first ecli commit

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

@@ -1,130 +0,0 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
-// All rights reserved.
-
-// ast.go
-package expr
-
-import (
-	"strings"
-)
-
-//-------- ast
-
-type ast struct {
-	forest []*term
-	root   *term
-}
-
-func NewAst() *ast {
-	return &ast{}
-}
-
-func (expr *ast) TypeName() string {
-	return "Expression"
-}
-
-func (expr *ast) ToForest() {
-	if expr.root != nil {
-		if expr.forest == nil {
-			expr.forest = make([]*term, 0)
-		}
-		expr.forest = append(expr.forest, expr.root)
-		expr.root = nil
-	}
-}
-
-func (expr *ast) String() string {
-	var sb strings.Builder
-	if expr.root == nil {
-		sb.WriteString("(nil)")
-	} else {
-		expr.root.toString(&sb)
-	}
-	return sb.String()
-}
-
-func (expr *ast) addTokens(tokens ...*Token) (err error) {
-	for _, tk := range tokens {
-		if _, err = expr.addToken(tk); err != nil {
-			break
-		}
-	}
-	return
-}
-
-// func (expr *ast) addToken(tk *Token) (err error) {
-// 	_, err = expr.addToken2(tk)
-// 	return
-// }
-
-func (expr *ast) addToken(tk *Token) (t *term, err error) {
-	if t = newTerm(tk); t != nil {
-		err = expr.addTerm(t)
-	} else {
-		err = tk.Errorf("unexpected token %q", tk.String())
-	}
-	return
-}
-
-func (expr *ast) addTerm(node *term) (err error) {
-	if expr.root == nil {
-		expr.root = node
-	} else {
-		expr.root, err = expr.insert(expr.root, node)
-	}
-	return
-}
-
-func (expr *ast) insert(tree, node *term) (root *term, err error) {
-	if tree.getPriority() < node.getPriority() {
-		root = tree
-		if tree.isComplete() {
-			var subRoot *term
-			last := tree.removeLastChild()
-			if subRoot, err = expr.insert(last, node); err == nil {
-				subRoot.setParent(tree)
-			}
-		} else {
-			node.setParent(tree)
-		}
-	} else if !node.isLeaf() {
-		root = node
-		tree.setParent(node)
-	} else {
-		err = node.Errorf("two adjacent operators: %q and %q", tree, node)
-	}
-	return
-}
-
-func (expr *ast) Finish() {
-	if expr.root == nil && expr.forest != nil && len(expr.forest) >= 1 {
-		expr.root = expr.forest[len(expr.forest)-1]
-		expr.forest = expr.forest[0 : len(expr.forest)-1]
-	}
-}
-
-func (expr *ast) Eval(ctx ExprContext) (result any, err error) {
-	expr.Finish()
-
-	if expr.root != nil {
-		// initDefaultVars(ctx)
-		if expr.forest != nil {
-			for _, root := range expr.forest {
-				if result, err = root.compute(ctx); err == nil {
-					ctx.UnsafeSetVar(ControlLastResult, result)
-				} else {
-					//err = fmt.Errorf("error in expression nr %d: %v", i+1, err)
-					break
-				}
-			}
-		}
-		if err == nil {
-			if result, err = expr.root.compute(ctx); err == nil {
-				ctx.UnsafeSetVar(ControlLastResult, result)
-			}
-		}
-		// } else {
-		// 	err = errors.New("empty expression")
-	}
-	return
-}

bind-expr-functions.go

@@ -1,23 +1,27 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
 // All rights reserved.
 
 // 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
+	expr   kern.Expr
-	defCtx ExprContext
+	defCtx kern.ExprContext
 }
 
-func (functor *exprFunctor) GetParams() (params []ExprFuncParam) {
+func (functor *exprFunctor) GetParams() (params []kern.ExprFuncParam) {
 	return functor.params
 }
 
-func newExprFunctor(e Expr, params []ExprFuncParam, ctx ExprContext) *exprFunctor {
+func newExprFunctor(e kern.Expr, params []kern.ExprFuncParam, ctx kern.ExprContext) *exprFunctor {
-	var defCtx ExprContext
+	var defCtx kern.ExprContext
 	if ctx != nil {
 		defCtx = ctx
 	}
@@ -28,17 +32,17 @@ func (functor *exprFunctor) TypeName() string {
 	return "ExprFunctor"
 }
 
-func (functor *exprFunctor) GetDefinitionContext() ExprContext {
+func (functor *exprFunctor) GetDefinitionContext() kern.ExprContext {
 	return functor.defCtx
 }
 
-func (functor *exprFunctor) InvokeNamed(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+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.(Functor); ok {
+			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)
 			}
@@ -51,7 +55,7 @@ func (functor *exprFunctor) InvokeNamed(ctx ExprContext, name string, args map[s
 		}
 	}
 	if missing != nil {
-		err = ErrMissingParams(name, missing)
+		err = kern.ErrMissingParams(name, missing)
 	} else {
 		result, err = functor.expr.Eval(ctx)
 	}

bind-go-functions.go

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

builtin-base.go

@@ -1,4 +1,4 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
 // All rights reserved.
 
 // builtin-base.go
@@ -9,77 +9,84 @@ import (
 	"math"
 	"strconv"
 	"strings"
+
+	"git.portale-stac.it/go-pkg/expr/kern"
+	"git.portale-stac.it/go-pkg/expr/scan"
 )
 
 const (
 	ParamDenominator = "denominator"
 )
 
-func isNilFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+func isNilFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
-	result = args[ParamValue] == nil
+	result = args[kern.ParamValue] == nil
 	return
 }
 
-func isIntFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+func isIntFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
-	result = IsInteger(args[ParamValue])
+	result = kern.IsInteger(args[kern.ParamValue])
 	return
 }
 
-func isFloatFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+func isFloatFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
-	result = IsFloat(args[ParamValue])
+	result = kern.IsFloat(args[kern.ParamValue])
 	return
 }
 
-func isBoolFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+func isBoolFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
-	result = IsBool(args[ParamValue])
+	result = kern.IsBool(args[kern.ParamValue])
 	return
 }
 
-func isStringFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+func isStringFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
-	result = IsString(args[ParamValue])
+	result = kern.IsString(args[kern.ParamValue])
 	return
 }
 
-func isFractionFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+func isFractionFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
-	result = IsFract(args[ParamValue])
+	result = kern.IsFraction(args[kern.ParamValue])
 	return
 }
 
-func isRationalFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+func isRationalFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
-	result = IsRational(args[ParamValue])
+	result = kern.IsRational(args[kern.ParamValue])
 	return
 }
 
-func isListFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+func isListFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
-	result = IsList(args[ParamValue])
+	result = kern.IsList(args[kern.ParamValue])
 	return
 }
 
-func isDictionaryFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+func isDictionaryFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
-	result = IsDict(args[ParamValue])
+	result = kern.IsDict(args[kern.ParamValue])
 	return
 }
 
-func boolFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+func boolFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
-	switch v := args[ParamValue].(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 map[string]any) (result any, err error) {
+func intFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
-	switch v := args[ParamValue].(type) {
+	switch v := args[kern.ParamValue].(type) {
 	case int64:
 		result = v
 	case float64:
@@ -95,14 +102,16 @@ func intFunc(ctx ExprContext, name string, args map[string]any) (result any, err
 		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 map[string]any) (result any, err error) {
+func decFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
-	switch v := args[ParamValue].(type) {
+	switch v := args[kern.ParamValue].(type) {
 	case int64:
 		result = float64(v)
 	case float64:
@@ -118,16 +127,16 @@ func decFunc(ctx ExprContext, name string, args map[string]any) (result any, err
 		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 stringFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+func stringFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
-	switch v := args[ParamValue].(type) {
+	switch v := args[kern.ParamValue].(type) {
 	case int64:
 		result = strconv.FormatInt(v, 10)
 	case float64:
@@ -140,129 +149,188 @@ func stringFunc(ctx ExprContext, name string, args map[string]any) (result any,
 		}
 	case string:
 		result = v
-	case *FractionType:
+	case *kern.FractionType:
 		result = v.ToString(0)
-	case Formatter:
+	case kern.Formatter:
 		result = v.ToString(0)
 	case fmt.Stringer:
 		result = v.String()
 	default:
-		err = ErrCantConvert(name, v, "string")
+		err = kern.ErrCantConvert(name, v, "string")
 	}
 	return
 }
 
-func fractFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+func fractFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
-	switch v := args[ParamValue].(type) {
+	switch v := args[kern.ParamValue].(type) {
 	case int64:
 		var den int64 = 1
 
 		var ok bool
 		if den, ok = args[ParamDenominator].(int64); !ok {
-			err = ErrExpectedGot(name, "integer", args[ParamDenominator])
+			err = kern.ErrExpectedGot(name, "integer", args[ParamDenominator])
 		} else if den == 0 {
-			err = ErrFuncDivisionByZero(name)
+			err = kern.ErrFuncDivisionByZero(name)
 		}
 
 		if err == nil {
-			result = newFraction(v, den)
+			result = kern.NewFraction(v, den)
 		}
 	case float64:
-		result, err = float64ToFraction(v)
+		result, err = kern.Float64ToFraction(v)
 	case bool:
 		if v {
-			result = newFraction(1, 1)
+			result = kern.NewFraction(1, 1)
 		} else {
-			result = newFraction(0, 1)
+			result = kern.NewFraction(0, 1)
 		}
 	case string:
-		result, err = makeGeneratingFraction(v)
+		result, err = kern.MakeGeneratingFraction(v)
-	case *FractionType:
+	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 ExprContext, name string, args map[string]any) (result any, err error) {
+func evalFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
-	if source, ok := args[ParamSource].(string); ok {
+	if source, ok := args[kern.ParamSource].(string); ok {
-		var expr Expr
+		var ast kern.Expr
 
 		parser := NewParser()
 		if ctx == nil {
-			ctx = NewSimpleStore()
+			ctx = NewSimpleStoreWithoutGlobalContext()
 		}
 
 		r := strings.NewReader(source)
-		scanner := NewScanner(r, DefaultTranslations())
+		scanner := scan.NewScanner(r, scan.DefaultTranslations())
 
-		if expr, err = parser.Parse(scanner); err == nil {
+		if ast, err = parser.Parse(scanner); err == nil {
-			CtrlEnable(ctx, control_export_all)
+			CtrlEnable(ctx, kern.ControlExportAll)
-			result, err = expr.Eval(ctx)
+			result, err = ast.Eval(ctx)
 		}
 	} else {
-		err = ErrWrongParamType(name, ParamSource, TypeString, args[ParamSource])
+		err = kern.ErrWrongParamType(name, kern.ParamSource, kern.TypeString, args[kern.ParamSource])
 	}
 	return
 }
 
-func varFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+func varFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
 	var varName string
 	var ok bool
 
-	if varName, ok = args[ParamName].(string); !ok {
+	if varName, ok = args[kern.ParamName].(string); !ok {
-		return nil, ErrWrongParamType(name, ParamName, TypeString, args[ParamName])
+		return nil, kern.ErrWrongParamType(name, kern.ParamName, kern.TypeString, args[kern.ParamName])
 	}
 
-	if result, ok = args[ParamValue]; ok && result != nil {
+	if result, ok = args[kern.ParamValue]; ok && result != nil {
 		ctx.GetParent().UnsafeSetVar(varName, result)
 		// } else {
-		// 	err = ErrWrongParamType(name, ParamSource, TypeString, args[ParamSource])
+		// 	err = expr.ErrWrongParamType(name, expr.ParamSource, expr.TypeString, args[expr.ParamSource])
 		// }
 	} else if result, ok = ctx.GetVar(varName); !ok {
-		err = ErrUnknownVar(name, varName)
+		err = kern.ErrUnknownVar(name, varName)
 	}
 	return
 }
 
+func setFunc(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])
+	}
+
+	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 charFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
+	var ord int
+
+	if n, ok := args[kern.ParamValue].(byte); ok {
+		ord = int(n)
+	} else if n, ok := args[kern.ParamValue].(int64); ok {
+		ord = int(n)
+	} else if n, ok := args[kern.ParamValue].(int); ok {
+		ord = n
+	} else {
+		return nil, kern.ErrWrongParamType(name, kern.ParamName, kern.TypeString, args[kern.ParamName])
+	}
+	if ord < 0 || ord > 255 {
+		err = kern.ErrFuncInvalidArg(name, fmt.Sprintf("character code must be in range 0-255, got %d", ord))
+	} else {
+		result = string(rune(ord))
+	}
+	return
+}
+
+func seqFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
+	list := kern.NewLinkedList()
+	items := args[kern.ParamValue].([]any)
+	for _, arg := range items {
+		list.PushBack(arg)
+	}
+	result = list
+	return
+}
+
 //// import
 
-func ImportBuiltinsFuncs(ctx ExprContext) {
+func ImportBuiltinsFuncs(ctx kern.ExprContext) {
-	anyParams := []ExprFuncParam{
+	anyParams := []kern.ExprFuncParam{
-		NewFuncParam(ParamValue),
+		kern.NewFuncParam(kern.ParamValue),
 	}
 
-	ctx.RegisterFunc("isNil", NewGolangFunctor(isNilFunc), TypeBoolean, anyParams)
+	ctx.RegisterFunc("isNil", kern.NewGolangFunctor(isNilFunc), kern.TypeBoolean, anyParams)
-	ctx.RegisterFunc("isInt", NewGolangFunctor(isIntFunc), TypeBoolean, anyParams)
+	ctx.RegisterFunc("isInt", kern.NewGolangFunctor(isIntFunc), kern.TypeBoolean, anyParams)
-	ctx.RegisterFunc("isFloat", NewGolangFunctor(isFloatFunc), TypeBoolean, anyParams)
+	ctx.RegisterFunc("isFloat", kern.NewGolangFunctor(isFloatFunc), kern.TypeBoolean, anyParams)
-	ctx.RegisterFunc("isBool", NewGolangFunctor(isBoolFunc), TypeBoolean, anyParams)
+	ctx.RegisterFunc("isBool", kern.NewGolangFunctor(isBoolFunc), kern.TypeBoolean, anyParams)
-	ctx.RegisterFunc("isString", NewGolangFunctor(isStringFunc), TypeBoolean, anyParams)
+	ctx.RegisterFunc("isString", kern.NewGolangFunctor(isStringFunc), kern.TypeBoolean, anyParams)
-	ctx.RegisterFunc("isFract", NewGolangFunctor(isFractionFunc), TypeBoolean, anyParams)
+	ctx.RegisterFunc("isFract", kern.NewGolangFunctor(isFractionFunc), kern.TypeBoolean, anyParams)
-	ctx.RegisterFunc("isRational", NewGolangFunctor(isRationalFunc), TypeBoolean, anyParams)
+	ctx.RegisterFunc("isRational", kern.NewGolangFunctor(isRationalFunc), kern.TypeBoolean, anyParams)
-	ctx.RegisterFunc("isList", NewGolangFunctor(isListFunc), TypeBoolean, anyParams)
+	ctx.RegisterFunc("isList", kern.NewGolangFunctor(isListFunc), kern.TypeBoolean, anyParams)
-	ctx.RegisterFunc("isDict", NewGolangFunctor(isDictionaryFunc), TypeBoolean, anyParams)
+	ctx.RegisterFunc("isDict", kern.NewGolangFunctor(isDictionaryFunc), kern.TypeBoolean, anyParams)
 
-	ctx.RegisterFunc("bool", NewGolangFunctor(boolFunc), TypeBoolean, anyParams)
+	ctx.RegisterFunc("bool", kern.NewGolangFunctor(boolFunc), kern.TypeBoolean, anyParams)
-	ctx.RegisterFunc("int", NewGolangFunctor(intFunc), TypeInt, anyParams)
+	ctx.RegisterFunc("int", kern.NewGolangFunctor(intFunc), kern.TypeInt, anyParams)
-	ctx.RegisterFunc("dec", NewGolangFunctor(decFunc), TypeFloat, anyParams)
+	ctx.RegisterFunc("dec", kern.NewGolangFunctor(decFunc), kern.TypeFloat, anyParams)
-	ctx.RegisterFunc("string", NewGolangFunctor(stringFunc), TypeString, anyParams)
+	ctx.RegisterFunc("string", kern.NewGolangFunctor(stringFunc), kern.TypeString, anyParams)
-	ctx.RegisterFunc("fract", NewGolangFunctor(fractFunc), TypeFraction, []ExprFuncParam{
+	ctx.RegisterFunc("fract", kern.NewGolangFunctor(fractFunc), kern.TypeFraction, []kern.ExprFuncParam{
-		NewFuncParam(ParamValue),
+		kern.NewFuncParam(kern.ParamValue),
-		NewFuncParamFlagDef(ParamDenominator, PfDefault, int64(1)),
+		kern.NewFuncParamFlagDef(ParamDenominator, kern.PfDefault, int64(1)),
 	})
 
-	ctx.RegisterFunc("eval", NewGolangFunctor(evalFunc), TypeAny, []ExprFuncParam{
+	ctx.RegisterFunc("eval", kern.NewGolangFunctor(evalFunc), kern.TypeAny, []kern.ExprFuncParam{
-		NewFuncParam(ParamSource),
+		kern.NewFuncParam(kern.ParamSource),
 	})
 
-	ctx.RegisterFunc("var", NewGolangFunctor(varFunc), TypeAny, []ExprFuncParam{
+	ctx.RegisterFunc("var", kern.NewGolangFunctor(varFunc), kern.TypeAny, []kern.ExprFuncParam{
-		NewFuncParam(ParamName),
+		kern.NewFuncParam(kern.ParamName),
-		NewFuncParamFlagDef(ParamValue, PfDefault, nil),
+		kern.NewFuncParamFlagDef(kern.ParamValue, kern.PfDefault, nil),
+	})
+
+	ctx.RegisterFunc("set", kern.NewGolangFunctor(setFunc), kern.TypeAny, []kern.ExprFuncParam{
+		kern.NewFuncParam(kern.ParamName),
+		kern.NewFuncParam(kern.ParamValue),
+	})
+
+	ctx.RegisterFunc("char", kern.NewGolangFunctor(charFunc), kern.TypeString, []kern.ExprFuncParam{
+		kern.NewFuncParam(kern.ParamValue),
+	})
+
+	ctx.RegisterFunc("seq", kern.NewGolangFunctor(seqFunc), kern.TypeLinkedList, []kern.ExprFuncParam{
+		kern.NewFuncParamFlag(kern.ParamValue, kern.PfRepeat),
 	})
 }
 

builtin-fmt.go

@@ -1,4 +1,4 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
 // All rights reserved.
 
 // builtin-fmt.go
@@ -8,11 +8,13 @@ import (
 	"fmt"
 	"io"
 	"os"
+
+	"git.portale-stac.it/go-pkg/expr/kern"
 )
 
-func getStdout(ctx ExprContext) io.Writer {
+func getStdout(ctx kern.ExprContext) io.Writer {
 	var w io.Writer
-	if wany, exists := ctx.GetVar(ControlStdout); exists && wany != nil {
+	if wany, exists := ctx.GetVar(kern.ControlStdout); exists && wany != nil {
 		w, _ = wany.(io.Writer)
 	}
 	if w == nil {
@@ -21,9 +23,9 @@ func getStdout(ctx ExprContext) io.Writer {
 	return w
 }
 
-func printFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+func printFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
 	var n int = 0
-	if v, exists := args[ParamItem]; exists && v != nil {
+	if v, exists := args[kern.ParamItem]; exists && v != nil {
 		argv := v.([]any)
 		n, err = fmt.Fprint(getStdout(ctx), argv...)
 	}
@@ -31,9 +33,9 @@ func printFunc(ctx ExprContext, name string, args map[string]any) (result any, e
 	return
 }
 
-func printLnFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+func printLnFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
 	var n int = 0
-	if v, exists := args[ParamItem]; exists && v != nil {
+	if v, exists := args[kern.ParamItem]; exists && v != nil {
 		argv := v.([]any)
 		n, err = fmt.Fprintln(getStdout(ctx), argv...)
 	} else {
@@ -43,12 +45,12 @@ func printLnFunc(ctx ExprContext, name string, args map[string]any) (result any,
 	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),
+		kern.NewFuncParamFlag(kern.ParamItem, kern.PfRepeat),
 	})
-	ctx.RegisterFunc("println", NewGolangFunctor(printLnFunc), TypeInt, []ExprFuncParam{
+	ctx.RegisterFunc("println", kern.NewGolangFunctor(printLnFunc), kern.TypeInt, []kern.ExprFuncParam{
-		NewFuncParamFlag(ParamItem, PfRepeat),
+		kern.NewFuncParamFlag(kern.ParamItem, kern.PfRepeat),
 	})
 }
 

builtin-import.go

@@ -1,4 +1,4 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
 // All rights reserved.
 
 // builtin-import.go
@@ -7,32 +7,35 @@ package expr
 import (
 	"io"
 	"os"
+
+	"git.portale-stac.it/go-pkg/expr/kern"
+	"git.portale-stac.it/go-pkg/expr/scan"
 )
 
-func importFunc(ctx ExprContext, name string, args map[string]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 map[string]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 map[string]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)
-	if v, exists := args[ParamFilepath]; exists && v != nil {
+	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 {
@@ -41,10 +44,10 @@ func doImport(ctx ExprContext, name string, dirList []string, it Iterator) (resu
 		var file *os.File
 		if file, err = os.Open(sourceFilepath); err == nil {
 			defer file.Close()
-			var expr *ast
+			var expr *scan.Ast
-			scanner := NewScanner(file, DefaultTranslations())
+			scanner := scan.NewScanner(file, scan.DefaultTranslations())
 			parser := NewParser()
-			if expr, err = parser.parseGeneral(scanner, allowMultiExpr|allowVarRef, SymEos); err == nil {
+			if expr, err = parser.parseGeneral(scanner, allowMultiExpr|allowVarRef, scan.SymEos); err == nil {
 				result, err = expr.Eval(ctx)
 			}
 			if err != nil {
@@ -64,12 +67,12 @@ 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),
+		kern.NewFuncParamFlag(kern.ParamFilepath, kern.PfRepeat),
 	})
-	ctx.RegisterFunc("importAll", NewGolangFunctor(importAllFunc), TypeAny, []ExprFuncParam{
+	ctx.RegisterFunc("importAll", kern.NewGolangFunctor(importAllFunc), kern.TypeAny, []kern.ExprFuncParam{
-		NewFuncParamFlag(ParamFilepath, PfRepeat),
+		kern.NewFuncParamFlag(kern.ParamFilepath, kern.PfRepeat),
 	})
 }
 

builtin-iterator.go

@@ -1,4 +1,4 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
 // All rights reserved.
 
 // builtin-iterator.go
@@ -7,6 +7,8 @@ package expr
 import (
 	"fmt"
 	"io"
+
+	"git.portale-stac.it/go-pkg/expr/kern"
 )
 
 const (
@@ -15,22 +17,24 @@ const (
 	iterVarStatus     = "status"
 )
 
-func parseRunArgs(localCtx ExprContext, args map[string]any) (it Iterator, op Functor, err error) {
+func parseRunArgs(localCtx kern.ExprContext, args map[string]any) (it kern.Iterator, op kern.Functor, err error) {
 	var ok bool
 
-	if it, ok = args[ParamIterator].(Iterator); !ok {
+	if it, ok = args[kern.ParamIterator].(kern.Iterator); !ok {
-		err = fmt.Errorf("paramter %q must be an iterator, passed %v [%s]", ParamIterator, args[ParamIterator], TypeName(args[ParamIterator]))
+		err = fmt.Errorf("paramter %q must be an iterator, passed %v [%s]", kern.ParamIterator, args[kern.ParamIterator], kern.TypeName(args[kern.ParamIterator]))
 		return
 	}
 
-	if op, ok = args[iterParamOperator].(Functor); !ok && args[iterParamOperator] != nil {
+	if args[iterParamOperator] != nil {
-		err = fmt.Errorf("paramter %q must be a function, passed %v [%s]", iterParamOperator, args[iterParamOperator], TypeName(args[iterParamOperator]))
+		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 *DictType
+	var vars *kern.DictType
-	if vars, ok = args[iterParamVars].(*DictType); !ok && args[iterParamVars] != nil {
+	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], TypeName(args[iterParamVars]))
+		err = fmt.Errorf("paramter %q must be a dictionary, passed %v [%s]", iterParamVars, args[iterParamVars], kern.TypeName(args[iterParamVars]))
 		return
 	}
 
@@ -46,12 +50,12 @@ func parseRunArgs(localCtx ExprContext, args map[string]any) (it Iterator, op Fu
 	return
 }
 
-func runFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+func runFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
-	var it Iterator
+	var it kern.Iterator
 	var ok bool
-	var op Functor
+	var op kern.Functor
 	var v any
-	var usingDefaultOp = false
+	// var usingDefaultOp = false
 	var params map[string]any
 	var item any
 
@@ -60,42 +64,39 @@ func runFunc(ctx ExprContext, name string, args map[string]any) (result any, err
 
 	if it, op, err = parseRunArgs(localCtx, args); err != nil {
 		return
-	} else if op == nil {
-		op = NewGolangFunctor(printLnFunc)
-		usingDefaultOp = true
 	}
 
 	for item, err = it.Next(); err == nil; item, err = it.Next() {
-		if usingDefaultOp {
+		if op != nil {
-			params = map[string]any{ParamItem: []any{item}}
+			params = map[string]any{kern.ParamIndex: it.Index(), kern.ParamItem: item}
-		} else {
-			params = map[string]any{ParamIndex: it.Index(), ParamItem: item}
-		}
-
 			if v, err = op.InvokeNamed(localCtx, iterParamOperator, params); err != nil {
 				break
 			} else {
 				var success bool
-			if success, ok = ToBool(v); !success || !ok {
+				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 ExprContext) {
+func ImportIterFuncs(ctx kern.ExprContext) {
-	ctx.RegisterFunc("run", NewGolangFunctor(runFunc), TypeAny, []ExprFuncParam{
+	ctx.RegisterFunc("run", kern.NewGolangFunctor(runFunc), kern.TypeAny, []kern.ExprFuncParam{
-		NewFuncParam(ParamIterator),
+		kern.NewFuncParam(kern.ParamIterator),
-		NewFuncParamFlag(iterParamOperator, PfOptional),
+		kern.NewFuncParamFlag(iterParamOperator, kern.PfOptional),
-		NewFuncParamFlag(iterParamVars, PfOptional),
+		kern.NewFuncParamFlag(iterParamVars, kern.PfOptional),
 	})
 }
 

builtin-math-arith.go

@@ -1,4 +1,4 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
 // All rights reserved.
 
 // 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
@@ -86,64 +88,64 @@ func doAdd(ctx ExprContext, name string, it Iterator, count, level int) (result
 	return
 }
 
-func addFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+func addFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
-	argv := args[ParamValue].([]any)
+	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
@@ -162,19 +164,19 @@ func doMul(ctx ExprContext, name string, it Iterator, count, level int) (result
 	return
 }
 
-func mulFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+func mulFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
-	argv := args[ParamValue].([]any)
+	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", NewGolangFunctor(addFunc), TypeNumber, []ExprFuncParam{
+	ctx.RegisterFunc("add", kern.NewGolangFunctor(addFunc), kern.TypeNumber, []kern.ExprFuncParam{
-		NewFuncParamFlagDef(ParamValue, PfDefault|PfRepeat, int64(0)),
+		kern.NewFuncParamFlagDef(kern.ParamValue, kern.PfDefault|kern.PfRepeat, int64(0)),
 	})
 
-	ctx.RegisterFunc("mul", NewGolangFunctor(mulFunc), TypeNumber, []ExprFuncParam{
+	ctx.RegisterFunc("mul", kern.NewGolangFunctor(mulFunc), kern.TypeNumber, []kern.ExprFuncParam{
-		NewFuncParamFlagDef(ParamValue, PfDefault|PfRepeat, int64(1)),
+		kern.NewFuncParamFlagDef(kern.ParamValue, kern.PfDefault|kern.PfRepeat, int64(1)),
 	})
 }
 

builtin-os-file-iter-byte.go

@@ -0,0 +1,102 @@
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// builtin-os-file.go
+package expr
+
+import (
+	"git.portale-stac.it/go-pkg/expr/file"
+	"git.portale-stac.it/go-pkg/expr/kern"
+)
+
+const fileByteIteratorType = "fileByteIterator"
+
+type fileFileByteIterator struct {
+	fileIterBase
+	b byte
+}
+
+func newFileByteIterator(r *file.Reader, autoClose bool) *fileFileByteIterator {
+	return &fileFileByteIterator{
+		fileIterBase: fileIterBase{reader: r, index: -1, count: 0, autoClose: autoClose},
+		b:            0}
+}
+
+func (it *fileFileByteIterator) TypeName() string {
+	return fileByteIteratorType
+}
+
+func (it *fileFileByteIterator) String() string {
+	return it.repr(fileByteIteratorType)
+}
+
+func (it *fileFileByteIterator) Next() (item any, err error) { // must return io.EOF after the last item
+	if it.b, err = it.reader.ReadByte(); err == nil {
+		it.increment()
+		item = it.b
+	} else if it.autoClose {
+		it.Clean()
+	}
+	return
+}
+
+func (it *fileFileByteIterator) Current() (item any, err error) {
+	item = it.b
+	return
+}
+
+func (it *fileFileByteIterator) Reset() (err error) {
+	if err = it.reader.Reset(); err == nil {
+		it.reset()
+		it.b = 0
+	}
+	return
+}
+
+func (it *fileFileByteIterator) Clean() (err error) {
+	if it.reader.Valid() {
+		if err = it.reader.GetFile().Close(); err == nil {
+			it.reader = nil
+		}
+	}
+	it.reset()
+	it.b = 0
+	return
+}
+
+func (it *fileFileByteIterator) 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 fileByteIteratorFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
+	var handle *file.Reader
+	var invalidFileHandle any
+	var autoClose bool
+
+	if handle, invalidFileHandle, autoClose, err = initFileHandle(ctx, name, args); err == nil {
+		if handle != nil {
+			result = newFileByteIterator(handle, autoClose)
+		}
+	}
+
+	if err == nil && (handle == nil || invalidFileHandle != nil) {
+		err = errInvalidFileHandle(name, invalidFileHandle)
+	}
+	return
+}

builtin-os-file-iter-line.go

@@ -0,0 +1,105 @@
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// builtin-os-file.go
+package expr
+
+import (
+	"git.portale-stac.it/go-pkg/expr/file"
+	"git.portale-stac.it/go-pkg/expr/kern"
+)
+
+const fileLineIteratorType = "fileLineIterator"
+
+type fileFileLineIterator struct {
+	fileIterBase
+	line string
+}
+
+func newFileLineIterator(r *file.Reader, autoClose bool) *fileFileLineIterator {
+	return &fileFileLineIterator{
+		fileIterBase: fileIterBase{reader: r, index: -1, count: 0, autoClose: autoClose},
+		line:         "",
+	}
+}
+
+func (it *fileFileLineIterator) TypeName() string {
+	return fileLineIteratorType
+}
+
+func (it *fileFileLineIterator) String() string {
+	return it.repr(fileLineIteratorType)
+}
+
+func (it *fileFileLineIterator) Next() (item any, err error) { // must return io.EOF after the last item
+	if it.line, err = it.reader.ReadString('\n'); err == nil {
+		it.increment()
+		item = it.line[0 : len(it.line)-1]
+	} else if it.autoClose {
+		it.Clean()
+	}
+	return
+}
+
+func (it *fileFileLineIterator) Current() (item any, err error) {
+	if len(it.line) > 0 {
+		item = it.line[0 : len(it.line)-1]
+	}
+	return
+}
+
+func (it *fileFileLineIterator) Reset() (err error) {
+	if err = it.reader.Reset(); err == nil {
+		it.reset()
+		it.line = ""
+	}
+	return
+}
+
+func (it *fileFileLineIterator) Clean() (err error) {
+	if it.reader != nil {
+		if err = it.reader.Close(); err == nil {
+			it.reader = nil
+		}
+	}
+	it.reset()
+	it.line = ""
+	return
+}
+
+func (it *fileFileLineIterator) 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 fileLineIteratorFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
+	var handle *file.Reader
+	var invalidFileHandle any
+	var autoClose bool
+
+	if handle, invalidFileHandle, autoClose, err = initFileHandle(ctx, name, args); err == nil {
+		if handle != nil {
+			result = newFileLineIterator(handle, autoClose)
+		}
+	}
+
+	if err == nil && (handle == nil || invalidFileHandle != nil) {
+		err = errInvalidFileHandle(name, invalidFileHandle)
+	}
+	return
+}

builtin-os-file-iter.go

@@ -0,0 +1,71 @@
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// builtin-os-file.go
+package expr
+
+import (
+	"fmt"
+	"slices"
+
+	"git.portale-stac.it/go-pkg/expr/file"
+	"git.portale-stac.it/go-pkg/expr/kern"
+)
+
+const paramHandleOrPath = "handle-or-path"
+
+type fileIterBase struct {
+	reader    *file.Reader
+	index     int64
+	count     int64
+	autoClose bool
+}
+
+func (it *fileIterBase) Count() int64 {
+	return it.count
+}
+
+func (it *fileIterBase) Index() int64 {
+	return it.index
+}
+
+func (it *fileIterBase) HasOperation(name string) bool {
+	return slices.Contains([]string{kern.NextName, kern.ResetName, kern.IndexName, kern.CountName, kern.CurrentName, kern.CleanName}, name)
+}
+
+func (it *fileIterBase) reset() {
+	it.index = -1
+	it.count = 0
+}
+
+func (it *fileIterBase) increment() {
+	it.index++
+	it.count++
+}
+
+func (it *fileIterBase) repr(typeName string) string {
+	if it.reader.Valid() {
+		return fmt.Sprintf("$(%s@%q)", typeName, it.reader.GetName())
+	}
+	return fmt.Sprintf("$(%s@<nil>)", typeName)
+}
+
+func initFileHandle(ctx kern.ExprContext, name string, args map[string]any) (handle *file.Reader, invalidFileHandle any, autoClose bool, err error) {
+	var ok bool
+
+	if handle, ok = args[paramHandleOrPath].(*file.Reader); !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.(*file.Reader)
+				autoClose = true
+			}
+		} else {
+			invalidFileHandle = args[paramHandleOrPath]
+		}
+	}
+	return
+}

builtin-os-file.go

@@ -1,58 +1,21 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
 // All rights reserved.
 
 // builtin-os-file.go
 package expr
 
 import (
-	"bufio"
 	"fmt"
 	"io"
-	"os"
+
+	"git.portale-stac.it/go-pkg/expr/file"
+	"git.portale-stac.it/go-pkg/expr/kern"
 )
 
 const (
 	osLimitCh = "limitCh"
 )
 
-type osHandle interface {
-	getFile() *os.File
-}
-
-type osWriter struct {
-	fh     *os.File
-	writer *bufio.Writer
-}
-
-func (h *osWriter) TypeName() string {
-	return "osWriter"
-}
-
-func (h *osWriter) String() string {
-	return "writer"
-}
-
-func (h *osWriter) getFile() *os.File {
-	return h.fh
-}
-
-type osReader struct {
-	fh     *os.File
-	reader *bufio.Reader
-}
-
-func (h *osReader) TypeName() string {
-	return "osReader"
-}
-
-func (h *osReader) String() string {
-	return "reader"
-}
-
-func (h *osReader) getFile() *os.File {
-	return h.fh
-}
-
 func errMissingFilePath(funcName string) error {
 	return fmt.Errorf("%s(): missing or invalid file path", funcName)
 }
@@ -65,55 +28,58 @@ func errInvalidFileHandle(funcName string, v any) error {
 	}
 }
 
-func createFileFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+func openFileFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
-	if filePath, ok := args[ParamFilepath].(string); ok && len(filePath) > 0 {
+	if filePath, ok := args[kern.ParamFilepath].(string); ok && len(filePath) > 0 {
-		var fh *os.File
+		// var fh *os.File
-		if fh, err = os.Create(filePath); err == nil {
+		// if fh, err = os.Open(filePath); err == nil {
-			result = &osWriter{fh: fh, writer: bufio.NewWriter(fh)}
+		// 	result = file.NewReader(fh)
-		}
+		// }
+		result, err = file.OpenReader(filePath)
 	} else {
 		err = errMissingFilePath(name)
 	}
 	return
 }
 
-func openFileFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+func createFileFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
-	if filePath, ok := args[ParamFilepath].(string); ok && len(filePath) > 0 {
+	if filePath, ok := args[kern.ParamFilepath].(string); ok && len(filePath) > 0 {
-		var fh *os.File
+		// var fh *os.File
-		if fh, err = os.Open(filePath); err == nil {
+		// if fh, err = os.Create(filePath); err == nil {
-			result = &osReader{fh: fh, reader: bufio.NewReader(fh)}
+		// 	result = file.NewWriter(fh)
-		}
+		// }
+		result, err = file.CreateWriter(filePath)
 	} else {
 		err = errMissingFilePath(name)
 	}
 	return
 }
 
-func appendFileFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+func appendFileFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
-	if filePath, ok := args[ParamFilepath].(string); ok && len(filePath) > 0 {
+	if filePath, ok := args[kern.ParamFilepath].(string); ok && len(filePath) > 0 {
-		var fh *os.File
+		// var fh *os.File
-		if fh, err = os.OpenFile(filePath, os.O_APPEND|os.O_WRONLY|os.O_CREATE, 0660); err == nil {
+		// 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)}
+		// 	result = file.NewWriter(fh)
-		}
+		// }
+		result, err = file.AppendWriter(filePath)
 	} else {
 		err = errMissingFilePath(name)
 	}
 	return
 }
 
-func closeFileFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+func closeFileFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
-	var handle osHandle
+	var handle file.Handle
 	var invalidFileHandle any
 	var ok bool
 
-	if handle, ok = args[ParamHandle].(osHandle); !ok {
+	if handle, ok = args[kern.ParamHandle].(file.Handle); !ok {
-		invalidFileHandle = args[ParamHandle]
+		invalidFileHandle = args[kern.ParamHandle]
 	}
 
 	if handle != nil {
-		if fh := handle.getFile(); fh != nil {
+		if fh := handle.GetFile(); fh != nil {
-			if w, ok := handle.(*osWriter); ok {
+			if w, ok := handle.(*file.Writer); ok {
-				err = w.writer.Flush()
+				err = w.Flush()
 			}
 
 			if err == nil {
@@ -128,20 +94,21 @@ func closeFileFunc(ctx ExprContext, name string, args map[string]any) (result an
 	return
 }
 
-func fileWriteTextFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+func fileWriteTextFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
-	var handle osHandle
+	var handle file.Handle
 	var invalidFileHandle any
 	var ok bool
 
-	if handle, ok = args[ParamHandle].(osHandle); !ok {
+	if handle, ok = args[kern.ParamHandle].(file.Handle); !ok {
-		invalidFileHandle = args[ParamHandle]
+		invalidFileHandle = args[kern.ParamHandle]
 	}
 
 	if handle != nil {
-		if w, ok := handle.(*osWriter); ok {
+		if w, ok := handle.(*file.Writer); ok {
-			if v, exists := args[ParamItem]; exists {
+			if v, exists := args[kern.ParamItem]; exists {
 				argv := v.([]any)
-				result, err = fmt.Fprint(w.writer, argv...)
+				// result, err = fmt.Fprint(w.writer, argv...)
+				result, err = w.Write(argv...)
 			}
 		} else {
 			invalidFileHandle = handle
@@ -154,25 +121,25 @@ func fileWriteTextFunc(ctx ExprContext, name string, args map[string]any) (resul
 	return
 }
 
-func fileReadTextFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+func fileReadTextFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
-	var handle osHandle
+	var handle file.Handle
 	var invalidFileHandle any
 	var ok bool
 
 	result = nil
-	if handle, ok = args[ParamHandle].(osHandle); !ok || args[ParamHandle] == nil {
+	if handle, ok = args[kern.ParamHandle].(file.Handle); !ok || args[kern.ParamHandle] == nil {
-		invalidFileHandle = args[ParamHandle]
+		invalidFileHandle = args[kern.ParamHandle]
 	}
 
 	if handle != nil {
-		if r, ok := handle.(*osReader); ok {
+		if r, ok := handle.(*file.Reader); ok {
 			var limit byte = '\n'
 			var v string
 			if s, ok := args[osLimitCh].(string); ok && len(s) > 0 {
 				limit = s[0]
 			}
 
-			v, err = r.reader.ReadString(limit)
+			v, err = r.ReadString(limit)
 			if err == io.EOF {
 				err = nil
 			}
@@ -194,20 +161,20 @@ func fileReadTextFunc(ctx ExprContext, name string, args map[string]any) (result
 	return
 }
 
-func fileReadTextAllFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+func fileReadTextAllFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
-	var handle osHandle
+	var handle file.Handle
 	var invalidFileHandle any
 	var ok bool
 
 	result = nil
-	if handle, ok = args[ParamHandle].(osHandle); !ok || args[ParamHandle] == nil {
+	if handle, ok = args[kern.ParamHandle].(file.Handle); !ok || args[kern.ParamHandle] == nil {
-		invalidFileHandle = args[ParamHandle]
+		invalidFileHandle = args[kern.ParamHandle]
 	}
 
 	if handle != nil {
-		if r, ok := handle.(*osReader); ok {
+		if r, ok := handle.(*file.Reader); ok {
 			var b []byte
-			b, err = io.ReadAll(r.reader)
+			b, err = r.ReadAll()
 			result = string(b)
 		} else {
 			invalidFileHandle = handle
@@ -220,36 +187,45 @@ func fileReadTextAllFunc(ctx ExprContext, name string, args map[string]any) (res
 	return
 }
 
-func ImportOsFuncs(ctx ExprContext) {
+func ImportOsFuncs(ctx kern.ExprContext) {
-	ctx.RegisterFunc("fileOpen", NewGolangFunctor(openFileFunc), TypeFileHandle, []ExprFuncParam{
+	ctx.RegisterFunc("fileOpen", kern.NewGolangFunctor(openFileFunc), kern.TypeFileHandle, []kern.ExprFuncParam{
-		NewFuncParam(ParamFilepath),
+		kern.NewFuncParam(kern.ParamFilepath),
 	})
 
-	ctx.RegisterFunc("fileAppend", NewGolangFunctor(appendFileFunc), TypeFileHandle, []ExprFuncParam{
+	ctx.RegisterFunc("fileAppend", kern.NewGolangFunctor(appendFileFunc), kern.TypeFileHandle, []kern.ExprFuncParam{
-		NewFuncParam(ParamFilepath),
+		kern.NewFuncParam(kern.ParamFilepath),
 	})
 
-	ctx.RegisterFunc("fileCreate", NewGolangFunctor(createFileFunc), TypeFileHandle, []ExprFuncParam{
+	ctx.RegisterFunc("fileCreate", kern.NewGolangFunctor(createFileFunc), kern.TypeFileHandle, []kern.ExprFuncParam{
-		NewFuncParam(ParamFilepath),
+		kern.NewFuncParam(kern.ParamFilepath),
 	})
 
-	ctx.RegisterFunc("fileClose", NewGolangFunctor(closeFileFunc), TypeBoolean, []ExprFuncParam{
+	ctx.RegisterFunc("fileClose", kern.NewGolangFunctor(closeFileFunc), kern.TypeBoolean, []kern.ExprFuncParam{
-		NewFuncParam(ParamHandle),
+		kern.NewFuncParam(kern.ParamHandle),
 	})
 
-	ctx.RegisterFunc("fileWriteText", NewGolangFunctor(fileWriteTextFunc), TypeInt, []ExprFuncParam{
+	ctx.RegisterFunc("fileWriteText", kern.NewGolangFunctor(fileWriteTextFunc), kern.TypeInt, []kern.ExprFuncParam{
-		NewFuncParam(ParamHandle),
+		kern.NewFuncParam(kern.ParamHandle),
-		NewFuncParamFlagDef(ParamItem, PfDefault|PfRepeat, ""),
+		kern.NewFuncParamFlagDef(kern.ParamItem, kern.PfDefault|kern.PfRepeat, ""),
 	})
 
-	ctx.RegisterFunc("fileReadText", NewGolangFunctor(fileReadTextFunc), TypeString, []ExprFuncParam{
+	ctx.RegisterFunc("fileReadText", kern.NewGolangFunctor(fileReadTextFunc), kern.TypeString, []kern.ExprFuncParam{
-		NewFuncParam(ParamHandle),
+		kern.NewFuncParam(kern.ParamHandle),
-		NewFuncParamFlagDef(osLimitCh, PfDefault, "\n"),
+		kern.NewFuncParamFlagDef(osLimitCh, kern.PfDefault, "\n"),
 	})
 
-	ctx.RegisterFunc("fileReadTextAll", NewGolangFunctor(fileReadTextAllFunc), TypeString, []ExprFuncParam{
+	ctx.RegisterFunc("fileReadTextAll", kern.NewGolangFunctor(fileReadTextAllFunc), kern.TypeString, []kern.ExprFuncParam{
-		NewFuncParam(ParamHandle),
+		kern.NewFuncParam(kern.ParamHandle),
 	})
+
+	ctx.RegisterFunc("fileLineIterator", kern.NewGolangFunctor(fileLineIteratorFunc), kern.TypeIterator, []kern.ExprFuncParam{
+		kern.NewFuncParam(paramHandleOrPath),
+	})
+
+	ctx.RegisterFunc("fileByteIterator", kern.NewGolangFunctor(fileByteIteratorFunc), kern.TypeIterator, []kern.ExprFuncParam{
+		kern.NewFuncParam(paramHandleOrPath),
+	})
+
 }
 
 func init() {

builtin-string.go

@@ -1,4 +1,4 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
 // All rights reserved.
 
 // builtin-string.go
@@ -8,6 +8,8 @@ import (
 	"fmt"
 	"io"
 	"strings"
+
+	"git.portale-stac.it/go-pkg/expr/kern"
 )
 
 const (
@@ -15,7 +17,7 @@ const (
 )
 
 // --- 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() {
@@ -25,7 +27,7 @@ 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
 		}
 	}
@@ -36,45 +38,45 @@ func doJoinStr(funcName string, sep string, it Iterator) (result any, err error)
 	return
 }
 
-func joinStrFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+func joinStrFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
-	if sep, ok := args[ParamSeparator].(string); ok {
+	if sep, ok := args[kern.ParamSeparator].(string); ok {
-		if v, exists := args[ParamItem]; exists {
+		if v, exists := args[kern.ParamItem]; exists {
 			argv := v.([]any)
 			if len(argv) == 1 {
-				if ls, ok := argv[0].(*ListType); ok {
+				if ls, ok := argv[0].(*kern.ListType); ok {
 					result, err = doJoinStr(name, sep, NewListIterator(ls, nil))
-				} else if it, ok := argv[0].(Iterator); ok {
+				} else if it, ok := argv[0].(kern.Iterator); ok {
 					result, err = doJoinStr(name, sep, it)
 				} else if s, ok := argv[0].(string); ok {
 					result = s
 				} else {
-					err = ErrInvalidParameterValue(name, ParamItem, v)
+					err = kern.ErrInvalidParameterValue(name, kern.ParamItem, v)
 				}
 			} else {
 				result, err = doJoinStr(name, sep, NewArrayIterator(argv))
 			}
 		}
 	} else {
-		err = ErrWrongParamType(name, ParamSeparator, TypeString, args[ParamSeparator])
+		err = kern.ErrWrongParamType(name, kern.ParamSeparator, kern.TypeString, args[kern.ParamSeparator])
 	}
 	return
 }
 
-func subStrFunc(ctx ExprContext, name string, args map[string]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[ParamSource].(string); !ok {
+	if source, ok = args[kern.ParamSource].(string); !ok {
-		return nil, ErrWrongParamType(name, ParamSource, TypeString, args[ParamSource])
+		return nil, kern.ErrWrongParamType(name, kern.ParamSource, kern.TypeString, args[kern.ParamSource])
 	}
 
-	if start, err = ToGoInt(args[ParamStart], name+"()"); err != nil {
+	if start, err = kern.ToGoInt(args[kern.ParamStart], name+"()"); err != nil {
 		return
 	}
 
-	if count, err = ToGoInt(args[ParamCount], name+"()"); err != nil {
+	if count, err = kern.ToGoInt(args[kern.ParamCount], name+"()"); err != nil {
 		return
 	}
 
@@ -90,29 +92,29 @@ func subStrFunc(ctx ExprContext, name string, args map[string]any) (result any,
 	return
 }
 
-func trimStrFunc(ctx ExprContext, name string, args map[string]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[ParamSource].(string); !ok {
+	if source, ok = args[kern.ParamSource].(string); !ok {
-		return nil, ErrWrongParamType(name, ParamSource, TypeString, args[ParamSource])
+		return nil, kern.ErrWrongParamType(name, kern.ParamSource, kern.TypeString, args[kern.ParamSource])
 	}
 	result = strings.TrimSpace(source)
 	return
 }
 
-func startsWithStrFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+func startsWithStrFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
 	var source, prefix string
 	var ok bool
 
 	result = false
 
-	if source, ok = args[ParamSource].(string); !ok {
+	if source, ok = args[kern.ParamSource].(string); !ok {
-		return result, ErrWrongParamType(name, ParamSource, TypeString, args[ParamSource])
+		return result, kern.ErrWrongParamType(name, kern.ParamSource, kern.TypeString, args[kern.ParamSource])
 	}
 
-	if prefix, ok = args[ParamPrefix].(string); !ok {
+	if prefix, ok = args[kern.ParamPrefix].(string); !ok {
-		return result, ErrWrongParamType(name, ParamPrefix, TypeString, args[ParamPrefix])
+		return result, kern.ErrWrongParamType(name, kern.ParamPrefix, kern.TypeString, args[kern.ParamPrefix])
 	}
 	if strings.HasPrefix(source, prefix) {
 		result = true
@@ -125,7 +127,7 @@ func startsWithStrFunc(ctx ExprContext, name string, args map[string]any) (resul
 					break
 				}
 			} else {
-				err = fmt.Errorf("target item nr %d is %s, string expected", i+1, TypeName(targetSpec))
+				err = fmt.Errorf("target item nr %d is %s, string expected", i+1, kern.TypeName(targetSpec))
 				break
 			}
 		}
@@ -133,18 +135,18 @@ func startsWithStrFunc(ctx ExprContext, name string, args map[string]any) (resul
 	return
 }
 
-func endsWithStrFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+func endsWithStrFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
 	var source, suffix string
 	var ok bool
 
 	result = false
 
-	if source, ok = args[ParamSource].(string); !ok {
+	if source, ok = args[kern.ParamSource].(string); !ok {
-		return result, ErrWrongParamType(name, ParamSource, TypeString, args[ParamSource])
+		return result, kern.ErrWrongParamType(name, kern.ParamSource, kern.TypeString, args[kern.ParamSource])
 	}
 
-	if suffix, ok = args[ParamSuffix].(string); !ok {
+	if suffix, ok = args[kern.ParamSuffix].(string); !ok {
-		return result, ErrWrongParamType(name, ParamSuffix, TypeString, args[ParamSuffix])
+		return result, kern.ErrWrongParamType(name, kern.ParamSuffix, kern.TypeString, args[kern.ParamSuffix])
 	}
 	if strings.HasPrefix(source, suffix) {
 		result = true
@@ -157,7 +159,7 @@ func endsWithStrFunc(ctx ExprContext, name string, args map[string]any) (result
 					break
 				}
 			} else {
-				err = fmt.Errorf("target item nr %d is %s, string expected", i+1, TypeName(targetSpec))
+				err = fmt.Errorf("target item nr %d is %s, string expected", i+1, kern.TypeName(targetSpec))
 				break
 			}
 		}
@@ -165,24 +167,24 @@ func endsWithStrFunc(ctx ExprContext, name string, args map[string]any) (result
 	return
 }
 
-func splitStrFunc(ctx ExprContext, name string, args map[string]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[ParamSource].(string); !ok {
+	if source, ok = args[kern.ParamSource].(string); !ok {
-		return result, ErrWrongParamType(name, ParamSource, TypeString, args[ParamSource])
+		return result, kern.ErrWrongParamType(name, kern.ParamSource, kern.TypeString, args[kern.ParamSource])
 	}
 
-	if sep, ok = args[ParamSeparator].(string); !ok {
+	if sep, ok = args[kern.ParamSeparator].(string); !ok {
-		return nil, fmt.Errorf("separator param must be string, got %s (%v)", TypeName(args[ParamSeparator]), args[ParamSeparator])
+		return nil, fmt.Errorf("separator param must be string, got %s (%v)", kern.TypeName(args[kern.ParamSeparator]), args[kern.ParamSeparator])
 	}
 
-	if count64, ok := args[ParamCount].(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 %s (%v)", TypeName(args[ParamCount]), args[ParamCount])
+		return nil, fmt.Errorf("part count must be integer, got %s (%v)", kern.TypeName(args[kern.ParamCount]), args[kern.ParamCount])
 	}
 
 	if count > 0 {
@@ -192,7 +194,7 @@ func splitStrFunc(ctx ExprContext, name string, args map[string]any) (result any
 	} else {
 		parts = []string{}
 	}
-	list := make(ListType, len(parts))
+	list := make(kern.ListType, len(parts))
 	for i, part := range parts {
 		list[i] = part
 	}
@@ -200,20 +202,20 @@ func splitStrFunc(ctx ExprContext, name string, args map[string]any) (result any
 	return
 }
 
-func upperStrFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+func upperStrFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
-	if source, ok := args[ParamSource].(string); ok {
+	if source, ok := args[kern.ParamSource].(string); ok {
 		result = strings.ToUpper(source)
 	} else {
-		err = ErrWrongParamType(name, ParamSource, TypeString, args[ParamSource])
+		err = kern.ErrWrongParamType(name, kern.ParamSource, kern.TypeString, args[kern.ParamSource])
 	}
 	return
 }
 
-func lowerStrFunc(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+func lowerStrFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
-	if source, ok := args[ParamSource].(string); ok {
+	if source, ok := args[kern.ParamSource].(string); ok {
 		result = strings.ToLower(source)
 	} else {
-		err = ErrWrongParamType(name, ParamSource, TypeString, args[ParamSource])
+		err = kern.ErrWrongParamType(name, kern.ParamSource, kern.TypeString, args[kern.ParamSource])
 	}
 	return
 }
@@ -221,46 +223,46 @@ func lowerStrFunc(ctx ExprContext, name string, args map[string]any) (result any
 // --- 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),
+		kern.NewFuncParam(kern.ParamSeparator),
-		NewFuncParamFlag(ParamItem, PfRepeat),
+		kern.NewFuncParamFlag(kern.ParamItem, kern.PfRepeat),
 	})
 
-	ctx.RegisterFunc("strSub", NewGolangFunctor(subStrFunc), TypeString, []ExprFuncParam{
+	ctx.RegisterFunc("strSub", kern.NewGolangFunctor(subStrFunc), kern.TypeString, []kern.ExprFuncParam{
-		NewFuncParam(ParamSource),
+		kern.NewFuncParam(kern.ParamSource),
-		NewFuncParamFlagDef(ParamStart, PfDefault, int64(0)),
+		kern.NewFuncParamFlagDef(kern.ParamStart, kern.PfDefault, int64(0)),
-		NewFuncParamFlagDef(ParamCount, PfDefault, int64(-1)),
+		kern.NewFuncParamFlagDef(kern.ParamCount, kern.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),
+		kern.NewFuncParam(kern.ParamSource),
-		NewFuncParamFlagDef(ParamSeparator, PfDefault, ""),
+		kern.NewFuncParamFlagDef(kern.ParamSeparator, kern.PfDefault, ""),
-		NewFuncParamFlagDef(ParamCount, PfDefault, int64(-1)),
+		kern.NewFuncParamFlagDef(kern.ParamCount, kern.PfDefault, int64(-1)),
 	})
 
-	ctx.RegisterFunc("strTrim", NewGolangFunctor(trimStrFunc), TypeString, []ExprFuncParam{
+	ctx.RegisterFunc("strTrim", kern.NewGolangFunctor(trimStrFunc), kern.TypeString, []kern.ExprFuncParam{
-		NewFuncParam(ParamSource),
+		kern.NewFuncParam(kern.ParamSource),
 	})
 
-	ctx.RegisterFunc("strStartsWith", NewGolangFunctor(startsWithStrFunc), TypeBoolean, []ExprFuncParam{
+	ctx.RegisterFunc("strStartsWith", kern.NewGolangFunctor(startsWithStrFunc), kern.TypeBoolean, []kern.ExprFuncParam{
-		NewFuncParam(ParamSource),
+		kern.NewFuncParam(kern.ParamSource),
-		NewFuncParam(ParamPrefix),
+		kern.NewFuncParam(kern.ParamPrefix),
-		NewFuncParamFlag(strParamOther, PfRepeat),
+		kern.NewFuncParamFlag(strParamOther, kern.PfRepeat),
 	})
 
-	ctx.RegisterFunc("strEndsWith", NewGolangFunctor(endsWithStrFunc), TypeBoolean, []ExprFuncParam{
+	ctx.RegisterFunc("strEndsWith", kern.NewGolangFunctor(endsWithStrFunc), kern.TypeBoolean, []kern.ExprFuncParam{
-		NewFuncParam(ParamSource),
+		kern.NewFuncParam(kern.ParamSource),
-		NewFuncParam(ParamSuffix),
+		kern.NewFuncParam(kern.ParamSuffix),
-		NewFuncParamFlag(strParamOther, PfRepeat),
+		kern.NewFuncParamFlag(strParamOther, kern.PfRepeat),
 	})
 
-	ctx.RegisterFunc("strUpper", NewGolangFunctor(upperStrFunc), TypeString, []ExprFuncParam{
+	ctx.RegisterFunc("strUpper", kern.NewGolangFunctor(upperStrFunc), kern.TypeString, []kern.ExprFuncParam{
-		NewFuncParam(ParamSource),
+		kern.NewFuncParam(kern.ParamSource),
 	})
 
-	ctx.RegisterFunc("strLower", NewGolangFunctor(lowerStrFunc), TypeString, []ExprFuncParam{
+	ctx.RegisterFunc("strLower", kern.NewGolangFunctor(lowerStrFunc), kern.TypeString, []kern.ExprFuncParam{
-		NewFuncParam(ParamSource),
+		kern.NewFuncParam(kern.ParamSource),
 	})
 }
 

builtins-register.go

@@ -1,4 +1,4 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
 // All rights reserved.
 
 // 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)
 	}

cmd/ecli/.build.rc

@@ -0,0 +1,14 @@
+# Builder resource file
+# Created on gio 21 mag 2026, 15:35:18, CEST
+
+# Program name
+PROGRAM_NAME="ecli"
+
+# Program version
+PROGRAM_VERSION="$(<version.txt)"
+
+# Preset platform
+platform=("linux/amd64" "darwin/arm64")
+
+#--- end of file ---
+

cmd/ecli/build.bash

@@ -0,0 +1,199 @@
+#!/usr/bin/env bash
+# Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+# All rights reserved.
+
+
+RESOURCE_FILE=".build.rc"
+BUILD_REGISTER=".build_register"
+
+PROGRAM_NAME=""
+PROGRAM_VERSION=""
+
+function usage() {
+	prog=$(basename "${0}")
+	msgln "USAGE:"
+	#msgln "      ${prog} <program-name> <program-version> <os>/<platform>..."
+	msgln "      ${prog} <os>/<platform>..."
+	msgln "      ${prog} --local         Build the local exec"
+	msgln "      ${prog} --init          Create the resource file in the current directory"
+	msgln
+	if [ -r "${RESOURCE_FILE}" ]; then
+		msgln "Resource file '${RESOURCE_FILE}' content:"
+		cat >&2 ${RESOURCE_FILE}
+	else
+		msgln "Resource file '${RESOURCE_FILE}' not found"
+	fi
+}
+
+function msgln() {
+	echo >&2 "${1}"
+}
+
+function exitUsage() {
+	echo >&2 "${1}"
+	usage
+	exit 1
+}
+
+function exitMsg() {
+	echo >&2 "${1}"
+	exit 1
+}
+
+# CMDLINE: help
+if [ "${1}" == "help,," ] || [ "${1,,}" == "--help" ] || [ "${1,,}" == "-h" ]; then
+	usage
+	exit
+fi
+
+# CMDLINE: init
+if [ "${1,,}" == "--init" ]; then
+	cat >"${RESOURCE_FILE}" <<eot
+# Builder resource file
+# Created on $(date)
+
+# Program name
+PROGRAM_NAME="name"
+
+# Program version
+PROGRAM_VERSION="version"
+
+# Preset platform
+platform=("linux/amd64" "darwin/arm64")
+
+#--- end of file ---
+
+eot
+	msgln "Resource file '${RESOURCE_FILE}' create. Edit it to set valid values."
+	#${EDITOR-vi} "${RESOURCE_FILE}"
+	exit
+fi
+
+if [ -r "${RESOURCE_FILE}" ]; then
+	if ! source "${RESOURCE_FILE}"; then
+		exitMsg "Can't load build resource file '${RESOURCE_FILE}'"
+	fi
+fi
+
+if [ -z "${PROGRAM_NAME}" ]; then
+	exitUsage "Missing program name"
+fi
+
+if [ -z "${PROGRAM_VERSION}" ]; then
+	exitUsage "Missing program version"
+fi
+
+
+function getBuildCount() {
+	local reg ver count
+	if [ -r "${BUILD_REGISTER}" ]; then
+		reg=$(<"${BUILD_REGISTER}")
+	else
+		reg="${PROGRAM_VERSION} 0"
+	fi
+	read ver count <<<"${reg}"
+	if [ "${ver}" != "${PROGRAM_VERSION}" ]; then
+		count=0
+	fi
+	count=$((count+1))
+	echo >"${BUILD_REGISTER}" "${PROGRAM_VERSION} ${count}"
+	echo ${count}
+}
+
+function build() {
+	local target=${1} ext cmd
+	IFS=/ read os cpu <<<"${p}"
+	#msgln "OS=${os}; CPU=${cpu}"
+	ext=""
+	if [ "${os}" == 'windows' ]; then
+		ext=".exe"
+	fi
+	cmd="GOOS='${os}' GOARCH='${cpu}' go build -o '${PROGRAM_NAME}_v${PROGRAM_VERSION}_${os}_${cpu}${ext}'"
+	eval "${cmd}"
+}
+
+function buildLocal() {
+	local ext cmd
+	ext=""
+	if [[ "${OSTYPE}" =~ win.* ]]; then
+		ext=".exe"
+	fi
+	cmd="go build -o '${PROGRAM_NAME}${ext}'"
+	eval "${cmd}"
+}
+
+function gitTag() {
+	local gopath gopkg mod
+	local tag
+
+	if ! tag=$(git tag -l --sort=-version:refname "v[0-9]*.[0-9]*.[0-9]*"|head -1) || [ -z "${tag}" ]; then
+		gopath=$(go env GOPATH)
+		gopkg="${gopath}/pkg/mod/git.portale-stac.it/go-pkg"
+		if cd "${gopkg}" 2>/dev/null; then
+			mod=$(ls -1v |grep expr@|tail -1)
+			tag=${mod##*@}
+			cd - >/dev/null
+		fi
+	fi
+	echo ${tag}
+}
+
+function gitTagDate() {
+	local tag_name=${1}
+	local tag_date
+
+	if ! tag_date=$(git show --no-patch --format=%ci "${tag_name}") || [ -z "${tag_date}" ]; then
+		tag_date="n/a"
+	fi
+	echo ${tag_date}
+}
+
+function createVersionSource() {
+	local tag tag_date
+	tag=$(gitTag)
+	if [ -z "${tag}" ]; then
+		tag="n/a"
+	else
+		tag_date=$(gitTagDate "${tag}")
+	fi
+
+	cat >version.go <<eot
+// Copyright (c) 2024-$(date +%Y) Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// version.go
+package main
+
+const (
+	PROGNAME     = "${PROGRAM_NAME}"
+	VERSION      = "v${PROGRAM_VERSION}(build $(getBuildCount)),$(date +"%Y/%m/%d") (celestino.amoroso@portale-stac.it)"
+	EXPR_VERSION = "${tag}"
+	EXPR_DATE    = "${tag_date}"
+)
+eot
+}
+
+## -- TEST -- ##
+
+# echo "Tag: $(gitTag)"
+# echo "Tag Date: $(gitTagDate $(gitTag))"
+# exit 0
+
+## -- MAIN -- ##
+createVersionSource
+
+if [ "${1}" == "--local" ]; then
+	buildLocal
+	exit
+fi
+
+if [ ${#} -gt 0 ]; then
+	for p; do
+		build "${p}"
+	done
+else
+	for p in ${platform[@]}; do
+		build "${p}"
+	done
+fi
+

cmd/ecli/clean-older.bash

@@ -0,0 +1,84 @@
+#!/usr/bin/env bash
+# Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+# All rights reserved
+
+RESOURCE_FILE=".build.rc"
+BUILD_REGISTER=".build_register"
+
+
+PASSWORD=
+GITEA_USER="camoroso"
+GITEA_PASSWORD_FILE="${HOME}/.gitea_password"
+GITEA_OWNER="go-pkg"
+GITEA_HOST="https://git.portale-stac.it"
+GITEA_BASE_PATH="api/v1/packages"
+GITEA_PKG_TYPE="generic"
+
+
+function msgln() {
+	echo >&2 "${1}"
+}
+
+function exitMsg() {
+	echo >&2 "${1}"
+	exit 1
+}
+
+function readBuildCount() {
+	local reg ver count
+	if [ -r "${BUILD_REGISTER}" ]; then
+		reg=$(<"${BUILD_REGISTER}")
+	else
+		reg="${PROGRAM_VERSION} 0"
+	fi
+	read ver count <<<"${reg}"
+	if [ "${ver}" != "${PROGRAM_VERSION}" ]; then
+		count=0
+	fi
+	echo ${count}
+}
+
+if [ -r "${GITEA_PASSWORD_FILE}" ]; then
+	if ! PASSWORD=$(<"${GITEA_PASSWORD_FILE}"); then
+		exitMsg "Can're password file '${GITEA_PASSWORD_FILE}'"
+	fi
+else
+	exitMsg "Password file '${GITEA_PASSWORD_FILE}' not found"
+fi
+if [ -z "${PASSWORD}" ]; then
+	exitMsg "Empty password. Please, check file '${GITEA_PASSWORD_FILE}'"
+fi
+
+if [ -r "${RESOURCE_FILE}" ]; then
+	source "${RESOURCE_FILE}"
+else
+	exitMsg "resource file '${RESOURCE_FILE}' not found"
+fi
+
+if [ -r "${BUILD_REGISTER}" ]; then
+	BUILD_TAG=$(<"${BUILD_REGISTER}")
+else
+	exitMsg "build register file '${BUILD_REGISTER}' not found"
+fi
+url="${GITEA_HOST}/${GITEA_BASE_PATH}/${GITEA_OWNER}/${GITEA_PKG_TYPE}/${PROGRAM_NAME}/${PROGRAM_VERSION}/files"
+#echo "URL: ${url}"
+#echo $(curl --user "${GITEA_USER}:${PASSWORD}" -X GET ${url}|jq '.[]."name"')
+
+declare -a files=(
+$(curl --no-progress-meter --user "${GITEA_USER}:${PASSWORD}" -X GET ${url}|jq '.[]."name"')
+)
+
+for name in ${files[@]}; do
+	filename=${name:1:${#name}-2}
+	name_terminal=${filename##*_}
+	filever=${name_terminal%%.*}
+
+	if [ "${BUILD_TAG}" != "${PROGRAM_VERSION} ${filever}" ]; then
+		msgln "Deleting ${name}"
+	curl --no-progress-meter --user "${GITEA_USER}:${PASSWORD}" -X DELETE ${GITEA_HOST}/api/packages/${GITEA_OWNER}/${GITEA_PKG_TYPE}/${PROGRAM_NAME}/${PROGRAM_VERSION}/${filename}
+#	else
+#		echo "most recent version"
+	fi
+done
+
+#curl --user "${GITEA_USER}:${PASSWORD}" -X GET https://git.portale-stac.it/api/v1/packages/go-pkg/generic/ecli/1.7.0/files

cmd/ecli/commands.go

@@ -0,0 +1,236 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// commands.go
+package main
+
+import (
+	"fmt"
+	"io"
+	"os"
+	"strings"
+
+	"git.portale-stac.it/go-pkg/expr"
+	"git.portale-stac.it/go-pkg/expr/kern"
+	"git.portale-stac.it/go-pkg/utils"
+)
+
+type commandFunction func(opt *Options, ctx kern.ExprContext, args []string) (err error)
+
+type command struct {
+	name        string
+	description string
+	code        commandFunction
+}
+
+func (cmd *command) exec(opt *Options, ctx kern.ExprContext, args []string) (err error) {
+	return cmd.code(opt, ctx, args)
+}
+
+type commandHandler struct {
+	cmdIndex []string
+	commands map[string]*command
+}
+
+func NewCommandHandler() *commandHandler {
+	return &commandHandler{
+		cmdIndex: make([]string, 0, 20),
+		commands: make(map[string]*command),
+	}
+}
+
+// func (h *commandHandler) setContext(ctx expr.ExprContext) {
+// 	h.ctx = ctx
+// }
+
+func (h *commandHandler) add(name, description string, f commandFunction) {
+	h.cmdIndex = append(h.cmdIndex, name)
+	h.commands[name] = &command{name: name, description: description, code: f}
+}
+
+func (h *commandHandler) get(cmdLine string) (cmd *command, args []string) {
+	if len(cmdLine) > 0 {
+		tokens := strings.Split(cmdLine, " ")
+		name := tokens[0]
+		args = make([]string, 0, len(tokens)-1)
+		if cmd = h.commands[name]; cmd != nil && len(tokens) > 1 {
+			for _, tk := range tokens[1:] {
+				if tk != "" {
+					args = append(args, tk)
+				}
+			}
+		}
+	}
+	return
+}
+
+// ------
+var cmdHandler *commandHandler
+
+func (h *commandHandler) help() {
+	fmt.Fprintln(os.Stderr, `--- REPL commands:`)
+	for _, name := range h.cmdIndex {
+		cmd := h.commands[name]
+		fmt.Fprintf(os.Stderr, "%12s -- %s\n", cmd.name, cmd.description)
+	}
+	fmt.Fprint(os.Stderr, `
+--- Command line options:
+    -b <builtin>       Import builtin modules.
+                       <builtin> can be a list of module names or a glob-pattern.
+                       Use the special value 'all' or the pattern '*' to import all modules.
+    -B, --list-builtins  List all builtin module names
+    -e <expression>    Evaluate <expression> instead of standard-input
+    -i                 Force REPL operation when all -e occurences have been processed
+    -h, --help, help   Show this help menu
+    -m, --modules      List all builtin modules
+    --noout            Disable printing of expression results
+    -p                 Print prefix form
+    -t                 Print tree form
+    -v, --version      Show program version
+`)
+
+}
+
+// --------
+
+func cmdExit(opt *Options, ctx kern.ExprContext, args []string) (err error) {
+	return io.EOF
+}
+
+func cmdHelp(opt *Options, ctx kern.ExprContext, args []string) (err error) {
+	cmdHandler.help()
+	return
+}
+
+func cmdMultiLine(opt *Options, ctx kern.ExprContext, args []string) (err error) {
+	if opt.formOpt&kern.MultiLine == 0 {
+		opt.formOpt |= kern.MultiLine
+	} else {
+		opt.formOpt &= ^kern.MultiLine
+	}
+	return
+}
+
+func cmdTty(opt *Options, ctx kern.ExprContext, args []string) (err error) {
+	if opt.formOpt&kern.TTY == 0 {
+		opt.formOpt |= kern.TTY
+	} else {
+		opt.formOpt &= ^kern.TTY
+	}
+	return
+}
+
+func execFile(opt *Options, ctx kern.ExprContext, fileName string) (err error) {
+	var fh *os.File
+	if fh, err = os.Open(fileName); err == nil {
+		goBatch(opt, ctx, fh, false)
+		fh.Close()
+	}
+	return
+}
+
+func cmdSource(opt *Options, ctx kern.ExprContext, args []string) (err error) {
+	var target string
+	for _, arg := range args {
+		if len(arg) == 0 {
+			continue
+		}
+		// TODO migliorare questa parte: eventualmente valutare un'espressione
+		if target, err = checkStringLiteral(arg); err != nil {
+			break
+		}
+
+		if target, err = utils.ExpandPath(target); err != nil {
+			break
+		}
+
+		if isPattern(target) {
+			var fileNames []string
+			if fileNames, err = matchPathPattern(target); err == nil {
+				for _, fileName := range fileNames {
+					if err = execFile(opt, ctx, fileName); err != nil {
+						break
+					}
+				}
+			}
+		} else {
+			err = execFile(opt, ctx, target)
+		}
+
+		if err != nil {
+			break
+		}
+	}
+	return
+}
+
+func cmdModules(opt *Options, ctx kern.ExprContext, args []string) (err error) {
+	expr.IterateBuiltinModules(func(name, description string, imported bool) bool {
+		var check rune = ' '
+		if imported {
+			check = '*'
+		}
+		fmt.Printf("%c %20q: %s\n", check, name, description)
+		return true
+	})
+	return
+}
+
+func cmdBase(opt *Options, ctx kern.ExprContext, args []string) (err error) {
+	if len(args) == 0 {
+		fmt.Println(opt.base)
+	} else if args[0] == "2" {
+		opt.baseVerb = "0b%b"
+		opt.base = 2
+	} else if args[0] == "8" {
+		opt.baseVerb = "0o%o"
+		opt.base = 8
+	} else if args[0] == "10" {
+		opt.baseVerb = "%d"
+		opt.base = 10
+	} else if args[0] == "16" {
+		opt.baseVerb = "0x%x"
+		opt.base = 16
+	} else {
+		err = fmt.Errorf("invalid number base %s", args[0])
+	}
+	return
+}
+
+func cmdOutput(opt *Options, ctx kern.ExprContext, args []string) (err error) {
+	var outputArg string
+	if len(args) == 0 {
+		outputArg = "status"
+	} else {
+		outputArg = strings.ToLower(args[0])
+	}
+	switch outputArg {
+	case "on":
+		opt.output = true
+	case "off":
+		opt.output = false
+	case "status":
+		if opt.output {
+			fmt.Println("on")
+		} else {
+			fmt.Println("off")
+		}
+	default:
+		err = fmt.Errorf("output: unknown option %q", outputArg)
+	}
+	return
+}
+
+//------------------
+
+func setupCommands() {
+	cmdHandler = NewCommandHandler()
+	cmdHandler.add("base", "Set the integer output base: 2, 8, 10, or 16", cmdBase)
+	cmdHandler.add("exit", "Exit the program", cmdExit)
+	cmdHandler.add("help", "Show command list", cmdHelp)
+	cmdHandler.add("ml", "Enable/Disable multi-line output", cmdMultiLine)
+	cmdHandler.add("mods", "List builtin modules", cmdModules)
+	cmdHandler.add("output", "Enable/Disable printing expression results. Options 'on', 'off', 'status'", cmdOutput)
+	cmdHandler.add("source", "Load a file as input", cmdSource)
+	cmdHandler.add("tty", "Enable/Disable ansi output", cmdTty)
+}

cmd/ecli/ecli.adoc

@@ -0,0 +1,314 @@
+= Ecli
+Expression Calculator Interactive Tool
+:authors: Celestino Amoroso
+:email: celestino.amoroso@gmail.com
+:docinfo: shared
+:encoding: utf-8
+:toc: right
+:toclevels: 4
+:icons: font
+:icon-set: fi
+:numbered:
+:data-uri:
+:docinfo1:
+:sectlinks:
+:sectanchors:
+:source-highlighter: rouge
+:rouge-style: manni
+:stylesdir: /home/share/s3-howto/styles
+:stylesheet: adoc-colony.css
+
+// Workaround to manage double-column in back-tick quotes
+:2c: ::
+// Workaround to manage double-plus in back-tick quotes
+:plusplus: ++
+// Workaround to manage asterisk in back-tick quotes
+:star: *
+
+#Generated by Copilot#
+
+== Overview
+
+`ecli` (Expression Calculator Interactive Tool) is an interactive REPL (Read-Eval-Print Loop) application for evaluating expressions using the Expr package. It provides a powerful command-line interface for expression evaluation with support for multiple builtin modules, file operations, and interactive scripting.
+
+The tool combines the expression evaluation capabilities of the Expr package with an interactive shell environment, making it ideal for:
+
+- Interactive expression testing and prototyping
+- Batch expression evaluation from scripts
+- Data processing and transformation
+- Mathematical computations with fractions and complex operators
+
+== Getting Started
+
+=== Installation
+
+To build and install `ecli`:
+
+[source,bash]
+----
+cd cmd/ecli
+./build.bash
+----
+
+The compiled binary will be available as `ecli` in the current directory.
+
+=== Basic Usage
+
+Start the interactive REPL:
+
+[source,bash]
+----
+./ecli
+----
+
+You'll see the prompt `>>> ` where you can enter expressions to evaluate.
+
+=== Command Line Options
+
+[cols="1,4", options="header"]
+|===
+| Option | Description
+
+| `-e <expression>` | Evaluate an expression directly without entering REPL mode
+| `-i` | Force REPL operation after processing all `-e` options
+| `-b <builtin>` | Import builtin modules (comma-separated list, glob patterns, or 'all')
+| `-B, --list-builtins` | List all available builtin module names
+| `-m, --modules` | List all builtin modules
+| `-p` | Print expressions in prefix form
+| `-t` | Print expressions in tree form
+| `--noout` | Disable printing of expression results
+| `-h, --help` | Show help message
+| `-v, --version` | Show program version
+|===
+
+== Interactive Commands
+
+Within the REPL, you can use the following commands:
+
+[cols="2,5", options="header"]
+|===
+| Command | Description
+
+| `help` | Display available commands and command-line options
+| `exit` | Exit the REPL
+| `multiline` | Toggle multi-line input mode for complex expressions
+| `tty` | Toggle TTY mode
+| `source <file>` | Execute expressions from a file
+|===
+
+== Features
+
+=== Expression Evaluation
+
+`ecli` supports the full expression language provided by the Expr package, including:
+
+- **Arithmetic Operations**: Addition, subtraction, multiplication, division, modulo
+- **Bitwise Operations**: AND, OR, XOR, NOT, shift operations
+- **Boolean Logic**: AND, OR, NOT operations
+- **Relational Operators**: Comparison and equality operators
+- **String Operations**: Concatenation and string manipulation
+- **Iterators**: Range, list, and custom iterators
+- **Functions**: Builtin and user-defined functions
+- **Collections**: Lists, dictionaries, and linked lists
+- **Fractions**: Support for fractional arithmetic
+
+=== Builtin Modules
+
+`ecli` provides access to various builtin modules through the `-b` option:
+
+[cols="1,4", options="header"]
+|===
+| Module | Functionality
+
+| `base` | Core expression evaluation functions
+| `fmt` | String formatting and output functions
+| `string` | String manipulation functions
+| `math-arith` | Mathematical and arithmetic operations
+| `iterator` | Iterator-related functions
+| `os-file` | File I/O operations
+| `import` | Module import functionality
+|===
+
+Use `-B` or `--list-builtins` to see all available modules:
+
+[source,bash]
+----
+./ecli --list-builtins
+----
+
+== Examples
+
+=== Basic Arithmetic
+
+[source,bash]
+----
+>>> 2 + 3 * 4
+14
+>>> (2 + 3) * 4
+20
+----
+
+=== String Operations
+
+[source,bash]
+----
+>>> "hello" + " " + "world"
+hello world
+----
+
+=== Using Iterators
+
+[source,bash]
+----
+>>> [1, 2, 3, 4, 5] | map(. * 2)
+[2, 4, 6, 8, 10]
+----
+
+=== Evaluating from Command Line
+
+[source,bash]
+----
+./ecli -e "2 + 2"
+4
+----
+
+=== Loading Builtin Modules
+
+[source,bash]
+----
+./ecli -b "math-arith,string"
+----
+
+=== Loading Expressions from Files
+
+Inside the REPL:
+
+[source]
+----
+>>> source "expressions.expr"
+----
+
+Or from command line:
+
+[source,bash]
+----
+./ecli -e '@include "expressions.expr"'
+----
+
+== Configuration
+
+=== Resource Files
+
+`ecli` supports startup resource files:
+
+- `.ecli.rc` - Main configuration file
+- `.ecli.rc.d/` - Directory for modular configuration files
+
+These files are automatically loaded at startup if they exist in the current directory or home directory.
+
+== Building from Source
+
+=== Prerequisites
+
+- Go 1.18 or later
+- Make or bash shell
+
+=== Build Steps
+
+[source,bash]
+----
+cd cmd/ecli
+./build.bash
+----
+
+=== Build Artifacts
+
+The build process generates:
+
+- `ecli` - The main executable
+- `version.txt` - Version information
+- Platform-specific binaries (e.g., `ecli_v1.17.0_linux_amd64`, `ecli_v1.17.0_darwin_arm64`)
+
+== Advanced Usage
+
+=== Multi-line Input
+
+For complex expressions, toggle multi-line mode:
+
+[source]
+----
+>>> multiline
+>>> result = [1, 2, 3, 4, 5] 
+...   | filter(. > 2)
+...   | map(. * 2)
+>>> result
+[6, 8, 10]
+----
+
+=== Script Execution
+
+Create a file `calculations.expr`:
+
+[source]
+----
+x = 10
+y = 20
+result = x + y * 2
+----
+
+Execute it:
+
+[source,bash]
+----
+./ecli -e '@source "calculations.expr"' -e 'result'
+----
+
+=== Chaining Operations
+
+[source]
+----
+>>> data = [{"name": "alice", "age": 30}, {"name": "bob", "age": 25}]
+>>> data | map(.name)
+[alice, bob]
+----
+
+== Troubleshooting
+
+=== Expression Parsing Errors
+
+If you encounter parsing errors, check:
+
+- Bracket matching and quotation marks
+- Operator precedence
+- Variable and function names
+
+=== Module Loading Issues
+
+Verify available modules:
+
+[source,bash]
+----
+./ecli --list-builtins
+----
+
+=== File Not Found Errors
+
+Ensure file paths are:
+
+- Properly quoted in expressions
+- Relative to the current working directory or absolute paths
+- Readable by the current user
+
+== Related Documentation
+
+- link:../../../README.adoc[Expr Package Documentation]
+- Expr Expression Language Syntax
+- Builtin Modules Reference
+
+== Version History
+
+For version information and changes, see the link:version.txt[version file].
+
+== License
+
+Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com). All rights reserved.

cmd/ecli/go.mod

@@ -0,0 +1,15 @@
+module ecli
+
+go 1.24.0
+
+require (
+	git.portale-stac.it/go-pkg/expr v0.33.0
+	git.portale-stac.it/go-pkg/utils v0.3.0
+	github.com/ergochat/readline v0.1.3
+)
+
+require (
+	golang.org/x/exp v0.0.0-20251113190631-e25ba8c21ef6 // indirect
+	golang.org/x/sys v0.38.0 // indirect
+	golang.org/x/text v0.31.0 // indirect
+)

cmd/ecli/go.sum

@@ -0,0 +1,36 @@
+git.portale-stac.it/go-pkg/expr v0.1.0 h1:7xGEuUhdh6RRFaRbRnLVqVJBmHJWHfqjDBm2K0fIW2s=
+git.portale-stac.it/go-pkg/expr v0.1.0/go.mod h1:kUFEQkUMCJ1IiUKkL0P5/vznaAIzFI26Xf5P0rTXqR0=
+git.portale-stac.it/go-pkg/expr v0.2.0 h1:AAaVsV0uaC4EikKU91VuubIpbIN7wuya7t4avyFgg+0=
+git.portale-stac.it/go-pkg/expr v0.2.0/go.mod h1:DZqqZ3A9h4qEOs7yMvG4VZq7B/xhFsYqC3IKd3M2VKc=
+git.portale-stac.it/go-pkg/expr v0.17.0 h1:4ANGwJfwJO3AmnKka4Cf1AO9/ckGLMj8RIWeoDFKawQ=
+git.portale-stac.it/go-pkg/expr v0.17.0/go.mod h1:DZqqZ3A9h4qEOs7yMvG4VZq7B/xhFsYqC3IKd3M2VKc=
+git.portale-stac.it/go-pkg/expr v0.32.0 h1:ikXqHjJslIGkD79G1/51xe+c25TFi2CslJ6nu8mOuJY=
+git.portale-stac.it/go-pkg/expr v0.32.0/go.mod h1:R2TYIahLtD8YDgNEHtgHCQdoEUZ7yCQsMHyJXhJijmw=
+git.portale-stac.it/go-pkg/expr v0.33.0 h1:GJ7PPgA1689GSC/cUWGYm08jn7qMmkp0FMQf/As5sCw=
+git.portale-stac.it/go-pkg/expr v0.33.0/go.mod h1:R2TYIahLtD8YDgNEHtgHCQdoEUZ7yCQsMHyJXhJijmw=
+git.portale-stac.it/go-pkg/utils v0.2.0 h1:2l4IVUhElzjaIUJlahPG2DZTGb9x7OXuFTO4z1K6LmY=
+git.portale-stac.it/go-pkg/utils v0.2.0/go.mod h1:PebQ45Qbe89aMTd3wcbcx1bkpNRW4/frNLnpuyZYovU=
+git.portale-stac.it/go-pkg/utils v0.3.0 h1:kCJ3+XcekV7in/SieJjiswdtJKMBS0RTJMlG2fW5mK0=
+git.portale-stac.it/go-pkg/utils v0.3.0/go.mod h1:PebQ45Qbe89aMTd3wcbcx1bkpNRW4/frNLnpuyZYovU=
+github.com/ergochat/readline v0.1.0 h1:KEIiAnyH9qGZB4K8oq5mgDcExlEKwmZDcyyocgJiABc=
+github.com/ergochat/readline v0.1.0/go.mod h1:o3ux9QLHLm77bq7hDB21UTm6HlV2++IPDMfIfKDuOgY=
+github.com/ergochat/readline v0.1.1 h1:C8Uuo3ybB23GWOt0uxmHbGzKM9owmtXary6Clrj84s0=
+github.com/ergochat/readline v0.1.1/go.mod h1:o3ux9QLHLm77bq7hDB21UTm6HlV2++IPDMfIfKDuOgY=
+github.com/ergochat/readline v0.1.3 h1:/DytGTmwdUJcLAe3k3VJgowh5vNnsdifYT6uVaf4pSo=
+github.com/ergochat/readline v0.1.3/go.mod h1:o3ux9QLHLm77bq7hDB21UTm6HlV2++IPDMfIfKDuOgY=
+golang.org/x/exp v0.0.0-20251113190631-e25ba8c21ef6 h1:zfMcR1Cs4KNuomFFgGefv5N0czO2XZpUbxGUy8i8ug0=
+golang.org/x/exp v0.0.0-20251113190631-e25ba8c21ef6/go.mod h1:46edojNIoXTNOhySWIWdix628clX9ODXwPsQuG6hsK0=
+golang.org/x/sys v0.15.0 h1:h48lPFYpsTvQJZF4EKyI4aLHaev3CxivZmv7yZig9pc=
+golang.org/x/sys v0.15.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
+golang.org/x/sys v0.21.0 h1:rF+pYz3DAGSQAxAu1CbC7catZg4ebC4UIeIhKxBZvws=
+golang.org/x/sys v0.21.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
+golang.org/x/sys v0.38.0 h1:3yZWxaJjBmCWXqhN1qh02AkOnCQ1poK6oF+a7xWL6Gc=
+golang.org/x/sys v0.38.0/go.mod h1:OgkHotnGiDImocRcuBABYBEXf8A9a87e/uXjp9XT3ks=
+golang.org/x/text v0.3.7 h1:olpwvP2KacW1ZWvsR7uQhoyTYvKAupfQrRGBFM352Gk=
+golang.org/x/text v0.3.7/go.mod h1:u+2+/6zg+i71rQMx5EYifcz6MCKuco9NR6JIITiCfzQ=
+golang.org/x/text v0.9.0 h1:2sjJmO8cDvYveuX97RDLsxlyUxLl+GHoLxBiRdHllBE=
+golang.org/x/text v0.9.0/go.mod h1:e1OnstbJyHTd6l/uOt8jFFHp6TRDWZR/bV3emEE/zU8=
+golang.org/x/text v0.16.0 h1:a94ExnEXNtEwYLGJSIUxnWoxoRz/ZcCsV63ROupILh4=
+golang.org/x/text v0.16.0/go.mod h1:GhwF1Be+LQoKShO3cGOHzqOgRrGaYc9AvblQOmPVHnI=
+golang.org/x/text v0.31.0 h1:aC8ghyu4JhP8VojJ2lEHBnochRno1sgL6nEi9WGFGMM=
+golang.org/x/text v0.31.0/go.mod h1:tKRAlv61yKIjGGHX/4tP1LTbc13YSec1pxVEWXzfoeM=

cmd/ecli/graph.go

@@ -0,0 +1,18 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+//go:build graph
+
+// graph.go
+package main
+
+import (
+	"fmt"
+
+	"git.portale-stac.it/go-pkg/expr"
+)
+
+func printGraph() {
+	r := expr.NewExprReticle(ast)
+	fmt.Println(r.String())
+}

cmd/ecli/main.go

@@ -0,0 +1,415 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// main.go
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"os"
+	"strings"
+
+	"git.portale-stac.it/go-pkg/expr"
+	"git.portale-stac.it/go-pkg/expr/kern"
+	"git.portale-stac.it/go-pkg/expr/scan"
+	"git.portale-stac.it/go-pkg/utils"
+
+	// https://pkg.go.dev/github.com/ergochat/readline#section-readme
+	"github.com/ergochat/readline"
+)
+
+const (
+	intro = PROGNAME + ` -- Expressions calculator ` + VERSION + `
+	Based on the Expr package ` + EXPR_VERSION + ` (` + EXPR_DATE + `) 
+	Type help to get the list of available commands
+	See also https://git.portale-stac.it/go-pkg/expr/src/branch/main/README.adoc
+`
+	mainPrompt = ">>> "
+	contPrompt = "... "
+
+	historyFile = "~/.expr_history"
+)
+
+// ------
+
+func errOptValueRequired(opt string) error {
+	return fmt.Errorf("option %q requires a value", opt)
+}
+
+func about() string {
+	return PROGNAME + " -- " + VERSION + "; Expr package " + EXPR_VERSION
+}
+
+func importBuiltins(ctx kern.ExprContext, opt *Options) (err error) {
+	for _, spec := range opt.builtin {
+		if moduleSpec, ok := spec.(string); ok {
+			if moduleSpec == "all" {
+				moduleSpec = "*"
+			}
+			_, err = expr.ImportInContextByGlobPattern(ctx, moduleSpec)
+		} else if moduleSpec, ok := spec.([]string); ok {
+			notFoundList := make([]string, 0)
+			for _, name := range moduleSpec {
+				if !expr.ImportInContext(ctx, name) {
+					notFoundList = append(notFoundList, name)
+				}
+			}
+			if len(notFoundList) > 0 {
+				err = fmt.Errorf("not found modules: %s", strings.Join(notFoundList, ","))
+			}
+		}
+	}
+	return
+}
+
+func initReadlineConfig(cfg *readline.Config) {
+	if histfile, err := utils.ExpandPath(historyFile); err == nil {
+		cfg.HistoryFile = histfile
+	}
+	cfg.Undo = true
+	cfg.DisableAutoSaveHistory = true
+
+}
+
+func goInteractiveReadline(opt *Options, ctx kern.ExprContext, r io.Reader) {
+	var sb strings.Builder
+	var cfg readline.Config
+	initReadlineConfig(&cfg)
+	rl, err := readline.NewFromConfig(&cfg)
+	if err != nil {
+		goInteractive(opt, ctx, r)
+		return
+	}
+	defer rl.Close()
+
+	fmt.Print(intro)
+	rl.SetPrompt(mainPrompt)
+	for line, err := rl.ReadLine(); err == nil; line, err = rl.ReadLine() {
+		if continuation(&sb, line) {
+			rl.SetPrompt(contPrompt)
+			continue
+		}
+
+		rl.SetPrompt(mainPrompt)
+		sb.WriteString(line)
+		source := strings.TrimSpace(sb.String())
+		if source != "" && !strings.HasPrefix(source, "//") {
+			if cmd, args := cmdHandler.get(source); cmd != nil {
+				rl.SaveToHistory(source)
+				if err = cmd.exec(opt, ctx, args); err != nil {
+					if err == io.EOF {
+						err = nil
+						break
+					} else {
+						fmt.Fprintln(os.Stderr, "Eval Error:", err)
+						break
+					}
+				}
+			} else {
+				rl.SaveToHistory(source)
+				r := strings.NewReader(source)
+				compute(opt, ctx, r, true)
+			}
+		}
+		sb.Reset()
+	}
+	fmt.Println()
+}
+
+func goInteractive(opt *Options, ctx kern.ExprContext, r io.Reader) {
+	var sb strings.Builder
+	fmt.Print(intro)
+	fmt.Print(mainPrompt)
+	reader := bufio.NewReaderSize(r, 1024)
+	for line, err := reader.ReadString('\n'); err == nil && line != "exit\n"; line, err = reader.ReadString('\n') {
+		if continuation(&sb, line) {
+			continue
+		}
+
+		sb.WriteString(line)
+		source := strings.TrimSpace(sb.String())
+		// fmt.Printf("source=%q\n", source)
+		if source != "" && !strings.HasPrefix(source, "//") {
+			if cmd, args := cmdHandler.get(source); cmd != nil {
+				if err = cmd.exec(opt, ctx, args); err != nil {
+					break
+				}
+			} else {
+				r := strings.NewReader(source)
+				compute(opt, ctx, r, true)
+			}
+		}
+		sb.Reset()
+		fmt.Print(mainPrompt)
+	}
+	fmt.Println()
+}
+
+func continuation(sb *strings.Builder, line string) (cont bool) {
+	line = strings.TrimSpace(line)
+	if strings.HasSuffix(line, "\\") {
+		sb.WriteString(line[0 : len(line)-1])
+		cont = true
+	} else if strings.HasSuffix(line, ";") {
+		sb.WriteString(line)
+		cont = true
+	} else if len(line) > 0 {
+		if scan.StringEndsWithOperator(line) {
+			sb.WriteString(line)
+			cont = true
+		} else {
+			fullInput := sb.String() + line
+			if strings.Count(fullInput, "(") > strings.Count(fullInput, ")") ||
+				strings.Count(fullInput, "[") > strings.Count(fullInput, "]") ||
+				strings.Count(fullInput, "{") > strings.Count(fullInput, "}") {
+				sb.WriteString(line)
+				cont = true
+			}
+		}
+	}
+
+	return
+}
+
+func goBatch(opt *Options, ctx kern.ExprContext, r io.Reader, outputEnabled bool) {
+	var sb strings.Builder
+	reader := bufio.NewReaderSize(r, 1024)
+	for line, err := reader.ReadString('\n'); err == nil && line != "exit\n"; line, err = reader.ReadString('\n') {
+		if continuation(&sb, line) {
+			continue
+		}
+		sb.WriteString(line)
+		source := strings.TrimSpace(sb.String())
+		// fmt.Printf("source=%q\n", source)
+		if source != "" && !strings.HasPrefix(source, "//") {
+			if cmd, args := cmdHandler.get(source); cmd != nil {
+				if err = cmd.exec(opt, ctx, args); err != nil {
+					fmt.Fprintln(os.Stderr, "Eval Error:", err)
+					break
+				}
+			} else {
+				r := strings.NewReader(source)
+				compute(opt, ctx, r, outputEnabled)
+			}
+		}
+		sb.Reset()
+	}
+}
+
+func compute(opt *Options, ctx kern.ExprContext, r io.Reader, outputEnabled bool) {
+	scanner := scan.NewScanner(r, scan.DefaultTranslations())
+	parser := expr.NewParser()
+
+	if ast, err := parser.Parse(scanner); err == nil {
+		if opt.printPrefix {
+			fmt.Println(ast)
+		}
+		if opt.printTree {
+			printGraph()
+		}
+
+		if result, err := ast.Eval(ctx); err == nil {
+			if outputEnabled && opt.output {
+				printResult(opt, result)
+			}
+		} else {
+			fmt.Fprintln(os.Stderr, "Eval Error:", err)
+		}
+	} else {
+		fmt.Fprintln(os.Stderr, "Parse Error:", err)
+	}
+}
+
+func printResult(opt *Options, result any) {
+	if f, ok := result.(kern.Formatter); ok {
+		fmt.Println(f.ToString(opt.formOpt))
+	} else if kern.IsInteger(result) {
+		fmt.Printf(opt.baseVerb, result)
+		fmt.Println()
+	} else if kern.IsString(result) {
+		fmt.Printf("\"%s\"\n", result)
+	} else {
+		fmt.Println(result)
+	}
+}
+
+func isReaderTerminal(r io.Reader) bool {
+	if fh, ok := r.(*os.File); ok {
+		return utils.StreamIsTerminal(fh)
+	}
+	return false
+}
+
+func registerLocalFunctions(ctx kern.ExprContext) {
+	const (
+		devParamProp   = "prop"
+		devParamDigits = "digits"
+	)
+
+	aboutFunc := func(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
+		result = about()
+		return
+	}
+
+	ctrlListFunc := func(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
+		vars := ctx.EnumVars(func(name string) bool {
+			return len(name) > 0 && name[0] == '_'
+		})
+		result = kern.ListFromStrings(vars)
+		return
+	}
+
+	ctrlFunc := func(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
+		varName, _ := args[devParamProp].(string)
+		if len(args) == 1 {
+			result = expr.GlobalCtrlGet(ctx, varName)
+		} else {
+			result = expr.GlobalCtrlSet(ctx, varName, args[kern.ParamValue])
+		}
+		return
+	}
+
+	envSetFunc := func(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
+		var varName, value string
+		var ok bool
+		if varName, ok = args[kern.ParamName].(string); !ok {
+			err = kern.ErrExpectedGot(name, kern.TypeString, args[kern.ParamName])
+			return
+		}
+		if value, ok = args[kern.ParamValue].(string); !ok {
+			err = kern.ErrExpectedGot(name, kern.TypeString, args[kern.ParamValue])
+			return
+		}
+		if err = os.Setenv(varName, value); err == nil {
+			result = value
+		}
+		return
+	}
+
+	envGetFunc := func(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 {
+			err = kern.ErrExpectedGot(name, kern.TypeString, args[kern.ParamName])
+			return
+		}
+
+		if result, ok = os.LookupEnv(varName); !ok {
+			err = fmt.Errorf("environment variable %q does not exist", varName)
+		}
+		return
+	}
+
+	envListFunc := func(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
+		env := os.Environ()
+		vars := make([]string, 0, len(env))
+		for _, e := range env {
+			name, _, _ := strings.Cut(e, "=")
+			vars = append(vars, name)
+		}
+		result = kern.ListFromStrings(vars)
+		return
+	}
+
+	binFunc := func(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
+		var value, digits int64
+		var ok bool
+		var sb strings.Builder
+
+		if value, ok = args[kern.ParamValue].(int64); !ok {
+			err = kern.ErrExpectedGot(name, kern.TypeInt, args[kern.ParamValue])
+			return
+		}
+		if digits, ok = args[devParamDigits].(int64); !ok {
+			err = kern.ErrExpectedGot(name, kern.TypeInt, args[devParamDigits])
+			return
+		}
+		if digits != 64 && digits != 32 && digits != 16 && digits != 8 {
+			err = fmt.Errorf("%s param allows 8, 16, 32, or 64 values only", devParamDigits)
+			return
+		}
+
+		mask := uint64(0)
+		for i := 0; i < int(digits); i++ {
+			mask |= (1 << i)
+		}
+		maskedValue := uint64(value) & mask
+		// if maskedValue != uint64(value) {
+		// 	err = fmt.Errorf("%s param (%d) is not compatible with the value (%d) of %s param", expr.ParamValue, value, digits, devParamDigits)
+		// 	return
+		// }
+
+		for i := int(digits) - 1; i >= 0; i-- {
+			if maskedValue&(1<<i) == 0 {
+				sb.WriteByte('0')
+			} else {
+				sb.WriteByte('1')
+			}
+		}
+
+		result = sb.String()
+		return
+	}
+
+	ctx.RegisterFunc("about", kern.NewGolangFunctor(aboutFunc), kern.TypeString, []kern.ExprFuncParam{})
+	ctx.RegisterFunc("ctrlList", kern.NewGolangFunctor(ctrlListFunc), kern.TypeListOfStrings, []kern.ExprFuncParam{})
+	ctx.RegisterFunc("ctrl", kern.NewGolangFunctor(ctrlFunc), kern.TypeAny, []kern.ExprFuncParam{
+		kern.NewFuncParam(devParamProp),
+		kern.NewFuncParamFlag(kern.ParamValue, kern.PfOptional),
+	})
+	ctx.RegisterFunc("envSet", kern.NewGolangFunctor(envSetFunc), kern.TypeString, []kern.ExprFuncParam{
+		kern.NewFuncParam(kern.ParamName),
+		kern.NewFuncParam(kern.ParamValue),
+	})
+	ctx.RegisterFunc("envGet", kern.NewGolangFunctor(envGetFunc), kern.TypeString, []kern.ExprFuncParam{
+		kern.NewFuncParam(kern.ParamName),
+	})
+	ctx.RegisterFunc("envList", kern.NewGolangFunctor(envListFunc), kern.TypeListOfStrings, []kern.ExprFuncParam{})
+
+	ctx.RegisterFunc("bin", kern.NewGolangFunctor(binFunc), kern.TypeInt, []kern.ExprFuncParam{
+		kern.NewFuncParam(kern.ParamValue),
+		kern.NewFuncParamFlagDef(devParamDigits, kern.PfOptional|kern.PfDefault, int64(8)),
+	})
+}
+
+func main() {
+	setupCommands()
+	opt := NewOptions()
+	opt.loadRc()
+	if err := opt.parseArgs(); err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		os.Exit(1)
+	}
+
+	ctx := expr.NewSimpleStore()
+
+	if err := importBuiltins(ctx, opt); err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		os.Exit(1)
+	}
+
+	registerLocalFunctions(ctx)
+
+	if len(opt.expressions) == opt.rcCount || opt.forceInteractive {
+		opt.expressions = append(opt.expressions, os.Stdin)
+	}
+
+	for _, input := range opt.expressions {
+		if isReaderTerminal(input) {
+			goInteractiveReadline(opt, ctx, input)
+		} else {
+			_, enableOutput := input.(*strings.Reader)
+			goBatch(opt, ctx, input, enableOutput)
+			if f, ok := input.(*os.File); ok {
+				f.Close()
+			}
+		}
+	}
+
+	// TODO: why did I added these lines?
+	// if opt.output {
+	// 	printResult(opt, ctx.GetLast())
+	// }
+}

cmd/ecli/match.go

@@ -0,0 +1,49 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// match.go
+package main
+
+import (
+	"os"
+	"path"
+	"path/filepath"
+	"strings"
+)
+
+func matchFilePattern(dirName string, pattern string, join bool) (fileList []string, err error) {
+	var entries []os.DirEntry
+	if entries, err = os.ReadDir(dirName); err == nil {
+		for _, entry := range entries {
+			if entry.Type().IsRegular() {
+				var match bool
+				if match, err =filepath.Match(pattern, entry.Name()); err != nil {
+					fileList = nil
+					break
+				}
+				if match {
+					if fileList == nil {
+						fileList = make([]string, 0, 1)
+					}
+					if join {
+						fileList = append(fileList, path.Join(dirName, entry.Name()))
+					} else {
+						fileList = append(fileList, entry.Name())
+					}
+				}
+			}
+		}
+	}
+	return
+}
+
+func matchPathPattern(pathPattern string) (fileList []string, err error) {
+	dirName := path.Dir(pathPattern)
+	pattern := path.Base(pathPattern)
+	return matchFilePattern(dirName, pattern, true) 
+}
+
+
+func isPattern(name string) bool{
+	return strings.ContainsAny(name, "*?[]")
+} 

cmd/ecli/match_test.go

@@ -0,0 +1,36 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// main.go
+package main
+
+import (
+	"path"
+	"slices"
+	"testing"
+)
+
+func TestIsPattern(t *testing.T) {
+	target := "non-pattern"
+	if isPattern(target) {
+		t.Errorf("%q recognized as a pattern", target)
+	}
+
+	target = "pattern/*.expr"
+	if !isPattern(target) {
+		t.Errorf("%q not recognized as a pattern", target)
+	}
+}
+
+func TestMatchFilePattern(t *testing.T) {
+	target := "./go.*sum"
+	dirName := path.Dir(target)
+	pattern := path.Base(target)
+	if matchedFiles, err := matchFilePattern(dirName, pattern, true); err == nil {
+		if slices.Compare(matchedFiles, []string{"go.sum", "go.work.sum"}) != 0 {
+			t.Errorf("Matched file list is not correct: %v", matchedFiles)
+		}
+	} else {
+		t.Errorf("Got error: %v", err)
+	}
+}

cmd/ecli/options.go

@@ -0,0 +1,140 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// options.go
+package main
+
+import (
+	"fmt"
+	"io"
+	"os"
+	"strings"
+
+	"git.portale-stac.it/go-pkg/expr"
+	"git.portale-stac.it/go-pkg/expr/kern"
+	"git.portale-stac.it/go-pkg/utils"
+)
+
+type Options struct {
+	printTree        bool
+	printPrefix      bool
+	forceInteractive bool
+	builtin          []any
+	expressions      []io.Reader
+	formOpt          kern.FmtOpt
+	baseVerb         string
+	base             int
+	output           bool
+	rcCount          int
+}
+
+func NewOptions() *Options {
+	return &Options{
+		expressions: make([]io.Reader, 0),
+		builtin:     make([]any, 0),
+		formOpt:     kern.Base10,
+		baseVerb:    "%d",
+		base:        10,
+		output:      true,
+		rcCount:     0,
+	}
+}
+
+func (opt *Options) loadRc() {
+	var rcPath string
+	var fh *os.File
+	var err error
+
+	rcList := []string{
+		".ecli.rc",
+		"~/.ecli.rc",
+		"~/.config/expr/ecli.rc",
+		"~/.dev-expr.rc", // OBSOLETE, to be removed in future releases
+	}
+	for _, rcFile := range rcList {
+		if rcPath, err = utils.ExpandPath(rcFile); err != nil {
+			return
+		}
+		if fh, err = os.Open(rcPath); err == nil {
+			opt.expressions = append(opt.expressions, fh) // rc should be the first source to be read
+			opt.rcCount++
+			break
+		}
+	}
+}
+
+func listBuiltins() {
+	expr.IterateBuiltinModules(func(name, description string, imported bool) bool {
+		if imported {
+			name = "*" + name
+		}
+		fmt.Printf("%20q: %s\n", name, description)
+		return true
+	})
+}
+
+func (opt *Options) parseArgs() (err error) {
+	for i := 1; i < len(os.Args) && err == nil; i++ {
+		arg := os.Args[i]
+		switch arg {
+		case "-i":
+			opt.forceInteractive = true
+		case "-t":
+			opt.printTree = true
+		case "-p":
+			opt.printPrefix = true
+		case "-e":
+			if i+1 < len(os.Args) {
+				i++
+				spec := os.Args[i]
+				if strings.HasPrefix(spec, "@") {
+					var f *os.File
+					if f, err = os.Open(spec[1:]); err == nil {
+						opt.expressions = append(opt.expressions, f)
+					} else {
+						return
+					}
+				} else {
+					if len(spec) > 0 && spec[len(spec)-1] != '\n' {
+						spec += "\n"
+					}
+					opt.expressions = append(opt.expressions, strings.NewReader(spec))
+				}
+			} else {
+				err = errOptValueRequired(arg)
+			}
+		case "-b":
+			if i+1 < len(os.Args) {
+				i++
+				specs := strings.Split(os.Args[i], ",")
+				if len(specs) == 1 {
+					opt.builtin = append(opt.builtin, specs[0])
+				} else {
+					opt.builtin = append(opt.builtin, specs)
+				}
+			} else {
+				err = errOptValueRequired(arg)
+			}
+		case "-B", "--list-builtins":
+			listBuiltins()
+			os.Exit(0)
+		case "-m", "--modules":
+			expr.IterateBuiltinModules(func(name, description string, _ bool) bool {
+				fmt.Printf("%20q: %s\n", name, description)
+				return true
+			})
+			os.Exit(0)
+		case "--noout":
+			opt.output = false
+		case "-h", "--help", "help":
+			cmdHandler.help()
+			os.Exit(0)
+		case "-v", "--version", "version", "about":
+			fmt.Println(about())
+			os.Exit(0)
+		default:
+			err = fmt.Errorf("invalid option nr %d %q", i+1, arg)
+		}
+	}
+	return
+}

cmd/ecli/publish.bash

@@ -0,0 +1,79 @@
+#!/usr/bin/env bash
+# Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+# All rights reserved.
+
+RESOURCE_FILE=".build.rc"
+BUILD_REGISTER=".build_register"
+PASSWORD=
+GITEA_USER="camoroso"
+GITEA_PASSWORD_FILE="${HOME}/.gitea_password"
+GITEA_OWNER="go-pkg"
+GITEA_HOST="https://git.portale-stac.it"
+GITEA_BASE_PATH="api/packages"
+GITEA_PKG_TYPE="generic"
+
+function exitMsg() {
+	echo >&2 "${1}"
+	exit 1
+}
+
+function readBuildCount() {
+	local reg ver count
+	if [ -r "${BUILD_REGISTER}" ]; then
+		reg=$(<"${BUILD_REGISTER}")
+	else
+		reg="${PROGRAM_VERSION} 0"
+	fi
+	read ver count <<<"${reg}"
+	if [ "${ver}" != "${PROGRAM_VERSION}" ]; then
+		count=0
+	fi
+	echo ${count}
+}
+
+if [ -r "${GITEA_PASSWORD_FILE}" ]; then
+	if ! PASSWORD=$(<"${GITEA_PASSWORD_FILE}"); then
+		exitMsg "Can're password file '${GITEA_PASSWORD_FILE}'"
+	fi
+else
+	exitMsg "Password file '${GITEA_PASSWORD_FILE}' not found"
+fi
+if [ -z "${PASSWORD}" ]; then
+	exitMsg "Empty password. Please, check file '${GITEA_PASSWORD_FILE}'"
+fi
+
+if ! ./build.bash; then
+	exitMsg "Build program failed"
+fi
+
+if ! source "${RESOURCE_FILE}"; then
+	exitMsg "Loading resource file failed"
+fi
+
+if ! exeList=$(echo 2>/dev/null ${PROGRAM_NAME}_v${PROGRAM_VERSION}_*); then
+	exitMsg "No executable found"
+fi
+
+buildCount=$(readBuildCount)
+fileCount=0
+for exe in ${exeList}; do
+	if [ "${exe/tar.gz/}" != "${exe}" ]; then
+		continue
+	fi
+	((fileCount++))
+	dir="${exe}_${buildCount}"
+	dist="${dir}.tar.gz"
+	rm -f "${dist}"
+	printf "%2d: %-30s  -->  %s\n" "${fileCount}" "${exe}" "${dist}"
+	mkdir "${dir}"
+	cp "${exe}" "${dir}/${PROGRAM_NAME}"
+	tar czf "${dist}" "${dir}"
+	rm -fR "${dir}"
+
+	url="${GITEA_HOST}/${GITEA_BASE_PATH}/${GITEA_OWNER}/${GITEA_PKG_TYPE}/${PROGRAM_NAME}/${PROGRAM_VERSION}/${dist}"
+#	echo "${url}"
+	curl --user "${USER}:${PASSWORD}" --upload-file "${dist}" "${url}"
+
+	rm -f "${dist}"
+done
+

cmd/ecli/util-string.go

@@ -0,0 +1,23 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// util-string.go
+package main
+
+import (
+	"fmt"
+)
+
+func checkStringLiteral(literal string) (value string, err error) {
+	length := len(literal)
+	if length >= 2 {
+		if (literal[0] == '"' && literal[length-1] == '"') || literal[0] == '\'' && literal[length-1] == '\'' {
+			value = literal[1 : length-1]
+		} else {
+			err = fmt.Errorf("unquoted or partially quoted string literal: `%s`", literal)
+		}
+	} else {
+		err = fmt.Errorf("invalid string literal: `%s`", literal)
+	}
+	return
+}

cmd/ecli/version.txt

@@ -0,0 +1 @@
+1.17.0

data-cursor.go

@@ -1,4 +1,4 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
 // All rights reserved.
 
 // data-cursors.go
@@ -7,24 +7,26 @@ package expr
 import (
 	"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
 	initState bool // true if no item has produced yet (this replace di initial Next() call in the contructor)
 	// cursorValid bool // true if resource is nil or if clean has not yet been called
-	index     int
+	index     int64
-	count     int
+	count     int64
 	current   any
 	lastErr   error
 	resource  any
-	nextFunc  Functor
+	nextFunc  kern.Functor
-	cleanFunc Functor
+	cleanFunc kern.Functor
-	resetFunc Functor
+	resetFunc kern.Functor
 }
 
-func NewDataCursor(ctx ExprContext, ds map[string]Functor, resource any) (dc *dataCursor) {
+func NewDataCursor(ctx kern.ExprContext, ds map[string]kern.Functor, resource any) (dc *dataCursor) {
 	dc = &dataCursor{
 		ds:        ds,
 		initState: true,
@@ -35,14 +37,14 @@ func NewDataCursor(ctx ExprContext, ds map[string]Functor, resource any) (dc *da
 		lastErr:   nil,
 		resource:  resource,
 		ctx:       ctx.Clone(),
-		nextFunc:  ds[NextName],
+		nextFunc:  ds[kern.NextName],
-		cleanFunc: ds[CleanName],
+		cleanFunc: ds[kern.CleanName],
-		resetFunc: ds[ResetName],
+		resetFunc: ds[kern.ResetName],
 	}
 	return
 }
 
-func (dc *dataCursor) Context() ExprContext {
+func (dc *dataCursor) Context() kern.ExprContext {
 	return dc.ctx
 }
 
@@ -79,27 +81,27 @@ func (dc *dataCursor) String() string {
 }
 
 func (dc *dataCursor) HasOperation(name string) (exists bool) {
-	exists = slices.Contains([]string{CleanName, ResetName, CurrentName, IndexName}, name)
+	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 map[string]any) (value any, err error) {
-	if name == IndexName {
+	if name == kern.IndexName {
 		value = int64(dc.Index())
-	} else if name == CleanName {
+	} else if name == kern.CleanName {
 		err = dc.Clean()
-	} else if name == ResetName {
+	} else if name == kern.ResetName {
 		err = dc.Reset()
-	} else if functor, ok := dc.ds[name]; ok && isFunctor(functor) {
+	} else if functor, ok := dc.ds[name]; ok && kern.IsFunctor(functor) {
-		ctx := cloneContext(dc.ctx)
+		ctx := kern.CloneContext(dc.ctx)
 		value, err = functor.InvokeNamed(ctx, name, args)
-		exportObjects(dc.ctx, ctx)
+		kern.ExportObjects(dc.ctx, ctx)
 	} else {
-		err = errNoOperation(name)
+		err = kern.ErrNoOperation(name)
 	}
 	return
 }
@@ -127,10 +129,10 @@ func (dc *dataCursor) CallOperation(name string, args map[string]any) (value any
 
 func (dc *dataCursor) Reset() (err error) {
 	if dc.resetFunc != nil {
-		ctx := cloneContext(dc.ctx)
+		ctx := kern.CloneContext(dc.ctx)
-		actualParams := bindActualParams(dc.resetFunc, []any{dc.resource})
+		actualParams := kern.BindActualParams(dc.resetFunc, []any{dc.resource})
-		_, err = dc.resetFunc.InvokeNamed(ctx, ResetName, actualParams)
+		_, err = dc.resetFunc.InvokeNamed(ctx, kern.ResetName, actualParams)
-		exportObjects(dc.ctx, ctx)
+		kern.ExportObjects(dc.ctx, ctx)
 	}
 	dc.index = -1
 	dc.count = 0
@@ -142,10 +144,10 @@ func (dc *dataCursor) Reset() (err error) {
 
 func (dc *dataCursor) Clean() (err error) {
 	if dc.cleanFunc != nil {
-		ctx := cloneContext(dc.ctx)
+		ctx := kern.CloneContext(dc.ctx)
-		actualParams := bindActualParams(dc.cleanFunc, []any{dc.resource})
+		actualParams := kern.BindActualParams(dc.cleanFunc, []any{dc.resource})
-		_, err = dc.cleanFunc.InvokeNamed(ctx, CleanName, actualParams)
+		_, err = dc.cleanFunc.InvokeNamed(ctx, kern.CleanName, actualParams)
-		exportObjects(dc.ctx, ctx)
+		kern.ExportObjects(dc.ctx, ctx)
 	}
 	dc.lastErr = io.EOF
 	return
@@ -178,13 +180,13 @@ func (dc *dataCursor) Current() (item any, err error) { // must return io.EOF at
 	return
 }
 
-func (dc *dataCursor) checkFilter(filter Functor, item any) (accepted bool, err error) {
+func (dc *dataCursor) checkFilter(filter kern.Functor, item any) (accepted bool, err error) {
 	var v any
 	var ok bool
-	ctx := cloneContext(dc.ctx)
+	ctx := kern.CloneContext(dc.ctx)
 
-	actualParams := bindActualParams(filter, []any{item, dc.index})
+	actualParams := kern.BindActualParams(filter, []any{item, dc.index})
-	if v, err = filter.InvokeNamed(ctx, FilterName, actualParams); err == nil && v != nil {
+	if v, err = filter.InvokeNamed(ctx, kern.FilterName, actualParams); err == nil && v != nil {
 		if accepted, ok = v.(bool); !ok {
 			accepted = true // NOTE: A non-boolean value that is not nil means the item has been accepted
 		}
@@ -192,10 +194,10 @@ func (dc *dataCursor) checkFilter(filter Functor, item any) (accepted bool, err
 	return
 }
 
-func (dc *dataCursor) mapItem(mapper Functor, item any) (mappedItem any, err error) {
+func (dc *dataCursor) mapItem(mapper kern.Functor, item any) (mappedItem any, err error) {
-	ctx := cloneContext(dc.ctx)
+	ctx := kern.CloneContext(dc.ctx)
-	actualParams := bindActualParams(mapper, []any{item, dc.index})
+	actualParams := kern.BindActualParams(mapper, []any{item, dc.index})
-	mappedItem, err = mapper.InvokeNamed(ctx, MapName, actualParams)
+	mappedItem, err = mapper.InvokeNamed(ctx, kern.MapName, actualParams)
 	return
 }
 
@@ -213,15 +215,15 @@ func (dc *dataCursor) Next() (current any, err error) { // must return io.EOF af
 		return
 	}
 	current = dc.current
-	filter := dc.ds[FilterName]
+	filter := dc.ds[kern.FilterName]
-	mapper := dc.ds[MapName]
+	mapper := dc.ds[kern.MapName]
 	var item any
 	for item == nil && dc.lastErr == nil {
-		ctx := cloneContext(dc.ctx)
+		ctx := kern.CloneContext(dc.ctx)
 		dc.index++
 
-		actualParams := bindActualParams(dc.nextFunc, []any{dc.resource, dc.index})
+		actualParams := kern.BindActualParams(dc.nextFunc, []any{dc.resource, dc.index})
-		if item, dc.lastErr = dc.nextFunc.InvokeNamed(ctx, NextName, actualParams); dc.lastErr == nil {
+		if item, dc.lastErr = dc.nextFunc.InvokeNamed(ctx, kern.NextName, actualParams); dc.lastErr == nil {
 			if item == nil {
 				dc.lastErr = io.EOF
 			} else {
@@ -239,7 +241,7 @@ func (dc *dataCursor) Next() (current any, err error) { // must return io.EOF af
 				}
 			}
 		}
-		exportObjects(dc.ctx, ctx)
+		kern.ExportObjects(dc.ctx, ctx)
 	}
 	dc.current = item
 	if dc.lastErr != nil {
@@ -296,10 +298,10 @@ func (dc *dataCursor) Next() (current any, err error) { // must return io.EOF af
 // 	return
 // }
 
-func (dc *dataCursor) Index() int {
+func (dc *dataCursor) Index() int64 {
 	return dc.index - 1
 }
 
-func (dc *dataCursor) Count() int {
+func (dc *dataCursor) Count() int64 {
 	return dc.count
 }

dict-iterator.go

@@ -0,0 +1,225 @@
+// Copyright (c) 2024-2026 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)
+				}
+			}
+		}
+	}
+
+	if err == nil {
+		dictIt.makeKeys(*dict, sortType)
+		it = dictIt
+	}
+	return
+}
+
+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 := 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-context.go

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

file/coverage.html

@@ -0,0 +1,322 @@
+
+<!DOCTYPE html>
+<html>
+	<head>
+		<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
+		<title>file: Go Coverage Report</title>
+		<style>
+			body {
+				background: black;
+				color: rgb(80, 80, 80);
+			}
+			body, pre, #legend span {
+				font-family: Menlo, monospace;
+				font-weight: bold;
+			}
+			#topbar {
+				background: black;
+				position: fixed;
+				top: 0; left: 0; right: 0;
+				height: 42px;
+				border-bottom: 1px solid rgb(80, 80, 80);
+			}
+			#content {
+				margin-top: 50px;
+			}
+			#nav, #legend {
+				float: left;
+				margin-left: 10px;
+			}
+			#legend {
+				margin-top: 12px;
+			}
+			#nav {
+				margin-top: 10px;
+			}
+			#legend span {
+				margin: 0 5px;
+			}
+			.cov0 { color: rgb(192, 0, 0) }
+.cov1 { color: rgb(128, 128, 128) }
+.cov2 { color: rgb(116, 140, 131) }
+.cov3 { color: rgb(104, 152, 134) }
+.cov4 { color: rgb(92, 164, 137) }
+.cov5 { color: rgb(80, 176, 140) }
+.cov6 { color: rgb(68, 188, 143) }
+.cov7 { color: rgb(56, 200, 146) }
+.cov8 { color: rgb(44, 212, 149) }
+.cov9 { color: rgb(32, 224, 152) }
+.cov10 { color: rgb(20, 236, 155) }
+
+		</style>
+	</head>
+	<body>
+		<div id="topbar">
+			<div id="nav">
+				<select id="files">
+				
+				<option value="file0">git.portale-stac.it/go-pkg/expr/file/file.go (88.9%)</option>
+				
+				<option value="file1">git.portale-stac.it/go-pkg/expr/file/reader.go (77.8%)</option>
+				
+				<option value="file2">git.portale-stac.it/go-pkg/expr/file/writer.go (100.0%)</option>
+				
+				</select>
+			</div>
+			<div id="legend">
+				<span>not tracked</span>
+			
+				<span class="cov0">not covered</span>
+				<span class="cov8">covered</span>
+			
+			</div>
+		</div>
+		<div id="content">
+		
+		<pre class="file" id="file0" style="display: none">// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// file.go
+package file
+
+import (
+        "os"
+
+        "git.portale-stac.it/go-pkg/expr/kern"
+)
+
+type Handle interface {
+        kern.Typer
+        GetFile() *os.File
+        GetName() string
+        Valid() bool
+        Close() error
+}
+
+type handleBase struct {
+        fh *os.File
+}
+
+func (h *handleBase) GetFile() *os.File <span class="cov0" title="0">{
+        return h.fh
+}</span>
+
+func (h *handleBase) GetName() (name string) <span class="cov8" title="1">{
+        if h.fh != nil </span><span class="cov8" title="1">{
+                name = h.fh.Name()
+        }</span>
+        <span class="cov8" title="1">return</span>
+}
+
+func (h *handleBase) Valid() bool <span class="cov8" title="1">{
+        return h.fh != nil
+}</span>
+
+func (h *handleBase) Close() (err error) <span class="cov8" title="1">{
+        if h.fh != nil </span><span class="cov8" title="1">{
+                err = h.fh.Close()
+                h.fh = nil
+        }</span>
+        <span class="cov8" title="1">return</span>
+}
+</pre>
+		
+		<pre class="file" id="file1" style="display: none">// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// reader.go
+package file
+
+import (
+        "bufio"
+        "io"
+        "os"
+)
+
+type Reader struct {
+        // fh     *os.File
+        handleBase
+        reader *bufio.Reader
+}
+
+func NewReader(fh *os.File) *Reader <span class="cov8" title="1">{
+        return &amp;Reader{handleBase: handleBase{fh: fh}, reader: bufio.NewReader(fh)}
+}</span>
+
+func OpenReader(filePath string) (r *Reader, err error) <span class="cov8" title="1">{
+        var fh *os.File
+        if fh, err = os.Open(filePath); err == nil </span><span class="cov8" title="1">{
+                r = NewReader(fh)
+        }</span>
+        <span class="cov8" title="1">return</span>
+}
+
+func (h *Reader) TypeName() string <span class="cov8" title="1">{
+        return "fileReader"
+}</span>
+
+func (h *Reader) String() string <span class="cov8" title="1">{
+        return "reader"
+}</span>
+
+func (h *Reader) Valid() bool <span class="cov8" title="1">{
+        return h.handleBase.Valid() &amp;&amp; h.reader != nil
+}</span>
+
+func (w *Reader) Close() (err error) <span class="cov8" title="1">{
+        w.reader = nil
+        err = w.handleBase.Close()
+        return
+}</span>
+
+func (h *Reader) ReadByte() (b byte, err error) <span class="cov8" title="1">{
+        if h.reader != nil </span><span class="cov8" title="1">{
+                b, err = h.reader.ReadByte()
+        }</span> else<span class="cov0" title="0"> {
+                err = io.ErrClosedPipe
+        }</span>
+        <span class="cov8" title="1">return</span>
+}
+
+func (h *Reader) ReadAll() (p []byte, err error) <span class="cov8" title="1">{
+        if h.reader != nil </span><span class="cov8" title="1">{
+                p, err = io.ReadAll(h.reader)
+        }</span> else<span class="cov0" title="0"> {
+                err = io.ErrClosedPipe
+        }</span>
+        <span class="cov8" title="1">return</span>
+}
+
+func (h *Reader) ReadString(delim byte) (s string, err error) <span class="cov0" title="0">{
+        if h.reader != nil </span><span class="cov0" title="0">{
+                s, err = h.reader.ReadString(delim)
+        }</span> else<span class="cov0" title="0"> {
+                err = io.ErrClosedPipe
+        }</span>
+        <span class="cov0" title="0">return</span>
+}
+
+func (h *Reader) Reset() (err error) <span class="cov8" title="1">{
+        if h.fh != nil </span><span class="cov8" title="1">{
+                if _, err = h.fh.Seek(0, 0); err == nil </span><span class="cov8" title="1">{
+                        h.reader.Reset(h.fh)
+                }</span>
+        }
+        <span class="cov8" title="1">return</span>
+}
+</pre>
+		
+		<pre class="file" id="file2" style="display: none">// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// writer.go
+package file
+
+import (
+        "bufio"
+        "fmt"
+        "os"
+)
+
+type Writer struct {
+        // fh     *os.File
+        handleBase
+        writer *bufio.Writer
+}
+
+func NewWriter(fh *os.File) *Writer <span class="cov8" title="1">{
+        return &amp;Writer{handleBase: handleBase{fh: fh}, writer: bufio.NewWriter(fh)}
+}</span>
+
+func CreateWriter(filePath string) (w *Writer, err error) <span class="cov8" title="1">{
+        var fh *os.File
+        if fh, err = os.Create(filePath); err == nil </span><span class="cov8" title="1">{
+                w = NewWriter(fh)
+        }</span>
+        <span class="cov8" title="1">return</span>
+}
+
+func AppendWriter(filePath string) (w *Writer, err error) <span class="cov8" title="1">{
+        var fh *os.File
+        if fh, err = os.OpenFile(filePath, os.O_APPEND|os.O_WRONLY, 0644); err == nil </span><span class="cov8" title="1">{
+                w = NewWriter(fh)
+        }</span>
+        <span class="cov8" title="1">return</span>
+}
+
+func (w *Writer) TypeName() string <span class="cov8" title="1">{
+        return "fileWriter"
+}</span>
+
+func (w *Writer) String() string <span class="cov8" title="1">{
+        return "writer"
+}</span>
+
+func (w *Writer) Valid() bool <span class="cov8" title="1">{
+        return w.handleBase.Valid() &amp;&amp; w.writer != nil
+}</span>
+
+func (w *Writer) Close() (err error) <span class="cov8" title="1">{
+        var err1 error
+        if w.writer != nil </span><span class="cov8" title="1">{
+                err1 = w.Flush()
+                w.writer = nil
+        }</span>
+        <span class="cov8" title="1">if err = w.handleBase.Close(); err == nil </span><span class="cov8" title="1">{
+                err = err1
+        }</span>
+        <span class="cov8" title="1">return</span>
+}
+
+func (w *Writer) Flush() (err error) <span class="cov8" title="1">{
+        if w.writer != nil </span><span class="cov8" title="1">{
+                err = w.writer.Flush()
+        }</span>
+        <span class="cov8" title="1">return</span>
+}
+
+func (w *Writer) Write(args ...any) (n int, err error) <span class="cov8" title="1">{
+        if w.writer != nil </span><span class="cov8" title="1">{
+                n, err = fmt.Fprint(w.writer, args...)
+        }</span>
+        <span class="cov8" title="1">return</span>
+}
+
+func (w *Writer) Writef(format string, args ...any) (n int, err error) <span class="cov8" title="1">{
+        if w.writer != nil </span><span class="cov8" title="1">{
+                n, err = fmt.Fprintf(w.writer, format, args...)
+        }</span>
+        <span class="cov8" title="1">return</span>
+}
+</pre>
+		
+		</div>
+	</body>
+	<script>
+	(function() {
+		var files = document.getElementById('files');
+		var visible;
+		files.addEventListener('change', onChange, false);
+		function select(part) {
+			if (visible)
+				visible.style.display = 'none';
+			visible = document.getElementById(part);
+			if (!visible)
+				return;
+			files.value = part;
+			visible.style.display = 'block';
+			location.hash = part;
+		}
+		function onChange() {
+			select(files.value);
+			window.scrollTo(0, 0);
+		}
+		if (location.hash != "") {
+			select(location.hash.substr(1));
+		}
+		if (!visible) {
+			select("file0");
+		}
+	})();
+	</script>
+</html>

file/file.go

@@ -0,0 +1,46 @@
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// file.go
+package file
+
+import (
+	"os"
+
+	"git.portale-stac.it/go-pkg/expr/kern"
+)
+
+type Handle interface {
+	kern.Typer
+	GetFile() *os.File
+	GetName() string
+	Valid() bool
+	Close() error
+}
+
+type handleBase struct {
+	fh *os.File
+}
+
+func (h *handleBase) GetFile() *os.File {
+	return h.fh
+}
+
+func (h *handleBase) GetName() (name string) {
+	if h.fh != nil {
+		name = h.fh.Name()
+	}
+	return
+}
+
+func (h *handleBase) Valid() bool {
+	return h.fh != nil
+}
+
+func (h *handleBase) Close() (err error) {
+	if h.fh != nil {
+		err = h.fh.Close()
+		h.fh = nil
+	}
+	return
+}

file/reader.go

@@ -0,0 +1,83 @@
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// reader.go
+package file
+
+import (
+	"bufio"
+	"io"
+	"os"
+)
+
+type Reader struct {
+	// fh     *os.File
+	handleBase
+	reader *bufio.Reader
+}
+
+func NewReader(fh *os.File) *Reader {
+	return &Reader{handleBase: handleBase{fh: fh}, reader: bufio.NewReader(fh)}
+}
+
+func OpenReader(filePath string) (r *Reader, err error) {
+	var fh *os.File
+	if fh, err = os.Open(filePath); err == nil {
+		r = NewReader(fh)
+	}
+	return
+}
+
+func (h *Reader) TypeName() string {
+	return "fileReader"
+}
+
+func (h *Reader) String() string {
+	return "reader"
+}
+
+func (h *Reader) Valid() bool {
+	return h.handleBase.Valid() && h.reader != nil
+}
+
+func (w *Reader) Close() (err error) {
+	w.reader = nil
+	err = w.handleBase.Close()
+	return
+}
+
+func (h *Reader) ReadByte() (b byte, err error) {
+	if h.reader != nil {
+		b, err = h.reader.ReadByte()
+	} else {
+		err = io.ErrClosedPipe
+	}
+	return
+}
+
+func (h *Reader) ReadAll() (p []byte, err error) {
+	if h.reader != nil {
+		p, err = io.ReadAll(h.reader)
+	} else {
+		err = io.ErrClosedPipe
+	}
+	return
+}
+
+func (h *Reader) ReadString(delim byte) (s string, err error) {
+	if h.reader != nil {
+		s, err = h.reader.ReadString(delim)
+	} else {
+		err = io.ErrClosedPipe
+	}
+	return
+}
+
+func (h *Reader) Reset() (err error) {
+	if h.fh != nil {
+		if _, err = h.fh.Seek(0, 0); err == nil {
+			h.reader.Reset(h.fh)
+		}
+	}
+	return
+}

file/t_reader_test.go

@@ -0,0 +1,62 @@
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// reader.go
+package file
+
+import "testing"
+
+func TestOpenReader(t *testing.T) {
+	r, err := OpenReader("t_reader_test.go")
+	if err != nil {
+		t.Fatalf("OpenReader failed: %v", err)
+	}
+	defer r.Close()
+
+	if !r.Valid() {
+		t.Fatal("Reader should be valid after opening")
+	}
+
+	if r.TypeName() != "fileReader" {
+		t.Fatalf("Expected TypeName 'fileReader', got '%s'", r.TypeName())
+	}
+
+	if r.String() != "reader" {
+		t.Fatalf("Expected String 'reader', got '%s'", r.String())
+	}
+
+	// GetName may return either "t_reader_test.go" or "./t_reader_test.go" depending on the environment
+	name := r.GetName()
+	if (name != "t_reader_test.go") && (name != "./t_reader_test.go") {
+		t.Fatalf("Expected GetName 't_reader_test.go' or './t_reader_test.go', got '%s'", name)
+	}
+
+	// Test reading a byte
+	b, err := r.ReadByte()
+	if err != nil {
+		t.Fatalf("ReadByte failed: %v", err)
+	}
+	if b == 0 {
+		t.Fatal("ReadByte should not return zero byte")
+	}
+
+	err = r.Reset()
+	if err != nil {
+		t.Fatalf("Reset failed: %v", err)
+	}
+
+	if s, err := r.ReadString('\n'); err != nil {
+		t.Fatalf("ReadString failed: %v", err)
+	} else {
+		t.Logf("ReadString: %s", s)
+	}
+
+	// Test reading all content
+	content, err := r.ReadAll()
+	if err != nil {
+		t.Fatalf("ReadAll failed: %v", err)
+	}
+	if len(content) == 0 {
+		t.Fatal("ReadAll should return non-empty content")
+	}
+}

file/t_writer_test.go

@@ -0,0 +1,69 @@
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// writer.go
+package file
+
+import "testing"
+
+func TestCreateWriter(t *testing.T) {
+	w, err := CreateWriter("/tmp/test_writer.txt")
+	if err != nil {
+		t.Fatalf("CreateWriter failed: %v", err)
+	}
+	defer w.Close()
+
+	if !w.Valid() {
+		t.Fatal("Writer should be valid after creation")
+	}
+
+	if w.TypeName() != "fileWriter" {
+		t.Fatalf("Expected TypeName 'fileWriter', got '%s'", w.TypeName())
+	}
+
+	if w.String() != "writer" {
+		t.Fatalf("Expected String 'writer', got '%s'", w.String())
+	}
+
+	name := w.GetName()
+	if name != "/tmp/test_writer.txt" {
+		t.Fatalf("Expected GetName '/tmp/test_writer.txt', got '%s'", name)
+	}
+
+	if n, err := w.Write("Hello, World!\n"); err != nil {
+		t.Fatalf("Write failed: %v", err)
+	} else if n != len("Hello, World!\n") {
+		t.Fatalf("Expected to write %d bytes, wrote %d", len("Hello, World!\n"), n)
+	}
+
+	if n, err := w.Writef("This is a %s.\n", "test"); err != nil {
+		t.Fatalf("Writef failed: %v", err)
+	} else if n != len("This is a test.\n") {
+		t.Fatalf("Expected to write %d bytes, wrote %d", len("This is a test.\n"), n)
+	}
+}
+
+func TestAppendWriter(t *testing.T) {
+	w, err := AppendWriter("/tmp/test_writer.txt")
+	if err != nil {
+		t.Fatalf("AppendWriter failed: %v", err)
+	}
+	defer w.Close()
+
+	if !w.Valid() {
+		t.Fatal("Writer should be valid after opening for append")
+	}
+
+	if w.TypeName() != "fileWriter" {
+		t.Fatalf("Expected TypeName 'fileWriter', got '%s'", w.TypeName())
+	}
+
+	if w.String() != "writer" {
+		t.Fatalf("Expected String 'writer', got '%s'", w.String())
+	}
+
+	name := w.GetName()
+	if name != "/tmp/test_writer.txt" {
+		t.Fatalf("Expected GetName '/tmp/test_writer.txt', got '%s'", name)
+	}
+}

file/writer.go

@@ -0,0 +1,82 @@
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// writer.go
+package file
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+)
+
+type Writer struct {
+	// fh     *os.File
+	handleBase
+	writer *bufio.Writer
+}
+
+func NewWriter(fh *os.File) *Writer {
+	return &Writer{handleBase: handleBase{fh: fh}, writer: bufio.NewWriter(fh)}
+}
+
+func CreateWriter(filePath string) (w *Writer, err error) {
+	var fh *os.File
+	if fh, err = os.Create(filePath); err == nil {
+		w = NewWriter(fh)
+	}
+	return
+}
+
+func AppendWriter(filePath string) (w *Writer, err error) {
+	var fh *os.File
+	if fh, err = os.OpenFile(filePath, os.O_APPEND|os.O_WRONLY, 0644); err == nil {
+		w = NewWriter(fh)
+	}
+	return
+}
+
+func (w *Writer) TypeName() string {
+	return "fileWriter"
+}
+
+func (w *Writer) String() string {
+	return "writer"
+}
+
+func (w *Writer) Valid() bool {
+	return w.handleBase.Valid() && w.writer != nil
+}
+
+func (w *Writer) Close() (err error) {
+	var err1 error
+	if w.writer != nil {
+		err1 = w.Flush()
+		w.writer = nil
+	}
+	if err = w.handleBase.Close(); err == nil {
+		err = err1
+	}
+	return
+}
+
+func (w *Writer) Flush() (err error) {
+	if w.writer != nil {
+		err = w.writer.Flush()
+	}
+	return
+}
+
+func (w *Writer) Write(args ...any) (n int, err error) {
+	if w.writer != nil {
+		n, err = fmt.Fprint(w.writer, args...)
+	}
+	return
+}
+
+func (w *Writer) Writef(format string, args ...any) (n int, err error) {
+	if w.writer != nil {
+		n, err = fmt.Fprintf(w.writer, format, args...)
+	}
+	return
+}

function.go

@@ -1,386 +0,0 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
-// All rights reserved.
-
-// function.go
-package expr
-
-import (
-	"fmt"
-	"strconv"
-	"strings"
-)
-
-// ---- Function template
-type FuncTemplate func(ctx ExprContext, name string, args map[string]any) (result any, err error)
-
-// ---- 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
-}
-
-// --- Functions
-
-// funcInfo implements ExprFunc
-type funcInfo struct {
-	name         string
-	minArgs      int
-	maxArgs      int
-	functor      Functor
-	formalParams []ExprFuncParam
-	returnType   string
-}
-
-func newFuncInfo(name string, functor Functor, returnType string, params []ExprFuncParam) (info *funcInfo, err error) {
-	var minArgs = 0
-	var maxArgs = 0
-	for _, p := range params {
-		if maxArgs == -1 {
-			return nil, fmt.Errorf("no more params can be specified after the ellipsis symbol: %q", p.Name())
-		}
-		if p.IsDefault() || p.IsOptional() {
-			maxArgs++
-		} else if maxArgs == minArgs {
-			minArgs++
-			maxArgs++
-		} else {
-			return nil, fmt.Errorf("can't specify non-optional param after optional ones: %q", p.Name())
-		}
-		if p.IsRepeat() {
-			minArgs--
-			maxArgs = -1
-		}
-	}
-
-	info = &funcInfo{
-		name: name, minArgs: minArgs, maxArgs: maxArgs, functor: functor, returnType: returnType, formalParams: params,
-	}
-	functor.SetFunc(info)
-	return info, nil
-}
-
-func (info *funcInfo) Params() []ExprFuncParam {
-	return info.formalParams
-}
-
-func (info *funcInfo) ReturnType() string {
-	return info.returnType
-}
-
-func (info *funcInfo) ToString(opt FmtOpt) string {
-	var sb strings.Builder
-	if len(info.Name()) == 0 {
-		sb.WriteString("func")
-	} else {
-		sb.WriteString(info.Name())
-	}
-	sb.WriteByte('(')
-	if info.formalParams != nil {
-		for i, p := range info.formalParams {
-			if i > 0 {
-				sb.WriteString(", ")
-			}
-			sb.WriteString(p.Name())
-
-			if p.IsDefault() {
-				sb.WriteByte('=')
-				if s, ok := p.DefaultValue().(string); ok {
-					sb.WriteByte('"')
-					sb.WriteString(s)
-					sb.WriteByte('"')
-				} else {
-					sb.WriteString(fmt.Sprintf("%v", p.DefaultValue()))
-				}
-			}
-		}
-	}
-	if info.maxArgs < 0 {
-		sb.WriteString(" ...")
-	}
-	sb.WriteString("):")
-	if len(info.returnType) > 0 {
-		sb.WriteString(info.returnType)
-	} else {
-		sb.WriteString(TypeAny)
-	}
-	sb.WriteString("{}")
-	return sb.String()
-}
-
-func (info *funcInfo) Name() string {
-	return info.name
-}
-
-func (info *funcInfo) MinArgs() int {
-	return info.minArgs
-}
-
-func (info *funcInfo) MaxArgs() int {
-	return info.maxArgs
-}
-
-func (info *funcInfo) Functor() Functor {
-	return info.functor
-}
-
-func (info *funcInfo) AllocContext(parentCtx ExprContext) (ctx ExprContext) {
-	if defCtx := info.functor.GetDefinitionContext(); defCtx != nil {
-		ctx = defCtx.Clone()
-		ctx.SetParent(defCtx)
-	} else {
-		ctx = parentCtx.Clone()
-		ctx.SetParent(parentCtx)
-	}
-	return
-}
-
-func (info *funcInfo) ParamSpec(paramName string) ExprFuncParam {
-	for _, spec := range info.formalParams {
-		if spec.Name() == paramName {
-			return spec
-		}
-	}
-	return nil
-}
-
-func initActualParams(ctx ExprContext, info ExprFunc, callTerm *term) (actualParams map[string]any, err error) {
-	var varArgs []any
-	var varName string
-
-	namedParamsStarted := false
-
-	formalParams := info.Params()
-	actualParams = make(map[string]any, len(formalParams))
-	if callTerm == nil {
-		return
-	}
-
-	for i, tree := range callTerm.children {
-		var paramValue any
-		paramCtx := ctx.Clone()
-		if paramValue, err = tree.compute(paramCtx); err != nil {
-			break
-		}
-		if paramName, namedParam := getAssignVarName(tree); namedParam {
-			if info.ParamSpec(paramName) == nil {
-				err = fmt.Errorf("%s(): unknown param %q", info.Name(), paramName)
-				break
-			}
-			actualParams[paramName] = paramValue
-			namedParamsStarted = true
-		} else if !namedParamsStarted {
-			if varArgs != nil {
-				varArgs = append(varArgs, paramValue)
-			} else if i < len(formalParams) {
-				spec := formalParams[i]
-				if spec.IsRepeat() {
-					varArgs = make([]any, 0, len(callTerm.children)-i)
-					varArgs = append(varArgs, paramValue)
-					varName = spec.Name()
-				} else {
-					actualParams[spec.Name()] = paramValue
-				}
-			} else {
-				err = ErrTooManyParams(info.Name(), len(formalParams), len(callTerm.children))
-				break
-			}
-		} else {
-			err = fmt.Errorf("%s(): positional param nr %d not allowed after named params", info.Name(), i+1)
-			break
-		}
-	}
-	if err == nil {
-		if varArgs != nil {
-			actualParams[varName] = varArgs
-		}
-	}
-	return
-}
-
-func (info *funcInfo) PrepareCall(name string, actualParams map[string]any) (err error) {
-	passedCount := len(actualParams)
-	if info.MinArgs() > passedCount {
-		err = ErrTooFewParams(name, info.MinArgs(), info.MaxArgs(), passedCount)
-		return
-	}
-
-	if passedCount < len(info.formalParams) {
-		for _, p := range info.formalParams {
-			if _, exists := actualParams[p.Name()]; !exists {
-				if !p.IsDefault() {
-					break
-				}
-				if p.IsRepeat() {
-					varArgs := make([]any, 1)
-					varArgs[0] = p.DefaultValue()
-					actualParams[p.Name()] = varArgs
-				} else {
-					actualParams[p.Name()] = p.DefaultValue()
-				}
-			}
-		}
-	}
-
-	if info.MaxArgs() >= 0 && info.MaxArgs() < len(actualParams) {
-		err = ErrTooManyParams(name, info.MaxArgs(), len(actualParams))
-	}
-	return
-}
-
-// ----- Call a function ---
-
-func getAssignVarName(t *term) (name string, ok bool) {
-	if ok = t.symbol() == SymEqual; ok {
-		name = t.children[0].source()
-	}
-	return
-}
-
-func CallFunctionByTerm(parentCtx ExprContext, name string, callTerm *term) (result any, err error) {
-	var actualParams map[string]any
-	if info, exists := GetFuncInfo(parentCtx, name); exists {
-		if actualParams, err = initActualParams(parentCtx, info, callTerm); err == nil {
-			ctx := info.AllocContext(parentCtx)
-			if err = info.PrepareCall(name, actualParams); err == nil {
-				functor := info.Functor()
-				result, err = functor.InvokeNamed(ctx, name, actualParams)
-				exportObjectsToParent(ctx)
-			}
-		}
-	} else {
-		err = fmt.Errorf("unknown function %s()", name)
-	}
-	return
-}
-
-func CallFunctionByArgs(parentCtx ExprContext, name string, args []any) (result any, err error) {
-	var actualParams map[string]any
-	if info, exists := GetFuncInfo(parentCtx, name); exists {
-		functor := info.Functor()
-		actualParams = bindActualParams(functor, args)
-		ctx := info.AllocContext(parentCtx)
-		if err = info.PrepareCall(name, actualParams); err == nil {
-			result, err = functor.InvokeNamed(ctx, name, actualParams)
-			exportObjectsToParent(ctx)
-		}
-	} else {
-		err = fmt.Errorf("unknown function %s()", name)
-	}
-	return
-}
-
-func CallFunctionByParams(parentCtx ExprContext, name string, actualParams map[string]any) (result any, err error) {
-	//var actualParams map[string]any
-	if info, exists := GetFuncInfo(parentCtx, name); exists {
-		functor := info.Functor()
-		ctx := info.AllocContext(parentCtx)
-		if err = info.PrepareCall(name, actualParams); err == nil {
-			result, err = functor.InvokeNamed(ctx, name, actualParams)
-			exportObjectsToParent(ctx)
-		}
-	} else {
-		err = fmt.Errorf("unknown function %s()", name)
-	}
-	return
-}
-
-func GetParam(args map[string]any, paramName string, paramNum int) (value any, exists bool) {
-	if value, exists = args[paramName]; !exists {
-		if paramNum > 0 && paramNum <= len(args) {
-			value, exists = args["arg"+strconv.Itoa(paramNum)]
-		}
-	}
-	return
-}
-
-func bindActualParams(functor Functor, args []any) (actualParams map[string]any) {
-	formalParams := functor.GetParams()
-	actualParams = make(map[string]any, len(args))
-	for i, arg := range args {
-		if i < len(formalParams) {
-			actualParams[formalParams[i].Name()] = arg
-		} else {
-			actualParams["arg"+strconv.Itoa(i+1)] = arg
-		}
-	}
-	return
-}

global-context.go

@@ -1,4 +1,4 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
 // All rights reserved.
 
 // global-context.go
@@ -7,20 +7,25 @@ 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) {
+	if globalCtx := ctx.GetGlobal(); globalCtx != nil {
 		var mod *builtinModule
 		if mod, exists = builtinModuleRegister[name]; exists {
 			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) {
+	if globalCtx := ctx.GetGlobal(); globalCtx != nil {
 		var matched bool
 		for name, mod := range builtinModuleRegister {
 			if matched, err = filepath.Match(pattern, name); err == nil {
@@ -33,75 +38,37 @@ func ImportInContextByGlobPattern(pattern string) (count int, err error) {
 				break
 			}
 		}
-	return
-}
-
-func GetVar(ctx ExprContext, name string) (value any, exists bool) {
-	if value, exists = ctx.GetVar(name); !exists {
-		value, exists = globalCtx.GetVar(name)
 	}
 	return
 }
 
-func GetLocalFuncInfo(ctx ExprContext, name string) (item ExprFunc, exists bool) {
+func fixCtrlVar(name string) string {
-	var v any
-	if len(name) > 0 {
-		if v, exists = ctx.GetVar(name); exists && isFunctor(v) {
-			f, _ := v.(Functor)
-			item = f.GetFunc()
-		} else {
-			item, exists = ctx.GetFuncInfo(name)
-		}
-	}
-	return
-}
-
-func GetFuncInfo(ctx ExprContext, name string) (item ExprFunc, exists bool) {
-	// if len(name) > 0 {
-	// 	if item, exists = GetLocalFuncInfo(ctx, name); exists {
-	// 		ownerCtx = ctx
-	// 	} else if item, exists = globalCtx.GetFuncInfo(name); exists {
-	// 		ownerCtx = globalCtx
-	// 	}
-	// }
-	item, exists, _ = GetFuncInfoAndOwner(ctx, name)
-	return
-}
-
-func GetFuncInfoAndOwner(ctx ExprContext, name string) (item ExprFunc, exists bool, ownerCtx ExprContext) {
-	if len(name) > 0 {
-		if item, exists = GetLocalFuncInfo(ctx, name); exists {
-			ownerCtx = ctx
-		} else if item, exists = globalCtx.GetFuncInfo(name); exists {
-			ownerCtx = globalCtx
-		}
-	}
-	return
-}
-
-func GlobalCtrlSet(name string, newValue any) (currentValue any) {
 	if !strings.HasPrefix(name, "_") {
 		name = "_" + name
 	}
-	currentValue, _ = globalCtx.GetVar(name)
+	return name
+}
 
+func GlobalCtrlSet(ctx kern.ExprContext, name string, newValue any) (currentValue any) {
+	if globalCtx := ctx.GetGlobal(); globalCtx != nil {
+		name = fixCtrlVar(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
+		name = fixCtrlVar(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 = fixCtrlVar(name)
-		name = "_" + name
+	if v, exists := ctx.GetVar(name); exists && kern.IsBool(v) {
-	}
-	if v, exists := ctx.GetVar(name); exists && IsBool(v) {
 		currentStatus, _ = v.(bool)
 	}
 
@@ -109,11 +76,9 @@ 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 = fixCtrlVar(name)
-		name = "_" + name
+	if v, exists := ctx.GetVar(name); exists && kern.IsBool(v) {
-	}
-	if v, exists := ctx.GetVar(name); exists && IsBool(v) {
 		currentStatus, _ = v.(bool)
 	}
 
@@ -121,36 +86,39 @@ 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
+// 	return
-}
+// }
 
-func getControlString(name string) (s string, exists bool) {
+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 init() {
+func InitGlobal() (ctx kern.ExprContext) {
-	globalCtx = NewSimpleStore()
+	ctx = NewSimpleStoreWithoutGlobalContext()
-	initDefaultVars(globalCtx)
+	kern.InitDefaultVars(ctx)
-	ImportBuiltinsFuncs(globalCtx)
+	ImportBuiltinsFuncs(ctx)
+	return
 }

go.sum

@@ -1,4 +1,2 @@
-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).
+// Copyright (c) 2024-2026 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

@@ -1,4 +1,4 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
 // All rights reserved.
 
 // helpers.go
@@ -9,13 +9,17 @@ import (
 	"io"
 	"os"
 	"strings"
+
+	"git.portale-stac.it/go-pkg/expr/kern"
+	"git.portale-stac.it/go-pkg/expr/scan"
+	"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
+	var tree *scan.Ast
 
 	r := strings.NewReader(source)
-	scanner := NewScanner(r, DefaultTranslations())
+	scanner := scan.NewScanner(r, scan.DefaultTranslations())
 	parser := NewParser()
 
 	if tree, err = parser.Parse(scanner); err == nil {
@@ -34,21 +38,21 @@ 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),
+					kern.NewFuncParamFlagDef(kern.ParamValue, kern.PfDefault|kern.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)
@@ -65,9 +69,9 @@ 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
+	var tree *scan.Ast
-	scanner := NewScanner(r, DefaultTranslations())
+	scanner := scan.NewScanner(r, scan.DefaultTranslations())
 	parser := NewParser()
 
 	if tree, err = parser.Parse(scanner); err == nil {
@@ -76,7 +80,7 @@ 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

@@ -1,4 +1,4 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
 // All rights reserved.
 
 // 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 (
@@ -19,8 +22,8 @@ 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
 }
@@ -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
 }
 
@@ -76,14 +79,27 @@ 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 = ExpandPath(dir); err != nil {
+		if dir, err = util.ExpandPath(dir); err != nil {
 			continue
 		}
-		if fullPath := path.Join(dir, filename); isFile(fullPath) {
+		fullPath := path.Join(dir, filename)
+		if isFile(fullPath) {
 			filePath = fullPath
 			break
 		}
+
+		// subdir := strings.TrimSuffix(filename, suffix)
+		// if fullPath := path.Join(dir, subdir, filename); isFile(fullPath) {
+		// 	filePath = fullPath
+		// 	break
+		// }
 	}
 	return
 }
@@ -94,7 +110,7 @@ func isPathRelative(filePath string) bool {
 }
 
 func makeFilepath(filename string, dirList []string) (filePath string, err error) {
-	if filename, err = ExpandPath(filename); err != nil {
+	if filename, err = util.ExpandPath(filename); err != nil {
 		return
 	}
 

int-iterator.go

@@ -0,0 +1,141 @@
+// Copyright (c) 2024-2026 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 NewIntIteratorA(args ...any) (it *IntIterator, err error) {
+	return NewIntIterator(args)
+}
+
+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 +1,55 @@
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// iter-factory.go
+package expr
+
+import (
+	"slices"
+
+	"git.portale-stac.it/go-pkg/expr/kern"
+	"git.portale-stac.it/go-pkg/expr/scan"
+)
+
+func NewFormalIterator(value any) (it kern.Iterator) {
+	if value == nil {
+		it = NewArrayIterator([]any{})
+	} else {
+		it = NewArrayIterator([]any{value})
+	}
+	return
+}
+
+func NewIterator(ctx kern.ExprContext, value any, ops []*scan.Term) (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.LinkedList:
+		it = NewLinkedListIterator(v, nil)
+	case *kern.DictType:
+		it, err = NewDictIterator(v, nil)
+	case []any:
+		it = NewArrayIterator(v)
+	case kern.Iterator:
+		// var exprs []*scan.Term
+		it, err = NewIterIter(v, ctx, ops)
+	default:
+		it = NewArrayIterator([]any{value})
+	}
+	return
+}
+
+func HasIterStandardOperations(name string) bool {
+	return slices.Contains([]string{kern.NextName, kern.ResetName, kern.IndexName, kern.CountName, kern.CurrentName, kern.CleanName}, name)
+}
+
+// func HasIterOperations(name string, ops ...string) bool {
+// 	return slices.Contains([]string{
+// 		kern.NextName, kern.ResetName, kern.IndexName, kern.CountName, kern.CurrentName, kern.CleanName,
+// 	}, name) ||
+// 		slices.Contains(ops, name)
+// }

iter-iter.go

@@ -0,0 +1,135 @@
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// iter-iter.go
+package expr
+
+import (
+	"fmt"
+	"io"
+
+	"git.portale-stac.it/go-pkg/expr/kern"
+	"git.portale-stac.it/go-pkg/expr/scan"
+)
+
+const iterIterType = "IterIter"
+
+type IterIter struct {
+	it       kern.Iterator
+	count    int64
+	index    int64
+	ctx      kern.ExprContext
+	exprList []*scan.Term
+	current  any
+}
+
+func NewIterIter(it kern.Iterator, ctx kern.ExprContext, exprs []*scan.Term) (iter kern.Iterator, err error) {
+	if ctx == nil {
+		err = fmt.Errorf("context is required for %s", iterIterType)
+	} else if it == nil {
+		err = fmt.Errorf("source iterator is required for %s", iterIterType)
+	} else {
+		iter = &IterIter{it: it, count: 0, index: -1, ctx: ctx, exprList: exprs, current: nil}
+	}
+	return
+}
+
+func (it *IterIter) String() string {
+	return fmt.Sprintf("$(%s)", it.it)
+}
+
+func (it *IterIter) TypeName() string {
+	return iterIterType
+}
+
+func (it *IterIter) HasOperation(name string) bool {
+	return HasIterStandardOperations(name)
+}
+
+func (it *IterIter) 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 *IterIter) Current() (item any, err error) {
+	if it.current != nil {
+		item = it.current
+	} else if len(it.exprList) > 0 {
+		// Evaluate the expression list and use the result as the current item
+		var exprValue any
+		for _, expr := range it.exprList {
+			if exprValue, err = expr.Compute(it.ctx); err != nil {
+				break
+			}
+			it.ctx.UnsafeSetVar(kern.ControlLastResult, exprValue)
+		}
+		if err == nil {
+			item = exprValue
+		}
+	} else {
+		var exists bool
+		if it.current, exists = it.ctx.GetVar("_"); !exists {
+			err = fmt.Errorf("current item not available")
+		} else {
+			item = it.current
+		}
+	}
+	return
+}
+
+func (it *IterIter) Next() (item any, err error) {
+	var src any
+
+	it.current = nil
+	ctx := it.ctx
+	for src, err = it.it.Next(); src == nil && err == nil; src, err = it.it.Next() {
+	}
+
+	if err == nil {
+		if src == nil {
+			err = io.EOF
+		} else {
+			ctx.UnsafeSetVar("_", src)
+			ctx.UnsafeSetVar("__", it.it.Index())
+			ctx.UnsafeSetVar("_#", it.it.Count())
+			item, err = it.Current()
+			ctx.DeleteVar("_#")
+			ctx.DeleteVar("__")
+			ctx.DeleteVar("_")
+		}
+	}
+	return
+}
+
+func (it *IterIter) Index() int64 {
+	return it.index
+}
+
+func (it *IterIter) Count() int64 {
+	return it.count
+}
+
+func (it *IterIter) Reset() error {
+	it.index = -1
+	it.count = 0
+	return nil
+}
+
+func (it *IterIter) Clean() error {
+	return nil
+}

iterator.go

@@ -1,48 +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"
-	FilterName  = "filter"
-	MapName     = "map"
-)
-
-type Iterator interface {
-	Typer
-	Next() (item any, err error) // must return io.EOF after the last item
-	Current() (item any, err error)
-	Index() int
-	Count() int
-}
-
-type ExtIterator interface {
-	Iterator
-	Reset() error
-	Clean() error
-	HasOperation(name string) bool
-	CallOperation(name string, args map[string]any) (value any, err error)
-}
-
-func errNoOperation(name string) error {
-	return fmt.Errorf("no %s() function defined in the data-source", name)
-}
-
-// func errInvalidDataSource() error {
-// 	return errors.New("invalid data-source")
-// }

kern/bind-go-functions.go

@@ -0,0 +1,23 @@
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// bind-go-function.go
+package kern
+
+// ---- Linking with Go functions
+type GolangFunctor struct {
+	BaseFunctor
+	f FuncTemplate
+}
+
+func NewGolangFunctor(f FuncTemplate) *GolangFunctor {
+	return &GolangFunctor{f: f}
+}
+
+func (functor *GolangFunctor) TypeName() string {
+	return "GoFunctor"
+}
+
+func (functor *GolangFunctor) InvokeNamed(ctx ExprContext, name string, args map[string]any) (result any, err error) {
+	return functor.f(ctx, name, args)
+}

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/clone-value.go

@@ -0,0 +1,30 @@
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// clone-value.go
+package kern
+
+func Clone(v any) (c any) {
+	if v == nil {
+		return
+	}
+	switch unboxed := v.(type) {
+	case int64:
+		c = unboxed
+	case float64:
+		c = unboxed
+	case string:
+		c = unboxed
+	case bool:
+		c = unboxed
+	case *ListType:
+		c = unboxed.Clone()
+	case *DictType:
+		c = unboxed.Clone()
+	case *LinkedList:
+		c = unboxed.Clone()
+	default:
+		c = v
+	}
+	return
+}

kern/common-errors.go

@@ -1,8 +1,8 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
 // All rights reserved.
 
 // common-errors.go
-package expr
+package kern
 
 import (
 	"fmt"
@@ -34,7 +34,7 @@ func ErrCantConvert(funcName string, value any, kind string) error {
 }
 
 func ErrExpectedGot(funcName string, kind string, value any) error {
-	return fmt.Errorf("%s(): expected %s, got %s (%v)", funcName, kind, TypeName(value), value)
+	return fmt.Errorf("%s(): expected %s, got %s (%#v)", funcName, kind, TypeName(value), value)
 }
 
 func ErrFuncDivisionByZero(funcName string) error {
@@ -52,7 +52,7 @@ func ErrFuncDivisionByZero(funcName string) error {
 // }
 
 func ErrInvalidParameterValue(funcName, paramName string, paramValue any) error {
-	return fmt.Errorf("%s(): invalid value %s (%v) for parameter %q", funcName, TypeName(paramValue), paramValue, paramName)
+	return fmt.Errorf("%s(): invalid value %s (%#v) for parameter %q", funcName, TypeName(paramValue), paramValue, paramName)
 }
 
 func undefArticle(s string) (article string) {
@@ -84,8 +84,12 @@ func ErrUnknownVar(funcName, varName string) error {
 	return fmt.Errorf("%s(): unknown variable %q", funcName, varName)
 }
 
+func ErrFuncInvalidArg(funcName, details string) error {
+	return fmt.Errorf("%s(): invalid argument -- %s", funcName, details)
+}
+
 // --- Operator errors
 
-func ErrLeftOperandMustBeVariable(leftTerm, opTerm *term) error {
+func ErrLeftOperandMustBeVariable(leftTerm, opTerm Term) error {
-	return leftTerm.Errorf("left operand of %q must be a variable", opTerm.source())
+	return leftTerm.Errorf("left operand of %q must be a variable", opTerm.Source())
 }

kern/common-params.go

@@ -1,8 +1,8 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
 // All rights reserved.
 
 // common-params.go
-package expr
+package kern
 
 const (
 	ParamArgs      = "args"

kern/common-type-names.go

@@ -1,8 +1,8 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
 // All rights reserved.
 
 // common-type-names.go
-package expr
+package kern
 
 const (
 	TypeAny           = "any"
@@ -13,10 +13,12 @@ const (
 	TypeFileHandle    = "file-handle"
 	TypeInt           = "integer"
 	TypeItem          = "item"
+	TypeIterator      = "iterator"
 	TypeNumber        = "number"
 	TypePair          = "pair"
 	TypeString        = "string"
 	TypeDict          = "dict"
 	TypeListOf        = "list-of-"
 	TypeListOfStrings = "list-of-strings"
+	TypeLinkedList    = "linked-list"
 )

kern/compare.go

@@ -0,0 +1,41 @@
+// 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 IsLinkedList(value1) && IsLinkedList(value2) {
+		ll1 := value1.(*LinkedList)
+		ll2 := value2.(*LinkedList)
+		equal = ll1.Equals(ll2)
+	} 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

@@ -1,10 +1,10 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
 // 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()
 	}
@@ -25,8 +25,8 @@ 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] == '@') && !(name[0] == '_') }) {
@@ -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

@@ -1,8 +1,10 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
 // All rights reserved.
 
 // control.go
-package expr
+package kern
+
+import "strings"
 
 // Preset control variables
 const (
@@ -16,7 +18,7 @@ const (
 
 // Other control variables
 const (
-	control_export_all = "_export_all"
+	ControlExportAll = "_export_all"
 )
 
 // Initial values
@@ -24,13 +26,34 @@ 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) {
+func InitDefaultVars(ctx ExprContext) {
 	if _, exists := ctx.GetVar(ControlPreset); exists {
 		return
 	}

kern/dict-type.go

@@ -1,8 +1,8 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
 // All rights reserved.
 
 // dict-type.go
-package expr
+package kern
 
 import (
 	"fmt"
@@ -10,8 +10,15 @@ import (
 	"strings"
 )
 
+const DictTypeName = "dict"
+
 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
@@ -32,7 +39,7 @@ func NewDict(dictAny map[any]any) (dict *DictType) {
 	return
 }
 
-func newDict(dictAny map[any]*term) (dict *DictType) {
+func newDict(dictAny map[any]Term) (dict *DictType) {
 	// TODO Change with a call to NewDict()
 	var d DictType
 	if dictAny != nil {
@@ -69,9 +76,11 @@ func (dict *DictType) toMultiLine(sb *strings.Builder, opt FmtOpt) {
 
 			sb.WriteString(nest)
 			if key, ok := name.(string); ok {
-				sb.WriteString(string('"') + key + string('"'))
+				sb.WriteByte('"')
+				sb.WriteString(key)
+				sb.WriteByte('"')
 			} else {
-				sb.WriteString(fmt.Sprintf("%v", name))
+				fmt.Fprintf(sb, "%v", name)
 			}
 			sb.WriteString(": ")
 			if f, ok := value.(Formatter); ok {
@@ -79,7 +88,7 @@ func (dict *DictType) toMultiLine(sb *strings.Builder, opt FmtOpt) {
 			} else if _, ok = value.(Functor); ok {
 				sb.WriteString("func(){}")
 			} else {
-				sb.WriteString(fmt.Sprintf("%v", value))
+				fmt.Fprintf(sb, "%v", value)
 			}
 		}
 		sb.WriteByte('\n')
@@ -103,17 +112,19 @@ func (dict *DictType) ToString(opt FmtOpt) string {
 				sb.WriteString(", ")
 			}
 			if s, ok := key.(string); ok {
-				sb.WriteString(string('"') + s + string('"'))
+				sb.WriteByte('"')
+				sb.WriteString(s)
+				sb.WriteByte('"')
 			} else {
-				sb.WriteString(fmt.Sprintf("%v", key))
+				fmt.Fprintf(&sb, "%v", key)
 			}
 			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))
+				fmt.Fprintf(&sb, "%#v", value)
 			}
 		}
 		sb.WriteByte('}')
@@ -126,10 +137,10 @@ func (dict *DictType) String() string {
 }
 
 func (dict *DictType) TypeName() string {
-	return "dict"
+	return DictTypeName
 }
 
-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
@@ -138,15 +149,24 @@ 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
+		(*c)[k] = Clone(v)
 	}
 	return
 }
 
-func (dict *DictType) merge(second *DictType) {
+func (dict *DictType) Merge(second *DictType) {
 	if second != nil {
 		for k, v := range *second {
 			(*dict)[k] = v
@@ -154,8 +174,21 @@ 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 +1,63 @@
+// Copyright (c) 2024-2026 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)
+
+	ToDict() (dict *DictType)
+	ToString(opt FmtOpt) string
+}
+
+func ContextToDict(ctx ExprContext) (dict *DictType) {
+	var keys []string
+	// Variables
+	keys = ctx.EnumVars(nil)
+	vars := MakeDict()
+	for _, key := range keys {
+		value, _ := ctx.GetVar(key)
+		vars.SetItem(key, value)
+	}
+
+	// Functions
+	keys = ctx.EnumFuncs(func(name string) bool { return true })
+	funcs := MakeDict()
+	for _, key := range keys {
+		funcInfo, _ := ctx.GetFuncInfo(key)
+		funcs.SetItem(key, funcInfo)
+	}
+
+	dict = MakeDict()
+	dict.SetItem("vars", vars)
+	dict.SetItem("funcs", funcs)
+	return
+}
+
+func ContextToString(ctx ExprContext, opt FmtOpt) string {
+	dict := ctx.ToDict()
+	return dict.ToString(opt)
+}

kern/expr-function.go

@@ -1,8 +1,8 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
 // All rights reserved.
 
 // expr-function.go
-package expr
+package kern
 
 // ---- Functor interface
 type Functor interface {
@@ -37,3 +37,8 @@ type ExprFunc interface {
 	PrepareCall(name string, actualParams map[string]any) (err error)
 	AllocContext(parentCtx ExprContext) (ctx ExprContext)
 }
+
+func IsFunctor(v any) (ok bool) {
+	_, ok = v.(Functor)
+	return
+}

kern/expr.go

@@ -1,8 +1,8 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
 // All rights reserved.
 
 // expr.go
-package expr
+package kern
 
 // ----Expression interface
 type Expr interface {

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

@@ -1,10 +1,13 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
 // All rights reserved.
 
 // formatter.go
-package expr
+package kern
 
-import "fmt"
+import (
+	"fmt"
+	"strings"
+)
 
 type FmtOpt uint32 // lower 16 bits hold a bit-mask, higher 16 bits hold an indentation number
 
@@ -46,7 +49,19 @@ type Formatter interface {
 	ToString(options FmtOpt) string
 }
 
-func getFormatted(v any, opt FmtOpt) (text string) {
+func Format(sb *strings.Builder, item any, opt FmtOpt) {
+	if s, ok := item.(string); ok {
+		sb.WriteByte('"')
+		sb.WriteString(s)
+		sb.WriteByte('"')
+	} else if formatter, ok := item.(Formatter); ok {
+		sb.WriteString(formatter.ToString(opt))
+	} else {
+		fmt.Fprintf(sb, "%v", item)
+	}
+}
+
+func GetFormatted(v any, opt FmtOpt) (text string) {
 	if v == nil {
 		text = "(nil)"
 	} else if s, ok := v.(string); ok {

kern/fraction-type.go

@@ -1,8 +1,8 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
 // 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 {
@@ -33,21 +33,22 @@ 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
 	if len(s) == 0 {
 		goto exit
 	}
-	if s[0] == '-' {
+	switch s[0] {
+	case '-':
 		sign = int64(-1)
 		s = s[1:]
-	} else if s[0] == '+' {
+	case '+':
 		s = s[1:]
 	}
 	//	if strings.HasSuffix(s, "()") {
@@ -59,7 +60,7 @@ func makeGeneratingFraction(s string) (f *FractionType, err error) {
 		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 {
@@ -76,7 +77,7 @@ 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)
@@ -103,7 +104,7 @@ func makeGeneratingFraction(s string) (f *FractionType, err error) {
 				den *= mul
 			}
 			num -= sub
-			f = newFraction(sign*num, den)
+			f = NewFraction(sign*num, den)
 		}
 	}
 exit:
@@ -113,7 +114,15 @@ 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)
 }
 
@@ -168,7 +177,7 @@ 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
 	}
@@ -189,21 +198,21 @@ 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
 }
 
@@ -212,11 +221,12 @@ 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)
-	if f == nil {
+		} else {
 			err = ErrExpectedGot("fract", TypeFraction, v)
 		}
+	}
 	return
 }
 
@@ -230,12 +240,12 @@ 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 {
@@ -250,7 +260,7 @@ 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
@@ -265,8 +275,9 @@ func cmpAnyFract(af1, af2 any) (result int, err error) {
 //	=0 if af1 == af2
 //	>0 if af1 > af2
 func cmpFract(f1, f2 *FractionType) (result int) {
+	if f1 != nil && f2 != nil {
 		f2.num = -f2.num
-	f := sumFract(f1, f2)
+		f := SumFract(f1, f2)
 		if f.num < 0 {
 			result = -1
 		} else if f.num > 0 {
@@ -274,16 +285,17 @@ func cmpFract(f1, f2 *FractionType) (result int) {
 		} 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 {
@@ -292,7 +304,7 @@ 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
@@ -306,7 +318,7 @@ 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
@@ -345,7 +357,7 @@ 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
@@ -355,7 +367,19 @@ 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/func-info.go

@@ -0,0 +1,164 @@
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// func-info.go
+package kern
+
+import (
+	"fmt"
+	"strings"
+)
+
+// --- Functions
+
+// FuncInfo implements expr.ExprFunc
+type FuncInfo struct {
+	name         string
+	minArgs      int
+	maxArgs      int
+	functor      Functor
+	formalParams []ExprFuncParam
+	returnType   string
+}
+
+func NewFuncInfo(name string, functor Functor, returnType string, params []ExprFuncParam) (info *FuncInfo, err error) {
+	var minArgs = 0
+	var maxArgs = 0
+	for _, p := range params {
+		if maxArgs == -1 {
+			return nil, fmt.Errorf("no more params can be specified after the ellipsis symbol: %q", p.Name())
+		}
+		if p.IsDefault() || p.IsOptional() {
+			maxArgs++
+		} else if maxArgs == minArgs {
+			minArgs++
+			maxArgs++
+		} else {
+			return nil, fmt.Errorf("can't specify non-optional param after optional ones: %q", p.Name())
+		}
+		if p.IsRepeat() {
+			minArgs--
+			maxArgs = -1
+		}
+	}
+
+	info = &FuncInfo{
+		name: name, minArgs: minArgs, maxArgs: maxArgs, functor: functor, returnType: returnType, formalParams: params,
+	}
+	functor.SetFunc(info)
+	return info, nil
+}
+
+func (info *FuncInfo) Params() []ExprFuncParam {
+	return info.formalParams
+}
+
+func (info *FuncInfo) ReturnType() string {
+	return info.returnType
+}
+
+func (info *FuncInfo) ToString(opt FmtOpt) string {
+	var sb strings.Builder
+	if len(info.Name()) == 0 {
+		sb.WriteString("func")
+	} else {
+		sb.WriteString(info.Name())
+	}
+	sb.WriteByte('(')
+	if info.formalParams != nil {
+		for i, p := range info.formalParams {
+			if i > 0 {
+				sb.WriteString(", ")
+			}
+			sb.WriteString(p.Name())
+
+			if p.IsDefault() {
+				sb.WriteByte('=')
+				if s, ok := p.DefaultValue().(string); ok {
+					sb.WriteByte('"')
+					sb.WriteString(s)
+					sb.WriteByte('"')
+				} else {
+					sb.WriteString(fmt.Sprintf("%v", p.DefaultValue()))
+				}
+			}
+		}
+	}
+	if info.maxArgs < 0 {
+		sb.WriteString(" ...")
+	}
+	sb.WriteString("):")
+	if len(info.returnType) > 0 {
+		sb.WriteString(info.returnType)
+	} else {
+		sb.WriteString(TypeAny)
+	}
+	sb.WriteString("{}")
+	return sb.String()
+}
+
+func (info *FuncInfo) Name() string {
+	return info.name
+}
+
+func (info *FuncInfo) MinArgs() int {
+	return info.minArgs
+}
+
+func (info *FuncInfo) MaxArgs() int {
+	return info.maxArgs
+}
+
+func (info *FuncInfo) Functor() Functor {
+	return info.functor
+}
+
+func (info *FuncInfo) AllocContext(parentCtx ExprContext) (ctx ExprContext) {
+	if defCtx := info.functor.GetDefinitionContext(); defCtx != nil {
+		ctx = defCtx.Clone()
+		ctx.SetParent(defCtx)
+	} else {
+		ctx = parentCtx.Clone()
+		ctx.SetParent(parentCtx)
+	}
+	return
+}
+
+func (info *FuncInfo) ParamSpec(paramName string) ExprFuncParam {
+	for _, spec := range info.formalParams {
+		if spec.Name() == paramName {
+			return spec
+		}
+	}
+	return nil
+}
+
+func (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
+}

kern/function.go

@@ -0,0 +1,273 @@
+// Copyright (c) 2024-2026 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)
+
+// ---- 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 FuncParamFlags uint16
+
+const (
+	PfDefault FuncParamFlags = 1 << iota
+	PfOptional
+	PfRepeat
+)
+
+type funcParamInfo struct {
+	name         string
+	flags        FuncParamFlags
+	defaultValue any
+}
+
+func NewFuncParam(name string) ExprFuncParam {
+	return &funcParamInfo{name: name}
+}
+
+func NewFuncParamFlag(name string, flags FuncParamFlags) ExprFuncParam {
+	return &funcParamInfo{name: name, flags: flags}
+}
+
+func NewFuncParamFlagDef(name string, flags FuncParamFlags, 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 +1,95 @@
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// iterator.go
+package kern
+
+import (
+	// "errors"
+	"fmt"
+	"slices"
+)
+
+// 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
+}
+
+type IteratorBase struct {
+	ItemIndex int64
+	ItemCount int64
+	current   any
+}
+
+func (it *IteratorBase) Current() (item any, err error) {
+	return it.current, nil
+}
+
+func (it *IteratorBase) Index() int64 {
+	return it.ItemIndex
+}
+
+func (it *IteratorBase) Count() int64 {
+	return it.ItemCount
+}
+
+func (it *IteratorBase) HasOperation(name string) bool {
+	return slices.Contains([]string{NextName, IndexName, CountName, CurrentName}, name)
+}
+
+func (it *IteratorBase) Clean() (err error) {
+	return
+}
+
+func (it *IteratorBase) Reset() (err error) {
+	it.ItemIndex = -1
+	it.ItemCount = 0
+	it.current = nil
+	return
+}
+
+func (it *IteratorBase) Increment() {
+	it.ItemIndex++
+	it.ItemCount++
+}
+
+func (it *IteratorBase) SetCurrent(v any) {
+	it.current = v
+}

kern/linked-list-type.go

@@ -0,0 +1,130 @@
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// linked-list-type.go
+package kern
+
+import (
+	"strings"
+)
+
+const LinkedListTypeName = "lisked-list"
+const MaxUint64Allowed = uint64(9_223_372_036_854_775_807)
+
+func IsLinkedList(v any) (ok bool) {
+	_, ok = v.(*LinkedList)
+	return ok
+}
+
+func NewLinkedListA(listAny ...any) (list *LinkedList) {
+	if listAny == nil {
+		listAny = []any{}
+	}
+	list = NewLinkedList()
+	for _, item := range listAny {
+		list.PushBack(FixAnyNumber(item))
+	}
+	return
+}
+
+func LinkedListFromStrings(stringList []string) (list *LinkedList) {
+	list = NewLinkedList()
+	for _, s := range stringList {
+		list.PushBack(s)
+	}
+	return
+}
+
+func (ls *LinkedList) ToString(opt FmtOpt) (s string) {
+	indent := GetFormatIndent(opt)
+	flags := GetFormatFlags(opt)
+
+	var sb strings.Builder
+	sb.WriteString("[<")
+	if ls.Len() > 0 {
+		innerOpt := MakeFormatOptions(flags, indent+1)
+		nest := strings.Repeat("  ", indent+1)
+
+		if flags&MultiLine != 0 {
+			sb.WriteByte('\n')
+			sb.WriteString(nest)
+		}
+
+		i := 0
+		for item := ls.FirstNode(); item != nil; item = item.Next() {
+			if i > 0 {
+				if flags&MultiLine != 0 {
+					sb.WriteString(",\n")
+					sb.WriteString(nest)
+				} else {
+					sb.WriteString(", ")
+				}
+			}
+			// data := item.Data()
+			// if s, ok := data.(string); ok {
+			// 	sb.WriteByte('"')
+			// 	sb.WriteString(s)
+			// 	sb.WriteByte('"')
+			// } else if formatter, ok := data.(Formatter); ok {
+			// 	sb.WriteString(formatter.ToString(innerOpt))
+			// } else {
+			// 	fmt.Fprintf(&sb, "%v", data)
+			// }
+			Format(&sb, item.Data(), innerOpt)
+			i++
+		}
+		if flags&MultiLine != 0 {
+			sb.WriteByte('\n')
+			sb.WriteString(strings.Repeat("  ", indent))
+		}
+	}
+	sb.WriteString(">]")
+	s = sb.String()
+	if flags&Truncate != 0 && len(s) > TruncateSize {
+		s = TruncateString(s)
+	}
+	return
+}
+
+func (ls *LinkedList) String() string {
+	return ls.ToString(0)
+}
+
+func (ls *LinkedList) TypeName() string {
+	return LinkedListTypeName
+}
+
+// func (ls *LinkedList) Contains(t *ListType) (answer bool) {
+// 	if len(*ls) >= len(*t) {
+// 		answer = true
+// 		for _, item := range *t {
+// 			if answer = ls.IndexDeepSameCmp(item) >= 0; !answer {
+// 				break
+// 			}
+// 		}
+// 	}
+// 	return
+// }
+
+func (ls1 *LinkedList) Equals(ls2 *LinkedList) (answer bool) {
+	if ls2 != nil && ls1.Len() == ls2.Len() {
+		answer = true
+		i2 := ls2.FirstNode()
+		for i1 := ls1.FirstNode(); i1 != nil; i1 = i1.Next() {
+			if !Equal(i1.Data(), i2.Data()) {
+				answer = false
+				break
+			}
+			i2 = i2.Next()
+		}
+	}
+	return
+}
+
+func (ls1 *LinkedList) Clone() (ls2 *LinkedList) {
+	ls2 = NewLinkedListA()
+	for i1 := ls1.FirstNode(); i1 != nil; i1 = i1.Next() {
+		ls2.PushBack(Clone(i1.Data()))
+	}
+	return
+}

kern/linked-list.go

@@ -0,0 +1,284 @@
+// simple-list project slist.go
+package kern
+
+import (
+	"fmt"
+)
+
+type ListNode struct {
+	data any
+	next *ListNode
+}
+
+func (node *ListNode) Next() *ListNode {
+	return node.next
+}
+
+func (self *ListNode) Data() any {
+	return self.data
+}
+
+type LinkedList struct {
+	count int
+	first *ListNode
+	last  *ListNode
+}
+
+func NewLinkedList() (list *LinkedList) {
+	list = &LinkedList{0, nil, nil}
+	return
+}
+
+func (ls *LinkedList) Len() int {
+	return ls.count
+}
+
+func (ls *LinkedList) Empty() bool {
+	return ls.count == 0
+}
+
+func (ls *LinkedList) PushFront(data any) *ListNode {
+	ls.first = &ListNode{data, ls.first}
+	if ls.last == nil {
+		ls.last = ls.first
+	}
+	ls.count++
+	return ls.first
+}
+
+func (ls *LinkedList) SeqPushFront(data any) (result *LinkedList) {
+	switch seq := data.(type) {
+	case Iterator:
+		result = ls.IterPushFront(seq)
+	default:
+		ls.PushFront(data)
+		result = ls
+	}
+	return
+}
+
+func (ls *LinkedList) IterPushFront(it Iterator) *LinkedList {
+	for item, err1 := it.Next(); err1 == nil; item, err1 = it.Next() {
+		ls.PushFront(item)
+	}
+	return ls
+}
+
+func (ls *LinkedList) PushBack(data any) (node *ListNode) {
+	node = &ListNode{data, nil}
+	if ls.last != nil {
+		ls.last.next = node
+	}
+	ls.last = node
+	if ls.first == nil {
+		ls.first = node
+	}
+	ls.count++
+	return
+}
+
+func (ls *LinkedList) SeqPushBack(data any) (result *LinkedList) {
+	switch seq := data.(type) {
+	case Iterator:
+		result = ls.IterPushBack(seq)
+	default:
+		ls.PushBack(data)
+		result = ls
+	}
+	return
+}
+
+func (ls *LinkedList) IterPushBack(it Iterator) *LinkedList {
+	for item, err1 := it.Next(); err1 == nil; item, err1 = it.Next() {
+		ls.PushBack(item)
+	}
+	return ls
+}
+
+func (ls *LinkedList) FirstNode() *ListNode {
+	return ls.first
+}
+
+func (ls *LinkedList) First() (data any, err error) {
+	if ls.first != nil {
+		data = ls.first.data
+	} else {
+		err = errorListEmpty()
+	}
+	return
+}
+
+func (ls *LinkedList) LastNode() *ListNode {
+	return ls.last
+}
+
+func (ls *LinkedList) Last() (data interface{}, err error) {
+	if ls.last != nil {
+		data = ls.last.data
+	} else {
+		err = errorListEmpty()
+	}
+	return
+}
+
+func (ls *LinkedList) NodeAt(index int) (node *ListNode, err error) {
+	if ls.count == 0 {
+		err = errorListEmpty()
+	} else if index > ls.count {
+		err = errorOutOfRange()
+	} else if index == ls.count-1 {
+		node = ls.last
+	} else {
+		current := ls.first
+		for range index {
+			current = current.next
+		}
+		node = current
+	}
+	return
+}
+
+func (ls *LinkedList) At(index int) (data interface{}, err error) {
+	node, err := ls.NodeAt(index)
+	if err == nil {
+		data = node.data
+	}
+	return
+}
+
+func (ls *LinkedList) Insert(index int, data any) *ListNode {
+	var prev *ListNode
+
+	prev = nil
+	current := ls.first
+	for pos := 0; current != nil && pos < index; pos++ {
+		prev = current
+		current = current.next
+	}
+
+	node := &ListNode{data, current}
+
+	if prev != nil {
+		prev.next = node
+	}
+
+	if ls.first == current {
+		ls.first = node
+	}
+	if node.next == nil {
+		ls.last = node
+	}
+	ls.count++
+	return node
+}
+
+func (ls *LinkedList) PushBackStringArray(items []string) {
+	for _, v := range items {
+		ls.PushBack(v)
+	}
+}
+
+func (ls *LinkedList) Sub(start, end int) (subList *LinkedList) {
+	subList = NewLinkedList()
+	if node, err := ls.NodeAt(start); err == nil {
+		for i := start; i < end && node != nil; i++ {
+			subList.PushBack(node.data)
+			node = node.next
+		}
+	}
+	return
+}
+
+// type TraverseOperator func(index int, elem interface{}, userData interface{}) (err error)
+
+// func (self *LinkedList) Traverse(op TraverseOperator, user_data interface{}) (err error) {
+// 	index := int(0)
+// 	for current := self.first; current != nil; current = current.next {
+// 		err = op(index, current.data, user_data)
+// 		if err != nil {
+// 			break
+// 		}
+// 		index++
+// 	}
+// 	return
+// }
+
+// func (self *LinkedList) Traverse2(observer Observer, abortOnError bool) (err error) {
+// 	index := int(0)
+// 	for current := self.first; current != nil; current = current.next {
+// 		err = observer.Observe(current, index)
+// 		if err != nil && abortOnError {
+// 			break
+// 		}
+// 		index++
+// 	}
+// 	return
+// }
+
+type EqualFunc func(current, target any) bool
+
+func (ls *LinkedList) FindFirst(eqFunc EqualFunc, targetData any) (targetNode *ListNode) {
+	for current := ls.first; current != nil && targetNode == nil; current = current.next {
+		if eqFunc(current.data, targetData) {
+			targetNode = current
+		}
+	}
+	return
+}
+
+func (ls *LinkedList) FindNext(eqFunc EqualFunc, startNode *ListNode) (targetNode *ListNode) {
+	if startNode != nil {
+		for current := startNode.next; current != nil && targetNode == nil; current = current.next {
+			if eqFunc(current.data, startNode.Data()) {
+				targetNode = current
+			}
+		}
+	}
+	return
+}
+
+// type DataFeeder func(user_data interface{}) interface{}
+// type NodeObserver func(node *ListNode, index int, userData interface{})
+
+// func (self *LinkedList) FeedTail(feeder DataFeeder, feederUserData interface{}, observer NodeObserver, observerUserData interface{}) (count int) {
+// 	count = 0
+// 	for item := feeder(feederUserData); item != nil; item = feeder(feederUserData) {
+// 		// fmt.Println("Item", count, item)
+// 		node := self.PushBack(item)
+// 		if observer != nil {
+// 			observer(node, count, observerUserData)
+// 		}
+// 		count++
+// 	}
+// 	return
+// }
+
+// func (self *LinkedList) FeedTail2(feeder Feeder, observer Observer, abortOnError bool) (count int, err error) {
+// 	count = 0
+// 	// item := feeder.Next()
+// 	for item, err1 := feeder.Next(); item != nil; item, err1 = feeder.Next() {
+// 		if err1 != nil {
+// 			if err == nil {
+// 				err = err1
+// 			}
+// 			if abortOnError {
+// 				break
+// 			}
+// 		}
+// 		// fmt.Println("Item", count, item)
+// 		node := self.PushBack(item)
+// 		if observer != nil {
+// 			observer.Observe(node, count)
+// 		}
+// 		count++
+// 	}
+// 	return
+// }
+
+func errorListEmpty() error {
+	return fmt.Errorf("List is empty")
+}
+
+func errorOutOfRange() error {
+	return fmt.Errorf("Out of range")
+}

kern/list-type.go

@@ -1,8 +1,8 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
 // All rights reserved.
 
 // list-type.go
-package expr
+package kern
 
 import (
 	"fmt"
@@ -12,23 +12,21 @@ 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 {
-//			ls[i] = item
-//		}
 		copy(ls, listAny)
 		list = &ls
 	}
@@ -75,15 +73,7 @@ func (ls *ListType) ToString(opt FmtOpt) (s string) {
 					sb.WriteString(", ")
 				}
 			}
-			if s, ok := item.(string); ok {
+			Format(&sb, item, innerOpt)
-				sb.WriteByte('"')
-				sb.WriteString(s)
-				sb.WriteByte('"')
-			} else if formatter, ok := item.(Formatter); ok {
-				sb.WriteString(formatter.ToString(innerOpt))
-			} else {
-				sb.WriteString(fmt.Sprintf("%v", item))
-			}
 		}
 		if flags&MultiLine != 0 {
 			sb.WriteByte('\n')
@@ -106,22 +96,11 @@ func (ls *ListType) TypeName() string {
 	return "list"
 }
 
-// func (list *ListType) indexDeepCmp(target any) (index int) {
+func (ls *ListType) Contains(t *ListType) (answer bool) {
-// 	index = -1
-// 	for i, item := range *list {
-// 		if reflect.DeepEqual(item, target) {
-// 			index = i
-// 			break
-// 		}
-// 	}
-// 	return
-// }
-
-func (ls *ListType) contains(t *ListType) (answer bool) {
 	if len(*ls) >= len(*t) {
 		answer = true
 		for _, item := range *t {
-			if answer = ls.indexDeepSameCmp(item) >= 0; !answer {
+			if answer = ls.IndexDeepSameCmp(item) >= 0; !answer {
 				break
 			}
 		}
@@ -129,12 +108,38 @@ func (ls *ListType) contains(t *ListType) (answer bool) {
 	return
 }
 
-func (list *ListType) indexDeepSameCmp(target any) (index int) {
+func (ls *ListType) Equals(ls2 ListType) (answer bool) {
+	if ls2 != nil && len(*ls) == len(ls2) {
+		answer = true
+		for index, i1 := range *ls {
+			// if !reflect.DeepEqual(i1, ls2[index]) {
+			// 	answer = false
+			// 	break
+			// }
+			if !Equal(i1, ls2[index]) {
+				answer = false
+				break
+			}
+		}
+	}
+	return
+}
+
+func (ls1 *ListType) Clone() (ls2 *ListType) {
+	ls := make(ListType, len(*ls1))
+	for i, item := range *ls1 {
+		ls[i] = Clone(item)
+	}
+	ls2 = &ls
+	return
+}
+
+func (ls *ListType) IndexDeepSameCmp(target any) (index int) {
 	var eq bool
 	var err error
 	index = -1
-	for i, item := range *list {
+	for i, item := range *ls {
-		if eq, err = deepSame(item, target, sameContent); err != nil {
+		if eq, err = deepSame(item, target, SameContent); err != nil {
 			break
 		} else if eq {
 			index = i
@@ -144,13 +149,13 @@ 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
 			}
@@ -159,19 +164,19 @@ 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
 			}
 		}
@@ -184,12 +189,15 @@ func deepSame(a, b any, deepCmp deepFuncTemplate) (eq bool, err error) {
 	return
 }
 
-func (list *ListType) setItem(index int64, value any) (err error) {
+func (ls *ListType) SetItem(index int64, value any) (err error) {
-	if index >= 0 && index < int64(len(*list)) {
+	if index >= 0 && index < int64(len(*ls)) {
-		(*list)[index] = value
+		(*ls)[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(*ls)-1)
 	}
 	return
 }
 
+func (ls *ListType) AppendItem(value any) {
+	*ls = append(*ls, value)
+}

kern/number.go

@@ -0,0 +1,120 @@
+// 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 FixAnyNumber(v any) (fixed any) {
+	switch unboxed := v.(type) {
+	case int:
+		fixed = int64(unboxed)
+	case int8:
+		fixed = int64(unboxed)
+	case int16:
+		fixed = int64(unboxed)
+	case int32:
+		fixed = int64(unboxed)
+	case uint:
+		fixed = int64(unboxed)
+	case uint8:
+		fixed = int64(unboxed)
+	case uint16:
+		fixed = int64(unboxed)
+	case uint32:
+		fixed = int64(unboxed)
+	case uint64:
+		if unboxed <= MaxUint64Allowed {
+			fixed = int64(unboxed)
+		} else {
+			fixed = float64(unboxed)
+		}
+	case float32:
+		fixed = float64(unboxed)
+	default:
+		fixed = v
+	}
+	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) 2024-2026 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) 2024-2026 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) 2024-2026 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) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// lib-ext-windows.go
+package expr
+
+const SHAREDLIBRARY_EXTENSION = ".dll"

linked-list-iterator.go

@@ -0,0 +1,102 @@
+// Copyright (c) 2024-2026 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 LinkedListIterator struct {
+	a       *kern.LinkedList
+	count   int64
+	index   int64
+	current *kern.ListNode
+}
+
+func NewLinkedListIterator(list *kern.LinkedList, args []any) (it *LinkedListIterator) {
+	it = &LinkedListIterator{a: list, count: 0, index: -1, current: list.FirstNode()}
+	return
+}
+
+func (it *LinkedListIterator) String() string {
+	var l = int64(0)
+	if it.a != nil {
+		l = int64(it.a.Len())
+	}
+	return fmt.Sprintf("$([<#%d>])", l)
+}
+
+func (it *LinkedListIterator) TypeName() string {
+	return "LinkedListIterator"
+}
+
+func (it *LinkedListIterator) HasOperation(name string) bool {
+	yes := slices.Contains([]string{kern.NextName, kern.ResetName, kern.IndexName, kern.CountName, kern.CurrentName}, name)
+	return yes
+}
+
+func (it *LinkedListIterator) 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 *LinkedListIterator) Current() (item any, err error) {
+	if it.current != nil {
+		item = it.current.Data()
+	} else {
+		err = io.EOF
+	}
+	return
+}
+
+func (it *LinkedListIterator) Next() (item any, err error) {
+	if it.current != nil {
+		item = it.current.Data()
+		it.current = it.current.Next()
+		it.index++
+		it.count++
+	} else {
+		err = io.EOF
+	}
+	return
+}
+
+func (it *LinkedListIterator) Index() int64 {
+	return it.index
+}
+
+func (it *LinkedListIterator) Count() int64 {
+	return it.count
+}
+
+func (it *LinkedListIterator) Reset() error {
+	it.current = it.a.FirstNode()
+	it.index = -1
+	it.count = 0
+	return nil
+}
+
+func (it *LinkedListIterator) Clean() error {
+	return nil
+}

list-iterator.go

@@ -1,4 +1,4 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
 // All rights reserved.
 
 // list-iterator.go
@@ -7,40 +7,43 @@ package expr
 import (
 	"fmt"
 	"io"
+	"slices"
+
+	"git.portale-stac.it/go-pkg/expr/kern"
 )
 
 type ListIterator struct {
-	a     *ListType
+	a     *kern.ListType
-	count int
+	count int64
-	index int
+	index int64
-	start int
+	start int64
-	stop  int
+	stop  int64
-	step  int
+	step  int64
 }
 
-func NewListIterator(list *ListType, args []any) (it *ListIterator) {
+func NewListIterator(list *kern.ListType, args []any) (it *ListIterator) {
 	var argc int = 0
-	listLen := len(([]any)(*list))
+	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 := ToGoInt(args[0], "start index"); err == nil {
+		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 := ToGoInt(args[1], "stop index"); err == nil {
+			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 := ToGoInt(args[2], "step"); err == nil {
+				if i, err := kern.ToGoInt64(args[2], "step"); err == nil {
 					if i < 0 {
 						i = -i
 					}
@@ -58,31 +61,16 @@ func NewListIterator(list *ListType, args []any) (it *ListIterator) {
 }
 
 func NewArrayIterator(array []any) (it *ListIterator) {
-	it = &ListIterator{a: (*ListType)(&array), count: 0, index: -1, start: 0, stop: len(array) - 1, step: 1}
+	it = &ListIterator{a: (*kern.ListType)(&array), count: 0, index: -1, start: 0, stop: int64(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
+	var l = int64(0)
 	if it.a != nil {
-		l = len(*it.a)
+		l = int64(len(*it.a))
 	}
-	return fmt.Sprintf("$(#%d)", l)
+	return fmt.Sprintf("$([#%d])", l)
 }
 
 func (it *ListIterator) TypeName() string {
@@ -90,26 +78,27 @@ func (it *ListIterator) TypeName() string {
 }
 
 func (it *ListIterator) HasOperation(name string) bool {
-	yes := name == NextName || name == ResetName || name == IndexName || name == CountName || name == CurrentName
+	//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 NextName:
+	case kern.NextName:
 		v, err = it.Next()
-	case ResetName:
+	case kern.ResetName:
 		err = it.Reset()
-	case CleanName:
+	case kern.CleanName:
 		err = it.Clean()
-	case IndexName:
+	case kern.IndexName:
 		v = int64(it.Index())
-	case CurrentName:
+	case kern.CurrentName:
 		v, err = it.Current()
-	case CountName:
+	case kern.CountName:
 		v = it.count
 	default:
-		err = errNoOperation(name)
+		err = kern.ErrNoOperation(name)
 	}
 	return
 }
@@ -117,13 +106,13 @@ func (it *ListIterator) CallOperation(name string, args map[string]any) (v any,
 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 {
+		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 < len(a) && it.index >= it.stop && it.index <= it.start {
+		if it.start < int64(len(a)) && it.index >= it.stop && it.index <= it.start {
 			item = a[it.index]
 		} else {
 			err = io.EOF
@@ -141,20 +130,20 @@ func (it *ListIterator) Next() (item any, err error) {
 	return
 }
 
-func (it *ListIterator) Index() int {
+func (it *ListIterator) Index() int64 {
 	return it.index
 }
 
-func (it *ListIterator) Count() int {
+func (it *ListIterator) Count() int64 {
 	return it.count
 }
 
-func (it *ListIterator) Reset() (error) {
+func (it *ListIterator) Reset() error {
 	it.index = it.start - it.step
 	it.count = 0
 	return nil
 }
 
-func (it *ListIterator) Clean() (error) {
+func (it *ListIterator) Clean() error {
 	return nil
 }

operand-dict.go

@@ -1,32 +1,43 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
 // All rights reserved.
 
 // operand-dict.go
 package expr
 
+import (
+	"git.portale-stac.it/go-pkg/expr/kern"
+	"git.portale-stac.it/go-pkg/expr/scan"
+)
 
 // -------- dict term
-func newDictTerm(args map[any]*term) *term {
+func newDictTerm(args map[any]*scan.Term) *scan.Term {
-	return &term{
+	return &scan.Term{
-		tk:       *NewValueToken(0, 0, SymDict, "{}", args),
+		Tk:       *scan.NewValueToken(0, 0, scan.SymDict, "{}", args),
-		parent:   nil,
+		Parent:   nil,
-		children: nil,
+		Children: nil,
-		position: posLeaf,
+		Position: scan.PosLeaf,
-		priority: priValue,
+		Priority: scan.PriValue,
-		evalFunc: evalDict,
+		EvalFunc: evalDict,
 	}
 }
 
 // -------- dict func
-func evalDict(ctx ExprContext, opTerm *term) (v any, err error) {
+func evalDict(ctx kern.ExprContext, opTerm *scan.Term) (v any, err error) {
-	dict, _ := opTerm.value().(map[any]*term)
+	dict, _ := opTerm.Value().(map[any]*scan.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
+		var keyValue any
+		if keyValue, err = (key.(*scan.Term)).Compute(ctx); err == nil {
+			if kern.IsInteger(keyValue) || kern.IsString(keyValue) {
+				items[keyValue] = param
+			} else {
+				err = key.(*scan.Term).Errorf("dict key can be integer or string, got %s", kern.TypeName(keyValue))
+			}
+		}
 	}
 	if err == nil {
 		v = &items

operand-expr.go

@@ -1,30 +1,35 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
 // All rights reserved.
 
 // operand-expr.go
 package expr
 
-import "fmt"
+import (
+	"fmt"
+
+	"git.portale-stac.it/go-pkg/expr/kern"
+	"git.portale-stac.it/go-pkg/expr/scan"
+)
 
 // -------- expr term
-func newExprTerm(root *term) *term {
+func newExprTerm(root *scan.Term) *scan.Term {
-	tk := NewValueToken(root.tk.row, root.tk.col, SymExpression, root.source(), root)
+	tk := scan.NewValueToken(root.Tk.Row(), root.Tk.Col(), scan.SymExpression, root.Source(), root)
-	return &term{
+	return &scan.Term{
-		tk:       *tk,
+		Tk:       *tk,
-		parent:   nil,
+		Parent:   nil,
-		children: nil,
+		Children: nil,
-		position: posLeaf,
+		Position: scan.PosLeaf,
-		priority: priValue,
+		Priority: scan.PriValue,
-		evalFunc: evalExpr,
+		EvalFunc: evalExpr,
 	}
 }
 
 // -------- eval expr
-func evalExpr(ctx ExprContext, opTerm *term) (v any, err error) {
+func evalExpr(ctx kern.ExprContext, opTerm *scan.Term) (v any, err error) {
-	if expr, ok := opTerm.value().(*term); ok {
+	if ast, ok := opTerm.Value().(*scan.Term); ok {
-		v, err = expr.compute(ctx)
+		v, err = ast.Compute(ctx)
 	} else {
-		err = fmt.Errorf("expression expected, got %T", opTerm.value())
+		err = fmt.Errorf("expression expected, got %T", opTerm.Value())
 	}
 	return
 }

operand-func.go

@@ -1,4 +1,4 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
 // All rights reserved.
 
 // operand-func.go
@@ -6,27 +6,34 @@ package expr
 
 import (
 	"errors"
+
+	"git.portale-stac.it/go-pkg/expr/kern"
+	"git.portale-stac.it/go-pkg/expr/scan"
 )
 
 // -------- function call term
-func newFuncCallTerm(tk *Token, args []*term) *term {
+func newFuncCallTerm(tk *scan.Token, args []*scan.Term) *scan.Term {
-	return &term{
+	var pos scan.TermPosition = scan.PosLeaf
-		tk:       *tk,
+	if len(args) > 0 {
-		parent:   nil,
+		pos = scan.PosMultifix
-		children: args,
+	}
-		position: posLeaf,
+	return &scan.Term{
-		priority: priValue,
+		Tk:       *tk,
-		evalFunc: evalFuncCall,
+		Parent:   nil,
+		Children: args,
+		Position: pos,
+		Priority: scan.PriValue,
+		EvalFunc: evalFuncCall,
 	}
 }
 
 // -------- eval func call
 // func _evalFuncCall(ctx ExprContext, opTerm *term) (v any, err error) {
-// 	name, _ := opTerm.tk.Value.(string)
+// 	name, _ := opTerm.Tk.Value.(string)
-// 	params := make([]any, len(opTerm.children), len(opTerm.children)+5)
+// 	params := make([]any, len(opTerm.Children), len(opTerm.Children)+5)
-// 	for i, tree := range opTerm.children {
+// 	for i, tree := range opTerm.Children {
 // 		var param any
-// 		if param, err = tree.compute(ctx); err != nil {
+// 		if param, err = tree.Compute(ctx); err != nil {
 // 			break
 // 		}
 // 		params[i] = param
@@ -38,42 +45,42 @@ func newFuncCallTerm(tk *Token, args []*term) *term {
 // 	return
 // }
 
-func evalFuncCall(ctx ExprContext, opTerm *term) (v any, err error) {
+func evalFuncCall(ctx kern.ExprContext, opTerm *scan.Term) (v any, err error) {
-	name, _ := opTerm.tk.Value.(string)
+	name, _ := opTerm.Tk.Value.(string)
-	v, err = CallFunctionByTerm(ctx, name, opTerm)
+	v, err = kern.CallFunctionByTerm(ctx, name, opTerm)
 	return
 }
 
 // -------- function definition term
-func newFuncDefTerm(tk *Token, args []*term) *term {
+func newFuncDefTerm(tk *scan.Token, args []*scan.Term) *scan.Term {
-	return &term{
+	return &scan.Term{
-		tk:       *tk, // value is the expression body
+		Tk:       *tk, // value is the expression body
-		parent:   nil,
+		Parent:   nil,
-		children: args, // function params
+		Children: args, // function params
-		position: posLeaf,
+		Position: scan.PosLeaf,
-		priority: priValue,
+		Priority: scan.PriValue,
-		evalFunc: evalFuncDef,
+		EvalFunc: evalFuncDef,
 	}
 }
 
 // -------- eval func def
-func evalFuncDef(ctx ExprContext, opTerm *term) (v any, err error) {
+func evalFuncDef(ctx kern.ExprContext, opTerm *scan.Term) (v any, err error) {
-	bodySpec := opTerm.value()
+	bodySpec := opTerm.Value()
-	if expr, ok := bodySpec.(*ast); ok {
+	if ast, ok := bodySpec.(*scan.Ast); ok {
-		paramList := make([]ExprFuncParam, 0, len(opTerm.children))
+		paramList := make([]kern.ExprFuncParam, 0, len(opTerm.Children))
-		for _, param := range opTerm.children {
+		for _, param := range opTerm.Children {
 			var defValue any
-			flags := paramFlags(0)
+			flags := kern.FuncParamFlags(0)
-			if len(param.children) > 0 {
+			if len(param.Children) > 0 {
-				flags |= PfDefault
+				flags |= kern.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 := kern.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

@@ -1,4 +1,4 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
 // All rights reserved.
 
 // operand-iterator.go
@@ -7,29 +7,32 @@ package expr
 import (
 	"slices"
 	"strings"
+
+	"git.portale-stac.it/go-pkg/expr/kern"
+	"git.portale-stac.it/go-pkg/expr/scan"
 )
 
 // -------- iterator term
 
-func newIteratorTerm(tk *Token, args []*term) *term {
+func newIteratorTerm(tk *scan.Token, args []*scan.Term) *scan.Term {
-	tk.Sym = SymIterator
+	tk.Sym = scan.SymIterator
-	return &term{
+	return &scan.Term{
-		tk:       *tk,
+		Tk:       *tk,
-		parent:   nil,
+		Parent:   nil,
-		children: args,
+		Children: args,
-		position: posLeaf,
+		Position: scan.PosLeaf,
-		priority: priValue,
+		Priority: scan.PriValue,
-		evalFunc: evalIterator,
+		EvalFunc: evalIterator,
 	}
 }
 
 // -------- eval iterator
 
-func evalTermArray(ctx ExprContext, terms []*term) (values []any, err error) {
+func evalTermArray(ctx kern.ExprContext, terms []*scan.Term) (values []any, err error) {
 	values = make([]any, len(terms))
 	for i, t := range terms {
 		var value any
-		if value, err = t.compute(ctx); err == nil {
+		if value, err = t.Compute(ctx); err == nil {
 			values[i] = value
 		} else {
 			break
@@ -38,25 +41,25 @@ func evalTermArray(ctx ExprContext, terms []*term) (values []any, err error) {
 	return
 }
 
-func evalFirstChild(ctx ExprContext, iteratorTerm *term) (value any, err error) {
+func evalFirstChild(ctx kern.ExprContext, iteratorTerm *scan.Term) (value any, err error) {
-	if len(iteratorTerm.children) < 1 || iteratorTerm.children[0] == nil {
+	if len(iteratorTerm.Children) < 1 || iteratorTerm.Children[0] == nil {
 		err = iteratorTerm.Errorf("missing the data-source parameter")
 		return
 	}
 
-	value, err = iteratorTerm.children[0].compute(ctx)
+	value, err = iteratorTerm.Children[0].Compute(ctx)
 	return
 }
 
-func getDataSourceDict(iteratorTerm *term, firstChildValue any) (ds map[string]Functor, err error) {
+func getDataSourceDict(iteratorTerm *scan.Term, firstChildValue any) (ds map[string]kern.Functor, err error) {
-	if dictAny, ok := firstChildValue.(*DictType); ok {
+	if dictAny, ok := firstChildValue.(*kern.DictType); ok {
-		requiredFields := []string{NextName}
+		requiredFields := []string{kern.NextName}
 		fieldsMask := 0b1
 		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.(Functor); ok {
+				if functor, ok := item.(kern.Functor); ok {
 					ds[key] = functor
 					if index := slices.Index(requiredFields, key); index >= 0 {
 						foundFields |= 1 << index
@@ -72,66 +75,119 @@ func getDataSourceDict(iteratorTerm *term, firstChildValue any) (ds map[string]F
 					missingFields = append(missingFields, field)
 				}
 			}
-			err = iteratorTerm.children[0].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, opTerm *term) (v any, err error) {
+func evalIterator(ctx kern.ExprContext, opTerm *scan.Term) (v any, err error) {
 	var firstChildValue any
-	var ds map[string]Functor
+	var ds map[string]kern.Functor
 
 	if firstChildValue, err = evalFirstChild(ctx, opTerm); err != nil {
 		return
 	}
 
-	if ds, err = getDataSourceDict(opTerm, firstChildValue); err != nil {
+	if ds, err = getDataSourceDict(opTerm, firstChildValue); err != nil && ds == nil {
 		return
 	}
+	err = nil
 
 	if ds != nil {
+		if len(ds) > 0 {
 			var dc *dataCursor
 			dcCtx := ctx.Clone()
-		if initFunc, exists := ds[InitName]; exists && initFunc != nil {
+			if initFunc, exists := ds[kern.InitName]; exists && initFunc != nil {
 				var args []any
 				var resource any
-			if len(opTerm.children) > 1 {
+				if len(opTerm.Children) > 1 {
-				if args, err = evalTermArray(ctx, opTerm.children[1:]); err != nil {
+					if args, err = evalTermArray(ctx, opTerm.Children[1:]); err != nil {
 						return
 					}
 				} else {
 					args = []any{}
 				}
 
-			actualParams := bindActualParams(initFunc, args)
+				actualParams := kern.BindActualParams(initFunc, args)
 
 				initCtx := ctx.Clone()
-			if resource, err = initFunc.InvokeNamed(initCtx, InitName, actualParams); err != nil {
+				if resource, err = initFunc.InvokeNamed(initCtx, kern.InitName, actualParams); err != nil {
 					return
 				}
-			exportObjects(dcCtx, initCtx)
+				kern.ExportObjects(dcCtx, initCtx)
 				dc = NewDataCursor(dcCtx, ds, resource)
 			} else {
 				dc = NewDataCursor(dcCtx, ds, nil)
 			}
 
 			v = dc
-	} else if list, ok := firstChildValue.(*ListType); ok {
+		} else {
+			if dictIt, ok := firstChildValue.(*kern.DictType); ok {
 				var args []any
-		if args, err = evalSibling(ctx, opTerm.children, nil); err == nil {
+				if args, err = evalSiblings(ctx, opTerm.Children, nil); err == nil {
-			v = NewListIterator(list, args)
+					v, err = NewDictIterator(dictIt, args)
 				}
 			} else {
-		var list []any
+				err = opTerm.Children[0].Errorf("the data-source must be a dictionary")
-		if list, err = evalSibling(ctx, opTerm.children, firstChildValue); err == nil {
+			}
-			v = NewArrayIterator(list)
+		}
+	} else if list, ok := firstChildValue.(*kern.ListType); ok {
+		var args []any
+		if args, err = evalSiblings(ctx, opTerm.Children, nil); err == nil {
+			v = NewListIterator(list, args)
+		}
+	} else if list, ok := firstChildValue.(*kern.LinkedList); ok {
+		var args []any
+		if args, err = evalSiblings(ctx, opTerm.Children, nil); err == nil {
+			v = NewLinkedListIterator(list, args)
+		}
+	} else if intVal, ok := firstChildValue.(int64); ok {
+		var args []any
+		if args, err = evalSiblings(ctx, opTerm.Children, intVal); err == nil {
+			v, err = NewIntIterator(args)
+		}
+	} else if it, ok := firstChildValue.(kern.Iterator); ok {
+		v, err = NewIterIter(it, ctx, opTerm.Children[1:])
+	} else {
+		var siblings []any
+		if siblings, err = evalSiblings(ctx, opTerm.Children, firstChildValue); err == nil {
+			v = NewArrayIterator(siblings)
 		}
 	}
 	return
 }
 
-func evalSibling(ctx ExprContext, terms []*term, firstChildValue any) (list []any, err error) {
+// func evalIterIter(ctx kern.ExprContext, firstChildValue any, siblings []any) (v any, err error) {
+// 	var op kern.Functor
+// 	var args map[string]any
+
+// 	if it, ok := firstChildValue.(kern.Iterator); ok {
+// 		if len(siblings) > 1 {
+// 			if op, ok = siblings[1].(kern.Functor); ok {
+// 				args = make(map[string]any, len(siblings)-2)
+// 				for i, arg := range siblings[2:] {
+// 					switch a := arg.(type) {
+// 					case *kern.DictType:
+// 						for keyAny, item := range *a {
+// 							if key, ok := keyAny.(string); ok {
+// 								args[key] = item
+// 							}
+// 						}
+// 					default:
+// 						args["arg"+strconv.Itoa(i+1)] = arg
+// 					}
+// 				}
+// 			} else if op == nil {
+// 				return nil, fmt.Errorf("the first sibling parameter must be a functor to be used as operation for the iterator")
+// 			}
+// 		}
+// 		v, err = NewIterIter(it, ctx, op, args)
+// 	}
+// 	return
+// }
+
+func evalSiblings(ctx kern.ExprContext, terms []*scan.Term, firstChildValue any) (list []any, err error) {
 	items := make([]any, 0, len(terms))
 	for i, tree := range terms {
 		var param any
@@ -140,7 +196,7 @@ 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-linked-list.go

@@ -0,0 +1,43 @@
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// operand-list.go
+package expr
+
+import (
+	"git.portale-stac.it/go-pkg/expr/kern"
+	"git.portale-stac.it/go-pkg/expr/scan"
+)
+
+// -------- list term
+// func newLinkedListTermA(args ...*scan.Term) *scan.Term {
+// 	return newLinkedListTerm(0, 0, args)
+// }
+
+func newLinkedListTerm(row, col int, args []*scan.Term) *scan.Term {
+	return &scan.Term{
+		Tk:       *scan.NewValueToken(row, col, scan.SymLinkedList, "[<>]", args),
+		Parent:   nil,
+		Children: nil,
+		Position: scan.PosLeaf,
+		Priority: scan.PriValue,
+		EvalFunc: evalLinkedList,
+	}
+}
+
+// -------- list func
+func evalLinkedList(ctx kern.ExprContext, opTerm *scan.Term) (v any, err error) {
+	list, _ := opTerm.Value().([]*scan.Term)
+	items := kern.NewLinkedList()
+	for _, tree := range list {
+		var param any
+		if param, err = tree.Compute(ctx); err != nil {
+			break
+		}
+		items.PushBack(param)
+	}
+	if err == nil {
+		v = items
+	}
+	return
+}

operand-list.go

@@ -1,32 +1,37 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
 // All rights reserved.
 
 // operand-list.go
 package expr
 
+import (
+	"git.portale-stac.it/go-pkg/expr/kern"
+	"git.portale-stac.it/go-pkg/expr/scan"
+)
+
 // -------- list term
-func newListTermA(args ...*term) *term {
+func newListTermA(args ...*scan.Term) *scan.Term {
 	return newListTerm(0, 0, args)
 }
 
-func newListTerm(row, col int, args []*term) *term {
+func newListTerm(row, col int, args []*scan.Term) *scan.Term {
-	return &term{
+	return &scan.Term{
-		tk:       *NewValueToken(row, col, SymList, "[]", args),
+		Tk:       *scan.NewValueToken(row, col, scan.SymList, "[]", args),
-		parent:   nil,
+		Parent:   nil,
-		children: nil,
+		Children: nil,
-		position: posLeaf,
+		Position: scan.PosLeaf,
-		priority: priValue,
+		Priority: scan.PriValue,
-		evalFunc: evalList,
+		EvalFunc: evalList,
 	}
 }
 
 // -------- list func
-func evalList(ctx ExprContext, opTerm *term) (v any, err error) {
+func evalList(ctx kern.ExprContext, opTerm *scan.Term) (v any, err error) {
-	list, _ := opTerm.value().([]*term)
+	list, _ := opTerm.Value().([]*scan.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

@@ -1,33 +1,38 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
 // All rights reserved.
 
 // operand-literal.go
 package expr
 
+import (
+	"git.portale-stac.it/go-pkg/expr/kern"
+	"git.portale-stac.it/go-pkg/expr/scan"
+)
+
 // -------- literal term
-func newLiteralTerm(tk *Token) *term {
+func newLiteralTerm(tk *scan.Token) *scan.Term {
-	return &term{
+	return &scan.Term{
-		tk:       *tk,
+		Tk:       *tk,
-		parent:   nil,
+		Parent:   nil,
-		children: nil,
+		Children: nil,
-		position: posLeaf,
+		Position: scan.PosLeaf,
-		priority: priValue,
+		Priority: scan.PriValue,
-		evalFunc: evalLiteral,
+		EvalFunc: evalLiteral,
 	}
 }
 
 // -------- eval func
-func evalLiteral(ctx ExprContext, opTerm *term) (v any, err error) {
+func evalLiteral(ctx kern.ExprContext, opTerm *scan.Term) (v any, err error) {
-	v = opTerm.tk.Value
+	v = opTerm.Tk.Value
 	return
 }
 
 // init
 func init() {
-	registerTermConstructor(SymString, newLiteralTerm)
+	scan.RegisterTermConstructor(scan.SymString, newLiteralTerm)
-	registerTermConstructor(SymInteger, newLiteralTerm)
+	scan.RegisterTermConstructor(scan.SymInteger, newLiteralTerm)
-	registerTermConstructor(SymFloat, newLiteralTerm)
+	scan.RegisterTermConstructor(scan.SymFloat, newLiteralTerm)
-	registerTermConstructor(SymFraction, newLiteralTerm)
+	scan.RegisterTermConstructor(scan.SymFraction, newLiteralTerm)
-	registerTermConstructor(SymBool, newLiteralTerm)
+	scan.RegisterTermConstructor(scan.SymBool, newLiteralTerm)
-	registerTermConstructor(SymKwNil, newLiteralTerm)
+	scan.RegisterTermConstructor(scan.SymKwNil, newLiteralTerm)
 }

operand-selector-case.go

@@ -1,4 +1,4 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
 // All rights reserved.
 
 // operand-selector-case.go
@@ -7,19 +7,22 @@ package expr
 import (
 	"fmt"
 	"strings"
+
+	"git.portale-stac.it/go-pkg/expr/kern"
+	"git.portale-stac.it/go-pkg/expr/scan"
 )
 
 // -------- selector case term
 
 type selectorCase struct {
-	filterList *term
+	filterList *scan.Term
-	caseExpr   Expr
+	caseExpr   kern.Expr
 }
 
 func (sc *selectorCase) String() string {
 	var sb strings.Builder
 	if sc.filterList != nil {
-		sc.filterList.toString(&sb)
+		sc.filterList.ToString(&sb)
 		sb.WriteByte(' ')
 	}
 	sb.WriteByte('{')
@@ -28,23 +31,23 @@ func (sc *selectorCase) String() string {
 	return sb.String()
 }
 
-func newSelectorCaseTerm(row, col int, filterList *term, caseExpr Expr) *term {
+func newSelectorCaseTerm(row, col int, filterList *scan.Term, caseExpr kern.Expr) *scan.Term {
-	tk := NewValueToken(row, col, SymSelectorCase, "", &selectorCase{filterList: filterList, caseExpr: caseExpr})
+	tk := scan.NewValueToken(row, col, scan.SymSelectorCase, "", &selectorCase{filterList: filterList, caseExpr: caseExpr})
-	return &term{
+	return &scan.Term{
-		tk:       *tk,
+		Tk:       *tk,
-		parent:   nil,
+		Parent:   nil,
-		children: nil,
+		Children: nil,
-		position: posLeaf,
+		Position: scan.PosLeaf,
-		priority: priValue,
+		Priority: scan.PriValue,
-		evalFunc: evalSelectorCase,
+		EvalFunc: evalSelectorCase,
 	}
 }
 
 // -------- eval selector case
-func evalSelectorCase(ctx ExprContext, opTerm *term) (v any, err error) {
+func evalSelectorCase(ctx kern.ExprContext, opTerm *scan.Term) (v any, err error) {
 	var ok bool
-	if v, ok = opTerm.value().(*selectorCase); !ok {
+	if v, ok = opTerm.Value().(*selectorCase); !ok {
-		err = fmt.Errorf("selector-case expected, got %T", opTerm.value())
+		err = fmt.Errorf("selector-case expected, got %T", opTerm.Value())
 	}
 	return
 }

operand-var.go

@@ -1,31 +1,36 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
 // All rights reserved.
 
 // operand-var.go
 package expr
 
-import "fmt"
+import (
+	"fmt"
+
+	"git.portale-stac.it/go-pkg/expr/kern"
+	"git.portale-stac.it/go-pkg/expr/scan"
+)
 
 // -------- variable term
-func newVarTerm(tk *Token) *term {
+func newVarTerm(tk *scan.Token) *scan.Term {
-	t := &term{
+	t := &scan.Term{
-		tk:       *tk,
+		Tk:       *tk,
-		parent:   nil,
+		Parent:   nil,
-		children: nil,
+		Children: nil,
-		position: posLeaf,
+		Position: scan.PosLeaf,
-		priority: priValue,
+		Priority: scan.PriValue,
-		evalFunc: evalVar,
+		EvalFunc: evalVar,
 	}
-	t.tk.Sym = SymVariable
+	t.Tk.Sym = scan.SymVariable
 	return t
 }
 
 // -------- eval func
-func evalVar(ctx ExprContext, opTerm *term) (v any, err error) {
+func evalVar(ctx kern.ExprContext, opTerm *scan.Term) (v any, err error) {
 	var exists bool
-	name := opTerm.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)
@@ -36,5 +41,5 @@ func evalVar(ctx ExprContext, opTerm *term) (v any, err error) {
 
 // init
 func init() {
-	registerTermConstructor(SymIdentifier, newVarTerm)
+	scan.RegisterTermConstructor(scan.SymIdentifier, newVarTerm)
 }

operator-assign.go

@@ -1,34 +1,60 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
 // All rights reserightChilded.
 
 // operator-assign.go
 package expr
 
+import (
+	"git.portale-stac.it/go-pkg/expr/kern"
+	"git.portale-stac.it/go-pkg/expr/scan"
+	"git.portale-stac.it/go-pkg/expr/util"
+)
+
 //-------- assign term
 
-func newAssignTerm(tk *Token) (inst *term) {
+func newAssignTerm(tk *scan.Token) (inst *scan.Term) {
-	return &term{
+	return &scan.Term{
-		tk:       *tk,
+		Tk:       *tk,
-		children: make([]*term, 0, 2),
+		Children: make([]*scan.Term, 0, 2),
-		position: posInfix,
+		Position: scan.PosInfix,
-		priority: priAssign,
+		Priority: scan.PriAssign,
-		evalFunc: evalAssign,
+		EvalFunc: evalAssign,
 	}
 }
 
-func assignCollectionItem(ctx ExprContext, collectionTerm, keyListTerm *term, value any) (err error) {
+func evalAssign(ctx kern.ExprContext, opTerm *scan.Term) (v any, err error) {
+	v, err = generalEvalAssign(ctx, opTerm, false)
+	return
+}
+
+func newDeepCopyAssignTerm(tk *scan.Token) (inst *scan.Term) {
+	return &scan.Term{
+		Tk:       *tk,
+		Children: make([]*scan.Term, 0, 2),
+		Position: scan.PosInfix,
+		Priority: scan.PriAssign,
+		EvalFunc: evalDeepCopyAssign,
+	}
+}
+
+func evalDeepCopyAssign(ctx kern.ExprContext, opTerm *scan.Term) (v any, err error) {
+	v, err = generalEvalAssign(ctx, opTerm, true)
+	return
+}
+
+func assignCollectionItem(ctx kern.ExprContext, collectionTerm, keyListTerm *scan.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 {
@@ -37,60 +63,99 @@ 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 *scan.Term, v any, deepCopy bool) (err error) {
-	if leftTerm.symbol() == SymIndex {
+	if leftTerm.Symbol() == scan.SymIndex {
-		err = assignCollectionItem(ctx, leftTerm.children[0], leftTerm.children[1], v)
+		err = assignCollectionItem(ctx, leftTerm.Children[0], leftTerm.Children[1], v)
 	} else {
-		ctx.UnsafeSetVar(leftTerm.source(), v)
+		if deepCopy {
+			v = kern.Clone(v)
+		}
+		ctx.UnsafeSetVar(leftTerm.Source(), v)
 	}
 	return
 }
 
-func evalAssign(ctx ExprContext, opTerm *term) (v any, err error) {
+func evalAssignDictItem(ctx kern.ExprContext, dotTerm *scan.Term, valueTerm kern.Term) (v any, err error) {
-	if err = opTerm.checkOperands(); err != nil {
+	var ok bool
+	var dictAny, dotKey any
+	var dict *kern.DictType
+
+	if err = dotTerm.CheckOperands(); err != nil {
 		return
 	}
 
-	leftTerm := opTerm.children[0]
+	dotLeftTerm := dotTerm.GetChild(0)
-	leftSym := leftTerm.symbol()
+	if dictAny, err = dotLeftTerm.Compute(ctx); err != nil {
-	if leftSym != SymVariable && leftSym != SymIndex {
+		return
-		err = leftTerm.tk.Errorf("left operand of %q must be a variable or a collection's item", opTerm.tk.source)
+	}
+	if dict, ok = dictAny.(*kern.DictType); !ok {
+		err = dotTerm.Tk.ErrorExpectedGot(kern.DictTypeName)
 		return
 	}
 
-	rightChild := opTerm.children[1]
+	dotRightTerm := dotTerm.Children[1]
+	dotRightSym := dotRightTerm.Symbol()
+	if dotRightSym == scan.SymVariable || dotRightSym == scan.SymString {
+		dotKey = util.UnquoteString(dotRightTerm.Source())
+	} else if dotKey, err = dotRightTerm.Compute(ctx); err != nil {
+		return
+	}
 
-	if v, err = rightChild.compute(ctx); err == nil {
+	if v, err = valueTerm.Compute(ctx); err != nil {
-		if functor, ok := v.(Functor); ok {
+		return
-			if leftSym == SymVariable {
+	}
+
+	dict.SetItem(dotKey, v)
+	return
+}
+
+func generalEvalAssign(ctx kern.ExprContext, opTerm *scan.Term, deepCopy bool) (v any, err error) {
+	if err = opTerm.CheckOperands(); err != nil {
+		return
+	}
+
+	leftTerm := opTerm.Children[0]
+	leftSym := leftTerm.Symbol()
+	if leftSym == scan.SymDot {
+		return evalAssignDictItem(ctx, opTerm.Children[0], opTerm.GetChild(1))
+	} else if leftSym != scan.SymVariable && leftSym != scan.SymIndex {
+		err = leftTerm.Tk.Errorf("left operand of %q must be a variable or a collection's item", opTerm.Tk.Source())
+		return
+	}
+
+	rightChild := opTerm.Children[1]
+
+	if v, err = rightChild.Compute(ctx); err == nil {
+		if functor, ok := v.(kern.Functor); ok {
+			if leftSym == scan.SymVariable {
 				if info := functor.GetFunc(); info != nil {
-					ctx.RegisterFunc(leftTerm.source(), info.Functor(), info.ReturnType(), info.Params())
+					ctx.RegisterFunc(leftTerm.Source(), info.Functor(), info.ReturnType(), info.Params())
 				} else if funcDef, ok := functor.(*exprFunctor); ok {
-					paramSpecs := ForAll(funcDef.params, func(p ExprFuncParam) ExprFuncParam { return p })
+					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())
+					err = opTerm.Errorf("unknown function %s()", rightChild.Source())
 				}
 			} else {
-				err = assignValue(ctx, leftTerm, v)
+				err = assignValue(ctx, leftTerm, v, deepCopy)
 			}
 		} else {
-			err = assignValue(ctx, leftTerm, v)
+			err = assignValue(ctx, leftTerm, v, deepCopy)
 		}
 	}
 	if err != nil {
@@ -101,29 +166,29 @@ func evalAssign(ctx ExprContext, opTerm *term) (v any, err error) {
 
 //-------- assign term
 
-func newOpAssignTerm(tk *Token) (inst *term) {
+func newOpAssignTerm(tk *scan.Token) (inst *scan.Term) {
-	return &term{
+	return &scan.Term{
-		tk:       *tk,
+		Tk:       *tk,
-		children: make([]*term, 0, 2),
+		Children: make([]*scan.Term, 0, 2),
-		position: posInfix,
+		Position: scan.PosInfix,
-		priority: priAssign,
+		Priority: scan.PriAssign,
-		evalFunc: evalOpAssign,
+		EvalFunc: evalOpAssign,
 	}
 }
 
-func getCollectionItemValue(ctx ExprContext, collectionTerm, keyListTerm *term) (value any, err error) {
+func getCollectionItemValue(ctx kern.ExprContext, collectionTerm, keyListTerm *scan.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 {
@@ -132,13 +197,13 @@ func getCollectionItemValue(ctx ExprContext, collectionTerm, keyListTerm *term)
 	}
 
 	switch collection := collectionValue.(type) {
-	case *ListType:
+	case *kern.ListType:
 		if index, ok := keyValue.(int64); ok {
 			value = (*collection)[index]
 		} 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:
 		value = (*collection)[keyValue]
 	default:
 		err = collectionTerm.Errorf("collection expected")
@@ -146,58 +211,58 @@ func getCollectionItemValue(ctx ExprContext, collectionTerm, keyListTerm *term)
 	return
 }
 
-func getAssignValue(ctx ExprContext, leftTerm *term) (value any, err error) {
+func getAssignValue(ctx kern.ExprContext, leftTerm *scan.Term) (value any, err error) {
-	if leftTerm.symbol() == SymIndex {
+	if leftTerm.Symbol() == scan.SymIndex {
-		value, err = getCollectionItemValue(ctx, leftTerm.children[0], leftTerm.children[1])
+		value, err = getCollectionItemValue(ctx, leftTerm.Children[0], leftTerm.Children[1])
 	} else {
-		value, _ = ctx.GetVar(leftTerm.source())
+		value, _ = ctx.GetVar(leftTerm.Source())
 	}
 	return
 }
 
-func evalOpAssign(ctx ExprContext, opTerm *term) (v any, err error) {
+func evalOpAssign(ctx kern.ExprContext, opTerm *scan.Term) (v any, err error) {
 	var rightValue, leftValue any
-	if err = opTerm.checkOperands(); err != nil {
+	if err = opTerm.CheckOperands(); err != nil {
 		return
 	}
 
-	leftTerm := opTerm.children[0]
+	leftTerm := opTerm.Children[0]
-	leftSym := leftTerm.symbol()
+	leftSym := leftTerm.Symbol()
-	if leftSym != SymVariable && leftSym != SymIndex {
+	if leftSym != scan.SymVariable && leftSym != scan.SymIndex {
-		err = leftTerm.tk.Errorf("left operand of %q must be a variable or a collection's item", opTerm.tk.source)
+		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]
+	rightChild := opTerm.Children[1]
 
-	if rightValue, err = rightChild.compute(ctx); err == nil {
+	if rightValue, err = rightChild.Compute(ctx); err == nil {
 		if leftValue, err = getAssignValue(ctx, leftTerm); err == nil {
-			switch opTerm.symbol() {
+			switch opTerm.Symbol() {
-			case SymPlusEqual:
+			case scan.SymPlusEqual:
 				v, err = sumValues(opTerm, leftValue, rightValue)
-			case SymMinusEqual:
+			case scan.SymMinusEqual:
 				v, err = diffValues(opTerm, leftValue, rightValue)
-			case SymStarEqual:
+			case scan.SymStarEqual:
 				v, err = mulValues(opTerm, leftValue, rightValue)
-			case SymSlashEqual:
+			case scan.SymSlashEqual:
 				v, err = divValues(opTerm, leftValue, rightValue)
-			case SymPercEqual:
+			case scan.SymPercEqual:
 				v, err = remainderValues(opTerm, leftValue, rightValue)
-			case SymAmpersandEqual:
+			case scan.SymAmpersandEqual:
 				v, err = bitwiseAnd(opTerm, leftValue, rightValue)
-			case SymVertBarEqual:
+			case scan.SymVertBarEqual:
 				v, err = bitwiseOr(opTerm, leftValue, rightValue)
-			case SymCaretEqual:
+			case scan.SymCaretEqual:
 				v, err = bitwiseXor(opTerm, leftValue, rightValue)
-			case SymDoubleLessEqual:
+			case scan.SymDoubleLessEqual:
 				v, err = bitLeftShift(opTerm, leftValue, rightValue)
-			case SymDoubleGreaterEqual:
+			case scan.SymDoubleGreaterEqual:
 				v, err = bitRightShift(opTerm, leftValue, rightValue)
 			default:
-				err = opTerm.Errorf("unsupported assign operator %q", opTerm.source())
+				err = opTerm.Errorf("unsupported assign operator %q", opTerm.Source())
 			}
 			if err == nil {
-				err = assignValue(ctx, leftTerm, v)
+				err = assignValue(ctx, leftTerm, v, false)
 			}
 		}
 	}
@@ -206,15 +271,16 @@ func evalOpAssign(ctx ExprContext, opTerm *term) (v any, err error) {
 
 // init
 func init() {
-	registerTermConstructor(SymEqual, newAssignTerm)
+	scan.RegisterTermConstructor(scan.SymEqual, newAssignTerm)
-	registerTermConstructor(SymPlusEqual, newOpAssignTerm)
+	scan.RegisterTermConstructor(scan.SymColonEqual, newDeepCopyAssignTerm)
-	registerTermConstructor(SymMinusEqual, newOpAssignTerm)
+	scan.RegisterTermConstructor(scan.SymPlusEqual, newOpAssignTerm)
-	registerTermConstructor(SymStarEqual, newOpAssignTerm)
+	scan.RegisterTermConstructor(scan.SymMinusEqual, newOpAssignTerm)
-	registerTermConstructor(SymSlashEqual, newOpAssignTerm)
+	scan.RegisterTermConstructor(scan.SymStarEqual, newOpAssignTerm)
-	registerTermConstructor(SymPercEqual, newOpAssignTerm)
+	scan.RegisterTermConstructor(scan.SymSlashEqual, newOpAssignTerm)
-	registerTermConstructor(SymDoubleLessEqual, newOpAssignTerm)
+	scan.RegisterTermConstructor(scan.SymPercEqual, newOpAssignTerm)
-	registerTermConstructor(SymDoubleGreaterEqual, newOpAssignTerm)
+	scan.RegisterTermConstructor(scan.SymDoubleLessEqual, newOpAssignTerm)
-	registerTermConstructor(SymAmpersandEqual, newOpAssignTerm)
+	scan.RegisterTermConstructor(scan.SymDoubleGreaterEqual, newOpAssignTerm)
-	registerTermConstructor(SymVertBarEqual, newOpAssignTerm)
+	scan.RegisterTermConstructor(scan.SymAmpersandEqual, newOpAssignTerm)
-	registerTermConstructor(SymCaretEqual, newOpAssignTerm)
+	scan.RegisterTermConstructor(scan.SymVertBarEqual, newOpAssignTerm)
+	scan.RegisterTermConstructor(scan.SymCaretEqual, newOpAssignTerm)
 }

operator-bitwise.go

@@ -1,50 +1,55 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
 // All rights reserved.
 
 // operator-bitwise.go
 package expr
 
+import (
+	"git.portale-stac.it/go-pkg/expr/kern"
+	"git.portale-stac.it/go-pkg/expr/scan"
+)
+
 //-------- Bitwise NOT term
 
-func newBitwiseNotTerm(tk *Token) (inst *term) {
+func newBitwiseNotTerm(tk *scan.Token) (inst *scan.Term) {
-	return &term{
+	return &scan.Term{
-		tk:       *tk,
+		Tk:       *tk,
-		children: make([]*term, 0, 1),
+		Children: make([]*scan.Term, 0, 1),
-		position: posPrefix,
+		Position: scan.PosPrefix,
-		priority: priBitwiseNot,
+		Priority: scan.PriBitwiseNot,
-		evalFunc: evalBitwiseNot,
+		EvalFunc: evalBitwiseNot,
 	}
 }
 
-func evalBitwiseNot(ctx ExprContext, opTerm *term) (v any, err error) {
+func evalBitwiseNot(ctx kern.ExprContext, opTerm *scan.Term) (v any, err error) {
 	var value any
 
-	if value, err = opTerm.evalPrefix(ctx); err != nil {
+	if value, err = opTerm.EvalPrefix(ctx); err != nil {
 		return
 	}
 
-	if IsInteger(value) {
+	if kern.IsInteger(value) {
 		i, _ := value.(int64)
 		v = ^i
 	} else {
-		err = opTerm.errIncompatibleType(value)
+		err = opTerm.ErrIncompatiblePrefixPostfixType(value)
 	}
 	return
 }
 
 //-------- Bitwise AND term
 
-func newBitwiseAndTerm(tk *Token) (inst *term) {
+func newBitwiseAndTerm(tk *scan.Token) (inst *scan.Term) {
-	return &term{
+	return &scan.Term{
-		tk:       *tk,
+		Tk:       *tk,
-		children: make([]*term, 0, 2),
+		Children: make([]*scan.Term, 0, 2),
-		position: posInfix,
+		Position: scan.PosInfix,
-		priority: priBitwiseAnd,
+		Priority: scan.PriBitwiseAnd,
-		evalFunc: evalBitwiseAnd,
+		EvalFunc: evalBitwiseAnd,
 	}
 }
 
-func bitwiseAnd(opTerm *term, leftValue, rightValue any) (v any, err error) {
+func bitwiseAnd(opTerm *scan.Term, leftValue, rightValue any) (v any, err error) {
 	var leftInt, rightInt int64
 	var lok, rok bool
 
@@ -54,15 +59,15 @@ func bitwiseAnd(opTerm *term, leftValue, rightValue any) (v any, err error) {
 	if lok && rok {
 		v = leftInt & rightInt
 	} else {
-		err = opTerm.errIncompatibleTypes(leftValue, rightValue)
+		err = opTerm.ErrIncompatibleTypes(leftValue, rightValue)
 	}
 	return
 }
 
-func evalBitwiseAnd(ctx ExprContext, opTerm *term) (v any, err error) {
+func evalBitwiseAnd(ctx kern.ExprContext, opTerm *scan.Term) (v any, err error) {
 	var leftValue, rightValue any
 
-	if leftValue, rightValue, err = opTerm.evalInfix(ctx); err != nil {
+	if leftValue, rightValue, err = opTerm.EvalInfix(ctx); err != nil {
 		return
 	}
 	v, err = bitwiseAnd(opTerm, leftValue, rightValue)
@@ -71,17 +76,17 @@ func evalBitwiseAnd(ctx ExprContext, opTerm *term) (v any, err error) {
 
 //-------- Bitwise OR term
 
-func newBitwiseOrTerm(tk *Token) (inst *term) {
+func newBitwiseOrTerm(tk *scan.Token) (inst *scan.Term) {
-	return &term{
+	return &scan.Term{
-		tk:       *tk,
+		Tk:       *tk,
-		children: make([]*term, 0, 2),
+		Children: make([]*scan.Term, 0, 2),
-		position: posInfix,
+		Position: scan.PosInfix,
-		priority: priBitwiseOr,
+		Priority: scan.PriBitwiseOr,
-		evalFunc: evalBitwiseOr,
+		EvalFunc: evalBitwiseOr,
 	}
 }
 
-func bitwiseOr(opTerm *term, leftValue, rightValue any) (v any, err error) {
+func bitwiseOr(opTerm *scan.Term, leftValue, rightValue any) (v any, err error) {
 	var leftInt, rightInt int64
 	var lok, rok bool
 
@@ -91,15 +96,15 @@ func bitwiseOr(opTerm *term, leftValue, rightValue any) (v any, err error) {
 	if lok && rok {
 		v = leftInt | rightInt
 	} else {
-		err = opTerm.errIncompatibleTypes(leftValue, rightValue)
+		err = opTerm.ErrIncompatibleTypes(leftValue, rightValue)
 	}
 	return
 }
 
-func evalBitwiseOr(ctx ExprContext, opTerm *term) (v any, err error) {
+func evalBitwiseOr(ctx kern.ExprContext, opTerm *scan.Term) (v any, err error) {
 	var leftValue, rightValue any
 
-	if leftValue, rightValue, err = opTerm.evalInfix(ctx); err != nil {
+	if leftValue, rightValue, err = opTerm.EvalInfix(ctx); err != nil {
 		return
 	}
 
@@ -109,17 +114,17 @@ func evalBitwiseOr(ctx ExprContext, opTerm *term) (v any, err error) {
 
 //-------- Bitwise XOR term
 
-func newBitwiseXorTerm(tk *Token) (inst *term) {
+func newBitwiseXorTerm(tk *scan.Token) (inst *scan.Term) {
-	return &term{
+	return &scan.Term{
-		tk:       *tk,
+		Tk:       *tk,
-		children: make([]*term, 0, 2),
+		Children: make([]*scan.Term, 0, 2),
-		position: posInfix,
+		Position: scan.PosInfix,
-		priority: priBitwiseOr,
+		Priority: scan.PriBitwiseXor,
-		evalFunc: evalBitwiseXor,
+		EvalFunc: evalBitwiseXor,
 	}
 }
 
-func bitwiseXor(opTerm *term, leftValue, rightValue any) (v any, err error) {
+func bitwiseXor(opTerm *scan.Term, leftValue, rightValue any) (v any, err error) {
 	var leftInt, rightInt int64
 	var lok, rok bool
 
@@ -129,15 +134,15 @@ func bitwiseXor(opTerm *term, leftValue, rightValue any) (v any, err error) {
 	if lok && rok {
 		v = leftInt ^ rightInt
 	} else {
-		err = opTerm.errIncompatibleTypes(leftValue, rightValue)
+		err = opTerm.ErrIncompatibleTypes(leftValue, rightValue)
 	}
 	return
 }
 
-func evalBitwiseXor(ctx ExprContext, opTerm *term) (v any, err error) {
+func evalBitwiseXor(ctx kern.ExprContext, opTerm *scan.Term) (v any, err error) {
 	var leftValue, rightValue any
 
-	if leftValue, rightValue, err = opTerm.evalInfix(ctx); err != nil {
+	if leftValue, rightValue, err = opTerm.EvalInfix(ctx); err != nil {
 		return
 	}
 
@@ -147,8 +152,8 @@ func evalBitwiseXor(ctx ExprContext, opTerm *term) (v any, err error) {
 
 // init
 func init() {
-	registerTermConstructor(SymTilde, newBitwiseNotTerm)
+	scan.RegisterTermConstructor(scan.SymTilde, newBitwiseNotTerm)
-	registerTermConstructor(SymAmpersand, newBitwiseAndTerm)
+	scan.RegisterTermConstructor(scan.SymAmpersand, newBitwiseAndTerm)
-	registerTermConstructor(SymVertBar, newBitwiseOrTerm)
+	scan.RegisterTermConstructor(scan.SymVertBar, newBitwiseOrTerm)
-	registerTermConstructor(SymCaret, newBitwiseXorTerm)
+	scan.RegisterTermConstructor(scan.SymCaret, newBitwiseXorTerm)
 }

operator-bool.go

@@ -1,52 +1,57 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
 // All rights reserved.
 
 // operator-bool.go
 package expr
 
-import "fmt"
+import (
+	"fmt"
+
+	"git.portale-stac.it/go-pkg/expr/kern"
+	"git.portale-stac.it/go-pkg/expr/scan"
+)
 
 //-------- NOT term
 
-func newNotTerm(tk *Token) (inst *term) {
+func newNotTerm(tk *scan.Token) (inst *scan.Term) {
-	return &term{
+	return &scan.Term{
-		tk:       *tk,
+		Tk:       *tk,
-		children: make([]*term, 0, 1),
+		Children: make([]*scan.Term, 0, 1),
-		position: posPrefix,
+		Position: scan.PosPrefix,
-		priority: priNot,
+		Priority: scan.PriNot,
-		evalFunc: evalNot,
+		EvalFunc: evalNot,
 	}
 }
 
-func evalNot(ctx ExprContext, opTerm *term) (v any, err error) {
+func evalNot(ctx kern.ExprContext, opTerm *scan.Term) (v any, err error) {
 	var rightValue any
 
-	if rightValue, err = opTerm.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 = opTerm.errIncompatibleType(rightValue)
+		err = opTerm.ErrIncompatiblePrefixPostfixType(rightValue)
 	}
 	return
 }
 
 //-------- AND term
 
-func newAndTerm(tk *Token) (inst *term) {
+func newAndTerm(tk *scan.Token) (inst *scan.Term) {
-	return &term{
+	return &scan.Term{
-		tk:       *tk,
+		Tk:       *tk,
-		children: make([]*term, 0, 2),
+		Children: make([]*scan.Term, 0, 2),
-		position: posInfix,
+		Position: scan.PosInfix,
-		priority: priAnd,
+		Priority: scan.PriAnd,
-		evalFunc: evalAnd,
+		EvalFunc: evalAnd,
 	}
 }
 
-func evalAnd(ctx ExprContext, self *term) (v any, err error) {
+func evalAnd(ctx kern.ExprContext, self *scan.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)
@@ -54,47 +59,48 @@ 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 *scan.Term) (v any, err error) {
 	var leftValue, rightValue any
 	var leftBool, rightBool bool
 	var lok, rok bool
 
-	if leftValue, rightValue, err = self.evalInfix(ctx); err != nil {
+	if leftValue, rightValue, err = self.EvalInfix(ctx); err != nil {
 		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
 	} else {
-		err = self.errIncompatibleTypes(leftValue, rightValue)
+		err = self.ErrIncompatibleTypes(leftValue, rightValue)
 	}
 	return
 }
 
-func evalAndWithShortcut(ctx ExprContext, self *term) (v any, err error) {
+func evalAndWithShortcut(ctx kern.ExprContext, self *scan.Term) (v any, err error) {
 	var leftValue, rightValue any
 
-	if err = self.checkOperands(); err != nil {
+	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 %s as left operand type of 'AND' operator, it must be bool", TypeName(leftValue))
+		// 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)
+			err = self.ErrIncompatibleTypes(leftValue, rightValue)
 		}
 	}
 	return
@@ -102,18 +108,18 @@ func evalAndWithShortcut(ctx ExprContext, self *term) (v any, err error) {
 
 //-------- OR term
 
-func newOrTerm(tk *Token) (inst *term) {
+func newOrTerm(tk *scan.Token) (inst *scan.Term) {
-	return &term{
+	return &scan.Term{
-		tk:       *tk,
+		Tk:       *tk,
-		children: make([]*term, 0, 2),
+		Children: make([]*scan.Term, 0, 2),
-		position: posInfix,
+		Position: scan.PosInfix,
-		priority: priOr,
+		Priority: scan.PriOr,
-		evalFunc: evalOr,
+		EvalFunc: evalOr,
 	}
 }
 
-func evalOr(ctx ExprContext, self *term) (v any, err error) {
+func evalOr(ctx kern.ExprContext, self *scan.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)
@@ -121,47 +127,47 @@ 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 *scan.Term) (v any, err error) {
 	var leftValue, rightValue any
 	var leftBool, rightBool bool
 	var lok, rok bool
 
-	if leftValue, rightValue, err = self.evalInfix(ctx); err != nil {
+	if leftValue, rightValue, err = self.EvalInfix(ctx); err != nil {
 		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
 	} else {
-		err = self.errIncompatibleTypes(leftValue, rightValue)
+		err = self.ErrIncompatibleTypes(leftValue, rightValue)
 	}
 	return
 }
 
-func evalOrWithShortcut(ctx ExprContext, self *term) (v any, err error) {
+func evalOrWithShortcut(ctx kern.ExprContext, self *scan.Term) (v any, err error) {
 	var leftValue, rightValue any
 
-	if err = self.checkOperands(); err != nil {
+	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 %s as left operand type of 'OR' operator, it must be bool", TypeName(leftValue))
+		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)
+			err = self.ErrIncompatibleTypes(leftValue, rightValue)
 		}
 	}
 	return
@@ -169,7 +175,7 @@ func evalOrWithShortcut(ctx ExprContext, self *term) (v any, err error) {
 
 // init
 func init() {
-	registerTermConstructor(SymNot, newNotTerm)
+	scan.RegisterTermConstructor(scan.SymNot, newNotTerm)
-	registerTermConstructor(SymAnd, newAndTerm)
+	scan.RegisterTermConstructor(scan.SymAnd, newAndTerm)
-	registerTermConstructor(SymOr, newOrTerm)
+	scan.RegisterTermConstructor(scan.SymOr, newOrTerm)
 }

operator-builtin.go

@@ -1,47 +1,55 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
 // All rights reserved.
 
 // operator-builtin.go
 package expr
 
-import "io"
+import (
+	"io"
+
+	"git.portale-stac.it/go-pkg/expr/kern"
+	"git.portale-stac.it/go-pkg/expr/scan"
+)
 
 //-------- builtin term
 
-func newBuiltinTerm(tk *Token) (inst *term) {
+func newBuiltinTerm(tk *scan.Token) (inst *scan.Term) {
-	return &term{
+	return &scan.Term{
-		tk:       *tk,
+		Tk:       *tk,
-		children: make([]*term, 0, 1),
+		Children: make([]*scan.Term, 0, 1),
-		position: posPrefix,
+		Position: scan.PosPrefix,
-		priority: priSign,
+		Priority: scan.PriSign,
-		evalFunc: evalBuiltin,
+		EvalFunc: evalBuiltin,
 	}
 }
 
-func evalBuiltin(ctx ExprContext, opTerm *term) (v any, err error) {
+func evalBuiltin(ctx kern.ExprContext, opTerm *scan.Term) (v any, err error) {
 	var childValue any
 
-	if childValue, err = opTerm.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(ctx, childValue, nil); 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 = opTerm.Errorf("unknown builtin module %q", module)
 					break
 				}
 			} else {
-				err = opTerm.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
 			}
 		}
@@ -57,5 +65,5 @@ func evalBuiltin(ctx ExprContext, opTerm *term) (v any, err error) {
 
 // init
 func init() {
-	registerTermConstructor(SymKwBuiltin, newBuiltinTerm)
+	scan.RegisterTermConstructor(scan.SymKwBuiltin, newBuiltinTerm)
 }

operator-but.go

@@ -1,27 +1,32 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
 // All rights reserved.
 
 // operator-but.go
 package expr
 
+import (
+	"git.portale-stac.it/go-pkg/expr/kern"
+	"git.portale-stac.it/go-pkg/expr/scan"
+)
+
 //-------- but term
 
-func newButTerm(tk *Token) (inst *term) {
+func newButTerm(tk *scan.Token) (inst *scan.Term) {
-	return &term{
+	return &scan.Term{
-		tk:       *tk,
+		Tk:       *tk,
-		children: make([]*term, 0, 2),
+		Children: make([]*scan.Term, 0, 2),
-		position: posInfix,
+		Position: scan.PosInfix,
-		priority: priBut,
+		Priority: scan.PriBut,
-		evalFunc: evalBut,
+		EvalFunc: evalBut,
 	}
 }
 
-func evalBut(ctx ExprContext, opTerm *term) (v any, err error) {
+func evalBut(ctx kern.ExprContext, opTerm *scan.Term) (v any, err error) {
-	_, v, err = opTerm.evalInfix(ctx)
+	_, v, err = opTerm.EvalInfix(ctx)
 	return
 }
 
 // init
 func init() {
-	registerTermConstructor(SymKwBut, newButTerm)
+	scan.RegisterTermConstructor(scan.SymKwBut, newButTerm)
 }

operator-cat.go

@@ -0,0 +1,151 @@
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// operator-cat.go
+package expr
+
+import (
+	"fmt"
+	"io"
+
+	"git.portale-stac.it/go-pkg/expr/kern"
+	"git.portale-stac.it/go-pkg/expr/scan"
+)
+
+//-------- cat term
+
+func newCatTerm(tk *scan.Token) (inst *scan.Term) {
+	return &scan.Term{
+		Tk:       *tk,
+		Children: make([]*scan.Term, 0, 2),
+		Position: scan.PosInfix,
+		Priority: scan.PriIterOp,
+		EvalFunc: evalCat,
+	}
+}
+
+func evalCat(ctx kern.ExprContext, opTerm *scan.Term) (v any, err error) {
+	var leftValue, rightValue any
+	var itLeft, itRight kern.Iterator
+	// var item any
+	var ok bool
+
+	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, ok = leftValue.(kern.Iterator); !ok {
+		if itLeft, err = NewIterator(ctx, leftValue, nil); err != nil {
+			return nil, fmt.Errorf("left operand of JOIN must be an iterable data-source; got %s", kern.TypeName(leftValue))
+		}
+	}
+
+	if itRight, ok = rightValue.(kern.Iterator); !ok {
+		if itRight, err = NewIterator(ctx, rightValue, nil); 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
+	v = newCatIterator(itLeft, itRight)
+	return
+}
+
+const catIteratorType = "cat"
+
+type catIterator struct {
+	kern.IteratorBase
+	itLeft    kern.Iterator
+	itRight   kern.Iterator
+	itCurrent kern.Iterator
+}
+
+func newCatIterator(itLeft, itRight kern.Iterator) (it *catIterator) {
+	it = &catIterator{
+		IteratorBase: kern.IteratorBase{},
+		itLeft:       itLeft,
+		itRight:      itRight,
+		itCurrent:    itLeft,
+	}
+	it.Reset()
+	return
+}
+
+func (it *catIterator) TypeName() string {
+	return catIteratorType
+}
+
+func (it *catIterator) String() string {
+	return fmt.Sprintf("$(%s %s %s)", it.itLeft, catIteratorType, it.itRight)
+}
+
+func (it *catIterator) Next() (item any, err error) {
+	if it.itCurrent == nil {
+		err = io.EOF
+	} else {
+		if item, err = it.itCurrent.Next(); err == nil {
+			it.Increment()
+		} else if err == io.EOF {
+			if it.itCurrent == it.itLeft {
+				it.itCurrent = it.itRight
+			} else {
+				return
+			}
+			if item, err = it.itCurrent.Next(); err == nil {
+				it.Increment()
+			} else {
+				it.itCurrent = nil
+			}
+		}
+	}
+	it.SetCurrent(item)
+	return
+}
+
+// func (it *catIterator) Reset() (err error) {
+// 	err = it.itLeft.Reset()
+// 	it.IteratorBase.Reset()
+// 	return
+// }
+
+func (it *catIterator) 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 = it.Index()
+	case kern.CurrentName:
+		v, err = it.Current()
+	case kern.CountName:
+		v = it.Count()
+	default:
+		err = kern.ErrNoOperation(name)
+	}
+	return
+}
+
+// init
+func init() {
+	scan.RegisterTermConstructor(scan.SymKwCat, newCatTerm)
+}

operator-context.go

@@ -1,60 +1,69 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
 // All rights reserved.
 
 // operator-context-value.go
 package expr
 
+import (
+	"io"
+
+	"git.portale-stac.it/go-pkg/expr/kern"
+	"git.portale-stac.it/go-pkg/expr/scan"
+)
+
 //-------- context term
 
-func newContextTerm(tk *Token) (inst *term) {
+func newContextTerm(tk *scan.Token) (inst *scan.Term) {
-	return &term{
+	return &scan.Term{
-		tk:       *tk,
+		Tk:       *tk,
-		children: make([]*term, 0, 1),
+		Children: make([]*scan.Term, 0, 1),
-		position: posPrefix,
+		Position: scan.PosPrefix,
-		priority: priIncDec,
+		Priority: scan.PriIncDec,
-		evalFunc: evalContextValue,
+		EvalFunc: evalContextValue,
 	}
 }
 
-func evalContextValue(ctx ExprContext, opTerm *term) (v any, err error) {
+func evalContextValue(ctx kern.ExprContext, opTerm *scan.Term) (v any, err error) {
 	var childValue any
+	var sourceCtx kern.ExprContext
 
-	var sourceCtx ExprContext
+	if len(opTerm.Children) == 0 {
-	if len(opTerm.children) == 0 {
 		sourceCtx = ctx
-	} else if opTerm.children[0].symbol() == SymVariable && opTerm.children[0].source() == "global" {
+	} else if opTerm.Children[0].Symbol() == scan.SymVariable && opTerm.Children[0].Source() == "global" {
-		sourceCtx = globalCtx
+		sourceCtx = ctx.GetGlobal()
-	} else if childValue, err = opTerm.evalPrefix(ctx); err == nil {
+	} else if childValue, err = opTerm.EvalPrefix(ctx); err == nil {
 		if dc, ok := childValue.(*dataCursor); ok {
 			sourceCtx = dc.ctx
 		}
+	} else {
+		return
 	}
 
 	if sourceCtx != nil {
-		if formatter, ok := sourceCtx.(DictFormat); ok {
+		v = sourceCtx.ToDict()
-			v = formatter.ToDict()
+	} else if childValue != nil {
-		} else if formatter, ok := sourceCtx.(Formatter); ok {
+		it, ok := childValue.(kern.Iterator)
-			v = formatter.ToString(0)
+		if !ok {
-		} else {
+			it, err = NewIterator(ctx, childValue, nil)
-			// keys := sourceCtx.EnumVars(func(name string) bool { return name[0] != '_' })
-			keys := sourceCtx.EnumVars(nil)
-			d := make(map[string]any)
-			for _, key := range keys {
-				d[key], _ = sourceCtx.GetVar(key)
 		}
-			keys = sourceCtx.EnumFuncs(func(name string) bool { return true })
+		if err == nil {
-			for _, key := range keys {
+			var item any
-				d[key], _ = sourceCtx.GetFuncInfo(key)
+			values := kern.NewLinkedListA()
+			for item, err = it.Next(); err == nil; item, err = it.Next() {
+				values.PushBack(item)
+			}
+			if err == io.EOF {
+				err = nil
+				v = values
 			}
-			v = d
 		}
 	} else {
-		err = opTerm.errIncompatibleType(childValue)
+		err = opTerm.ErrIncompatiblePrefixPostfixType(childValue)
 	}
 	return
 }
 
 // init
 func init() {
-	registerTermConstructor(SymDoubleDollar, newContextTerm)
+	scan.RegisterTermConstructor(scan.SymDoubleDollar, newContextTerm)
 }

operator-ctrl.go

@@ -1,27 +1,32 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
 // All rights reserved.
 
 // operator-ctrl.go
 package expr
 
+import (
+	"git.portale-stac.it/go-pkg/expr/kern"
+	"git.portale-stac.it/go-pkg/expr/scan"
+)
+
 //-------- export all term
 
-func newExportAllTerm(tk *Token) (inst *term) {
+func newExportAllTerm(tk *scan.Token) (inst *scan.Term) {
-	return &term{
+	return &scan.Term{
-		tk:       *tk,
+		Tk:       *tk,
-		children: nil,
+		Children: nil,
-		position: posLeaf,
+		Position: scan.PosLeaf,
-		priority: priValue,
+		Priority: scan.PriValue,
-		evalFunc: evalExportAll,
+		EvalFunc: evalExportAll,
 	}
 }
 
-func evalExportAll(ctx ExprContext, opTerm *term) (v any, err error) {
+func evalExportAll(ctx kern.ExprContext, opTerm *scan.Term) (v any, err error) {
-	CtrlEnable(ctx, control_export_all)
+	CtrlEnable(ctx, kern.ControlExportAll)
 	return
 }
 
 // init
 func init() {
-	registerTermConstructor(SymDoubleAt, newExportAllTerm)
+	scan.RegisterTermConstructor(scan.SymDoubleAt, newExportAllTerm)
 }

operator-default.go

@@ -1,38 +1,43 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
 // All rights reserved.
 
 // operator-default.go
 package expr
 
+import (
+	"git.portale-stac.it/go-pkg/expr/kern"
+	"git.portale-stac.it/go-pkg/expr/scan"
+)
+
 //-------- default term
 
-func newDefaultTerm(tk *Token) (inst *term) {
+func newDefaultTerm(tk *scan.Token) (inst *scan.Term) {
-	return &term{
+	return &scan.Term{
-		tk:       *tk,
+		Tk:       *tk,
-		children: make([]*term, 0, 2),
+		Children: make([]*scan.Term, 0, 2),
-		position: posInfix,
+		Position: scan.PosInfix,
-		priority: priDefault,
+		Priority: scan.PriDefault,
-		evalFunc: evalDefault,
+		EvalFunc: evalDefault,
 	}
 }
 
-func evalDefault(ctx ExprContext, opTerm *term) (v any, err error) {
+func evalDefault(ctx kern.ExprContext, opTerm *scan.Term) (v any, err error) {
 	var rightValue any
 
-	if err = opTerm.checkOperands(); err != nil {
+	if err = opTerm.CheckOperands(); err != nil {
 		return
 	}
 
-	leftTerm := opTerm.children[0]
+	leftTerm := opTerm.Children[0]
-	if leftTerm.tk.Sym != SymVariable {
+	if leftTerm.Tk.Sym != scan.SymVariable {
 		// err = leftTerm.Errorf("left operand of %q must be a variable", self.tk.source)
-		err = ErrLeftOperandMustBeVariable(leftTerm, opTerm)
+		err = kern.ErrLeftOperandMustBeVariable(leftTerm, opTerm)
 		return
 	}
 
-	if leftValue, exists := ctx.GetVar(leftTerm.source()); exists {
+	if leftValue, exists := ctx.GetVar(leftTerm.Source()); exists {
 		v = leftValue
-	} else if rightValue, err = opTerm.children[1].compute(ctx); err == nil {
+	} else if rightValue, err = opTerm.Children[1].Compute(ctx); err == nil {
 		v = rightValue
 	}
 	return
@@ -40,32 +45,32 @@ func evalDefault(ctx ExprContext, opTerm *term) (v any, err error) {
 
 //-------- alternate term
 
-func newAlternateTerm(tk *Token) (inst *term) {
+func newAlternateTerm(tk *scan.Token) (inst *scan.Term) {
-	return &term{
+	return &scan.Term{
-		tk:       *tk,
+		Tk:       *tk,
-		children: make([]*term, 0, 2),
+		Children: make([]*scan.Term, 0, 2),
-		position: posInfix,
+		Position: scan.PosInfix,
-		priority: priDefault,
+		Priority: scan.PriDefault,
-		evalFunc: evalAlternate,
+		EvalFunc: evalAlternate,
 	}
 }
 
-func evalAlternate(ctx ExprContext, opTerm *term) (v any, err error) {
+func evalAlternate(ctx kern.ExprContext, opTerm *scan.Term) (v any, err error) {
 	var rightValue any
 
-	if err = opTerm.checkOperands(); err != nil {
+	if err = opTerm.CheckOperands(); err != nil {
 		return
 	}
 
-	leftTerm := opTerm.children[0]
+	leftTerm := opTerm.Children[0]
-	if leftTerm.tk.Sym != SymVariable {
+	if leftTerm.Tk.Sym != scan.SymVariable {
 		// err = leftTerm.Errorf("left operand of %q must be a variable", self.tk.source)
-		err = ErrLeftOperandMustBeVariable(leftTerm, opTerm)
+		err = kern.ErrLeftOperandMustBeVariable(leftTerm, opTerm)
 		return
 	}
 
-	if leftValue, exists := ctx.GetVar(leftTerm.source()); exists && leftValue != nil {
+	if leftValue, exists := ctx.GetVar(leftTerm.Source()); exists && leftValue != nil {
-		if rightValue, err = opTerm.children[1].compute(ctx); err == nil {
+		if rightValue, err = opTerm.Children[1].Compute(ctx); err == nil {
 			v = rightValue
 		}
 	} else {
@@ -76,41 +81,41 @@ func evalAlternate(ctx ExprContext, opTerm *term) (v any, err error) {
 
 //-------- default assign term
 
-func newDefaultAssignTerm(tk *Token) (inst *term) {
+func newDefaultAssignTerm(tk *scan.Token) (inst *scan.Term) {
-	return &term{
+	return &scan.Term{
-		tk:       *tk,
+		Tk:       *tk,
-		children: make([]*term, 0, 2),
+		Children: make([]*scan.Term, 0, 2),
-		position: posInfix,
+		Position: scan.PosInfix,
-		priority: priDefault,
+		Priority: scan.PriDefault,
-		evalFunc: evalAssignDefault,
+		EvalFunc: evalAssignDefault,
 	}
 }
 
-func evalAssignDefault(ctx ExprContext, opTerm *term) (v any, err error) {
+func evalAssignDefault(ctx kern.ExprContext, opTerm *scan.Term) (v any, err error) {
 	var rightValue any
 
-	if err = opTerm.checkOperands(); err != nil {
+	if err = opTerm.CheckOperands(); err != nil {
 		return
 	}
 
-	leftTerm := opTerm.children[0]
+	leftTerm := opTerm.Children[0]
-	if leftTerm.tk.Sym != SymVariable {
+	if leftTerm.Tk.Sym != scan.SymVariable {
 		// err = leftTerm.Errorf("left operand of %q must be a variable", self.tk.source)
-		err = ErrLeftOperandMustBeVariable(leftTerm, opTerm)
+		err = kern.ErrLeftOperandMustBeVariable(leftTerm, opTerm)
 		return
 	}
 
-	if leftValue, exists := ctx.GetVar(leftTerm.source()); exists {
+	if leftValue, exists := ctx.GetVar(leftTerm.Source()); exists {
 		v = leftValue
-	} else if rightValue, err = opTerm.children[1].compute(ctx); err == nil {
+	} else if rightValue, err = opTerm.Children[1].Compute(ctx); err == nil {
-		if functor, ok := rightValue.(Functor); ok {
+		if functor, ok := rightValue.(kern.Functor); ok {
 			//ctx.RegisterFunc(leftTerm.source(), functor, 0, -1)
-			ctx.RegisterFunc(leftTerm.source(), functor, TypeAny, []ExprFuncParam{
+			ctx.RegisterFunc(leftTerm.Source(), functor, kern.TypeAny, []kern.ExprFuncParam{
-				NewFuncParamFlag(ParamValue, PfDefault|PfRepeat),
+				kern.NewFuncParamFlag(kern.ParamValue, kern.PfDefault|kern.PfRepeat),
 			})
 		} else {
 			v = rightValue
-			ctx.UnsafeSetVar(leftTerm.source(), rightValue)
+			ctx.UnsafeSetVar(leftTerm.Source(), rightValue)
 		}
 	}
 	return
@@ -118,7 +123,7 @@ func evalAssignDefault(ctx ExprContext, opTerm *term) (v any, err error) {
 
 // init
 func init() {
-	registerTermConstructor(SymDoubleQuestion, newDefaultTerm)
+	scan.RegisterTermConstructor(scan.SymDoubleQuestion, newDefaultTerm)
-	registerTermConstructor(SymQuestionEqual, newDefaultAssignTerm)
+	scan.RegisterTermConstructor(scan.SymQuestionEqual, newDefaultAssignTerm)
-	registerTermConstructor(SymQuestionExclam, newAlternateTerm)
+	scan.RegisterTermConstructor(scan.SymQuestionExclam, newAlternateTerm)
 }

operator-digest.go

@@ -0,0 +1,73 @@
+// Copyright (c) 2024-2026 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"
+	"git.portale-stac.it/go-pkg/expr/scan"
+)
+
+//-------- digest term
+
+func newDigestTerm(tk *scan.Token) (inst *scan.Term) {
+	return &scan.Term{
+		Tk:       *tk,
+		Children: make([]*scan.Term, 0, 2),
+		Position: scan.PosInfix,
+		Priority: scan.PriIterOp,
+		EvalFunc: evalDigest,
+	}
+}
+
+func evalDigest(ctx kern.ExprContext, opTerm *scan.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(ctx, leftValue, nil); 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() {
+	scan.RegisterTermConstructor(scan.SymKwDigest, newDigestTerm)
+}