 	return
 }

operator-ctrl.go

@@ -4,6 +4,10 @@
 // operator-ctrl.go
 package expr
 
+import (
+	"git.portale-stac.it/go-pkg/expr/kern"
+)
+
 //-------- export all term
 
 func newExportAllTerm(tk *Token) (inst *term) {
@@ -16,8 +20,8 @@ func newExportAllTerm(tk *Token) (inst *term) {
 	}
 }
 
-func evalExportAll(ctx ExprContext, self *term) (v any, err error) {
+func evalExportAll(ctx kern.ExprContext, opTerm *term) (v any, err error) {
-	CtrlEnable(ctx, control_export_all)
+	CtrlEnable(ctx, kern.ControlExportAll)
 	return
 }
 

operator-default.go

@@ -0,0 +1,128 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// operator-default.go
+package expr
+
+import (
+	"git.portale-stac.it/go-pkg/expr/kern"
+)
+
+//-------- 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 kern.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 = kern.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 kern.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 = kern.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 kern.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 = kern.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.(kern.Functor); ok {
+			//ctx.RegisterFunc(leftTerm.source(), functor, 0, -1)
+			ctx.RegisterFunc(leftTerm.Source(), functor, kern.TypeAny, []kern.ExprFuncParam{
+				NewFuncParamFlag(kern.ParamValue, PfDefault|PfRepeat),
+			})
+		} else {
+			v = rightValue
+			ctx.UnsafeSetVar(leftTerm.Source(), rightValue)
+		}
+	}
+	return
+}
+
+// init
+func init() {
+	registerTermConstructor(SymDoubleQuestion, newDefaultTerm)
+	registerTermConstructor(SymQuestionEqual, newDefaultAssignTerm)
+	registerTermConstructor(SymQuestionExclam, newAlternateTerm)
+}

operator-digest.go

@@ -0,0 +1,72 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// operator-digest.go
+package expr
+
+import (
+	"fmt"
+	"io"
+
+	"git.portale-stac.it/go-pkg/expr/kern"
+)
+
+//-------- digest term
+
+func newDigestTerm(tk *Token) (inst *term) {
+	return &term{
+		tk:       *tk,
+		children: make([]*term, 0, 2),
+		position: posInfix,
+		priority: priIterOp,
+		evalFunc: evalDigest,
+	}
+}
+
+func evalDigest(ctx kern.ExprContext, opTerm *term) (v any, err error) {
+	var leftValue, rightValue any
+	var it kern.Iterator
+	var item, lastValue any
+
+	if err = opTerm.checkOperands(); err != nil {
+		return
+	}
+
+	if leftValue, err = opTerm.children[0].Compute(ctx); err != nil {
+		return
+	}
+
+	if it, err = NewIterator(leftValue); err != nil {
+		return nil, fmt.Errorf("left operand of DIGEST must be an iterable data-source; got %s", kern.TypeName(leftValue))
+	}
+
+	lastValue = nil
+	for item, err = it.Next(); err == nil; item, err = it.Next() {
+		ctx.SetVar("_", item)
+		ctx.SetVar("__", it.Index())
+		ctx.SetVar("_#", it.Count())
+		if rightValue, err = opTerm.children[1].Compute(ctx); err == nil {
+			if rightValue == nil {
+				break
+			} else {
+				lastValue = rightValue
+			}
+		}
+		ctx.DeleteVar("_#")
+		ctx.DeleteVar("__")
+		ctx.DeleteVar("_")
+		if err != nil {
+			break
+		}
+	}
+	if err == io.EOF {
+		err = nil
+	}
+	v = lastValue
+	return
+}
+
+// init
+func init() {
+	registerTermConstructor(SymKwDigest, newDigestTerm)
+}

operator-dot.go

@@ -4,6 +4,10 @@
 // operator-dot.go
 package expr
 
+import (
+	"git.portale-stac.it/go-pkg/expr/kern"
+)
+
 // -------- dot term
 func newDotTerm(tk *Token) (inst *term) {
 	return &term{
@@ -15,24 +19,24 @@ func newDotTerm(tk *Token) (inst *term) {
 	}
 }
 
-func evalDot(ctx ExprContext, self *term) (v any, err error) {
+func evalDot(ctx kern.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:
+	case kern.ExtIterator:
 		if indexTerm.symbol() == SymVariable /*|| indexTerm.symbol() == SymString */ {
-			opName := indexTerm.source()
+			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
@@ -40,9 +44,25 @@ func evalDot(ctx ExprContext, self *term) (v any, err error) {
 		} else {
 			err = indexTerm.tk.ErrorExpectedGot("identifier")
 		}
+	case *kern.DictType:
+		var ok bool
+		s := opTerm.children[1].symbol()
+		if s == SymVariable || s == SymString {
+			src := opTerm.children[1].Source()
+			if len(src) > 1 && src[0] == '"' && src[len(src)-1] == '"' {
+				src = src[1 : len(src)-1]
+			}
+			if v, ok = unboxedValue.GetItem(src); !ok {
+				err = opTerm.errKeyNotFound(src)
+			}
+		} else if rightValue, err = opTerm.children[1].Compute(ctx); err == nil {
+			if v, ok = unboxedValue.GetItem(rightValue); !ok {
+				err = opTerm.errKeyNotFound(rightValue)
+			}
+		}
 	default:
-		if rightValue, err = self.children[1].compute(ctx); err == nil {
+		if rightValue, err = opTerm.children[1].Compute(ctx); err == nil {
-			err = self.errIncompatibleTypes(leftValue, rightValue)
+			err = opTerm.errIncompatibleTypes(leftValue, rightValue)
 		}
 	}
 	return

operator-fact.go

@@ -4,7 +4,11 @@
 // operator-fact.go
 package expr
 
-import "fmt"
+import (
+	"fmt"
+
+	"git.portale-stac.it/go-pkg/expr/kern"
+)
 
 //-------- fact term
 
@@ -18,14 +22,14 @@ func newFactTerm(tk *Token) (inst *term) {
 	}
 }
 
-func evalFact(ctx ExprContext, self *term) (v any, err error) {
+func evalFact(ctx kern.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
 	}
 
-	if IsInteger(leftValue) {
+	if kern.IsInteger(leftValue) {
 		if i, _ := leftValue.(int64); i >= 0 {
 			f := int64(1)
 			for k := int64(1); k <= i; k++ {
@@ -36,7 +40,7 @@ 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.errIncompatiblePrefixPostfixType(leftValue)
 	}
 	return
 }

operator-filter.go

@@ -0,0 +1,74 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// operator-filter.go
+package expr
+
+import (
+	"fmt"
+	"io"
+
+	"git.portale-stac.it/go-pkg/expr/kern"
+)
+
+//-------- map term
+
+func newFilterTerm(tk *Token) (inst *term) {
+	return &term{
+		tk:       *tk,
+		children: make([]*term, 0, 2),
+		position: posInfix,
+		priority: priIterOp,
+		evalFunc: evalFilter,
+	}
+}
+
+func evalFilter(ctx kern.ExprContext, opTerm *term) (v any, err error) {
+	var leftValue, rightValue any
+	var it kern.Iterator
+	var item any
+
+	if err = opTerm.checkOperands(); err != nil {
+		return
+	}
+
+	if leftValue, err = opTerm.children[0].Compute(ctx); err != nil {
+		return
+	}
+
+	if it, err = NewIterator(leftValue); err != nil {
+		return nil, fmt.Errorf("left operand of FILTER must be an iterable data-source; got %s", kern.TypeName(leftValue))
+	}
+
+	values := kern.NewListA()
+	for item, err = it.Next(); err == nil; item, err = it.Next() {
+		ctx.SetVar("_", item)
+		ctx.SetVar("__", it.Index())
+		ctx.SetVar("_#", it.Count())
+		if rightValue, err = opTerm.children[1].Compute(ctx); err == nil {
+			if success, valid := kern.ToBool(rightValue); valid {
+				if success {
+					values.AppendItem(item)
+				}
+			} else {
+				err = fmt.Errorf("filter expression must return a boolean or a castable to boolean, got %v [%T]", rightValue, rightValue)
+			}
+		}
+		ctx.DeleteVar("_#")
+		ctx.DeleteVar("__")
+		ctx.DeleteVar("_")
+		if err != nil {
+			break
+		}
+	}
+	if err == io.EOF {
+		err = nil
+	}
+	v = values
+	return
+}
+
+// init
+func init() {
+	registerTermConstructor(SymKwFilter, newFilterTerm)
+}

operator-fraction.go

@@ -7,8 +7,9 @@ package expr
 //https://www.youmath.it/lezioni/algebra-elementare/lezioni-di-algebra-e-aritmetica-per-scuole-medie/553-dalle-frazioni-a-numeri-decimali.html
 
 import (
-	"errors"
 	"fmt"
+
+	"git.portale-stac.it/go-pkg/expr/kern"
 )
 
 // -------- fraction term
@@ -24,12 +25,12 @@ func newFractionTerm(tk *Token) *term {
 }
 
 // -------- eval func
-func evalFraction(ctx ExprContext, self *term) (v any, err error) {
+func evalFraction(ctx kern.ExprContext, opTerm *term) (v any, err error) {
 	var numValue, denValue any
 	var num, den int64
 	var ok bool
 
-	if numValue, denValue, err = self.evalInfix(ctx); err != nil {
+	if numValue, denValue, err = opTerm.evalInfix(ctx); err != nil {
 		return
 	}
 	if num, ok = numValue.(int64); !ok {
@@ -41,7 +42,7 @@ func evalFraction(ctx ExprContext, self *term) (v any, err error) {
 		return
 	}
 	if den == 0 {
-		err = errors.New("division by zero")
+		err = opTerm.errDivisionByZero()
 		return
 	}
 
@@ -49,18 +50,26 @@ func evalFraction(ctx ExprContext, self *term) (v any, err error) {
 		den = -den
 		num = -num
 	}
-	g := gcd(num, den)
+	if num != 0 {
-	num = num / g
+		if g := kern.Gcd(num, den); g != 1 {
-	den = den / g
+			num = num / g
-	if den == 1 {
+			den = den / g
-		v = num
+		}
+		if den == 1 {
+			v = num
+		} else {
+			// v = &expr.FractionType{num, den}
+			v = kern.NewFraction(num, den)
+		}
 	} else {
-		v = &FractionType{num, den}
+		// v = &FractionType{0, den}
+		v = kern.NewFraction(0, den)
 	}
 	return
 }
 
 // init
 func init() {
-	registerTermConstructor(SymVertBar, newFractionTerm)
+	// registerTermConstructor(SymVertBar, newFractionTerm)
+	registerTermConstructor(SymColon, newFractionTerm)
 }

operator-groupby.go

@@ -0,0 +1,105 @@
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// operator-groupby.go
+package expr
+
+import (
+	"fmt"
+	"io"
+	"strconv"
+
+	"git.portale-stac.it/go-pkg/expr/kern"
+)
+
+//-------- group by term
+
+func newGroupByTerm(tk *Token) (inst *term) {
+	return &term{
+		tk:       *tk,
+		children: make([]*term, 0, 2),
+		position: posInfix,
+		priority: priIterOp,
+		evalFunc: evalGroupBy,
+	}
+}
+
+func evalGroupBy(ctx kern.ExprContext, opTerm *term) (v any, err error) {
+	var leftValue, rightValue any
+	var it kern.Iterator
+	var item any
+	var sKey string
+	var keyByIndex bool
+
+	if err = opTerm.checkOperands(); err != nil {
+		return
+	}
+
+	if leftValue, err = opTerm.children[0].Compute(ctx); err != nil {
+		return
+	}
+
+	if it, err = NewIterator(leftValue); err != nil {
+		return nil, fmt.Errorf("left operand of MAP must be an iterable data-source; got %s", kern.TypeName(leftValue))
+	}
+
+	rightTk := opTerm.children[1].tk
+	if rightTk.IsSymbol(SymVariable) && rightTk.source == "__" {
+		keyByIndex = true
+	} else if rightValue, err = opTerm.children[1].Compute(ctx); err != nil {
+		return
+	} else if kern.IsString(rightValue) {
+		sKey = rightValue.(string)
+	} else {
+		return nil, fmt.Errorf("right operand of GROUPBY must be a string or identifier '__'; got %s", kern.TypeName(rightValue))
+	}
+
+	values := kern.MakeDict()
+	for item, err = it.Next(); err == nil; item, err = it.Next() {
+		ctx.SetVar("_", item)
+		ctx.SetVar("__", it.Index())
+		ctx.SetVar("_#", it.Count())
+
+		var sItemKey string
+
+		if d, ok := item.(*kern.DictType); ok {
+			if keyByIndex || len(sKey) == 0 {
+				sItemKey = strconv.Itoa(int(it.Index()))
+			} else if d.HasKey(sKey) {
+				if keyValue, exists := d.GetItem(sKey); exists {
+					sItemKey = fmt.Sprintf("%v", keyValue)
+				} else {
+					sItemKey = "_"
+				}
+			} else {
+				sItemKey = "_"
+			}
+		} else {
+			sItemKey = strconv.Itoa(int(it.Index()))
+		}
+
+		var ls *kern.ListType
+		if lsAny, exists := values.GetItem(sItemKey); exists && lsAny != nil {
+			ls = lsAny.(*kern.ListType)
+		}
+		if ls == nil {
+			ls = kern.NewListA()
+		}
+		ls.AppendItem(item)
+		values.SetItem(sItemKey, ls)
+
+		ctx.DeleteVar("_#")
+		ctx.DeleteVar("__")
+		ctx.DeleteVar("_")
+	}
+	if err == io.EOF {
+		err = nil
+	}
+	v = values
+	return
+}
+
+// init
+func init() {
+	registerTermConstructor(SymKwGroupBy, newGroupByTerm)
+}

operator-in.go

@@ -4,6 +4,10 @@
 // operator-in.go
 package expr
 
+import (
+	"git.portale-stac.it/go-pkg/expr/kern"
+)
+
 //-------- in term
 
 func newInTerm(tk *Token) (inst *term) {
@@ -21,21 +25,21 @@ func newInTerm(tk *Token) (inst *term) {
 // 	return
 // }
 
-func evalIn(ctx ExprContext, self *term) (v any, err error) {
+func evalIn(ctx kern.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
 	}
 
-	if IsList(rightValue) {
+	if kern.IsList(rightValue) {
-		list, _ := rightValue.(*ListType)
+		list, _ := rightValue.(*kern.ListType)
-		v = list.indexDeepSameCmp(leftValue) >= 0
+		v = list.IndexDeepSameCmp(leftValue) >= 0
-	} else if IsDict(rightValue) {
+	} else if kern.IsDict(rightValue) {
-		dict, _ := rightValue.(*DictType)
+		dict, _ := rightValue.(*kern.DictType)
-		v = dict.hasKey(leftValue)
+		v = dict.HasKey(leftValue)
 	} else {
-		err = self.errIncompatibleTypes(leftValue, rightValue)
+		err = opTerm.errIncompatibleTypes(leftValue, rightValue)
 	}
 	return
 }

operator-include.go

@@ -4,6 +4,10 @@
 // operator-include.go
 package expr
 
+import (
+	"git.portale-stac.it/go-pkg/expr/kern"
+)
+
 //-------- include term
 
 func newIncludeTerm(tk *Token) (inst *term) {
@@ -16,37 +20,40 @@ func newIncludeTerm(tk *Token) (inst *term) {
 	}
 }
 
-func evalInclude(ctx ExprContext, self *term) (v any, err error) {
+func evalInclude(ctx kern.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) {
+	if kern.IsList(childValue) {
-		list, _ := childValue.([]any)
+		list, _ := childValue.(*kern.ListType)
-		for i, filePathSpec := range list {
+		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) {
+	} else if kern.IsString(childValue) {
 		filePath, _ := childValue.(string)
-		v, err = EvalFile(ctx, filePath)
+		if v, err = EvalFile(ctx, filePath); err == nil {
+			count++
+		}
 	} else {
-		err = self.errIncompatibleType(childValue)
+		err = opTerm.errIncompatiblePrefixPostfixType(childValue)
 	}
-	if err == nil {
+	if err != nil {
-		v = count
+		//v = count
+		v = nil
 	}
 	return
 }

operator-index.go

@@ -4,6 +4,10 @@
 // operator-index.go
 package expr
 
+import (
+	"git.portale-stac.it/go-pkg/expr/kern"
+)
+
 // -------- index term
 func newIndexTerm(tk *Token) (inst *term) {
 	return &term{
@@ -15,15 +19,15 @@ func newIndexTerm(tk *Token) (inst *term) {
 	}
 }
 
-func verifyKey(indexTerm *term, indexList *ListType) (index any, err error) {
+func verifyKey(indexList *kern.ListType) (index any, err error) {
 	index = (*indexList)[0]
 	return
 }
 
-func verifyIndex(indexTerm *term, indexList *ListType, maxValue int) (index int, err error) {
+func verifyIndex(indexTerm *term, indexList *kern.ListType, maxValue int) (index int, err error) {
 	var v int
 
-	if v, err = ToInt((*indexList)[0], "index expression"); err == nil {
+	if v, err = kern.ToGoInt((*indexList)[0], "index expression"); err == nil {
 		if v < 0 && v >= -maxValue {
 			v = maxValue + v
 		}
@@ -36,11 +40,11 @@ func verifyIndex(indexTerm *term, indexList *ListType, maxValue int) (index int,
 	return
 }
 
-func verifyRange(indexTerm *term, indexList *ListType, maxValue int) (startIndex, endIndex int, err error) {
+func verifyRange(indexTerm *term, indexList *kern.ListType, maxValue int) (startIndex, endIndex int, err error) {
 	v, _ := ((*indexList)[0]).(*intPair)
 	startIndex = v.a
 	endIndex = v.b
-	if endIndex == ConstLastIndex {
+	if endIndex == kern.ConstLastIndex {
 		endIndex = maxValue
 	}
 	if startIndex < 0 && startIndex >= -maxValue {
@@ -59,27 +63,27 @@ func verifyRange(indexTerm *term, indexList *ListType, maxValue int) (startIndex
 	return
 }
 
-func evalIndex(ctx ExprContext, self *term) (v any, err error) {
+func evalIndex(ctx kern.ExprContext, opTerm *term) (v any, err error) {
 	var leftValue, rightValue any
-	var indexList *ListType
+	var indexList *kern.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 {
+	if indexList, ok = rightValue.(*kern.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")
 		return
 	}
 
-	if IsInteger((*indexList)[0]) {
+	if kern.IsInteger((*indexList)[0]) {
 		switch unboxedValue := leftValue.(type) {
-		case *ListType:
+		case *kern.ListType:
 			var index int
 			if index, err = verifyIndex(indexTerm, indexList, len(*unboxedValue)); err == nil {
 				v = (*unboxedValue)[index]
@@ -89,24 +93,17 @@ func evalIndex(ctx ExprContext, self *term) (v any, err error) {
 			if index, err = verifyIndex(indexTerm, indexList, len(unboxedValue)); err == nil {
 				v = string(unboxedValue[index])
 			}
-		case *DictType:
+		case *kern.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) {
-		case *ListType:
+		case *kern.ListType:
 			var start, end int
 			if start, end, err = verifyRange(indexTerm, indexList, len(*unboxedValue)); err == nil {
-				sublist := ListType((*unboxedValue)[start:end])
+				sublist := kern.ListType((*unboxedValue)[start:end])
 				v = &sublist
 			}
 		case string:
@@ -115,28 +112,23 @@ 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) {
+	} else if kern.IsDict(leftValue) {
-		d := leftValue.(*DictType)
+		d := leftValue.(*kern.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
 }
 
-func getDictItem(d *DictType, indexTerm *term, indexList *ListType, rightValue any) (v any, err error) {
+func getDictItem(d *kern.DictType, indexTerm *term, indexList *kern.ListType, rightValue any) (v any, err error) {
 	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

@@ -4,15 +4,19 @@
 // operator-insert.go
 package expr
 
-//-------- insert term
+import (
+	"git.portale-stac.it/go-pkg/expr/kern"
+)
 
-func newInsertTerm(tk *Token) (inst *term) {
+//-------- prepend term
+
+func newPrependTerm(tk *Token) (inst *term) {
 	return &term{
 		tk:       *tk,
 		children: make([]*term, 0, 2),
 		position: posInfix,
-		priority: priAssign,
+		priority: priInsert,
-		evalFunc: evalInsert,
+		evalFunc: evalPrepend,
 	}
 }
 
@@ -21,47 +25,47 @@ func newAppendTerm(tk *Token) (inst *term) {
 		tk:       *tk,
 		children: make([]*term, 0, 2),
 		position: posInfix,
-		priority: priAssign,
+		priority: priInsert,
 		evalFunc: evalAppend,
 	}
 }
 
-func evalInsert(ctx ExprContext, self *term) (v any, err error) {
+func evalPrepend(ctx kern.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
 	}
 
-	if IsList(rightValue) {
+	if kern.IsList(rightValue) {
-		list, _ := rightValue.(*ListType)
+		list, _ := rightValue.(*kern.ListType)
-		newList := append(ListType{leftValue}, *list...)
+		newList := append(kern.ListType{leftValue}, *list...)
 		v = &newList
-		if self.children[1].symbol() == SymVariable {
+		if opTerm.children[1].symbol() == SymVariable {
-			ctx.UnsafeSetVar(self.children[1].source(), v)
+			ctx.UnsafeSetVar(opTerm.children[1].Source(), v)
 		}
 	} else {
-		err = self.errIncompatibleTypes(leftValue, rightValue)
+		err = opTerm.errIncompatibleTypes(leftValue, rightValue)
 	}
 	return
 }
 
-func evalAppend(ctx ExprContext, self *term) (v any, err error) {
+func evalAppend(ctx kern.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
 	}
 
-	if IsList(leftValue) {
+	if kern.IsList(leftValue) {
-		list, _ := leftValue.(*ListType)
+		list, _ := leftValue.(*kern.ListType)
 		newList := append(*list, rightValue)
 		v = &newList
-		if self.children[0].symbol() == SymVariable {
+		if opTerm.children[0].symbol() == SymVariable {
-			ctx.UnsafeSetVar(self.children[0].source(), v)
+			ctx.UnsafeSetVar(opTerm.children[0].Source(), v)
 		}
 	} else {
-		err = self.errIncompatibleTypes(leftValue, rightValue)
+		err = opTerm.errIncompatibleTypes(leftValue, rightValue)
 	}
 	return
 }
@@ -86,6 +90,6 @@ func evalAppend(ctx ExprContext, self *term) (v any, err error) {
 
 // init
 func init() {
-	registerTermConstructor(SymInsert, newInsertTerm)
+	registerTermConstructor(SymPlusGreater, newPrependTerm)
-	registerTermConstructor(SymAppend, newAppendTerm)
+	registerTermConstructor(SymLessPlus, newAppendTerm)
 }

operator-iter-value.go

@@ -4,6 +4,10 @@
 // operator-iter-value.go
 package expr
 
+import (
+	"git.portale-stac.it/go-pkg/expr/kern"
+)
+
 //-------- iter value term
 
 func newIterValueTerm(tk *Token) (inst *term) {
@@ -11,27 +15,28 @@ func newIterValueTerm(tk *Token) (inst *term) {
 		tk:       *tk,
 		children: make([]*term, 0, 1),
 		position: posPrefix,
-		priority: priIterValue,
+		priority: priDereference,
 		evalFunc: evalIterValue,
 	}
 }
 
-func evalIterValue(ctx ExprContext, self *term) (v any, err error) {
+func evalIterValue(ctx kern.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 {
+	if it, ok := childValue.(kern.Iterator); ok {
 		v, err = it.Current()
 	} else {
-		err = self.errIncompatibleType(childValue)
+		err = opTerm.errIncompatiblePrefixPostfixType(childValue)
 	}
 	return
 }
 
 // init
 func init() {
-	registerTermConstructor(SymOpenClosedRound, newIterValueTerm)
+	//	registerTermConstructor(SymOpenClosedRound, newIterValueTerm)
+	registerTermConstructor(SymDereference, newIterValueTerm)
 }

operator-join.go

@@ -0,0 +1,67 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// operator-join.go
+package expr
+
+import (
+	"fmt"
+	"io"
+
+	"git.portale-stac.it/go-pkg/expr/kern"
+)
+
+//-------- join term
+
+func newJoinTerm(tk *Token) (inst *term) {
+	return &term{
+		tk:       *tk,
+		children: make([]*term, 0, 2),
+		position: posInfix,
+		priority: priIterOp,
+		evalFunc: evalJoin,
+	}
+}
+
+func evalJoin(ctx kern.ExprContext, opTerm *term) (v any, err error) {
+	var leftValue, rightValue any
+	var itLeft, itRight kern.Iterator
+	var item any
+
+	if err = opTerm.checkOperands(); err != nil {
+		return
+	}
+
+	if leftValue, err = opTerm.children[0].Compute(ctx); err != nil {
+		return
+	}
+
+	if rightValue, err = opTerm.children[1].Compute(ctx); err != nil {
+		return
+	}
+
+	if itLeft, err = NewIterator(leftValue); err != nil {
+		return nil, fmt.Errorf("left operand of JOIN must be an iterable data-source; got %s", kern.TypeName(leftValue))
+	}
+
+	if itRight, err = NewIterator(rightValue); err != nil {
+		return nil, fmt.Errorf("right operand of JOIN must be an iterable data-source; got %s", kern.TypeName(rightValue))
+	}
+
+	values := kern.NewListA()
+	for _, it := range []kern.Iterator{itLeft, itRight} {
+		for item, err = it.Next(); err == nil; item, err = it.Next() {
+			values.AppendItem(item)
+		}
+	}
+	if err == io.EOF {
+		err = nil
+	}
+	v = values
+	return
+}
+
+// init
+func init() {
+	registerTermConstructor(SymKwJoin, newJoinTerm)
+}

operator-length.go

@@ -4,6 +4,10 @@
 // operator-length.go
 package expr
 
+import (
+	"git.portale-stac.it/go-pkg/expr/kern"
+)
+
 //-------- length term
 
 func newLengthTerm(tk *Token) (inst *term) {
@@ -16,32 +20,32 @@ func newLengthTerm(tk *Token) (inst *term) {
 	}
 }
 
-func evalLength(ctx ExprContext, self *term) (v any, err error) {
+func evalLength(ctx kern.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 IsList(childValue) {
+	if kern.IsList(childValue) {
-		ls, _ := childValue.(*ListType)
+		ls, _ := childValue.(*kern.ListType)
 		v = int64(len(*ls))
-	} else if IsString(childValue) {
+	} else if kern.IsString(childValue) {
 		s, _ := childValue.(string)
 		v = int64(len(s))
-	} else if IsDict(childValue) {
+	} else if kern.IsDict(childValue) {
-		// m, _ := childValue.(map[any]any)
+		m, _ := childValue.(*kern.DictType)
-		m, _ := childValue.(*DictType)
 		v = int64(len(*m))
-	} else if it, ok := childValue.(Iterator); ok {
+	} else if it, ok := childValue.(kern.Iterator); ok {
-		if extIt, ok := childValue.(ExtIterator); ok && extIt.HasOperation(countName) {
+		v = int64(it.Count())
-			count, _ := extIt.CallOperation(countName, nil)
+		// if extIt, ok := childValue.(ExtIterator); ok && extIt.HasOperation(CountName) {
-			v, _ = ToInt(count, "")
+		// 	count, _ := extIt.CallOperation(CountName, nil)
-		} else {
+		// 	v, _ = ToGoInt(count, "")
-			v = int64(it.Index() + 1)
+		// } else {
-		}
+		// 	v = int64(it.Index() + 1)
+		// }
 	} else {
-		err = self.errIncompatibleType(childValue)
+		err = opTerm.errIncompatiblePrefixPostfixType(childValue)
 	}
 	return
 }

operator-map.go

@@ -0,0 +1,70 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// operator-map.go
+package expr
+
+import (
+	"fmt"
+	"io"
+
+	"git.portale-stac.it/go-pkg/expr/kern"
+)
+
+//-------- map term
+
+func newMapTerm(tk *Token) (inst *term) {
+	return &term{
+		tk:       *tk,
+		children: make([]*term, 0, 2),
+		position: posInfix,
+		priority: priIterOp,
+		evalFunc: evalMap,
+	}
+}
+
+func evalMap(ctx kern.ExprContext, opTerm *term) (v any, err error) {
+	var leftValue, rightValue any
+	var it kern.Iterator
+	var item any
+
+	if err = opTerm.checkOperands(); err != nil {
+		return
+	}
+
+	if leftValue, err = opTerm.children[0].Compute(ctx); err != nil {
+		return
+	}
+
+	if it, err = NewIterator(leftValue); err != nil {
+		return nil, fmt.Errorf("left operand of MAP must be an iterable data-source; got %s", kern.TypeName(leftValue))
+	}
+
+	values := kern.NewListA()
+	for item, err = it.Next(); err == nil; item, err = it.Next() {
+		ctx.SetVar("_", item)
+		ctx.SetVar("__", it.Index())
+		ctx.SetVar("_#", it.Count())
+		if rightValue, err = opTerm.children[1].Compute(ctx); err == nil {
+			values.AppendItem(rightValue)
+		}
+		ctx.DeleteVar("_#")
+		ctx.DeleteVar("__")
+		ctx.DeleteVar("_")
+		if err != nil {
+			break
+		}
+	}
+	if err == io.EOF {
+		err = nil
+	}
+	if err == nil {
+		v = values
+	}
+	return
+}
+
+// init
+func init() {
+	registerTermConstructor(SymKwMap, newMapTerm)
+}

operator-plugin.go

@@ -5,7 +5,7 @@
 package expr
 
 import (
-	"io"
+	"git.portale-stac.it/go-pkg/expr/kern"
 )
 
 //-------- plugin term
@@ -20,33 +20,15 @@ func newPluginTerm(tk *Token) (inst *term) {
 	}
 }
 
-func evalPlugin(ctx ExprContext, self *term) (v any, err error) {
+func evalPlugin(ctx kern.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)
+	if count, err = importPluginFromSearchPath(ctx, childValue); err == nil {
-	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 {
 		v = int64(count)
 	}
 	return

operator-post-inc-dec.go

@@ -0,0 +1,97 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// operator-post-inc-dec.go
+package expr
+
+import (
+	"git.portale-stac.it/go-pkg/expr/kern"
+)
+
+// -------- post increment term
+
+func newPostIncTerm(tk *Token) *term {
+	return &term{
+		tk:       *tk,
+		parent:   nil,
+		children: make([]*term, 0, 1),
+		position: posPostfix,
+		priority: priIncDec,
+		evalFunc: evalPostInc,
+	}
+}
+
+func evalPostInc(ctx kern.ExprContext, opTerm *term) (v any, err error) {
+	var childValue any
+	if childValue, err = opTerm.evalPrefix(ctx); err != nil {
+		return
+	}
+
+	if it, ok := childValue.(kern.Iterator); ok {
+		var namePrefix string
+		v, err = it.Next()
+
+		if opTerm.children[0].symbol() == SymVariable {
+			namePrefix = opTerm.children[0].Source()
+		}
+		ctx.UnsafeSetVar(namePrefix+"_index", it.Index())
+		if c, err1 := it.Current(); err1 == nil {
+			ctx.UnsafeSetVar(namePrefix+"_current", c)
+		}
+
+		if it.HasOperation(kern.KeyName) {
+			if k, err1 := it.CallOperation(kern.KeyName, nil); err1 == nil {
+				ctx.UnsafeSetVar(namePrefix+"_key", k)
+			}
+		}
+		if it.HasOperation(kern.ValueName) {
+			if v1, err1 := it.CallOperation(kern.ValueName, nil); err1 == nil {
+				ctx.UnsafeSetVar(namePrefix+"_value", v1)
+			}
+		}
+	} else if kern.IsInteger(childValue) && opTerm.children[0].symbol() == SymVariable {
+		v = childValue
+		i, _ := childValue.(int64)
+		ctx.SetVar(opTerm.children[0].Source(), i+1)
+	} else {
+		err = opTerm.errIncompatiblePrefixPostfixType(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 kern.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 kern.IsInteger(childValue) && opTerm.children[0].symbol() == SymVariable {
+		v = childValue
+		i, _ := childValue.(int64)
+		ctx.SetVar(opTerm.children[0].Source(), i-1)
+	} else {
+		err = opTerm.errIncompatiblePrefixPostfixType(childValue)
+	}
+	return
+}
+
+// init
+func init() {
+	registerTermConstructor(SymDoublePlus, newPostIncTerm)
+	registerTermConstructor(SymDoubleMinus, newPostDecTerm)
+}

operator-post-inc.go

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

operator-pre-inc-dec.go

@@ -0,0 +1,73 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// operator-pre-inc-dec.go
+package expr
+
+import (
+	"git.portale-stac.it/go-pkg/expr/kern"
+)
+
+// -------- pre increment term
+
+func newPreIncTerm(tk *Token) *term {
+	return &term{
+		tk:       *tk,
+		parent:   nil,
+		children: make([]*term, 0, 1),
+		position: posPrefix,
+		priority: priIncDec,
+		evalFunc: evalPreInc,
+	}
+}
+
+func evalPreInc(ctx kern.ExprContext, opTerm *term) (v any, err error) {
+	var childValue any
+	if childValue, err = opTerm.evalPrefix(ctx); err != nil {
+		return
+	}
+
+	if kern.IsInteger(childValue) && opTerm.children[0].symbol() == SymVariable {
+		i := childValue.(int64) + 1
+		ctx.SetVar(opTerm.children[0].Source(), i)
+		v = i
+	} else {
+		err = opTerm.errIncompatiblePrefixPostfixType(childValue)
+	}
+	return
+}
+
+// -------- pre decrement term
+
+func newPreDecTerm(tk *Token) *term {
+	return &term{
+		tk:       *tk,
+		parent:   nil,
+		children: make([]*term, 0, 1),
+		position: posPrefix,
+		priority: priIncDec,
+		evalFunc: evalPreDec,
+	}
+}
+
+func evalPreDec(ctx kern.ExprContext, opTerm *term) (v any, err error) {
+	var childValue any
+	if childValue, err = opTerm.evalPrefix(ctx); err != nil {
+		return
+	}
+
+	if kern.IsInteger(childValue) && opTerm.children[0].symbol() == SymVariable {
+		i := childValue.(int64) - 1
+		ctx.SetVar(opTerm.children[0].Source(), i)
+		v = i
+	} else {
+		err = opTerm.errIncompatiblePrefixPostfixType(childValue)
+	}
+	return
+}
+
+// init
+func init() {
+	registerTermConstructor(SymPreInc, newPreIncTerm)
+	registerTermConstructor(SymPreDec, newPreDecTerm)
+}

operator-prod.go

@@ -5,17 +5,16 @@
 package expr
 
 import (
-	"errors"
 	"strings"
+
+	"git.portale-stac.it/go-pkg/expr/kern"
 )
 
 //-------- multiply term
 
 func newMultiplyTerm(tk *Token) (inst *term) {
 	return &term{
-		tk: *tk,
+		tk:       *tk,
-		// class:    classOperator,
-		// kind:     kindUnknown,
 		children: make([]*term, 0, 2),
 		position: posInfix,
 		priority: priProduct,
@@ -23,40 +22,42 @@ func newMultiplyTerm(tk *Token) (inst *term) {
 	}
 }
 
-func evalMultiply(ctx ExprContext, self *term) (v any, err error) {
+func mulValues(opTerm *term, leftValue, rightValue any) (v any, err error) {
-	var leftValue, rightValue any
+	if kern.IsString(leftValue) && kern.IsInteger(rightValue) {
-
-	if leftValue, rightValue, err = self.evalInfix(ctx); err != nil {
-		return
-	}
-
-	if IsString(leftValue) && IsInteger(rightValue) {
 		s, _ := leftValue.(string)
 		n, _ := rightValue.(int64)
 		v = strings.Repeat(s, int(n))
-	} else if isNumOrFract(leftValue) && isNumOrFract(rightValue) {
+	} else if kern.IsNumOrFract(leftValue) && kern.IsNumOrFract(rightValue) {
-		if IsFloat(leftValue) || IsFloat(rightValue) {
+		if kern.IsFloat(leftValue) || kern.IsFloat(rightValue) {
-			v = numAsFloat(leftValue) * numAsFloat(rightValue)
+			v = kern.NumAsFloat(leftValue) * kern.NumAsFloat(rightValue)
-		} else if isFraction(leftValue) || isFraction(rightValue) {
+		} else if kern.IsFraction(leftValue) || kern.IsFraction(rightValue) {
-			v, err = mulAnyFract(leftValue, rightValue)
+			v, err = kern.MulAnyFract(leftValue, rightValue)
 		} else {
 			leftInt, _ := leftValue.(int64)
 			rightInt, _ := rightValue.(int64)
 			v = leftInt * rightInt
 		}
 	} else {
-		err = self.errIncompatibleTypes(leftValue, rightValue)
+		err = opTerm.errIncompatibleTypes(leftValue, rightValue)
 	}
 	return
 }
 
+func evalMultiply(ctx kern.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,
+		tk:       *tk,
-		// class:    classOperator,
-		// kind:     kindUnknown,
 		children: make([]*term, 0, 2),
 		position: posInfix,
 		priority: priProduct,
@@ -64,37 +65,66 @@ func newDivideTerm(tk *Token) (inst *term) {
 	}
 }
 
-func evalDivide(ctx ExprContext, self *term) (v any, err error) {
+func divValues(opTerm *term, leftValue, rightValue any) (v any, err error) {
-	var leftValue, rightValue any
+	if kern.IsNumOrFract(leftValue) && kern.IsNumOrFract(rightValue) {
-
+		if kern.IsFloat(leftValue) || kern.IsFloat(rightValue) {
-	if leftValue, rightValue, err = self.evalInfix(ctx); err != nil {
+			d := kern.NumAsFloat(rightValue)
-		return
-	}
-
-	if isNumOrFract(leftValue) && isNumOrFract(rightValue) {
-		if IsFloat(leftValue) || IsFloat(rightValue) {
-			d := numAsFloat(rightValue)
 			if d == 0.0 {
-				err = errors.New("division by zero")
+				err = opTerm.errDivisionByZero()
 			} else {
-				v = numAsFloat(leftValue) / d
+				v = kern.NumAsFloat(leftValue) / d
 			}
-		} else if isFraction(leftValue) || isFraction(rightValue) {
+		} else if kern.IsFraction(leftValue) || kern.IsFraction(rightValue) {
-			v, err = divAnyFract(leftValue, rightValue)
+			v, err = kern.DivAnyFract(leftValue, rightValue)
 		} else {
 			leftInt, _ := leftValue.(int64)
 			if rightInt, _ := rightValue.(int64); rightInt == 0 {
-				err = errors.New("division by zero")
+				err = opTerm.errDivisionByZero()
 			} else {
 				v = leftInt / rightInt
 			}
 		}
+	} else if kern.IsString(leftValue) && kern.IsString(rightValue) {
+		source := leftValue.(string)
+		sep := rightValue.(string)
+		v = kern.ListFromStrings(strings.Split(source, sep))
+	} else if kern.IsString(leftValue) && kern.IsInteger(rightValue) {
+		source := leftValue.(string)
+		partSize := int(rightValue.(int64))
+		if partSize == 0 {
+			err = opTerm.errDivisionByZero()
+		} else {
+			partCount := len(source) / partSize
+			remainder := len(source) % partSize
+			listSize := partCount
+			if remainder > 0 {
+				listSize++
+			}
+			parts := make([]any, 0, listSize)
+			for i := 0; i < partCount; i++ {
+				parts = append(parts, source[i*partSize:(i+1)*partSize])
+			}
+			if remainder > 0 {
+				parts = append(parts, source[len(source)-remainder:])
+			}
+			v = kern.NewList(parts)
+		}
 	} else {
-		err = self.errIncompatibleTypes(leftValue, rightValue)
+		err = opTerm.errIncompatibleTypes(leftValue, rightValue)
 	}
 	return
 }
 
+func evalDivide(ctx kern.ExprContext, opTerm *term) (v any, err error) {
+	var leftValue, rightValue any
+
+	if leftValue, rightValue, err = opTerm.evalInfix(ctx); err != nil {
+		return
+	}
+
+	return divValues(opTerm, leftValue, rightValue)
+}
+
 //-------- divide as float term
 
 func newDivideAsFloatTerm(tk *Token) (inst *term) {
@@ -107,65 +137,66 @@ func newDivideAsFloatTerm(tk *Token) (inst *term) {
 	}
 }
 
-func evalDivideAsFloat(ctx ExprContext, self *term) (v any, err error) {
+func evalDivideAsFloat(ctx kern.ExprContext, floatDivTerm *term) (v any, err error) {
 	var leftValue, rightValue any
 
-	if leftValue, rightValue, err = self.evalInfix(ctx); err != nil {
+	if leftValue, rightValue, err = floatDivTerm.evalInfix(ctx); err != nil {
 		return
 	}
 
-	if isNumOrFract(leftValue) && isNumOrFract(rightValue) {
+	if kern.IsNumOrFract(leftValue) && kern.IsNumOrFract(rightValue) {
-		d := numAsFloat(rightValue)
+		d := kern.NumAsFloat(rightValue)
 		if d == 0.0 {
-			err = errors.New("division by zero")
+			err = floatDivTerm.errDivisionByZero()
 		} else {
-			v = numAsFloat(leftValue) / d
+			v = kern.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,
+		tk:       *tk,
-		// class:    classOperator,
-		// kind:     kindUnknown,
 		children: make([]*term, 0, 2),
 		position: posInfix,
 		priority: priProduct,
-		evalFunc: evalReminder,
+		evalFunc: evalRemainder,
 	}
 }
-
+func remainderValues(opTerm *term, leftValue, rightValue any) (v any, err error) {
-func evalReminder(ctx ExprContext, self *term) (v any, err error) {
+	if kern.IsInteger(leftValue) && kern.IsInteger(rightValue) {
-	var leftValue, rightValue any
-
-	if leftValue, rightValue, err = self.evalInfix(ctx); err != nil {
-		return
-	}
-
-	if IsInteger(leftValue) && IsInteger(rightValue) {
 		rightInt, _ := rightValue.(int64)
 		if rightInt == 0 {
-			err = errors.New("division by zero")
+			err = opTerm.errDivisionByZero()
 		} else {
 			leftInt, _ := leftValue.(int64)
 			v = leftInt % rightInt
 		}
 	} else {
-		err = self.errIncompatibleTypes(leftValue, rightValue)
+		err = opTerm.errIncompatibleTypes(leftValue, rightValue)
 	}
 	return
 }
 
+func evalRemainder(ctx kern.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

@@ -4,7 +4,11 @@
 // operator-range.go
 package expr
 
-import "fmt"
+import (
+	"fmt"
+
+	"git.portale-stac.it/go-pkg/expr/kern"
+)
 
 // -------- range term
 type intPair struct {
@@ -12,10 +16,10 @@ type intPair struct {
 }
 
 func (p *intPair) TypeName() string {
-	return TypePair
+	return kern.TypePair
 }
 
-func (p *intPair) ToString(opt FmtOpt) string {
+func (p *intPair) ToString(opt kern.FmtOpt) string {
 	return fmt.Sprintf("(%d, %d)", p.a, p.b)
 }
 
@@ -34,25 +38,30 @@ 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 kern.ExprContext, opTerm *term) (v any, err error) {
 	var leftValue, rightValue any
 
-	// if err = self.checkOperands(); err != nil {
+	if len(opTerm.children) == 0 {
-	// 	return
-	// }
-	if len(self.children) == 0 {
 		leftValue = int64(0)
 		rightValue = int64(-1)
-	} else if len(self.children) == 1 {
+	} else if len(opTerm.children) == 1 {
-		if leftValue, err = self.children[0].compute(ctx); err != nil {
+		if leftValue, err = opTerm.children[0].Compute(ctx); err != nil {
 			return
 		}
-		rightValue = int64(ConstLastIndex)
+		rightValue = int64(kern.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)) {
+	if !(kern.IsInteger(leftValue) && kern.IsInteger(rightValue)) {
-		err = self.errIncompatibleTypes(leftValue, rightValue)
+		// err = opTerm.errIncompatibleTypes(leftValue, rightValue)
+		err = errRangeInvalidSpecification(opTerm)
 		return
 	}
 
@@ -63,7 +72,15 @@ 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

@@ -4,7 +4,11 @@
 // operator-rel.go
 package expr
 
-import "reflect"
+import (
+	"reflect"
+
+	"git.portale-stac.it/go-pkg/expr/kern"
+)
 
 //-------- equal term
 
@@ -18,25 +22,25 @@ func newEqualTerm(tk *Token) (inst *term) {
 	}
 }
 
-type deepFuncTemplate func(a, b any) (eq bool, err error)
+// type deepFuncTemplate func(a, b any) (eq bool, err error)
 
-func equals(a, b any, deepCmp deepFuncTemplate) (eq bool, err error) {
+func equals(a, b any, deepCmp kern.DeepFuncTemplate) (eq bool, err error) {
-	if isNumOrFract(a) && isNumOrFract(b) {
+	if kern.IsNumOrFract(a) && kern.IsNumOrFract(b) {
-		if IsNumber(a) && IsNumber(b) {
+		if kern.IsNumber(a) && kern.IsNumber(b) {
-			if IsInteger(a) && IsInteger(b) {
+			if kern.IsInteger(a) && kern.IsInteger(b) {
 				li, _ := a.(int64)
 				ri, _ := b.(int64)
 				eq = li == ri
 			} else {
-				eq = numAsFloat(a) == numAsFloat(b)
+				eq = kern.NumAsFloat(a) == kern.NumAsFloat(b)
 			}
 		} else {
 			var cmp int
-			if cmp, err = cmpAnyFract(a, b); err == nil {
+			if cmp, err = kern.CmpAnyFract(a, b); err == nil {
 				eq = cmp == 0
 			}
 		}
-	} else if deepCmp != nil && IsList(a) && IsList(b) {
+	} else if deepCmp != nil && kern.IsList(a) && kern.IsList(b) {
 		eq, err = deepCmp(a, b)
 	} else {
 		eq = reflect.DeepEqual(a, b)
@@ -45,10 +49,10 @@ 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 kern.ExprContext, opTerm *term) (v any, err error) {
 	var leftValue, rightValue any
 
-	if leftValue, rightValue, err = self.evalInfix(ctx); err != nil {
+	if leftValue, rightValue, err = opTerm.evalInfix(ctx); err != nil {
 		return
 	}
 
@@ -68,9 +72,9 @@ func newNotEqualTerm(tk *Token) (inst *term) {
 	}
 }
 
-func evalNotEqual(ctx ExprContext, self *term) (v any, err error) {
+func evalNotEqual(ctx kern.ExprContext, opTerm *term) (v any, err error) {
-	if v, err = evalEqual(ctx, self); err == nil {
+	if v, err = evalEqual(ctx, opTerm); err == nil {
-		b, _ := ToBool(v)
+		b, _ := kern.ToBool(v)
 		v = !b
 	}
 	return
@@ -89,43 +93,43 @@ func newLessTerm(tk *Token) (inst *term) {
 }
 
 func lessThan(self *term, a, b any) (isLess bool, err error) {
-	if isNumOrFract(a) && isNumOrFract(b) {
+	if kern.IsNumOrFract(a) && kern.IsNumOrFract(b) {
-		if IsNumber(a) && IsNumber(b) {
+		if kern.IsNumber(a) && kern.IsNumber(b) {
-			if IsInteger(a) && IsInteger(b) {
+			if kern.IsInteger(a) && kern.IsInteger(b) {
 				li, _ := a.(int64)
 				ri, _ := b.(int64)
 				isLess = li < ri
 			} else {
-				isLess = numAsFloat(a) < numAsFloat(b)
+				isLess = kern.NumAsFloat(a) < kern.NumAsFloat(b)
 			}
 		} else {
 			var cmp int
-			if cmp, err = cmpAnyFract(a, b); err == nil {
+			if cmp, err = kern.CmpAnyFract(a, b); err == nil {
 				isLess = cmp < 0
 			}
 		}
-	} else if IsString(a) && IsString(b) {
+	} else if kern.IsString(a) && kern.IsString(b) {
 		ls, _ := a.(string)
 		rs, _ := b.(string)
 		isLess = ls < rs
 		// Inclusion test
-	} else if IsList(a) && IsList(b) {
+	} else if kern.IsList(a) && kern.IsList(b) {
-		aList, _ := a.(*ListType)
+		aList, _ := a.(*kern.ListType)
-		bList, _ := b.(*ListType)
+		bList, _ := b.(*kern.ListType)
-		isLess = len(*aList) < len(*bList) && bList.contains(aList)
+		isLess = len(*aList) < len(*bList) && bList.Contains(aList)
 	} else {
 		err = self.errIncompatibleTypes(a, b)
 	}
 	return
 }
 
-func evalLess(ctx ExprContext, self *term) (v any, err error) {
+func evalLess(ctx kern.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
 }
 
@@ -144,8 +148,8 @@ func newLessEqualTerm(tk *Token) (inst *term) {
 func lessThanOrEqual(self *term, a, b any) (isLessEq bool, err error) {
 	if isLessEq, err = lessThan(self, a, b); err == nil {
 		if !isLessEq {
-			if IsList(a) && IsList(b) {
+			if kern.IsList(a) && kern.IsList(b) {
-				isLessEq, err = sameContent(a, b)
+				isLessEq, err = kern.SameContent(a, b)
 			} else {
 				isLessEq, err = equals(a, b, nil)
 			}
@@ -154,14 +158,14 @@ 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 kern.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 +182,14 @@ func newGreaterTerm(tk *Token) (inst *term) {
 	}
 }
 
-func evalGreater(ctx ExprContext, self *term) (v any, err error) {
+func evalGreater(ctx kern.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 +205,14 @@ func newGreaterEqualTerm(tk *Token) (inst *term) {
 	}
 }
 
-func evalGreaterEqual(ctx ExprContext, self *term) (v any, err error) {
+func evalGreaterEqual(ctx kern.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

@@ -4,6 +4,10 @@
 // operator-selector.go
 package expr
 
+import (
+	"git.portale-stac.it/go-pkg/expr/kern"
+)
+
 //-------- selector term
 
 func newSelectorTerm(tk *Token) (inst *term) {
@@ -16,19 +20,29 @@ func newSelectorTerm(tk *Token) (inst *term) {
 	}
 }
 
-func trySelectorCase(ctx ExprContext, exprValue, caseSel any, caseIndex int) (match bool, selectedValue any, err error) {
+func trySelectorCase(ctx kern.ExprContext, exprValue, caseSel any, caseIndex int) (match bool, selectedValue any, err error) {
 	caseData, _ := caseSel.(*selectorCase)
 	if caseData.filterList == nil {
 		selectedValue, err = caseData.caseExpr.Eval(ctx)
 		match = true
 	} else if filterList, ok := caseData.filterList.value().([]*term); ok {
-		if len(filterList) == 0 && exprValue == int64(caseIndex) {
+		if len(filterList) == 0 {
-			selectedValue, err = caseData.caseExpr.Eval(ctx)
+			var valueAsInt = int64(0)
-			match = true
+			if b, ok := exprValue.(bool); ok {
+				if !b {
+					valueAsInt = 1
+				}
+			} else if valueAsInt, ok = exprValue.(int64); !ok {
+				return
+			}
+			if valueAsInt == int64(caseIndex) {
+				selectedValue, err = caseData.caseExpr.Eval(ctx)
+				match = true
+			}
 		} else {
 			var caseValue any
 			for _, caseTerm := range filterList {
-				if caseValue, err = caseTerm.compute(ctx); err != nil || caseValue == exprValue {
+				if caseValue, err = caseTerm.Compute(ctx); err != nil || caseValue == exprValue {
 					selectedValue, err = caseData.caseExpr.Eval(ctx)
 					match = true
 					break
@@ -39,19 +53,19 @@ func trySelectorCase(ctx ExprContext, exprValue, caseSel any, caseIndex int) (ma
 	return
 }
 
-func evalSelector(ctx ExprContext, self *term) (v any, err error) {
+func evalSelector(ctx kern.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 {
+	if exprValue, err = exprTerm.Compute(ctx); err != nil {
 		return
 	}
 
-	caseListTerm := self.children[1]
+	caseListTerm := opTerm.children[1]
 	caseList, _ := caseListTerm.value().([]*term)
 	for i, caseTerm := range caseList {
 		caseSel := caseTerm.value()

operator-shift.go

@@ -0,0 +1,81 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// operator-shift.go
+package expr
+
+import (
+	"git.portale-stac.it/go-pkg/expr/kern"
+)
+
+//-------- bit right shift term
+
+func newRightShiftTerm(tk *Token) (inst *term) {
+	return &term{
+		tk:       *tk,
+		children: make([]*term, 0, 2),
+		position: posInfix,
+		priority: priBinShift,
+		evalFunc: evalRightShift,
+	}
+}
+
+func bitRightShift(opTerm *term, leftValue, rightValue any) (v any, err error) {
+	if kern.IsInteger(leftValue) && kern.IsInteger(rightValue) {
+		leftInt := leftValue.(int64)
+		rightInt := rightValue.(int64)
+		v = leftInt >> rightInt
+	} else {
+		err = opTerm.errIncompatibleTypes(leftValue, rightValue)
+	}
+	return
+}
+
+func evalRightShift(ctx kern.ExprContext, opTerm *term) (v any, err error) {
+	var leftValue, rightValue any
+
+	if leftValue, rightValue, err = opTerm.evalInfix(ctx); err != nil {
+		return
+	}
+
+	v, err = bitRightShift(opTerm, leftValue, rightValue)
+	return
+}
+
+func newLeftShiftTerm(tk *Token) (inst *term) {
+	return &term{
+		tk:       *tk,
+		children: make([]*term, 0, 2),
+		position: posInfix,
+		priority: priBinShift,
+		evalFunc: evalLeftShift,
+	}
+}
+
+func bitLeftShift(opTerm *term, leftValue, rightValue any) (v any, err error) {
+	if kern.IsInteger(leftValue) && kern.IsInteger(rightValue) {
+		leftInt := leftValue.(int64)
+		rightInt := rightValue.(int64)
+		v = leftInt << rightInt
+	} else {
+		err = opTerm.errIncompatibleTypes(leftValue, rightValue)
+	}
+	return
+}
+
+func evalLeftShift(ctx kern.ExprContext, opTerm *term) (v any, err error) {
+	var leftValue, rightValue any
+
+	if leftValue, rightValue, err = opTerm.evalInfix(ctx); err != nil {
+		return
+	}
+
+	v, err = bitLeftShift(opTerm, leftValue, rightValue)
+	return
+}
+
+// init
+func init() {
+	registerTermConstructor(SymDoubleGreater, newRightShiftTerm)
+	registerTermConstructor(SymDoubleLess, newLeftShiftTerm)
+}

operator-sign.go

@@ -4,6 +4,10 @@
 // operator-sign.go
 package expr
 
+import (
+	"git.portale-stac.it/go-pkg/expr/kern"
+)
+
 //-------- plus sign term
 
 func newPlusSignTerm(tk *Token) (inst *term) {
@@ -28,29 +32,29 @@ func newMinusSignTerm(tk *Token) (inst *term) {
 	}
 }
 
-func evalSign(ctx ExprContext, self *term) (v any, err error) {
+func evalSign(ctx kern.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 kern.IsFloat(rightValue) {
-		if self.tk.Sym == SymChangeSign {
+		if opTerm.tk.Sym == SymChangeSign {
 			f, _ := rightValue.(float64)
 			v = -f
 		} else {
 			v = rightValue
 		}
-	} else if IsInteger(rightValue) {
+	} else if kern.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.errIncompatiblePrefixPostfixType(rightValue)
 	}
 	return
 }

operator-sum.go

@@ -7,6 +7,8 @@ package expr
 import (
 	"fmt"
 	"slices"
+
+	"git.portale-stac.it/go-pkg/expr/kern"
 )
 
 //-------- plus term
@@ -21,52 +23,54 @@ func newPlusTerm(tk *Token) (inst *term) {
 	}
 }
 
-func evalPlus(ctx ExprContext, self *term) (v any, err error) {
+func sumValues(plusTerm *term, leftValue, rightValue any) (v any, err error) {
-	var leftValue, rightValue any
+	if (kern.IsString(leftValue) && kern.IsNumberString(rightValue)) || (kern.IsString(rightValue) && kern.IsNumberString(leftValue)) {
-
-	if leftValue, rightValue, err = self.evalInfix(ctx); err != nil {
-		return
-	}
-
-	if (IsString(leftValue) && isNumberString(rightValue)) || (IsString(rightValue) && isNumberString(leftValue)) {
 		v = fmt.Sprintf("%v%v", leftValue, rightValue)
-	} else if IsNumber(leftValue) && IsNumber(rightValue) {
+	} else if kern.IsNumber(leftValue) && kern.IsNumber(rightValue) {
-		if IsFloat(leftValue) || IsFloat(rightValue) {
+		if kern.IsFloat(leftValue) || kern.IsFloat(rightValue) {
-			v = numAsFloat(leftValue) + numAsFloat(rightValue)
+			v = kern.NumAsFloat(leftValue) + kern.NumAsFloat(rightValue)
 		} else {
 			leftInt, _ := leftValue.(int64)
 			rightInt, _ := rightValue.(int64)
 			v = leftInt + rightInt
 		}
-	} else if IsList(leftValue) && IsList(rightValue) {
+	} else if kern.IsList(leftValue) && kern.IsList(rightValue) {
-		var leftList, rightList *ListType
+		var leftList, rightList *kern.ListType
-		leftList, _ = leftValue.(*ListType)
+		leftList, _ = leftValue.(*kern.ListType)
-		rightList, _ = rightValue.(*ListType)
+		rightList, _ = rightValue.(*kern.ListType)
 
-		sumList := make(ListType, 0, len(*leftList)+len(*rightList))
+		sumList := make(kern.ListType, 0, len(*leftList)+len(*rightList))
-		for _, item := range *leftList {
+		sumList = append(sumList, *leftList...)
-			sumList = append(sumList, item)
+		sumList = append(sumList, *rightList...)
-		}
-		for _, item := range *rightList {
-			sumList = append(sumList, item)
-		}
 		v = &sumList
-	} else if (isFraction(leftValue) && IsNumber(rightValue)) || (isFraction(rightValue) && IsNumber(leftValue)) {
+	} else if (kern.IsFraction(leftValue) && kern.IsNumber(rightValue)) || (kern.IsFraction(rightValue) && kern.IsNumber(leftValue)) {
-		if IsFloat(leftValue) || IsFloat(rightValue) {
+		if kern.IsFloat(leftValue) || kern.IsFloat(rightValue) {
-			v = numAsFloat(leftValue) + numAsFloat(rightValue)
+			v = kern.NumAsFloat(leftValue) + kern.NumAsFloat(rightValue)
 		} else {
-			v, err = sumAnyFract(leftValue, rightValue)
+			v, err = kern.SumAnyFract(leftValue, rightValue)
 		}
-	} else if IsDict(leftValue) && IsDict(rightValue) {
+	} else if kern.IsDict(leftValue) && kern.IsDict(rightValue) {
-		leftDict, _ := leftValue.(*DictType)
+		leftDict, _ := leftValue.(*kern.DictType)
-		rightDict, _ := rightValue.(*DictType)
+		rightDict, _ := rightValue.(*kern.DictType)
-		c := leftDict.clone()
+		c := leftDict.Clone()
-		c.merge(rightDict)
+		c.Merge(rightDict)
 		v = c
+	} else if kern.IsFraction(leftValue) && kern.IsFraction(rightValue) {
+		v, err = kern.SumAnyFract(leftValue, rightValue)
 	} else {
-		err = self.errIncompatibleTypes(leftValue, rightValue)
+		err = plusTerm.errIncompatibleTypes(leftValue, rightValue)
 	}
-	return
+	return v, err
+}
+
+func evalPlus(ctx kern.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
@@ -81,27 +85,21 @@ func newMinusTerm(tk *Token) (inst *term) {
 	}
 }
 
-func evalMinus(ctx ExprContext, self *term) (v any, err error) {
+func diffValues(minusTerm *term, leftValue, rightValue any) (v any, err error) {
-	var leftValue, rightValue any
+	if kern.IsNumOrFract(leftValue) && kern.IsNumOrFract(rightValue) {
-
+		if kern.IsFloat(leftValue) || kern.IsFloat(rightValue) {
-	if leftValue, rightValue, err = self.evalInfix(ctx); err != nil {
+			v = kern.NumAsFloat(leftValue) - kern.NumAsFloat(rightValue)
-		return
+		} else if kern.IsFraction(leftValue) || kern.IsFraction(rightValue) {
-	}
+			v, err = kern.SubAnyFract(leftValue, rightValue)
-
-	if isNumOrFract(leftValue) && isNumOrFract(rightValue) {
-		if IsFloat(leftValue) || IsFloat(rightValue) {
-			v = numAsFloat(leftValue) - numAsFloat(rightValue)
-		} else if isFraction(leftValue) || isFraction(rightValue) {
-			v, err = subAnyFract(leftValue, rightValue)
 		} else {
 			leftInt, _ := leftValue.(int64)
 			rightInt, _ := rightValue.(int64)
 			v = leftInt - rightInt
 		}
-	} else if IsList(leftValue) && IsList(rightValue) {
+	} else if kern.IsList(leftValue) && kern.IsList(rightValue) {
-		leftList, _ := leftValue.(*ListType)
+		leftList, _ := leftValue.(*kern.ListType)
-		rightList, _ := rightValue.(*ListType)
+		rightList, _ := rightValue.(*kern.ListType)
-		diffList := make(ListType, 0, len(*leftList)-len(*rightList))
+		diffList := make(kern.ListType, 0, len(*leftList)-len(*rightList))
 		for _, item := range *leftList {
 			if slices.Index(*rightList, item) < 0 {
 				diffList = append(diffList, item)
@@ -109,11 +107,21 @@ 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 kern.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 +1,73 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// operator-unset.go
+package expr
+
+import (
+	"strings"
+
+	"git.portale-stac.it/go-pkg/expr/kern"
+)
+
+//-------- 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 kern.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.errIncompatiblePrefixPostfixType(item)
+	}
+	return
+}
+
+func evalUnset(ctx kern.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 kern.IsList(childValue) {
+		list, _ := childValue.(*kern.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)
+}