function definition and usage rationalized

Also fixed mul() function that called doAdd() instead of doMul().

ast.go

@@ -60,10 +60,10 @@ func (self *ast) addToken(tk *Token) (err error) {
 }
 
 func (self *ast) addToken2(tk *Token) (t *term, err error) {
-	if t = newTerm(tk, nil); t != nil {
+	if t = newTerm(tk); t != nil {
 		err = self.addTerm(t)
 	} else {
-		err = tk.Errorf("No term constructor for token %q", tk.String())
+		err = tk.Errorf("unexpected token %q", tk.String())
 	}
 	return
 }
@@ -119,7 +119,7 @@ func (self *ast) eval(ctx ExprContext, preset bool) (result any, err error) {
 		if self.forest != nil {
 			for _, root := range self.forest {
 				if result, err = root.compute(ctx); err == nil {
-					ctx.setVar(ControlLastResult, result)
+					ctx.UnsafeSetVar(ControlLastResult, result)
 				} else {
 					//err = fmt.Errorf("error in expression nr %d: %v", i+1, err)
 					break
@@ -128,6 +128,7 @@ func (self *ast) eval(ctx ExprContext, preset bool) (result any, err error) {
 		}
 		if err == nil {
 			result, err = self.root.compute(ctx)
+			ctx.UnsafeSetVar(ControlLastResult, result)
 		}
 		// } else {
 		// 	err = errors.New("empty expression")

ast_test.go

@@ -44,7 +44,7 @@ func TestAddTokensBad(t *testing.T) {
 func TestAddUnknownTokens(t *testing.T) {
 	tk0 := NewToken(0, 0, SymPercent, "%")
 
-	wantErr := errors.New(`No term constructor for token "%"`)
+	wantErr := errors.New(`unexpected token "%"`)
 
 	tree := NewAst()
 	if gotErr := tree.addToken(tk0); gotErr != nil && gotErr.Error() != wantErr.Error() {

common-errors.go

@@ -0,0 +1,55 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// common-errors.go
+package expr
+
+import (
+	"fmt"
+)
+
+func errTooFewParams(minArgs, maxArgs, argCount int) (err error) {
+	if maxArgs < 0 {
+		err = fmt.Errorf("too few params -- expected %d or more, got %d", minArgs, argCount)
+	} else {
+		err = fmt.Errorf("too few params -- expected %d, got %d", minArgs, argCount)
+	}
+	return
+}
+
+func errTooMuchParams(maxArgs, argCount int) (err error) {
+	err = fmt.Errorf("too much params -- expected %d, got %d", maxArgs, argCount)
+	return
+}
+
+// --- General errors
+
+func errCantConvert(funcName string, value any, kind string) error {
+	return fmt.Errorf("%s() can't convert %T to %s", funcName, value, kind)
+}
+
+func errExpectedGot(funcName string, kind string, value any) error {
+	return fmt.Errorf("%s() expected %s, got %T (%v)", funcName, kind, value, value)
+}
+
+func errDivisionByZero(funcName string) error {
+	return fmt.Errorf("%s() division by zero", funcName)
+}
+
+// --- Parameter errors
+
+// func errOneParam(funcName string) error {
+// 	return fmt.Errorf("%s() requires exactly one param", funcName)
+// }
+
+func errMissingRequiredParameter(funcName, paramName string) error {
+	return fmt.Errorf("%s() missing required parameter %q", funcName, paramName)
+}
+
+func errInvalidParameterValue(funcName, paramName string, paramValue any) error {
+	return fmt.Errorf("%s() invalid value %T (%v) for parameter %q", funcName, paramValue, paramValue, paramName)
+}
+
+func errWrongParamType(funcName, paramName, paramType string, paramValue any) error {
+	return fmt.Errorf("%s() the %q parameter must be a %s, got a %T (%v)", funcName, paramName, paramType, paramValue, paramValue)
+}

common-params.go

@@ -0,0 +1,30 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// common-params.go
+package expr
+
+const (
+	paramCount     = "count"
+	paramItem      = "item"
+	paramParts     = "parts"
+	paramSeparator = "separator"
+	paramSource    = "source"
+	paramSuffix    = "suffix"
+	paramPrefix    = "prefix"
+	paramStart     = "start"
+	paramEnd       = "end"
+	paramValue     = "value"
+	paramEllipsis  = "..."
+	typeFilepath   = "filepath"
+	typeDirpath    = "dirpath"
+)
+
+// const (
+// 	typeInteger  = "int"
+// 	typeFloat    = "float"
+// 	typeString   = "string"
+// 	typeFraction = "fract"
+// 	typeList     = "list"
+// 	typeDict     = "dict"
+// )

common-type-names.go

@@ -0,0 +1,17 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// common-type-names.go
+package expr
+
+const (
+	typeAny      = "any"
+	typeBoolean  = "boolean"
+	typeFloat    = "float"
+	typeFraction = "fraction"
+	typeHandle   = "handle"
+	typeInt      = "integer"
+	typeItem     = "item"
+	typeNumber   = "number"
+	typeString   = "string"
+)

context-helpers.go

@@ -15,20 +15,24 @@ func exportVar(ctx ExprContext, name string, value any) {
 	if name[0] == '@' {
 		name = name[1:]
 	}
-	ctx.setVar(name, value)
+	ctx.UnsafeSetVar(name, value)
 }
 
 func exportFunc(ctx ExprContext, name string, info ExprFunc) {
 	if name[0] == '@' {
 		name = name[1:]
 	}
-	ctx.RegisterFunc(name, info.Functor(), info.MinArgs(), info.MaxArgs())
+	// ctx.RegisterFunc(name, info.Functor(), info.MinArgs(), info.MaxArgs())
+	// ctx.RegisterFuncInfo(name, info)
+	ctx.RegisterFunc(name, info.Functor(), info.ReturnType(), info.Params())
 }
 
 func exportObjects(destCtx, sourceCtx ExprContext) {
 	exportAll := isEnabled(sourceCtx, control_export_all)
+	// 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] == '@' }) {
+		// fmt.Printf("\tExporting %q\n", refName)
 		refValue, _ := sourceCtx.GetVar(refName)
 		exportVar(destCtx, refName, refValue)
 	}

context.go

@@ -4,28 +4,31 @@
 // context.go
 package expr
 
-// ---- Function template
-type FuncTemplate func(ctx ExprContext, name string, args []any) (result any, err error)
-
 // ---- Functor interface
 type Functor interface {
 	Invoke(ctx ExprContext, name string, args []any) (result any, err error)
+	SetFunc(info ExprFunc)
+	GetFunc() ExprFunc
 }
 
-type simpleFunctor struct {
+// ---- Function Param Info
-	f FuncTemplate
+type ExprFuncParam interface {
-}
+	Name() string
-
+	Type() string
-func (functor *simpleFunctor) Invoke(ctx ExprContext, name string, args []any) (result any, err error) {
+	IsOptional() bool
-	return functor.f(ctx, name, args)
+	IsRepeat() bool
+	DefaultValue() any
 }
 
 // ---- Function Info
 type ExprFunc interface {
+	Formatter
 	Name() string
 	MinArgs() int
 	MaxArgs() int
 	Functor() Functor
+	Params() []ExprFuncParam
+	ReturnType() string
 }
 
 // ----Expression Context
@@ -33,10 +36,12 @@ type ExprContext interface {
 	Clone() ExprContext
 	GetVar(varName string) (value any, exists bool)
 	SetVar(varName string, value any)
-	setVar(varName string, value any)
+	UnsafeSetVar(varName string, value any)
 	EnumVars(func(name string) (accept bool)) (varNames []string)
 	EnumFuncs(func(name string) (accept bool)) (funcNames []string)
 	GetFuncInfo(name string) (item ExprFunc, exists bool)
 	Call(name string, args []any) (result any, err error)
-	RegisterFunc(name string, f Functor, minArgs, maxArgs int)
+	// RegisterFunc(name string, f Functor, minArgs, maxArgs int)
+	RegisterFuncInfo(info ExprFunc)
+	RegisterFunc(name string, f Functor, returnType string, param []ExprFuncParam) error
 }

data-cursor.go

@@ -5,34 +5,119 @@
 package expr
 
 import (
+	"errors"
 	"io"
 )
 
-const (
-	initName    = "init"
-	nextName    = "next"
-	currentName = "current"
-)
-
 type dataCursor struct {
-	ds          map[any]*term
+	ds          map[string]Functor
 	ctx         ExprContext
 	index       int
 	resource    any
 	nextFunc    Functor
+	cleanFunc   Functor
+	resetFunc   Functor
 	currentFunc Functor
 }
 
-func newDataCursor(ctx ExprContext) (dc *dataCursor) {
+func newDataCursor(ctx ExprContext, ds map[string]Functor) (dc *dataCursor) {
 	dc = &dataCursor{
+		ds:    ds,
 		index: -1,
 		ctx:   ctx.Clone(),
 	}
 	return
 }
 
+// func mapToString(m map[string]Functor) string {
+// 	var sb strings.Builder
+// 	sb.WriteByte('{')
+// 	for key, _ := range m {
+// 		if sb.Len() > 1 {
+// 			sb.WriteString(fmt.Sprintf(", %q: func(){}", key))
+// 		} else {
+// 			sb.WriteString(fmt.Sprintf("%q: func(){}", key))
+// 		}
+// 	}
+// 	sb.WriteByte('}')
+// 	return sb.String()
+// }
+
 func (dc *dataCursor) String() string {
-	return "$(...)"
+	return "$()"
+	/*
+	   var sb strings.Builder
+	   sb.WriteString(fmt.Sprintf(`$(
+	   index: %d,
+	   ds:    %s,
+	   ctx:   `, dc.index, mapToString(dc.ds)))
+	   CtxToBuilder(&sb, dc.ctx, 1)
+	   sb.WriteByte(')')
+	   return sb.String()
+	*/
+}
+
+func (dc *dataCursor) HasOperation(name string) (exists bool) {
+	exists = name == indexName
+	if !exists {
+		f, ok := dc.ds[name]
+		exists = ok && isFunctor(f)
+	}
+	return
+}
+
+func (dc *dataCursor) CallOperation(name string, args []any) (value any, err error) {
+	if name == indexName {
+		value = int64(dc.Index())
+	} else if functor, ok := dc.ds[name]; ok && isFunctor(functor) {
+		if functor == dc.cleanFunc {
+			value, err = dc.Clean()
+		} else if functor == dc.resetFunc {
+			value, err = dc.Reset()
+		} else {
+			ctx := cloneContext(dc.ctx)
+			value, err = functor.Invoke(ctx, name, []any{})
+			exportObjects(dc.ctx, ctx)
+		}
+	} else {
+		err = errNoOperation(name)
+	}
+	return
+}
+
+func (dc *dataCursor) Reset() (success bool, err error) {
+	if dc.resetFunc != nil {
+		if dc.resource != nil {
+			ctx := cloneContext(dc.ctx)
+			if _, err = dc.resetFunc.Invoke(ctx, resetName, []any{dc.resource}); err == nil {
+				dc.index = -1
+			}
+			exportObjects(dc.ctx, ctx)
+		} else {
+			err = errInvalidDataSource()
+		}
+	} else {
+		err = errNoOperation(resetName)
+	}
+	success = err == nil
+	return
+}
+
+func (dc *dataCursor) Clean() (success bool, err error) {
+	if dc.cleanFunc != nil {
+		if dc.resource != nil {
+			ctx := cloneContext(dc.ctx)
+			_, err = dc.cleanFunc.Invoke(ctx, cleanName, []any{dc.resource})
+			dc.resource = nil
+			exportObjects(dc.ctx, ctx)
+		} else {
+			err = errInvalidDataSource()
+		}
+	} else {
+		err = errors.New("no 'clean' function defined in the data-source")
+	}
+	success = err == nil
+	return
 }
 
 func (dc *dataCursor) Current() (item any, err error) { // must return io.EOF at the last item
@@ -45,15 +130,22 @@ func (dc *dataCursor) Current() (item any, err error) { // must return io.EOF at
 }
 
 func (dc *dataCursor) Next() (item any, err error) { // must return io.EOF after the last item
-	ctx := cloneContext(dc.ctx)
+	if dc.resource != nil {
-	if item, err = dc.nextFunc.Invoke(ctx, nextName, []any{}); err == nil {
+		ctx := cloneContext(dc.ctx)
-		if item == nil {
+		// fmt.Printf("Entering Inner-Ctx [%p]: %s\n", ctx, CtxToString(ctx, 0))
-			err = io.EOF
+		if item, err = dc.nextFunc.Invoke(ctx, nextName, []any{dc.resource}); err == nil {
-		} else {
+			if item == nil {
-			dc.index++
+				err = io.EOF
+			} else {
+				dc.index++
+			}
 		}
+		// fmt.Printf("Exiting Inner-Ctx [%p]: %s\n", ctx, CtxToString(ctx, 0))
+		exportObjects(dc.ctx, ctx)
+		// fmt.Printf("Outer-Ctx [%p]: %s\n", dc.ctx, CtxToString(dc.ctx, 0))
+	} else {
+		err = errInvalidDataSource()
 	}
-	exportObjects(dc.ctx, ctx)
 	return
 }
 

dict_test.go

@@ -0,0 +1,150 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// dict_test.go
+package expr
+
+import (
+	"errors"
+
+	"strings"
+	"testing"
+)
+
+func TestDictParser(t *testing.T) {
+	section := "Dict"
+
+	type inputType struct {
+		source     string
+		wantResult any
+		wantErr    error
+	}
+
+	inputs := []inputType{
+		/*  1 */ {`{}`, map[any]any{}, nil},
+		/*  2 */ {`{123}`, nil, errors.New(`[1:6] expected ":", got "}"`)},
+		/*  3 */ {`{1:"one",2:"two",3:"three"}`, map[int64]any{int64(1): "one", int64(2): "two", int64(3): "three"}, nil},
+		/*  4 */ {`{1:"one",2:"two",3:"three"}.2`, "three", nil},
+		/*  5 */ {`#{1:"one",2:"two",3:"three"}`, int64(3), nil},
+		/*  6 */ {`{1:"one"} + {2:"two"}`, map[any]any{1: "one", 2: "two"}, nil},
+		/*  7 */ {`2 in {1:"one", 2:"two"}`, true, nil},
+	}
+
+	succeeded := 0
+	failed := 0
+
+	// inputs1 := []inputType{
+	// 	/*  7 */ {`add([1,4,3,2])`, int64(10), nil},
+	// }
+
+	for i, input := range inputs {
+		var expr *ast
+		var gotResult any
+		var gotErr error
+
+		ctx := NewSimpleStore()
+		ctx.SetVar("var1", int64(123))
+		ctx.SetVar("var2", "abc")
+		ImportMathFuncs(ctx)
+		parser := NewParser(ctx)
+
+		logTest(t, i+1, "Dict", input.source, input.wantResult, input.wantErr)
+
+		r := strings.NewReader(input.source)
+		scanner := NewScanner(r, DefaultTranslations())
+
+		good := true
+		if expr, gotErr = parser.Parse(scanner); gotErr == nil {
+			gotResult, gotErr = expr.Eval(ctx)
+		}
+
+		if (gotResult == nil && input.wantResult != nil) || (gotResult != nil && input.wantResult == nil) {
+			t.Errorf("%d: %q -> result = %v [%T], want %v [%T]", i+1, input.source, gotResult, gotResult, input.wantResult, input.wantResult)
+			good = false
+		}
+
+		if gotList, okGot := gotResult.([]any); okGot {
+			if wantList, okWant := input.wantResult.([]any); okWant {
+				if (gotList == nil && wantList != nil) || (gotList != nil && wantList == nil) {
+					t.Errorf("%d: %q -> result = %v [%T], want %v [%T]", i+1, input.source, gotResult, gotResult, input.wantResult, input.wantResult)
+					good = false
+				} else {
+					equal := len(gotList) == len(wantList)
+					if equal {
+						for i, gotItem := range gotList {
+							wantItem := wantList[i]
+							equal = gotItem == wantItem
+							if !equal {
+								break
+							}
+						}
+					}
+					if !equal {
+						t.Errorf("%d: %q -> result = %v [%T], want %v [%T]", i+1, input.source, gotResult, gotResult, input.wantResult, input.wantResult)
+						good = false
+					}
+				}
+			}
+		}
+
+		if gotErr != input.wantErr {
+			if input.wantErr == nil || gotErr == nil || (gotErr.Error() != input.wantErr.Error()) {
+				t.Errorf("%d: %q  -> err = <%v>, want <%v>", i+1, input.source, gotErr, input.wantErr)
+				good = false
+			}
+		}
+
+		if good {
+			succeeded++
+		} else {
+			failed++
+		}
+	}
+	t.Logf("%s -- test count: %d, succeeded: %d, failed: %d", section, len(inputs), succeeded, failed)
+}
+
+func TestDictToStringMultiLine(t *testing.T) {
+	var good bool
+	section := "dict-ToString-ML"
+	want := `{
+	"first": 1
+}`
+	args := map[any]*term{
+		"first": newLiteralTerm(NewValueToken(0, 0, SymInteger, "1", 1)),
+	}
+	dict := newDict(args)
+	got := dict.ToString(MultiLine)
+	// fmt.Printf("got=%q\n", got)
+
+	if good = got == want; !good {
+		t.Errorf("ToString(MultiLine): got = %q, want %q", got, want)
+	}
+
+	if good {
+		t.Logf("%s -- succeeded", section)
+	} else {
+		t.Logf("%s -- failed", section)
+	}
+}
+
+func TestDictToString(t *testing.T) {
+	var good bool
+	section := "dict-ToString-SL"
+	want := `{"first": 1}`
+	args := map[any]*term{
+		"first": newLiteralTerm(NewValueToken(0, 0, SymInteger, "1", 1)),
+	}
+	dict := newDict(args)
+	got := dict.ToString(0)
+	// fmt.Printf("got=%q\n", got)
+
+	if good = got == want; !good {
+		t.Errorf("ToString(0): got = %q, want %q", got, want)
+	}
+
+	if good {
+		t.Logf("%s -- succeeded", section)
+	} else {
+		t.Logf("%s -- failed", section)
+	}
+}

doc/Expr.adoc

@@ -22,49 +22,242 @@ Expressions calculator
 
 toc::[]
 
-#TODO: Work in progress#
+#TODO: Work in progress (last update on 2024/05/20, 06:58 a.m.)#
 
 == Expr
 _Expr_ is a GO package capable of analysing, interpreting and calculating expressions.
 
-
 === Concepts and terminology
 #TODO#
 
+image::expression-diagram.png[]
+
+=== `dev-expr` test tool
+`dev-expr` is a simple program that can be used to evaluate expressions interactively. As its name suggests, it was created for testing purpose.  In fact, in additon to the automatic verification test suite based on the Go test framework, `dev-expr` provides an important aid for quickly testing of new features during their development.
+
+`dev-expr` can work as a _REPL_, _**R**ead-**E**xecute-**P**rint-**L**oop_, or it can process expression acquired from files or standard input.
+
+The program can be downloaded from https://git.portale-stac.it/go-pkg/-/packages/generic/dev-expr/[dev-expr].
+
+Here are some examples of execution.
+
+.Run `dev-expr` in REPL mode and ask for help
+[source,shell]
+----
+# Type 'exit' or Ctrl+D to quit the program.
+
+[user]$ ./dev-expr
+expr -- Expressions calculator v1.7.1(build 2),2024/05/16 (celestino.amoroso@portale-stac.it)
+	Based on the Expr package v0.10.0
+	Type help to get the list of available commands
+	See also https://git.portale-stac.it/go-pkg/expr/src/branch/main/README.adoc
+
+>>> help
+--- REPL commands:
+      source -- Load a file as input
+         tty -- Enable/Disable ansi output <1>
+        base -- Set the integer output base: 2, 8, 10, or 16
+        exit -- Exit the program
+        help -- Show command list
+          ml -- Enable/Disable multi-line output
+        mods -- List builtin modules
+
+--- 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.
+    -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
+    -p                 Print prefix form
+    -t                 Print tree form <2>
+
+>>> 
+----
+
+<1> Only available for single fraction values
+<2> Work in progress
+
+.REPL examples
+[source,shell]
+----
+[user]$ ./dev-expr
+expr -- Expressions calculator v1.7.1(build 2),2024/05/16 (celestino.amoroso@portale-stac.it)
+	Based on the Expr package v0.10.0
+	Type help to get the list of available commands
+	See also https://git.portale-stac.it/go-pkg/expr/src/branch/main/README.adoc
+
+>>> 2+3
+5
+>>> 2+3*(4-1.5)
+9.5
+>>> 0xFD + 0b1 + 0o1 <1>
+255
+>>> 1|2 + 2|3 <2>
+7|6
+>>> ml <3>
+>>> 1|2 + 2|3
+7
+-
+6
+>>> 1+2 but 5|2+0.5 <4>
+3
+>>> 1+2; 5|2+0.5 <5>
+3
+>>>
+----
+
+<1> Number bases: 0x = hexadecimal, 0o = octal, 0b = binary.
+<2> Fractions: numerator | denominator.
+<3> Activate multi-line output of fractions.
+<4> But operator, see <<_but_operator>>.
+<5> Multi-expression: the same result of the previous single expression but this it is obtained with two separated calculations.
+
 == Data types
 _Expr_ supports numerical, string, relational, boolean expressions, and mixed-type lists.
 
 === Numbers
-Numbers can be integers (GO int64) or float (GO float64). In mixed operations involving integers and floats, integers are automatically promoted to floats.
+_Expr_ supports three type of numbers:
+
+. [blue]#Integers#
+. [blue]#Floats#
+. [blue]#Factions#
+
+In mixed operations involving integers, fractions and floats, automatic type promotion to the largest type take place.
+
+==== Integers
+__Expr__'s integers are a subset of the integer set. Internally they are stored as Golang _int64_ values.
+
+.Integer literal syntax
+====
+*_integer_* = [_sign_] _digit-seq_ +
+_sign_ = "**+**" | "**-**" +
+_digit-seq_ = _dec-seq_ | _bin-seq_ | _oct-seq_ | _hex-seq_ +
+_dec-seq_ = {__dec-digit__} +
+_dec-digit_ = "**0**"|"**1**"|...|"**9**" +
+_bin-seq_ = "**0b**"{__bin-digit__} +
+_bin-digit_ = "**0**"|"**1**" +
+_oct-seq_ = "**0o**"{__oct-digit__} +
+_oct-digit_ = "**0**"|"**1**"|...|"**7**" +
+_hex-seq_ = "**0x**"{__hex-digit__} +
+_hex-digit_ = "**0**"|"**1**"|...|"**9**"|"**a**"|...|"**z**"|"**A**"|...|"**Z**"
+====
+
+Value range: *-9223372036854775808* to *9223372036854775807*
 
 .Arithmetic operators
 [cols="^1,^2,6,4"]
 |===
 | Symbol    | Operation     | Description               | Examples
-
+| [blue]`+` | _sum_         | Add two values            | [blue]`-1 + 2` -> 1
-| [blue]`+` / [blue]`-` | _change sign_ | Change the sign of values | [blue]`-1` _[-1]_ +
+| [blue]`-` | _subtraction_ | Subtract the right value from the left one | [blue]`3 - 1` -> 2
-[blue]`-(+2)` _[-2]_
+| [blue]`*` | _product_     | Multiply two values       | [blue]`-1 * 2` -> -2
-
+| [blue]`/` | _Division_    | Divide the left value by the right one^(*)^ | [blue]`-10 / 2` -> 5
-| [blue]`+` | _sum_ | Add two values | [blue]`-1 + 2` _[1]_ +
+| [blue]`%` | _Modulo_      | Remainder of the integer division | [blue]`5 % 2` -> 1
-[blue]`4 + 0.5` _[4.5]_
-
-| [blue]`-` | _subtraction_ | Subtract the right value from the left one | [blue]`3 - 1` _[2]_ +
-[blue]`4 - 0.5` _[3.5]_
-
-| [blue]`*` | _product_ | Multiply two values | `-1 * 2` _[-2]_ +
-[blue]`4 * 0.5` _[2.0]_
-
-| [blue]`/` | _Division_ | Divide the left value by the right one | [blue]`-1 / 2` _[0]_ +
-[blue]`1.0 / 2` _[0.5]_
-
-| [blue]`./` | _Float division_ | Force float division | [blue]`-1 ./ 2` _[-0.5]_
-
-| [blue]`%` | _Modulo_ | Remainder of the integer division | [blue]`5 % 2` _[1]_
-
 |=== 
 
-=== String
+^(*)^ See also the _float division_ [blue]`./` below.
-Strings are character sequences enclosed between two double quote [blue]`"`. Example: [blue]`"I'm a string"`.
+
+
+==== Floats
+__Expr__'s floats are a subset of the rational number set. Note that they can't hold the exact value of an unlimited number; floats can only approximate them. Internally floats are stored as Golang's _float64_ values.
+
+
+.Float literal syntax
+====
+*_float_* = [_sign_] _dec-seq_ "**.**" [_dec-seq_] [("**e**"|"**E**") [_sign_] _dec-seq_] +
+_sign_ = "**+**" | "**-**" +
+_dec-seq_ = _see-integer-literal-syntax_
+====
+
+.Examples
+`>>>` [blue]`1.0` +
+[green]`1` +
+`>>>` [blue]`0.123` +
+[green]`0.123` +
+`>>>` [blue]`4.5e+3` +
+[green]`4500` +
+`>>>` [blue]`4.5E-33` +
+[green]`4.5e-33` +
+`>>>` [blue]`4.5E-3` +
+[green]`0.0045` +
+`>>>` [blue]`4.5E10` +
+[green]`4.5e+10`
+
+
+.Arithmetic operators
+[cols="^1,^2,6,4"]
+|===
+| Symbol    | Operation     | Description               | Examples
+| [blue]`+` | _sum_         | Add two values            | [blue]`4 + 0.5` -> 4.5
+| [blue]`-` | _subtraction_ | Subtract the right value from the left one | [blue]`4 - 0.5` -> 3.5
+| [blue]`*` | _product_     | Multiply two values       | [blue]`4 * 0.5` -> 2.0
+| [blue]`/` | _Division_    | Divide the left value by the right one | [blue]`1.0 / 2` -> 0.5
+| [blue]`./`| _Float division_ | Force float division   | [blue]`-1 ./ 2` -> -0.5
+|===
+
+==== Fractions
+_Expr_ also supports fractions. Fraction literals are made with two integers separated by a vertical bar `|`.
+
+.Fraction literal syntax
+====
+*_fraction_* = [__sign__] (_num-den-spec_ | _float-spec_) +
+_sign_ = "**+**" | "**-**" +
+_num-den-spec_ = _digit-seq_ "**|**" _digit-seq_ +
+_float-spec_ = _dec-seq_ "**.**" [_dec-seq_] "**(**" _dec-seq_ "**)**" +
+_dec-seq_ = _see-integer-literal-syntax_ +
+_digit-seq_ = _see-integer-literal-syntax_
+====
+
+.Examples
+// [source,go]
+// ----
+`>>>` [blue]`1 | 2` +
+[green]`1|2` +
+`>>>` [blue]`4|6`  [gray]_// Fractions are always reduced to their lowest terms_ +
+[green]`2|3` +
+`>>>` [blue]`1|2 + 2|3` +
+[green]`7|6` +
+`>>>` [blue]`1|2 * 2|3` +
+[green]`1|3` +
+`>>>` [blue]`1|2 / 1|3` +
+[green]`3|2` +
+`>>>` [blue]`1|2 ./ 1|3` [gray]_// Force decimal division_ +
+[green]`1.5` +
+`>>>` [blue]`-1|2` +
+[green]`-1|2` +
+`>>>` [blue]`1|-2` [gray]_// Invalid sign specification_ +
+[red]_Eval Error: [1:3] infix operator "|" requires two non-nil operands, got 1_ +
+`>>>` [blue]`1|(-2)` +
+[green]`-1|2`
+// ----
+
+Fractions can be used together with integers and floats in expressions.
+
+.Examples
+`>>>` [blue]`1|2 + 5` +
+[green]`11|2` +
+`>>>` [blue]`4 - 1|2` +
+[green]`7|2` +
+`>>>` [blue]`1.0 + 1|2` +
+[green]`1.5`
+
+
+
+=== Strings
+Strings are character sequences enclosed between two double quote [blue]`"`.
+
+.Examples
+`>>>` [blue]`"I'm a string"` +
+[green]`I'm a string` +
+`>>>` [blue]`"123abc?!"` +
+[green]`123abc?!` +
+`>>>` [blue]`"123\nabc"` +
+[green]`123` +
+[green]`abc` +
+`>>>` [blue]`"123\tabc"` +
+[green]`123{nbsp}{nbsp}{nbsp}{nbsp}abc`
 
 Some arithmetic operators can also be used with strings.
 
@@ -73,55 +266,75 @@ Some arithmetic operators can also be used with strings.
 |===
 | Symbol    | Operation     | Description               | Examples
 
-| [blue]`+` | _concatenation_ | Join two strings or two _stringable_ values | [blue]`"one" + "two"` _["onetwo"]_ +
+| [blue]`+` | _concatenation_ | Join two strings or two _stringable_ values | [blue]`"one" + "two"` -> _"onetwo"_ +
-[blue]`"one" + 2` _["one2"]_
+[blue]`"one" + 2` -> _"one2"_
 
-| [blue]`*` | _repeat_ | Make _n_ copy of a string  | [blue]`"one" * 2` _["oneone"]_
+| [blue]`*` | _repeat_ | Make _n_ copy of a string  | [blue]`"one" * 2` -> _"oneone"_
 |===
 
+The items of strings can be accessed using the dot `.` operator.
 
-=== Boolean
+.Item access syntax
-Boolean data type has two values only: _true_ and _false_. Relational and Boolean expressions produce Boolean values.
+====
+_item_ = _string-expr_ "**.**" _integer-expr_
+====
+
+.String examples
+`>>>` [blue]`s="abc"`  [gray]_// assign the string to variable s_ +
+[green]`abc` +
+`>>>` [blue]`s.1`      [gray]_// char at position 1 (starting from 0)_ +
+[green]`b` +
+`>>>` [blue]`s.(-1)`   [gray]_// char at position -1, the rightmost one_ +
+[green]`c` +
+`>>>` [blue]`\#s`       [gray]_// number of chars_ +
+[gren]`3` +
+`>>>` [blue]`#"abc"`   [gray]_// number of chars_ +
+[green]`3`
 
 
-.Relational operators
+=== Booleans
+Boolean data type has two values only: [blue]_true_ and [blue]_false_. Relational and boolean expressions result in boolean values.
+
+.Relational operators^(*)^
 [cols="^1,^2,6,4"]
 |===
 | Symbol    | Operation     | Description               | Examples
 
-| [blue]`==` | _Equal_ | True if the left value is equal to the right one | [blue]`5 == 2` _[false]_ +
+| [blue]`==` | _Equal_ | True if the left value is equal to the right one | [blue]`5 == 2` -> _false_ +
-[blue]`"a" == "a"` _[true]_
+[blue]`"a" == "a"` -> _true_
-| [blue]`!=` | _Not Equal_ | True if the left value is NOT equal to the right one | [blue]`5 != 2` _[true]_ +
+| [blue]`!=` | _Not Equal_ | True if the left value is NOT equal to the right one | [blue]`5 != 2` -> _true_ +
-[blue]`"a" != "a"` _[false]_
+[blue]`"a" != "a"` -> _false_
-| [blue]`<` | _Less_ | True if the left value is less than the right one | [blue]`5 < 2` _[false]_ +
+| [blue]`<` | _Less_ | True if the left value is less than the right one | [blue]`5 < 2` -> _false_ +
-[blue]`"a" < "b"` _[true]_
+[blue]`"a" < "b"` -> _true_
-| [blue]`\<=` | _Less or Equal_ | True if the left value is less than or equal to the right one | [blue]`5 \<= 2` _[false]_ +
+| [blue]`\<=` | _Less or Equal_ | True if the left value is less than or equal to the right one | [blue]`5 \<= 2` -> _false_ +
-[blue]`"b" \<= "b"` _[true]_
+[blue]`"b" \<= "b"` -> _true_
-| [blue]`>` | _Greater_ | True if the left value is greater than the right one | [blue]`5 > 2` _[true]_ +
+| [blue]`>` | _Greater_ | True if the left value is greater than the right one | [blue]`5 > 2` -> _true_ +
-[blue]`"a" < "b"` _[false]_
+[blue]`"a" < "b"` -> _false_
-| [blue]`>=` | _Greater or Equal_ | True if the left value is greater than or equal to the right one | [blue]`5 >= 2` _[true]_ +
+| [blue]`>=` | _Greater or Equal_ | True if the left value is greater than or equal to the right one | [blue]`5 >= 2` -> _true_ +
-[blue]`"b" \<= "b"` _[true]_
+[blue]`"b" \<= "b"` -> _true_
 |===
 
+^(*)^ See also the  [blue]`in` operator in the _list_ and _dictionary_ sections.
+
 
 .Boolean operators
 [cols="^2,^2,5,4"]
 |===
 | Symbol    | Operation     | Description               | Examples
 
-| [blue]`NOT` | _Not_ | True if the right value is false | [blue]`NOT true` _[false]_ +
+| [blue]`NOT` | _Not_ | True if the right value is false | [blue]`NOT true` -> _false_ +
-[blue]`NOT (2 < 1)` _[true]_
+[blue]`NOT (2 < 1)` -> _true_
 
-| [blue]`AND` / [blue]`&&` | _And_ | True if both left and right values are true  | [blue]`false && true` _[false]_ +
+| [blue]`AND` / [blue]`&&` | _And_ | True if both left and right values are true  | [blue]`false && true` -> _false_ +
-[blue]`"a" < "b" AND NOT (2 < 1)` _[true]_
+[blue]`"a" < "b" AND NOT (2 < 1)` -> _true_
 
-| [blue]`OR` / [blue]`\|\|` | _Or_ | True if at least one of the left and right values integers true| [blue]`false or true` _[true]_ +
+| [blue]`OR` / [blue]`\|\|` | _Or_ | True if at least one of the left and right values integers true| [blue]`false or true` -> _true_ +
-[blue]`"a" == "b" OR (2 == 1)` _[false]_
+[blue]`"a" == "b" OR (2 == 1)` -> _false_
 |===
 
 [CAUTION]
 ====
-Currently, boolean operations are evaluated using _short cut evaluation_. This means that, if the left expression of operators [blue]`and` and [blue]`or` is sufficient to establish the result of the whole operation, the right expression would not evaluated at all.
+Currently, boolean operations are evaluated using _short cut evaluation_. This means that, if the left expression of the [blue]`and` and [blue]`or` operators is sufficient to establish the result of the whole operation, the right expression would not evaluated at all.
 
 .Example
 [source,go]
@@ -131,128 +344,274 @@ Currently, boolean operations are evaluated using _short cut evaluation_. This m
 <1> This multi-expression returns _1_ because in the first expression the left value of [blue]`or` is _true_ and as a conseguence its right value is not computed. Therefore the _a_ variable only receives the integer _1_.
 ====
 
-=== List
+=== Lists
-_Expr_ supports list of mixed-type values, also specified by normal expressions.
+_Expr_ supports list of mixed-type values, also specified by normal expressions. Internally, _Expr_'s lists are Go arrays.
 
-.List examples
+.List literal syntax
-[source,go]
+====
-----
+*_list_* = _empty-list_ | _non-empty-list_ +
-[1, 2, 3]                   // List of integers
+_empty-list_ = "**[]**" +
-["one", "two", "three"]     // List of strings
+_non-empty-list_ = "**[**" _any-value_ {"**,**" _any-value} "**]**" +
-["one", 2, false, 4.1]      // List of mixed-types
+====
-["one"+1, 2.0*(9-2)]        // List of expressions
-[ [1,"one"], [2,"two"]]     // List of lists
-----
 
+.Examples
+`>>>` [blue]`[1,2,3]`                     [gray]_// List of integers_ +
+[green]`[1, 2, 3]` +
+`>>>` [blue]`["one", "two", "three"]`     [gray]_// List of strings_ +
+[green]`["one", "two", "three"]` +
+`>>>` [blue]`["one", 2, false, 4.1]`      [gray]_// List of mixed-types_ +
+[green]`["one", 2, false, 4.1]` +
+`>>>` [blue]`["one"+1, 2.0*(9-2)]`        [gray]_// List of expressions_ +
+[green]`["one1", 14]` +
+`>>>` [blue]`[ [1,"one"], [2,"two"]]`     [gray]_// List of lists_ +
+[green]`[[1, "one"], [2, "two"]]`
 
 .List operators
 [cols="^2,^2,5,4"]
 |===
 | Symbol    | Operation     | Description               | Examples
 
-| [blue]`+` | _Join_ | Joins two lists | [blue]`[1,2] + [3]` _[ [1,2,3] ]_
+| [blue]`+` | _Join_ | Joins two lists | [blue]`[1,2] + [3]` -> _[1,2,3]_
-
+| [blue]`-` | _Difference_ | Left list without elements in the right list  | [blue]`[1,2,3] - [2]` -> _[1,3]_
-| [blue]`-` | _Difference_ | Left list without elements in the right list  | [blue]`[1,2,3] - [2]` _[ [1,3] ]_
+| [blue]`>>` | _Front insertion_ | Insert an item in front | [blue]`0 >> [1,2]` -> _[0,1,2]_
+| [blue]`<<` | _Back insertion_ | Insert an item at end | [blue]`[1,2] << 3` -> _[1,2,3]_
+| [blue]`.` | _List item_ | Item at given position | [blue]`[1,2.3].1` -> _2_
+| [blue]`in` | _Item in list_ | True if item is in list | [blue]`2 in [1,2,3]` -> _true_ +
+[blue]`6 in [1,2,3]` -> _false_
 |===
 
-== Variables
+The items of array can be accessed using the dot `.` operator.
-A variable is an identifier with an assigned value. Variables are stored in the object that implements the _ExprContext_ interface.
+
+.Item access syntax
+====
+_item_ = _list-expr_ "**.**" _integer-expr_
+====
+
+.Items of list
+`>>>` [blue]`[1,2,3].1` +
+[green]`2` +
+`>>>` [blue]`list=[1,2,3]; list.1` +
+[green]`2` +
+`>>>` [blue]`["one","two","three"].1` +
+[green]`two` +
+`>>>` [blue]`list=["one","two","three"]; list.(2-1)` +
+[green]`two` +
+`>>>` [blue]`list.(-1)` +
+[green]`three` +
+`>>>` [blue]`list.(10)` +
+[red]`Eval Error: [1:9] index 10 out of bounds` +
+`>>>` [blue]`#list` +
+[green]`3` +
+`>>>` [blue]`index=2; ["a", "b", "c", "d"].index` +
+[green]`c`
+
+
+
+=== Dictionaries
+The _dictionary_, or _dict_, data-type is set of pairs _key/value_. It is also known as _map_ or _associative array_.
+
+Dictionary literals are sequences of pairs separated by comma [blue]`,` enclosed between brace brackets.
+
+.Dict literal syntax
+====
+*_dict_* = _empty-dict_ | _non-empty-dict_ +
+_empty-dict_ = "**{}**" +
+_non-empty-dict_ = "**{**" _key-scalar_ "**:**" _any-value_ {"**,**" _key-scalar_ "**:**" _any-value} "**}**" +
+====
 
 .Examples
-[source,go]
+`>>>` [blue]`{1:"one", 2:"two"}` +
-----
+[green]`{1: "one", 2: "two"}` +
-a=1
+`>>>` [blue]`{"one":1, "two": 2}` +
-x = 5.2 * (9-3)
+[green]`{"one": 1, "two": 2}` +
-x = 1; y = 2*x
+`>>>` [blue]`{"sum":1+2+3, "prod":1*2*3}` +
-----
+[green]`{"sum": 6, "prod": 6}`
+
+
+.Dict operators
+[cols="^2,^2,4,5"]
+|===
+| Symbol    | Operation     | Description               | Examples
+
+| [blue]`+` | _Join_ | Joins two dicts | [blue]`{1:"one"}+{6:"six"}` -> _{1: "one", 6: "six"}_
+| [blue]`.` | _Dict item value_ | Item value of given key | [blue]`{"one":1, "two":2}."two"` -> _2_
+| [blue]`in` | _Key in dict_ | True if key is in dict | [blue]`"one" in {"one":1, "two":2}` -> _true_ +
+[blue]`"six" in {"one":1, "two":2}` -> _false_
+|===
+
+
+== Variables
+_Expr_, like most programming languages, supports variables. A variable is an identifier with an assigned value. Variables are stored in _contexts_.
+
+.Variable literal syntax
+====
+*_variable_* = _identifier_ "*=*" _any-value_ +
+_identifier_ = _alpha_ {(_alpha_)|_dec-digit_|"*_*"} +
+__alpha__ = "*a*"|"*b*"|..."*z*"|"*A*"|"*B*"|..."*Z*"
+====
+
+NOTE: The assign operator [blue]`=` returns the value assigned to the variable.
+
+.Examples
+`>>>` [blue]`a=1` +
+[green]`1` +
+`>>>` [blue]`a_b=1+2` +
+[green]`1+2` +
+`>>>` [blue]`a_b` +
+[green]`3` +
+`>>>` [blue]`x = 5.2 * (9-3)`  [gray]_// The assigned value has the approximation error typical of the float data-type_ +
+[green]`31.200000000000003` +
+`>>>` [blue]`x = 1; y = 2*x` +
+[green]`2` +
+`>>>` [blue]`_a=2` +
+[red]`Parse Error: [1:2] unexpected token "_"` +
+`>>>` [blue]`1=2` +
+[red]`Parse Error: assign operator ("=") must be preceded by a variable`
+
 
 == Other operations
 
 === [blue]`;` operator
-The semicolon operator [blue]`;` is an infixed operator. It evaluates the left expression first and then the right expression. The latter is the final result.
+The semicolon operator [blue]`;` is an infixed pseudo-operator. It evaluates the left expression first and then the right expression. The value of the latter is the final result.
+
+An expression that contains [blue]`;` is called a _multi-expression_ and each component expressione is called a _sub-expression_.
 
 IMPORTANT: Technically [blue]`;` is not treated as a real operator. It acts as a separator in lists of expressions.
 
 TIP: [blue]`;` can be used to set some variables before the final calculation.
 
 .Example
-[source,go]
+`>>>` [blue]`a=1; b=2; c=3; a+b+c` +
-----
+[green]`6`
-a=1; b=2; c=3; a+b+c    // returns 6
+
-----
+The value of each sub-expression is stored in the automatica variable _last_.
+
+.Example
+`>>>` [blue]`2+3; b=last+10; last` +
+[green]`15`
+
 
 === [blue]`but` operator
-[blue]`but` is an infixed operator. Its operands can be any type of expression. It evaluates the left expression first, then the right expression. The value of the right expression is the final result. Examples: [blue]`5 but 2` returns 2, [blue]`x=2*3 but x-1` returns 5.
+[blue]`but` is an infixed operator. Its operands can be expressions of any type. It evaluates the left expression first, then the right expression. The value of the right expression is the final result.
 
-[blue]`but` is very similar to [blue]`;`. The only difference is that [blue]`;` can't be used inside parenthesis [blue]`(` and [blue]`)`.
+.Examples
+[blue]`5 but 2` +
+[green]`2` +
+[blue]`x=2*3 but x-1` +
+[green]`5`.
+
+[blue]`but` behavior is very similar to [blue]`;`. The only difference is that [blue]`;` is not a true operator and can't be used inside parenthesis [blue]`(` and [blue]`)`.
 
 === Assignment operator [blue]`=`
-The assignment operator [blue]`=` is used to define variable in the evaluation context or to change their value (see _ExprContext_).
+The assignment operator [blue]`=` is used to define variables or to change their value in the evaluation context (see _ExprContext_).
+
 The value on the left side of [blue]`=` must be an identifier. The value on the right side can be any expression and it becomes the result of the assignment operation.
 
 .Example
-[source,go]
+`>>>` [blue]`a=15+1`
-----
+[green]`16`
-a=15+1    // returns 16
+
-----
 
 === Selector operator [blue]`? : ::`
 The _selector operator_ is very similar to the _switch/case/default_ statement available in many programming languages.
 
-.Syntax
+.Selector literal Syntax
-[source,bnf]
+_selector-operator_ = _select-expression_ "*?*" _selector-case_ { "*:*" _selector-case_ } ["*::*" _default-multi-expression_] +
-----
+_selector-case_ = [_match-list_] _case-value_ +
-<selector-operator> ::= <expression> "?" <selector-case> { ":" <selector-case> } ["::" <case-value>]
+_match-list_ = "*[*" _item_ {"*,*" _items_} "*]*" +
-<selector-case> ::= [<list>] <case-value>
+_item_ = _expression_ +
-<case-value> ::= "{" <multi-expr> "}"
+_case-multi-expression_ = "*{*" _multi-expression_ "*}*" +
-<multi-expr> ::= <expr> {";" <expr>}
+_multi-expression_ = _expression_ { "*;*" _expression_ } +
-----
+_default-multi-expression_ = _multi-expression_
 
-.Example
+In other words, the selector operator evaluates the _select-expression_ on the left-hand side of the [blue]`?` symbol; it then compares the result obtained with the values listed in the __match-list__'s, from left to right. If the comparision finds a match with a value in a _match-list_, the associated _case-multi-expression_ is evaluted, and its result will be the final result of the selection operation.
-[source,go]
+
-----
+The match lists are optional. In that case, the position, from left to right, of the _selector-case_ is used as _match-list_. Of course, that only works if the _select-expression_ results in an integer.
-1 ? {"a"} : {"b"}                           // returns "b"
+
-10 ? {"a"} : {"b"} :: {"c"}                 // returns "c"
+The [blue]`:` symbol (colon) is the separator of the selector-cases. Note that if the value of the _select-expression_ does not match any _match-list_, an error will be issued. Therefore, it is strongly recommended to provide a default (multi-)expression introduced by the [blue]`::` symbol (double-colon). Also note that the default expression has no _match-list_.
-10 ? {"a"} :[true, 2+8] {"b"} :: {"c"}      // returns "b"
+
-10 ? {"a"} :[true, 2+8] {"b"} ::[10] {"c"}  // error:  "... case list in default clause"
+.Examples
-10 ? {"a"} :[10] {x="b" but x} :: {"c"}     // returns "b"
+`>>>` [blue]`1 ? {"a"} : {"b"}` +
-10 ? {"a"} :[10] {x="b"; x} :: {"c"}        // returns "b"
+[green]`b` +
-10 ? {"a"} : {"b"}                          // error:  "... no case catches the value (10) of the selection expression
+`>>>` [blue]`10 ? {"a"} : {"b"} :: {"c"}` +
-----
+[green]`c' +
+[green]`>>>` [blue]`10 ? {"a"} :[true, 2+8] {"b"} :: {"c"}` +
+[green]`b` +
+`>>>` [blue]`10 ? {"a"} :[true, 2+8] {"b"} ::[10] {"c"}` +
+[red]`Parse Error: [1:34] case list in default clause` +
+[green]`>>>` [blue]`10 ? {"a"} :[10] {x="b" but x} :: {"c"}` +
+[green]`b` +
+`>>>` [blue]`10 ? {"a"} :[10] {x="b"; x} :: {"c"}` +
+[green]`b` +
+`>>>` [blue]`10 ? {"a"} : {"b"}` +
+[red]`Eval Error: [1:3] no case catches the value (10) of the selection expression`
+
+
+=== Variable default value [blue]`??` and [blue]`?=`
+The left operand of these two operators must be a variable. The right operator can be any expression. They return the value of the variable if this is define; otherwise they return the value of the right expression.
+
+IMPORTANT: If the left variable is defined, the right expression is not evuated at all.
+
+The [blue]`??` do not change the status of the left variable.
+
+The [blue]`?=` assigns the calculated value of the right expression to the left variable.
+
+.Examples
+`>>>` [blue]`var ?? (1+2)`'
+[green]`3` +
+`>>>` [blue]`var` +
+[red]`Eval Error: undefined variable or function "var"` +
+`>>>` [blue]`var ?= (1+2)` +
+[green]`3` +
+`>>>` [blue]`var` +
+[green]`3`
+
+NOTE: These operators have a high priority, in particular higher than the operator [blue]`=`.
 
 == Priorities of operators
 The table below shows all supported operators by decreasing priorities.
 
 .Operators priorities
-[cols="^2,^2,^2,^5,<5"]
+[cols="^2,^2,^2,^5,^6"]
 |===
 | Priority | Operators     | Position | Operation | Operands and results
 
-1+|*FACT*| [blue]`!` | _Postfix_ | _Factorial_| _integer_ "!" -> _integer_
+.2+|*ITEM*| [blue]`.` | _Infix_ | _List item_| _list_ `"."` _integer_ -> _any_
-1+|*SIGN*| [blue]`+`, [blue]`-` | _Prefix_ | _Change-sign_| ("+"\|"-") _number_ -> _number_
+| [blue]`.` | _Infix_ | _Dict item_ | _dict_ `"."` _any_ -> _any_
-.5+|*PROD*| [blue]`*` | _Infix_ | _Product_ | _number_ "*" _number_ -> _number_
+.2+|*INC*| [blue]`++` | _Postfix_ | _Post increment_| _integer-variable_ `"++"` -> _integer_
-| [blue]`*` | _Infix_ | _String-repeat_ | _string_ "*" _integer_ -> _string_
+| [blue]`++` | _Postfix_ | _Next item_ | _iterator_ `"++"` -> _any_
-| [blue]`/` | _Infix_ | _Division_ | _number_ "/" _number_ -> _number_
+.1+|*FACT*| [blue]`!` | _Postfix_ | _Factorial_| _integer_ `"!"` -> _integer_
-| [blue]`./` | _Infix_ | _Float-division_ | __number__ "./" _number_ -> _float_
+.3+|*SIGN*| [blue]`+`, [blue]`-` | _Prefix_ | _Change-sign_| (`"+"`\|`"-"`) _number_ -> _number_
-| [blue]`%` | _Infix_ | _Integer-remainder_ | _integer_ "%" _integer_ -> _integer_
+| [blue]`#` | _Prefix_ | _Lenght-of_ | `"#"` _collection_ -> _integer_
-.5+|*SUM*| [blue]`+` | _Infix_ | _Sum_ | _number_ "+" _number_ -> _number_
+| [blue]`#` | _Prefix_ | _Size-of_ | `"#"` _iterator_ -> _integer_
-| [blue]`+` | _Infix_ |  _String-concat_ | (_string_\|_number_) "+" (_string_\|_number_) -> _string_
+.5+|*PROD*| [blue]`*` | _Infix_ | _Product_ | _number_ `"*"` _number_ -> _number_
-| [blue]`+` | _Infix_ |  _List-join_ | _list_ "+" _list_ -> _list_
+| [blue]`*` | _Infix_ | _String-repeat_ | _string_ `"*"` _integer_ -> _string_
-| [blue]`-` | _Infix_ | _Subtraction_ | _number_ "-" _number_ -> _number_
+| [blue]`/` | _Infix_ | _Division_ | _number_ `"/"` _number_ -> _number_
-| [blue]`-` | _Infix_ | _List-difference_ | _list_ "-" _list_ -> _list_
+| [blue]`./` | _Infix_ | _Float-division_ | __number__ `"./"` _number_ -> _float_
-.6+|*RELATION*| [blue]`<` | _Infix_ | _less_ | _comparable_ "<" _comparable_ -> _boolean_
+| [blue]`%` | _Infix_ | _Integer-remainder_ | _integer_ `"%"` _integer_ -> _integer_
-| [blue]`\<=` | _Infix_ |  _less-equal_ | _comparable_ "\<=" _comparable_ -> _boolean_
+.6+|*SUM*| [blue]`+` | _Infix_ | _Sum_ | _number_ `"+"` _number_ -> _number_
-| [blue]`>` | _Infix_ |  _greater_ | _comparable_ ">" _comparable_ -> _boolean_
+| [blue]`+` | _Infix_ |  _String-concat_ | (_string_\|_number_) `"+"` (_string_\|_number_) -> _string_
-| [blue]`>=` | _Infix_ |  _greater-equal_ | _comparable_ ">=" _comparable_ -> _boolean_
+| [blue]`+` | _Infix_ |  _List-join_ | _list_ `"+"` _list_ -> _list_
-| [blue]`==` | _Infix_ |  _equal_ | _comparable_ "==" _comparable_ -> _boolean_
+| [blue]`+` | _Infix_ |  _Dict-join_ | _dict_ `"+"` _dict_ -> _dict_
-| [blue]`!=` | _Infix_ |  _not-equal_ | _comparable_ "!=" _comparable_ -> _boolean_
+| [blue]`-` | _Infix_ | _Subtraction_ | _number_ `"-"` _number_ -> _number_
-.1+|*NOT*| [blue]`not` | _Prefix_ | _not_ | "not" _boolean_ -> _boolean_
+| [blue]`-` | _Infix_ | _List-difference_ | _list_ `"-"` _list_ -> _list_
-.2+|*AND*| [blue]`and` | _Infix_ | _and_ | _boolean_ "and" _boolean_ -> _boolean_
+.8+|*RELATION*| [blue]`<` | _Infix_ | _less_ | _comparable_ `"<"` _comparable_ -> _boolean_
-| [blue]`&&` | _Infix_ | _and_ | _boolean_ "&&" _boolean_ -> _boolean_
+| [blue]`\<=` | _Infix_ |  _less-equal_ | _comparable_ `"\<="` _comparable_ -> _boolean_
-.2+|*OR*| [blue]`or` | _Infix_ | _or_ | _boolean_ "or" _boolean_ -> _boolean_
+| [blue]`>` | _Infix_ |  _greater_ | _comparable_ `">"` _comparable_ -> _boolean_
-| [blue]`\|\|` | _Infix_ | _or_ | _boolean_ "\|\|" _boolean_ -> _boolean_
+| [blue]`>=` | _Infix_ |  _greater-equal_ | _comparable_ `">="` _comparable_ -> _boolean_
-.1+|*ASSIGN*| [blue]`=` | _Infix_ | _assignment_ | _identifier_ "=" _any_ -> _any_
+| [blue]`==` | _Infix_ |  _equal_ | _comparable_ `"=="` _comparable_ -> _boolean_
-.1+|*BUT*| [blue]`but` | _Infix_ | _but_ | _any_ "but" _any_ -> _any_
+| [blue]`!=` | _Infix_ |  _not-equal_ | _comparable_ `"!="` _comparable_ -> _boolean_
+| [blue]`in` | _Infix_ |  _member-of-list_ | _any_ `"in"` _list_ -> _boolean_
+| [blue]`in` | _Infix_ |  _key-of-dict_ | _any_ `"in"` _dict_ -> _boolean_
+.1+|*NOT*| [blue]`not` | _Prefix_ | _not_ | `"not"` _boolean_ -> _boolean_
+.2+|*AND*| [blue]`and` | _Infix_ | _and_ | _boolean_ `"and"` _boolean_ -> _boolean_
+| [blue]`&&` | _Infix_ | _and_ | _boolean_ `"&&"` _boolean_ -> _boolean_
+.2+|*OR*| [blue]`or` | _Infix_ | _or_ | _boolean_ `"or"` _boolean_ -> _boolean_
+| [blue]`\|\|` | _Infix_ | _or_ | _boolean_ `"\|\|"` _boolean_ -> _boolean_
+.3+|*ASSIGN*| [blue]`=` | _Infix_ | _assignment_ | _identifier_ "=" _any_ -> _any_
+| [blue]`>>` | _Infix_ | _front-insert_ | _any_ ">>" _list_ -> _list_
+| [blue]`<<` | _Infix_ | _back-insert_ | _list_ "<<" _any_ -> _list_
+ .1+|*BUT*| [blue]`but` | _Infix_ | _but_ | _any_ "but" _any_ -> _any_
 |===
 
 == Functions

expr_test.go

@@ -5,7 +5,6 @@
 package expr
 
 import (
-	"fmt"
 	"strings"
 	"testing"
 )
@@ -22,13 +21,8 @@ func TestExpr(t *testing.T) {
 		/*   2 */ {`fact=func(n){(n)?{1}::{n*fact(n-1)}}; fact(5)`, int64(120), nil},
 		/*   3 */ {`f=openFile("test-file.txt"); line=readFile(f); closeFile(f); line`, "uno", nil},
 		/*   4 */ {`mynot=func(v){int(v)?{true}::{false}}; mynot(0)`, true, nil},
-	}
+		/*   5 */ {`1 ? {1} : [1+0] {3*(1+1)}`, int64(6), nil},
-
+		/*   6 */ {`
-	succeeded := 0
-	failed := 0
-
-	inputs1 := []inputType{
-		/*   1 */ {`
 		ds={
 			"init":func(end){@end=end; @current=0 but true},
 			"current":func(){current},
@@ -42,18 +36,21 @@ func TestExpr(t *testing.T) {
 `, int64(1), nil},
 	}
 
-	for i, input := range inputs1 {
+	succeeded := 0
+	failed := 0
+
+	for i, input := range inputs {
 		var expr Expr
 		var gotResult any
 		var gotErr error
 
-		ctx := NewSimpleFuncStore()
+		ctx := NewSimpleStore()
 		// ImportMathFuncs(ctx)
 		// ImportImportFunc(ctx)
 		ImportOsFuncs(ctx)
 		parser := NewParser(ctx)
 
-		logTest(t, i+1, input.source, input.wantResult, input.wantErr)
+		logTest(t, i+1, "Expr", input.source, input.wantResult, input.wantErr)
 
 		r := strings.NewReader(input.source)
 		scanner := NewScanner(r, DefaultTranslations())
@@ -81,5 +78,5 @@ func TestExpr(t *testing.T) {
 			failed++
 		}
 	}
-	t.Log(fmt.Sprintf("test count: %d, succeeded count: %d, failed count: %d", len(inputs), succeeded, failed))
+	t.Logf("test count: %d, succeeded count: %d, failed count: %d", len(inputs), succeeded, failed)
 }

file-reader.expr

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

formatter.go

@@ -0,0 +1,65 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// formatter.go
+package expr
+
+import "fmt"
+
+type FmtOpt uint16
+
+const (
+	TTY FmtOpt = 1 << iota
+	MultiLine
+	Truncate
+	Base2
+	Base8
+	Base10
+	Base16
+)
+
+const (
+	TruncateEllipsis = "(...)"
+	MinTruncateSize  = 10
+	TruncateSize     = MinTruncateSize + 15
+)
+
+func TruncateString(s string) (trunc string) {
+	finalPart := len(s) - (MinTruncateSize - len(TruncateEllipsis))
+	trunc = s[0:len(s)-MinTruncateSize] + TruncateEllipsis + s[finalPart:]
+	return
+}
+
+type Formatter interface {
+	ToString(options FmtOpt) string
+}
+
+func getFormatted(v any, opt FmtOpt) (text string) {
+	if v == nil {
+		text = "(nil)"
+	} else if s, ok := v.(string); ok {
+		text = s
+	} else if formatter, ok := v.(Formatter); ok {
+		text = formatter.ToString(opt)
+	} else {
+		text = fmt.Sprintf("%v", v)
+	}
+	return
+}
+
+type Typer interface {
+	TypeName() string
+}
+
+func getTypeName(v any) (name string) {
+	if typer, ok := v.(Typer); ok {
+		name = typer.TypeName()
+	} else if IsInteger(v) {
+		name = "integer"
+	} else if IsFloat(v) {
+		name = "float"
+	} else {
+		name = fmt.Sprintf("%T", v)
+	}
+	return
+}

func-base.go

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

func-builtins.go

@@ -1,59 +0,0 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
-// All rights reserved.
-
-// func-builtins.go
-package expr
-
-import (
-	"math"
-	"strconv"
-)
-
-func isNilFunc(ctx ExprContext, name string, args []any) (result any, err error) {
-	if len(args) == 1 {
-		result = args[0] == nil
-	} else {
-		err = errOneParam(name)
-	}
-	return
-}
-
-func intFunc(ctx ExprContext, name string, args []any) (result any, err error) {
-	if len(args) == 1 {
-		switch v := args[0].(type) {
-		case int64:
-			result = v
-		case float64:
-			result = int64(math.Trunc(v))
-		case bool:
-			if v {
-				result = int64(1)
-			} else {
-				result = int64(0)
-			}
-		case string:
-			var i int
-			if i, err = strconv.Atoi(v); err == nil {
-				result = int64(i)
-			}
-		default:
-			err = errCantConvert(name, v, "int")
-		}
-	} else {
-		err = errOneParam(name)
-	}
-	return
-}
-
-func iteratorFunc(ctx ExprContext, name string, args []any) (result any, err error) {
-	return
-}
-
-func ImportBuiltinsFuncs(ctx ExprContext) {
-	ctx.RegisterFunc("isNil", &simpleFunctor{f: isNilFunc}, 1, -1)
-	ctx.RegisterFunc("int", &simpleFunctor{f: intFunc}, 1, -1)
-}
-
-func init() {
-	registerImport("builtins", ImportBuiltinsFuncs)
-}

func-common.go

@@ -1,17 +0,0 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
-// All rights reserved.
-
-// func-common.go
-package expr
-
-import (
-	"fmt"
-)
-
-func errOneParam(funcName string) error {
-	return fmt.Errorf("%s() requires exactly one param", funcName)
-}
-
-func errCantConvert(funcName string, value any, kind string) error {
-	return fmt.Errorf("%s() can't convert %T to %s", funcName, value, kind)
-}

func-import.go

@@ -20,7 +20,7 @@ func importFunc(ctx ExprContext, name string, args []any) (result any, err error
 	return importGeneral(ctx, name, args)
 }
 
-func includeFunc(ctx ExprContext, name string, args []any) (result any, err error) {
+func importAllFunc(ctx ExprContext, name string, args []any) (result any, err error) {
 	enable(ctx, control_export_all)
 	return importGeneral(ctx, name, args)
 }
@@ -30,12 +30,12 @@ func importGeneral(ctx ExprContext, name string, args []any) (result any, err er
 
 	dirList = addEnvImportDirs(dirList)
 	dirList = addPresetImportDirs(ctx, dirList)
-	result, err = doImport(ctx, name, dirList, NewFlatArrayIterator(args))
+	result, err = doImport(ctx, name, dirList, NewArrayIterator(args))
 	return
 }
 
 func checkStringParamExpected(funcName string, paramValue any, paramPos int) (err error) {
-	if !(isString(paramValue) /*|| isList(paramValue)*/) {
+	if !(IsString(paramValue) /*|| isList(paramValue)*/) {
 		err = fmt.Errorf("%s(): param nr %d has wrong type %T, string expected", funcName, paramPos+1, paramValue)
 	}
 	return
@@ -137,10 +137,14 @@ func doImport(ctx ExprContext, name string, dirList []string, it Iterator) (resu
 }
 
 func ImportImportFuncs(ctx ExprContext) {
-	ctx.RegisterFunc("import", &simpleFunctor{f: importFunc}, 1, -1)
+	ctx.RegisterFunc("import", newGolangFunctor(importFunc), typeAny, []ExprFuncParam{
-	ctx.RegisterFunc("include", &simpleFunctor{f: includeFunc}, 1, -1)
+		newFuncParamFlag(typeFilepath, pfRepeat),
+	})
+	ctx.RegisterFunc("importAll", newGolangFunctor(importAllFunc), typeAny, []ExprFuncParam{
+		newFuncParamFlag(typeFilepath, pfRepeat),
+	})
 }
 
 func init() {
-	registerImport("import", ImportImportFuncs)
+	registerImport("import", ImportImportFuncs, "Functions import() and include()")
 }

func-math.go

@@ -9,41 +9,65 @@ import (
 	"io"
 )
 
-func checkNumberParamExpected(funcName string, paramValue any, paramPos int) (err error) {
+func checkNumberParamExpected(funcName string, paramValue any, paramPos, level, subPos int) (err error) {
-	if !(isNumber(paramValue) || isList(paramValue)) {
+	if !(IsNumber(paramValue) || isFraction(paramValue)) /*|| isList(paramValue)*/ {
-		err = fmt.Errorf("%s(): param nr %d has wrong type %T, number expected", funcName, paramPos+1, 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) (result any, err error) {
+func doAdd(ctx ExprContext, name string, it Iterator, count, level int) (result any, err error) {
-	var sumAsFloat = false
+	var sumAsFloat, sumAsFract bool
 	var floatSum float64 = 0.0
 	var intSum int64 = 0
+	var fractSum *fraction
 	var v any
 
+	level++
+
 	for v, err = it.Next(); err == nil; v, err = it.Next() {
+		if list, ok := v.(*ListType); ok {
+			v = NewListIterator(list, nil)
+		}
 		if subIter, ok := v.(Iterator); ok {
-			if v, err = doAdd(ctx, name, subIter); err != nil {
+			if v, err = doAdd(ctx, name, subIter, count, level); err != nil {
 				break
 			}
-		} else {
+			if extIter, ok := v.(ExtIterator); ok && extIter.HasOperation(cleanName) {
-			if err = checkNumberParamExpected(name, v, it.Index()); err != nil {
+				if _, err = extIter.CallOperation(cleanName, nil); err != nil {
-				break
+					return
-			}
-			if array, ok := v.([]any); ok {
-				if v, err = doAdd(ctx, name, NewFlatArrayIterator(array)); err != nil {
-					break
 				}
 			}
+		} else if err = checkNumberParamExpected(name, v, count, level, it.Index()); err != nil {
+			break
+		}
+		count++
+
+		if !sumAsFloat {
+			if IsFloat(v) {
+				sumAsFloat = true
+				if sumAsFract {
+					floatSum = fractSum.toFloat()
+				} else {
+					floatSum = float64(intSum)
+				}
+			} else if !sumAsFract && isFraction(v) {
+				fractSum = newFraction(intSum, 1)
+				sumAsFract = true
+			}
 		}
 
-		if !sumAsFloat && isFloat(v) {
-			sumAsFloat = true
-			floatSum = float64(intSum)
-		}
 		if sumAsFloat {
 			floatSum += numAsFloat(v)
+		} else if sumAsFract {
+			var item *fraction
+			var ok bool
+			if item, ok = v.(*fraction); !ok {
+				iv, _ := v.(int64)
+				item = newFraction(iv, 1)
+			}
+			fractSum = sumFract(fractSum, item)
 		} else {
 			iv, _ := v.(int64)
 			intSum += iv
@@ -53,6 +77,8 @@ func doAdd(ctx ExprContext, name string, it Iterator) (result any, err error) {
 		err = nil
 		if sumAsFloat {
 			result = floatSum
+		} else if sumAsFract {
+			result = fractSum
 		} else {
 			result = intSum
 		}
@@ -61,33 +87,62 @@ func doAdd(ctx ExprContext, name string, it Iterator) (result any, err error) {
 }
 
 func addFunc(ctx ExprContext, name string, args []any) (result any, err error) {
-	result, err = doAdd(ctx, name, NewFlatArrayIterator(args))
+	result, err = doAdd(ctx, name, NewArrayIterator(args), 0, -1)
 	return
 }
 
-func doMul(ctx ExprContext, name string, it Iterator) (result any, err error) {
+func doMul(ctx ExprContext, name string, it Iterator, count, level int) (result any, err error) {
-	var mulAsFloat = false
+	var mulAsFloat, mulAsFract bool
 	var floatProd float64 = 1.0
 	var intProd int64 = 1
+	var fractProd *fraction
 	var v any
 
+	level++
 	for v, err = it.Next(); err == nil; v, err = it.Next() {
-		if err = checkNumberParamExpected(name, v, it.Index()); err != nil {
+		if list, ok := v.(*ListType); ok {
-			break
+			v = NewListIterator(list, nil)
 		}
-
+		if subIter, ok := v.(Iterator); ok {
-		if array, ok := v.([]any); ok {
+			if v, err = doMul(ctx, name, subIter, count, level); err != nil {
-			if v, err = doAdd(ctx, name, NewFlatArrayIterator(array)); err != nil {
+				break
+			}
+			if extIter, ok := v.(ExtIterator); ok && extIter.HasOperation(cleanName) {
+				if _, err = extIter.CallOperation(cleanName, nil); err != nil {
+					return
+				}
+			}
+		} else {
+			if err = checkNumberParamExpected(name, v, count, level, it.Index()); err != nil {
 				break
 			}
 		}
+		count++
 
-		if !mulAsFloat && isFloat(v) {
+		if !mulAsFloat {
-			mulAsFloat = true
+			if IsFloat(v) {
-			floatProd = float64(intProd)
+				mulAsFloat = true
+				if mulAsFract {
+					floatProd = fractProd.toFloat()
+				} else {
+					floatProd = float64(intProd)
+				}
+			} else if !mulAsFract && isFraction(v) {
+				fractProd = newFraction(intProd, 1)
+				mulAsFract = true
+			}
 		}
+
 		if mulAsFloat {
 			floatProd *= numAsFloat(v)
+		} else if mulAsFract {
+			var item *fraction
+			var ok bool
+			if item, ok = v.(*fraction); !ok {
+				iv, _ := v.(int64)
+				item = newFraction(iv, 1)
+			}
+			fractProd = mulFract(fractProd, item)
 		} else {
 			iv, _ := v.(int64)
 			intProd *= iv
@@ -97,6 +152,8 @@ func doMul(ctx ExprContext, name string, it Iterator) (result any, err error) {
 		err = nil
 		if mulAsFloat {
 			result = floatProd
+		} else if mulAsFract {
+			result = fractProd
 		} else {
 			result = intProd
 		}
@@ -105,15 +162,20 @@ func doMul(ctx ExprContext, name string, it Iterator) (result any, err error) {
 }
 
 func mulFunc(ctx ExprContext, name string, args []any) (result any, err error) {
-	result, err = doMul(ctx, name, NewFlatArrayIterator(args))
+	result, err = doMul(ctx, name, NewArrayIterator(args), 0, -1)
 	return
 }
 
 func ImportMathFuncs(ctx ExprContext) {
-	ctx.RegisterFunc("add", &simpleFunctor{f: addFunc}, 0, -1)
+	ctx.RegisterFunc("add", &golangFunctor{f: addFunc}, typeNumber, []ExprFuncParam{
-	ctx.RegisterFunc("mul", &simpleFunctor{f: mulFunc}, 0, -1)
+		newFuncParamFlagDef(paramValue, pfOptional|pfRepeat, 0),
+	})
+
+	ctx.RegisterFunc("mul", &golangFunctor{f: mulFunc}, typeNumber, []ExprFuncParam{
+		newFuncParamFlagDef(paramValue, pfOptional|pfRepeat, 1),
+	})
 }
 
 func init() {
-	registerImport("math.arith", ImportMathFuncs)
+	registerImport("math.arith", ImportMathFuncs, "Functions add() and mul()")
 }

func-os.go

@@ -126,7 +126,7 @@ func writeFileFunc(ctx ExprContext, name string, args []any) (result any, err er
 
 func readFileFunc(ctx ExprContext, name string, args []any) (result any, err error) {
 	var handle osHandle
-
+	result = nil
 	if len(args) > 0 {
 		handle, _ = args[0].(osHandle)
 	}
@@ -141,13 +141,16 @@ func readFileFunc(ctx ExprContext, name string, args []any) (result any, err err
 						limit = s[0]
 					}
 				}
-				if v, err = r.reader.ReadString(limit); err == nil || err == io.EOF {
+				if v, err = r.reader.ReadString(limit); err == nil {
 					if len(v) > 0 && v[len(v)-1] == limit {
 						result = v[0 : len(v)-1]
 					} else {
 						result = v
 					}
 				}
+				if err == io.EOF {
+					err = nil
+				}
 			}
 		}
 	}
@@ -155,14 +158,28 @@ func readFileFunc(ctx ExprContext, name string, args []any) (result any, err err
 }
 
 func ImportOsFuncs(ctx ExprContext) {
-	ctx.RegisterFunc("openFile", &simpleFunctor{f: openFileFunc}, 1, 1)
+	ctx.RegisterFunc("openFile", newGolangFunctor(openFileFunc), typeHandle, []ExprFuncParam{
-	ctx.RegisterFunc("appendFile", &simpleFunctor{f: appendFileFunc}, 1, 1)
+		newFuncParam(typeFilepath),
-	ctx.RegisterFunc("createFile", &simpleFunctor{f: createFileFunc}, 1, 1)
+	})
-	ctx.RegisterFunc("writeFile", &simpleFunctor{f: writeFileFunc}, 1, -1)
+	ctx.RegisterFunc("appendFile", newGolangFunctor(appendFileFunc), typeHandle, []ExprFuncParam{
-	ctx.RegisterFunc("readFile", &simpleFunctor{f: readFileFunc}, 1, 2)
+		newFuncParam(typeFilepath),
-	ctx.RegisterFunc("closeFile", &simpleFunctor{f: closeFileFunc}, 1, 1)
+	})
+	ctx.RegisterFunc("createFile", newGolangFunctor(createFileFunc), typeHandle, []ExprFuncParam{
+		newFuncParam(typeFilepath),
+	})
+	ctx.RegisterFunc("writeFile", newGolangFunctor(writeFileFunc), typeInt, []ExprFuncParam{
+		newFuncParam(typeHandle),
+		newFuncParamFlagDef(typeItem, pfOptional|pfRepeat, ""),
+	})
+	ctx.RegisterFunc("readFile", newGolangFunctor(readFileFunc), typeString, []ExprFuncParam{
+		newFuncParam(typeHandle),
+		newFuncParamFlagDef("limitCh", pfOptional, "\\n"),
+	})
+	ctx.RegisterFunc("closeFile", newGolangFunctor(closeFileFunc), typeBoolean, []ExprFuncParam{
+		newFuncParam(typeHandle),
+	})
 }
 
 func init() {
-	registerImport("os", ImportOsFuncs)
+	registerImport("os.file", ImportOsFuncs, "Operating system file functions")
 }

func-string.go

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

funcs_test.go

@@ -6,18 +6,10 @@ package expr
 
 import (
 	"errors"
-	"fmt"
-	"strings"
 	"testing"
 )
 
 func TestFuncs(t *testing.T) {
-	type inputType struct {
-		source     string
-		wantResult any
-		wantErr    error
-	}
-
 	inputs := []inputType{
 		/*   1 */ {`isNil(nil)`, true, nil},
 		/*   2 */ {`v=nil; isNil(v)`, true, nil},
@@ -28,55 +20,97 @@ func TestFuncs(t *testing.T) {
 		/*   7 */ {`int(3.9)`, int64(3), nil},
 		/*   8 */ {`int("432")`, int64(432), nil},
 		/*   9 */ {`int("1.5")`, nil, errors.New(`strconv.Atoi: parsing "1.5": invalid syntax`)},
-		/*  10 */ {`int("432", 4)`, nil, errors.New(`int() requires exactly one param`)},
+		/*  10 */ {`int("432", 4)`, nil, errors.New(`too much params -- expected 1, got 2`)},
 		/*  11 */ {`int(nil)`, nil, errors.New(`int() can't convert <nil> to int`)},
+		/*  12 */ {`two=func(){2}; two()`, int64(2), nil},
+		/*  13 */ {`double=func(x) {2*x}; (double(3))`, int64(6), nil},
+		/*  14 */ {`double=func(x){2*x}; double(3)`, int64(6), nil},
+		/*  15 */ {`double=func(x){2*x}; a=5; double(3+a) + 1`, int64(17), nil},
+		/*  16 */ {`double=func(x){2*x}; a=5; two=func() {2}; (double(3+a) + 1) * two()`, int64(34), nil},
+		/*  17 */ {`builtin "import"; import("./test-funcs.expr"); (double(3+a) + 1) * two()`, int64(34), nil},
+		/*  18 */ {`builtin "import"; import("test-funcs.expr"); (double(3+a) + 1) * two()`, int64(34), nil},
+		/*  19 */ {`@x="hello"; @x`, nil, errors.New(`[1:3] variable references are not allowed in top level expressions: "@x"`)},
+		/*  20 */ {`f=func(){@x="hello"}; f(); x`, "hello", nil},
+		/*  21 */ {`f=func(@y){@y=@y+1}; f(2); y`, int64(3), nil},
+		/*  22 */ {`f=func(@y){g=func(){@x=5}; @y=@y+g()}; f(2); y+x`, nil, errors.New(`undefined variable or function "x"`)},
+		/*  23 */ {`f=func(@y){g=func(){@x=5}; @z=g(); @y=@y+@z}; f(2); y+z`, int64(12), nil},
+		/*  24 */ {`f=func(@y){g=func(){@x=5}; g(); @z=x; @y=@y+@z}; f(2); y+z`, int64(12), nil},
+		/*  25 */ {`f=func(@y){g=func(){@x=5}; g(); @z=x; @x=@y+@z}; f(2); y+x`, int64(9), nil},
+		/*  26 */ {`builtin "import"; importAll("./test-funcs.expr"); six()`, int64(6), nil},
+		/*  27 */ {`builtin "import"; import("./sample-export-all.expr"); six()`, int64(6), nil},
+		/*  28 */ {`builtin "string"; joinStr("-", "one", "two", "three")`, "one-two-three", nil},
+		/*  29 */ {`builtin "string"; joinStr("-", ["one", "two", "three"])`, "one-two-three", nil},
+		/*  30 */ {`builtin "string"; ls= ["one", "two", "three"]; joinStr("-", ls)`, "one-two-three", nil},
+		/*  31 */ {`builtin "string"; ls= ["one", "two", "three"]; joinStr(1, ls)`, nil, errors.New(`joinStr() the "separator" parameter must be a string, got a int64 (1)`)},
+		/*  32 */ {`builtin "string"; ls= ["one", 2, "three"]; joinStr("-", ls)`, nil, errors.New(`joinStr() expected string, got int64 (2)`)},
+		/*  33 */ {`builtin "string"; "<"+trimStr("  bye bye  ")+">"`, "<bye bye>", nil},
+		/*  34 */ {`builtin "string"; subStr("0123456789", 1,2)`, "12", nil},
+		/*  35 */ {`builtin "string"; subStr("0123456789", -3,2)`, "78", nil},
+		/*  36 */ {`builtin "string"; subStr("0123456789", -3)`, "789", nil},
+		/*  37 */ {`builtin "string"; subStr("0123456789")`, "0123456789", nil},
+		/*  38 */ {`builtin "string"; startsWithStr("0123456789", "xyz", "012")`, true, nil},
+		/*  39 */ {`builtin "string"; startsWithStr("0123456789", "xyz", "0125")`, false, nil},
+		/*  40 */ {`builtin "string"; startsWithStr("0123456789")`, nil, errors.New(`too few params -- expected 2 or more, got 1`)},
+		/*  41 */ {`builtin "string"; endsWithStr("0123456789", "xyz", "789")`, true, nil},
+		/*  42 */ {`builtin "string"; endsWithStr("0123456789", "xyz", "0125")`, false, nil},
+		/*  43 */ {`builtin "string"; endsWithStr("0123456789")`, nil, errors.New(`too few params -- expected 2 or more, got 1`)},
+		/*  44 */ {`builtin "string"; splitStr("one-two-three", "-", )`, newListA("one", "two", "three"), nil},
+		/*  45 */ {`isInt(2+1)`, true, nil},
+		/*  46 */ {`isInt(3.1)`, false, nil},
+		/*  47 */ {`isFloat(3.1)`, true, nil},
+		/*  48 */ {`isString("3.1")`, true, nil},
+		/*  49 */ {`isString("3" + 1)`, true, nil},
+		/*  50 */ {`isList(["3",  1])`, true, nil},
+		/*  51 */ {`isDict({"a":"3",  "b":1})`, true, nil},
+		/*  52 */ {`isFract(1|3)`, true, nil},
+		/*  53 */ {`isFract(3|1)`, false, nil},
+		/*  54 */ {`isRational(3|1)`, true, nil},
+		/*  55 */ {`builtin "math.arith"; add(1,2)`, int64(3), nil},
+		/*  56 */ {`fract("2.2(3)")`, newFraction(67, 30), nil},
+		/*  57 */ {`fract("1.21(3)")`, newFraction(91, 75), nil},
+		/*  58 */ {`fract(1.21(3))`, newFraction(91, 75), nil},
+		/*  59 */ {`fract(1.21)`, newFraction(121, 100), nil},
+		/*  60 */ {`dec(2)`, float64(2), nil},
+		/*  61 */ {`dec(2.0)`, float64(2), nil},
+		/*  62 */ {`dec("2.0")`, float64(2), nil},
+		/*  63 */ {`dec(true)`, float64(1), nil},
+		/*  64 */ {`dec(true")`, nil, errors.New("[1:11] missing string termination \"")},
+		/*  65 */ {`builtin "string"; joinStr("-", [1, "two", "three"])`, nil, errors.New(`joinStr() expected string, got int64 (1)`)},
+		/*  66 */ {`dec()`, nil, errors.New(`too few params -- expected 1, got 0`)},
+		/*  67 */ {`dec(1,2,3)`, nil, errors.New(`too much params -- expected 1, got 3`)},
+		/*  68 */ {`builtin "string"; joinStr()`, nil, errors.New(`too few params -- expected 1 or more, got 0`)},
+		/*  69 */ /*{`builtin "string"; $$global`, `vars: {
+
+		}
+		funcs: {
+		    	add(any=0 ...) -> number,
+		    	dec(any) -> decimal,
+		    	endsWithStr(source, suffix) -> boolean,
+		    	fract(any, denominator=1) -> fraction,
+		    	import( ...) -> any,
+		    	importAll( ...) -> any,
+		    	int(any) -> integer,
+		    	isBool(any) -> boolean,
+		    	isDec(any) -> boolean,
+		    	isDict(any) -> boolean,
+		    	isFloat(any) -> boolean,
+		    	isFract(any) -> boolean,
+		    	isInt(any) -> boolean,
+		    	isList(any) -> boolean,
+		    	isNil(any) -> boolean,
+		    	isString(any) -> boolean,
+		    	joinStr(separator, item="" ...) -> string,
+		    	mul(any=1 ...) -> number,
+		    	splitStr(source, separator="", count=-1) -> list of string,
+		    	startsWithStr(source, prefix) -> boolean,
+		    	subStr(source, start=0, count=-1) -> string,
+		    	trimStr(source) -> string
+		}
+		`, nil},*/
 	}
 
-	succeeded := 0
+	t.Setenv("EXPR_PATH", ".")
-	failed := 0
 
-	// inputs1 := []inputType{
+	// parserTestSpec(t, "Func", inputs, 69)
-	// 	/*   1 */ {`0?{}`, nil, nil},
+	parserTest(t, "Func", inputs)
-	// }
-
-	for i, input := range inputs {
-		var expr Expr
-		var gotResult any
-		var gotErr error
-
-		ctx := NewSimpleFuncStore()
-		// ImportMathFuncs(ctx)
-		// ImportImportFunc(ctx)
-		// ImportOsFuncs(ctx)
-		parser := NewParser(ctx)
-
-		logTest(t, i+1, input.source, input.wantResult, input.wantErr)
-
-		r := strings.NewReader(input.source)
-		scanner := NewScanner(r, DefaultTranslations())
-
-		good := true
-		if expr, gotErr = parser.Parse(scanner); gotErr == nil {
-			gotResult, gotErr = expr.Eval(ctx)
-		}
-
-		if gotResult != input.wantResult {
-			t.Errorf("%d: %q -> result = %v [%T], want %v [%T]", i+1, input.source, gotResult, gotResult, input.wantResult, input.wantResult)
-			good = false
-		}
-
-		if gotErr != input.wantErr {
-			if input.wantErr == nil || gotErr == nil || (gotErr.Error() != input.wantErr.Error()) {
-				t.Errorf("%d: %q -> err = <%v>, want <%v>", i+1, input.source, gotErr, input.wantErr)
-				good = false
-			}
-		}
-
-		if good {
-			succeeded++
-		} else {
-			failed++
-		}
-	}
-	t.Log(fmt.Sprintf("test count: %d, succeeded count: %d, failed count: %d", len(inputs), succeeded, failed))
 }

function-register.go

@@ -1,47 +0,0 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
-// All rights reserved.
-
-// function-register.go
-package expr
-
-import (
-	"path/filepath"
-)
-
-var functionRegister map[string]func(ExprContext)
-
-func registerImport(name string, importFunc func(ExprContext)) {
-	if functionRegister == nil {
-		functionRegister = make(map[string]func(ExprContext))
-	}
-	functionRegister[name] = importFunc
-}
-
-func ImportInContext(ctx ExprContext, name string) (exists bool) {
-	var importFunc func(ExprContext)
-	if importFunc, exists = functionRegister[name]; exists {
-		importFunc(ctx)
-	}
-	return
-}
-
-func ImportInContextByGlobPattern(ctx ExprContext, pattern string) (count int, err error) {
-	var matched bool
-	for name, importFunc := range functionRegister {
-		if matched, err = filepath.Match(pattern, name); err == nil {
-			if matched {
-				count++
-				importFunc(ctx)
-			}
-		} else {
-			break
-		}
-	}
-	return
-}
-
-func init() {
-	if functionRegister == nil {
-		functionRegister = make(map[string]func(ExprContext))
-	}
-}

function.go

@@ -0,0 +1,232 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// function.go
+package expr
+
+import (
+	"fmt"
+	"strings"
+)
+
+// ---- Function template
+type FuncTemplate func(ctx ExprContext, name string, args []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() {<body>}"
+	}
+	return s
+}
+
+func (functor *baseFunctor) SetFunc(info ExprFunc) {
+	functor.info = info
+}
+
+func (functor *baseFunctor) GetFunc() ExprFunc {
+	return functor.info
+}
+
+// ---- Linking with the functions of Go
+type golangFunctor struct {
+	baseFunctor
+	f FuncTemplate
+}
+
+func newGolangFunctor(f FuncTemplate) *golangFunctor {
+	return &golangFunctor{f: f}
+}
+
+func (functor *golangFunctor) Invoke(ctx ExprContext, name string, args []any) (result any, err error) {
+	return functor.f(ctx, name, args)
+}
+
+// ---- Linking with the functions of Expr
+type exprFunctor struct {
+	baseFunctor
+	params []string
+	expr   Expr
+}
+
+func newExprFunctor(e Expr, params []string) *exprFunctor {
+	return &exprFunctor{expr: e, params: params}
+}
+
+func (functor *exprFunctor) Invoke(ctx ExprContext, name string, args []any) (result any, err error) {
+	for i, p := range functor.params {
+		if i < len(args) {
+			arg := args[i]
+			if funcArg, ok := arg.(Functor); ok {
+				// ctx.RegisterFunc(p, functor, 0, -1)
+				ctx.RegisterFunc(p, funcArg, typeAny, []ExprFuncParam{
+					newFuncParam(paramValue),
+				})
+			} else {
+				ctx.UnsafeSetVar(p, arg)
+			}
+		} else {
+			ctx.UnsafeSetVar(p, nil)
+		}
+	}
+	result, err = functor.expr.eval(ctx, false)
+	return
+}
+
+// ---- Function Parameters
+type paramFlags uint16
+
+const (
+	pfOptional paramFlags = 1 << iota
+	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 "any"
+}
+
+func (param *funcParamInfo) IsOptional() bool {
+	return (param.flags & pfOptional) != 0
+}
+
+func (param *funcParamInfo) IsRepeat() bool {
+	return (param.flags & pfRepeat) != 0
+}
+
+func (param *funcParamInfo) DefaultValue() any {
+	return param.defaultValue
+}
+
+// --- Functions
+type funcInfo struct {
+	name       string
+	minArgs    int
+	maxArgs    int
+	functor    Functor
+	params     []ExprFuncParam
+	returnType string
+}
+
+func newFuncInfo(name string, functor Functor, returnType string, params []ExprFuncParam) (info *funcInfo, err error) {
+	var minArgs = 0
+	var maxArgs = 0
+	if params != nil {
+		for _, p := range params {
+			if maxArgs == -1 {
+				return nil, fmt.Errorf("no more params can be specified after the ellipsis symbol: %q", p.Name())
+			}
+			if p.IsOptional() {
+				maxArgs++
+			} else if maxArgs == minArgs {
+				minArgs++
+				maxArgs++
+			} else {
+				return nil, fmt.Errorf("can't specify non-optional param after optional ones: %q", p.Name())
+			}
+			if p.IsRepeat() {
+				maxArgs = -1
+			}
+		}
+	}
+	info = &funcInfo{
+		name: name, minArgs: minArgs, maxArgs: maxArgs, functor: functor, returnType: returnType, params: params,
+	}
+	functor.SetFunc(info)
+	return info, nil
+}
+
+func newUnnamedFuncInfo(functor Functor, returnType string, params []ExprFuncParam) (info *funcInfo, err error) {
+	return newFuncInfo("unnamed", functor, returnType, params)
+}
+
+func (info *funcInfo) Params() []ExprFuncParam {
+	return info.params
+}
+
+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.params != nil {
+		for i, p := range info.params {
+			if i > 0 {
+				sb.WriteString(", ")
+			}
+			sb.WriteString(p.Name())
+
+			if p.IsOptional() {
+				sb.WriteByte('=')
+				if s, ok := p.DefaultValue().(string); ok {
+					sb.WriteByte('"')
+					sb.WriteString(s)
+					sb.WriteByte('"')
+				} else {
+					sb.WriteString(fmt.Sprintf("%v", p.DefaultValue()))
+				}
+			}
+		}
+	}
+	if info.maxArgs < 0 {
+		sb.WriteString(" ...")
+	}
+	sb.WriteString("): ")
+	if len(info.returnType) > 0 {
+		sb.WriteString(info.returnType)
+	} else {
+		sb.WriteString(typeAny)
+	}
+	sb.WriteString(" {<body>}")
+	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
+}

global-context.go

@@ -0,0 +1,55 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// global-context.go
+package expr
+
+import "path/filepath"
+
+var globalCtx *SimpleStore
+
+func ImportInContext(name string) (exists bool) {
+	var mod *module
+	if mod, exists = moduleRegister[name]; exists {
+		mod.importFunc(globalCtx)
+		mod.imported = true
+	}
+	return
+}
+
+func ImportInContextByGlobPattern(pattern string) (count int, err error) {
+	var matched bool
+	for name, mod := range moduleRegister {
+		if matched, err = filepath.Match(pattern, name); err == nil {
+			if matched {
+				count++
+				mod.importFunc(globalCtx)
+				mod.imported = true
+			}
+		} else {
+			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 GetFuncInfo(ctx ExprContext, name string) (item ExprFunc, exists bool, ownerCtx ExprContext) {
+	if item, exists = ctx.GetFuncInfo(name); exists {
+		ownerCtx = ctx
+	} else if item, exists = globalCtx.GetFuncInfo(name); exists {
+		ownerCtx = globalCtx
+	}
+	return
+}
+
+func init() {
+	globalCtx = NewSimpleStore()
+	ImportBuiltinsFuncs(globalCtx)
+}

helpers.go

@@ -6,6 +6,8 @@ package expr
 
 import (
 	"fmt"
+	"io"
+	"os"
 	"strings"
 )
 
@@ -32,12 +34,15 @@ func EvalStringA(source string, args ...Arg) (result any, err error) {
 }
 
 func EvalStringV(source string, args []Arg) (result any, err error) {
-	ctx := NewSimpleFuncStore()
+	ctx := NewSimpleStore()
 	for _, arg := range args {
 		if isFunc(arg.Value) {
 			if f, ok := arg.Value.(FuncTemplate); ok {
-				functor := &simpleFunctor{f: f}
+				functor := newGolangFunctor(f)
-				ctx.RegisterFunc(arg.Name, functor, 0, -1)
+				// ctx.RegisterFunc(arg.Name, functor, 0, -1)
+				ctx.RegisterFunc(arg.Name, functor, typeAny, []ExprFuncParam{
+					newFuncParamFlagDef(paramValue, pfOptional|pfRepeat, 0),
+				})
 			} else {
 				err = fmt.Errorf("invalid function specification: %q", arg.Name)
 			}
@@ -59,3 +64,24 @@ func EvalStringV(source string, args []Arg) (result any, err error) {
 	}
 	return
 }
+
+func EvalStream(ctx ExprContext, r io.Reader) (result any, err error) {
+	var tree *ast
+	scanner := NewScanner(r, DefaultTranslations())
+	parser := NewParser(ctx)
+
+	if tree, err = parser.Parse(scanner); err == nil {
+		result, err = tree.Eval(ctx)
+	}
+	return
+}
+
+func EvalFile(ctx ExprContext, filePath string) (result any, err error) {
+	var fh *os.File
+	if fh, err = os.Open(filePath); err != nil {
+		return nil, err
+	}
+	defer fh.Close()
+	result, err = EvalStream(ctx, fh)
+	return
+}

helpers_test.go

@@ -52,7 +52,7 @@ func TestEvalStringA(t *testing.T) {
 
 func TestEvalString(t *testing.T) {
 
-	ctx := NewSimpleVarStore()
+	ctx := NewSimpleStore()
 	ctx.SetVar("a", uint8(1))
 	ctx.SetVar("b", int8(2))
 	ctx.SetVar("f", 2.0)

int.list

@@ -0,0 +1,4 @@
+10
+20
+5
+12

iter-list.go

@@ -4,39 +4,129 @@
 // iter-list.go
 package expr
 
-import "io"
+import (
+	"fmt"
+	"io"
+)
 
-type FlatArrayIterator struct {
+type ListIterator struct {
-	a     []any
+	a     *ListType
+	count int
 	index int
+	start int
+	stop  int
+	step  int
 }
 
-func NewFlatArrayIterator(array []any) *FlatArrayIterator {
+func NewListIterator(list *ListType, args []any) (it *ListIterator) {
-	return &FlatArrayIterator{a: array, index: 0}
+	var argc int = 0
+	listLen := len(([]any)(*list))
+	if args != nil {
+		argc = len(args)
+	}
+	it = &ListIterator{a: list, count: 0, index: -1, start: 0, stop: listLen - 1, step: 1}
+	if argc >= 1 {
+		if i, err := toInt(args[0], "start index"); err == nil {
+			if i < 0 {
+				i = listLen + i
+			}
+			it.start = i
+		}
+		if argc >= 2 {
+			if i, err := toInt(args[1], "stop index"); err == nil {
+				if i < 0 {
+					i = listLen + i
+				}
+				it.stop = i
+			}
+			if argc >= 3 {
+				if i, err := toInt(args[2], "step"); err == nil {
+					if i < 0 {
+						i = -i
+					}
+					if it.start > it.stop {
+						it.step = -i
+					} else {
+						it.step = i
+					}
+				}
+			}
+		}
+	}
+	it.index = it.start - it.step
+	return
 }
 
-func (it *FlatArrayIterator) Current() (item any, err error) {
+func NewArrayIterator(array []any) (it *ListIterator) {
-	if it.index >= 0 && it.index < len(it.a) {
+	it = &ListIterator{a: (*ListType)(&array), count: 0, index: -1, start: 0, stop: len(array) - 1, step: 1}
-		item = it.a[it.index]
+	return
+}
+
+func NewAnyIterator(value any) (it *ListIterator) {
+	if value == nil {
+		it = NewArrayIterator([]any{})
+	} else if list, ok := value.(*ListType); ok {
+		it = NewListIterator(list, nil)
+	} else if array, ok := value.([]any); ok {
+		it = NewArrayIterator(array)
+	} else if it1, ok := value.(*ListIterator); ok {
+		it = it1
+	} else {
+		it = NewArrayIterator([]any{value})
+	}
+	return
+}
+
+func (it *ListIterator) String() string {
+	var l = 0
+	if it.a != nil {
+		l = len(*it.a)
+	}
+	return fmt.Sprintf("$(#%d)", l)
+}
+
+func (it *ListIterator) HasOperation(name string) bool {
+	yes := name == resetName || name == indexName || name == countName
+	return yes
+}
+
+func (it *ListIterator) CallOperation(name string, args []any) (v any, err error) {
+	switch name {
+	case resetName:
+		v, err = it.Reset()
+	case indexName:
+		v = int64(it.Index())
+	case countName:
+		v = it.count
+	default:
+		err = errNoOperation(name)
+	}
+	return
+}
+
+func (it *ListIterator) Current() (item any, err error) {
+	a := *(it.a)
+	if it.index >= 0 && it.index <= it.stop {
+		item = a[it.index]
 	} else {
 		err = io.EOF
 	}
 	return
 }
 
-func (it *FlatArrayIterator) Next() (item any, err error) {
+func (it *ListIterator) Next() (item any, err error) {
+	it.index += it.step
 	if item, err = it.Current(); err != io.EOF {
-		it.index++
+		it.count++
 	}
-	// if it.index < len(it.a) {
-	// 	item = it.a[it.index]
-	// 	it.index++
-	// } else {
-	// 	err = io.EOF
-	// }
 	return
 }
 
-func (it *FlatArrayIterator) Index() int {
+func (it *ListIterator) Index() int {
-	return it.index - 1
+	return it.index
+}
+
+func (it *ListIterator) Reset() (bool, error) {
+	it.index = it.start
+	return true, nil
 }

iterator.expr

@@ -0,0 +1,18 @@
+ds={
+	"init":func(end){@end=end; @current=0; @prev=@current},
+	"current":func(){prev},
+	"next":func(){
+		(current <= end) ? [true] {@current=current+1; @prev=current} :: {nil}
+	},
+	"reset":func(){@current=0; @prev=@current}
+}
+
+// Example
+//;
+//it=$(ds,3);
+//it++;
+//it."reset"
+//it++;
+//it++;
+//add(it)
+

iterator.go

@@ -4,8 +4,39 @@
 // iterator.go
 package expr
 
+import (
+	"errors"
+	"fmt"
+)
+
+// Operator names
+
+const (
+	initName    = "init"
+	cleanName   = "clean"
+	resetName   = "reset"
+	nextName    = "next"
+	currentName = "current"
+	indexName   = "index"
+	countName   = "count"
+)
+
 type Iterator interface {
 	Next() (item any, err error) // must return io.EOF after the last item
 	Current() (item any, err error)
 	Index() int
 }
+
+type ExtIterator interface {
+	Iterator
+	HasOperation(name string) bool
+	CallOperation(name string, args []any) (value any, err error)
+}
+
+func errNoOperation(name string) error {
+	return fmt.Errorf("no %q function defined in the data-source", name)
+}
+
+func errInvalidDataSource() error {
+	return errors.New("invalid data-source")
+}

iterator_test.go

@@ -0,0 +1,26 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// iterator_test.go
+package expr
+
+import "testing"
+
+func TestIteratorParser(t *testing.T) {
+	inputs := []inputType{
+		/*   1 */ {`include "iterator.expr"; it=$(ds,3); ()it`, int64(0), nil},
+		/*   2 */ {`include "iterator.expr"; it=$(ds,3); it++; it++`, int64(1), nil},
+		/*   3 */ {`include "iterator.expr"; it=$(ds,3); it++; it++; #it`, int64(2), nil},
+		/*   4 */ {`include "iterator.expr"; it=$(ds,3); it++; it++; it.reset; ()it`, int64(0), nil},
+		/*   5 */ {`builtin "math.arith"; include "iterator.expr"; it=$(ds,3); add(it)`, int64(6), nil},
+		/*   6 */ {`builtin "math.arith"; include "iterator.expr"; it=$(ds,3); mul(it)`, int64(0), nil},
+		/*   7 */ {`builtin "math.arith"; include "file-reader.expr"; it=$(ds,"int.list"); mul(it)`, int64(12000), nil},
+		/*   8 */ {`include "file-reader.expr"; it=$(ds,"int.list"); it++; it.index`, int64(0), nil},
+		/*  10 */ {`include "file-reader.expr"; it=$(ds,"int.list"); it.clean`, true, nil},
+		/*  11 */ {`it=$(1,2,3); it++`, int64(1), nil},
+	}
+	// inputs1 := []inputType{
+	// 	/*   1 */ {`0?{}`, nil, nil},
+	// }
+	parserTest(t, "Iterator", inputs)
+}

list_test.go

@@ -0,0 +1,122 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// list_test.go
+package expr
+
+import (
+	"errors"
+	"strings"
+	"testing"
+)
+
+func TestListParser(t *testing.T) {
+	section := "List"
+
+	type inputType struct {
+		source     string
+		wantResult any
+		wantErr    error
+	}
+
+	inputs := []inputType{
+		/*   1 */ {`[]`, []any{}, nil},
+		/*   2 */ {`[1,2,3]`, []any{int64(1), int64(2), int64(3)}, nil},
+		/*   3 */ {`[1,2,"hello"]`, []any{int64(1), int64(2), "hello"}, nil},
+		/*   4 */ {`[1+2, not true, "hello"]`, []any{int64(3), false, "hello"}, nil},
+		/*   5 */ {`[1,2]+[3]`, []any{int64(1), int64(2), int64(3)}, nil},
+		/*   6 */ {`[1,4,3,2]-[3]`, []any{int64(1), int64(4), int64(2)}, nil},
+		/*   7 */ {`add([1,4,3,2])`, int64(10), nil},
+		/*   8 */ {`add([1,[2,2],3,2])`, int64(10), nil},
+		/*   9 */ {`mul([1,4,3.0,2])`, float64(24.0), nil},
+		/*  10 */ {`add([1,"hello"])`, nil, errors.New(`add(): param nr 2 (2 in 1) has wrong type string, number expected`)},
+		/*  11 */ {`[a=1,b=2,c=3] but a+b+c`, int64(6), nil},
+		/*  12 */ {`[1,2,3] << 2+2`, []any{int64(1), int64(2), int64(3), int64(4)}, nil},
+		/*  13 */ {`2-1 >> [2,3]`, []any{int64(1), int64(2), int64(3)}, nil},
+		/*  14 */ {`[1,2,3].1`, int64(2), nil},
+		/*  15 */ {`ls=[1,2,3] but ls.1`, int64(2), nil},
+		/*  16 */ {`ls=[1,2,3] but ls.(-1)`, int64(3), nil},
+		/*  17 */ {`list=["one","two","three"]; list.10`, nil, errors.New(`[1:36] index 10 out of bounds`)},
+		/*  18 */ {`["a", "b", "c"]`, newListA("a", "b", "c"), nil},
+		/*  19 */ {`["a", "b", "c"]`, newList([]any{"a", "b", "c"}), nil},
+		/*  20 */ {`#["a", "b", "c"]`, int64(3), nil},
+		/*  21 */ {`"b" in ["a", "b", "c"]`, true, nil},
+		/*  22 */ {`a=[1,2]; (a)<<3`, []any{1, 2, 3}, nil},
+		/*  23 */ {`a=[1,2]; (a)<<3; 1`, []any{1, 2}, nil},
+
+		// /*  8 */ {`[int(x)|x=csv("test.csv",1,all(),1)]`, []any{int64(10), int64(40), int64(20)}, nil},
+		// /*  9 */ {`sum(@[int(x)|x=csv("test.csv",1,all(),1)])`, []any{int64(10), int64(40), int64(20)}, nil},
+	}
+
+	succeeded := 0
+	failed := 0
+
+	// inputs1 := []inputType{
+	// 	/*  7 */ {`add([1,4,3,2])`, int64(10), nil},
+	// }
+
+	for i, input := range inputs {
+		var expr *ast
+		var gotResult any
+		var gotErr error
+
+		ctx := NewSimpleStore()
+		// ctx.SetVar("var1", int64(123))
+		// ctx.SetVar("var2", "abc")
+		ImportMathFuncs(ctx)
+		parser := NewParser(ctx)
+
+		logTest(t, i+1, "List", input.source, input.wantResult, input.wantErr)
+
+		r := strings.NewReader(input.source)
+		scanner := NewScanner(r, DefaultTranslations())
+
+		good := true
+		if expr, gotErr = parser.Parse(scanner); gotErr == nil {
+			gotResult, gotErr = expr.Eval(ctx)
+		}
+
+		if (gotResult == nil && input.wantResult != nil) || (gotResult != nil && input.wantResult == nil) {
+			t.Errorf("%d: %q -> result = %v [%T], want %v [%T]", i+1, input.source, gotResult, gotResult, input.wantResult, input.wantResult)
+			good = false
+		}
+
+		if gotList, okGot := gotResult.([]any); okGot {
+			if wantList, okWant := input.wantResult.([]any); okWant {
+				if (gotList == nil && wantList != nil) || (gotList != nil && wantList == nil) {
+					t.Errorf("%d: %q -> result = %v [%T], want %v [%T]", i+1, input.source, gotResult, gotResult, input.wantResult, input.wantResult)
+					good = false
+				} else {
+					equal := len(gotList) == len(wantList)
+					if equal {
+						for i, gotItem := range gotList {
+							wantItem := wantList[i]
+							equal = gotItem == wantItem
+							if !equal {
+								break
+							}
+						}
+					}
+					if !equal {
+						t.Errorf("%d: %q -> result = %v [%T], want %v [%T]", i+1, input.source, gotResult, gotResult, input.wantResult, input.wantResult)
+						good = false
+					}
+				}
+			}
+		}
+
+		if gotErr != input.wantErr {
+			if input.wantErr == nil || gotErr == nil || (gotErr.Error() != input.wantErr.Error()) {
+				t.Errorf("%d: %q  -> err = <%v>, want <%v>", i+1, input.source, gotErr, input.wantErr)
+				good = false
+			}
+		}
+
+		if good {
+			succeeded++
+		} else {
+			failed++
+		}
+	}
+	t.Logf("%s -- test count: %d, succeeded: %d, failed: %d", section, len(inputs), succeeded, failed)
+}

module-register.go

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

operand-const.go

@@ -1,32 +0,0 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
-// All rights reserved.
-
-// operand-const.go
-package expr
-
-// -------- const term
-func newConstTerm(tk *Token) *term {
-	return &term{
-		tk:       *tk,
-		parent:   nil,
-		children: nil,
-		position: posLeaf,
-		priority: priValue,
-		evalFunc: evalConst,
-	}
-}
-
-// -------- eval func
-func evalConst(ctx ExprContext, self *term) (v any, err error) {
-	v = self.tk.Value
-	return
-}
-
-// init
-func init() {
-	registerTermConstructor(SymString, newConstTerm)
-	registerTermConstructor(SymInteger, newConstTerm)
-	registerTermConstructor(SymFloat, newConstTerm)
-	registerTermConstructor(SymBool, newConstTerm)
-	registerTermConstructor(SymKwNil, newConstTerm)
-}

operand-dict.go

@@ -4,6 +4,125 @@
 // operand-dict.go
 package expr
 
+import (
+	"fmt"
+	"reflect"
+	"strings"
+)
+
+type DictType map[any]any
+
+func newDict(dictAny map[any]*term) (dict *DictType) {
+	var d DictType
+	if dictAny != nil {
+		d = make(DictType, len(dictAny))
+		for i, item := range dictAny {
+			d[i] = item
+		}
+	} else {
+		d = make(DictType)
+	}
+	dict = &d
+	return
+}
+
+func (dict *DictType) toMultiLine(sb *strings.Builder, indent int) {
+	sb.WriteString(strings.Repeat("\t", indent))
+	sb.WriteString("{\n")
+
+	first := true
+	for name, value := range *dict {
+		if first {
+			first = false
+		} else {
+			sb.WriteByte(',')
+			sb.WriteByte('\n')
+		}
+
+		sb.WriteString(strings.Repeat("\t", indent+1))
+		if key, ok := name.(string); ok {
+			sb.WriteString(string('"') + key + string('"'))
+		} else {
+			sb.WriteString(fmt.Sprintf("%v", name))
+		}
+		sb.WriteString(": ")
+		if f, ok := value.(Formatter); ok {
+			sb.WriteString(f.ToString(MultiLine))
+		} else if _, ok = value.(Functor); ok {
+			sb.WriteString("func(){}")
+		} else {
+			sb.WriteString(fmt.Sprintf("%v", value))
+		}
+	}
+	sb.WriteString(strings.Repeat("\t", indent))
+	sb.WriteString("\n}")
+}
+
+func (dict *DictType) ToString(opt FmtOpt) string {
+	var sb strings.Builder
+	if opt&MultiLine != 0 {
+		dict.toMultiLine(&sb, 0)
+	} else {
+		sb.WriteByte('{')
+		first := true
+		for key, value := range *dict {
+			if first {
+				first = false
+			} else {
+				sb.WriteString(", ")
+			}
+			if s, ok := key.(string); ok {
+				sb.WriteString(string('"') + s + string('"'))
+			} else {
+				sb.WriteString(fmt.Sprintf("%v", key))
+			}
+			sb.WriteString(": ")
+			if formatter, ok := value.(Formatter); ok {
+				sb.WriteString(formatter.ToString(opt))
+			} else if t, ok := value.(*term); ok {
+				sb.WriteString(t.String())
+			} else {
+				sb.WriteString(fmt.Sprintf("%#v", value))
+			}
+		}
+		sb.WriteByte('}')
+	}
+	return sb.String()
+}
+
+func (dict *DictType) String() string {
+	return dict.ToString(0)
+}
+
+func (dict *DictType) TypeName() string {
+	return "dict"
+}
+
+func (dict *DictType) hasKey(target any) (ok bool) {
+	for key := range *dict {
+		if ok = reflect.DeepEqual(key, target); ok {
+			break
+		}
+	}
+	return
+}
+
+func (dict *DictType) clone() (c *DictType) {
+	c = newDict(nil)
+	for k, v := range *dict {
+		(*c)[k] = v
+	}
+	return
+}
+
+func (dict *DictType) merge(second *DictType) {
+	if second != nil {
+		for k, v := range *second {
+			(*dict)[k] = v
+		}
+	}
+}
+
 // -------- dict term
 func newDictTerm(args map[any]*term) *term {
 	return &term{
@@ -19,7 +138,7 @@ func newDictTerm(args map[any]*term) *term {
 // -------- dict func
 func evalDict(ctx ExprContext, self *term) (v any, err error) {
 	dict, _ := self.value().(map[any]*term)
-	items := make(map[any]any, len(dict))
+	items := make(DictType, len(dict))
 	for key, tree := range dict {
 		var param any
 		if param, err = tree.compute(ctx); err != nil {
@@ -28,7 +147,7 @@ func evalDict(ctx ExprContext, self *term) (v any, err error) {
 		items[key] = param
 	}
 	if err == nil {
-		v = items
+		v = &items
 	}
 	return
 }

operand-expr.go

@@ -7,7 +7,8 @@ package expr
 import "fmt"
 
 // -------- expr term
-func newExprTerm(tk *Token) *term {
+func newExprTerm(root *term) *term {
+	tk := NewValueToken(root.tk.row, root.tk.col, SymExpression, root.source(), root)
 	return &term{
 		tk:       *tk,
 		parent:   nil,
@@ -20,8 +21,8 @@ func newExprTerm(tk *Token) *term {
 
 // -------- eval expr
 func evalExpr(ctx ExprContext, self *term) (v any, err error) {
-	if expr, ok := self.value().(Expr); ok {
+	if expr, ok := self.value().(*term); ok {
-		v, err = expr.eval(ctx, false)
+		v, err = expr.compute(ctx)
 	} else {
 		err = fmt.Errorf("expression expected, got %T", self.value())
 	}

operand-func.go

@@ -6,6 +6,7 @@ package expr
 
 import (
 	"errors"
+	"fmt"
 )
 
 // -------- function call term
@@ -21,9 +22,28 @@ func newFuncCallTerm(tk *Token, args []*term) *term {
 }
 
 // -------- eval func call
+func checkFunctionCall(ctx ExprContext, name string, params []any) (err error) {
+	if info, exists, owner := GetFuncInfo(ctx, name); exists {
+		if info.MinArgs() > len(params) {
+			err = errTooFewParams(info.MinArgs(), info.MaxArgs(), len(params))
+		}
+		if err == nil && info.MaxArgs() >= 0 && info.MaxArgs() < len(params) {
+			err = errTooMuchParams(info.MaxArgs(), len(params))
+		}
+		if err == nil && owner != ctx {
+			// ctx.RegisterFunc(name, info.Functor(), info.MinArgs(), info.MaxArgs())
+			ctx.RegisterFuncInfo(info)
+		}
+	} else {
+		err = fmt.Errorf("unknown function %s()", name)
+	}
+	return
+}
+
 func evalFuncCall(parentCtx ExprContext, self *term) (v any, err error) {
 	ctx := cloneContext(parentCtx)
 	name, _ := self.tk.Value.(string)
+	// fmt.Printf("Call %s(), context: %p\n", name, ctx)
 	params := make([]any, len(self.children))
 	for i, tree := range self.children {
 		var param any
@@ -33,8 +53,10 @@ func evalFuncCall(parentCtx ExprContext, self *term) (v any, err error) {
 		params[i] = param
 	}
 	if err == nil {
-		if v, err = ctx.Call(name, params); err == nil {
+		if err = checkFunctionCall(ctx, name, params); err == nil {
-			exportObjects(parentCtx, ctx)
+			if v, err = ctx.Call(name, params); err == nil {
+				exportObjects(parentCtx, ctx)
+			}
 		}
 	}
 	return
@@ -43,9 +65,9 @@ func evalFuncCall(parentCtx ExprContext, self *term) (v any, err error) {
 // -------- function definition term
 func newFuncDefTerm(tk *Token, args []*term) *term {
 	return &term{
-		tk:       *tk,
+		tk:       *tk, // value is the expression body
 		parent:   nil,
-		children: args, // arg[0]=formal-param-list, arg[1]=*ast
+		children: args, // function params
 		position: posLeaf,
 		priority: priValue,
 		evalFunc: evalFuncDef,
@@ -54,27 +76,30 @@ func newFuncDefTerm(tk *Token, args []*term) *term {
 
 // -------- eval func def
 // TODO
-type funcDefFunctor struct {
+// type funcDefFunctor struct {
-	params []string
+// 	params []string
-	expr   Expr
+// 	expr   Expr
-}
+// }
 
-func (functor *funcDefFunctor) Invoke(ctx ExprContext, name string, args []any) (result any, err error) {
+// func (funcDef *funcDefFunctor) Invoke(ctx ExprContext, name string, args []any) (result any, err error) {
-	for i, p := range functor.params {
+// 	for i, p := range funcDef.params {
-		if i < len(args) {
+// 		if i < len(args) {
-			arg := args[i]
+// 			arg := args[i]
-			if functor, ok := arg.(Functor); ok {
+// 			if functor, ok := arg.(Functor); ok {
-				ctx.RegisterFunc(p, functor, 0, -1)
+// 				// ctx.RegisterFunc(p, functor, 0, -1)
-			} else {
+// 				ctx.RegisterFunc2(p, functor, typeAny, []ExprFuncParam{
-				ctx.setVar(p, arg)
+// 					newFuncParam(paramValue),
-			}
+// 				})
-		} else {
+// 			} else {
-			ctx.setVar(p, nil)
+// 				ctx.UnsafeSetVar(p, arg)
-		}
+// 			}
-	}
+// 		} else {
-	result, err = functor.expr.eval(ctx, false)
+// 			ctx.UnsafeSetVar(p, nil)
-	return
+// 		}
-}
+// 	}
+// 	result, err = funcDef.expr.eval(ctx, false)
+// 	return
+// }
 
 func evalFuncDef(ctx ExprContext, self *term) (v any, err error) {
 	bodySpec := self.value()
@@ -83,10 +108,11 @@ func evalFuncDef(ctx ExprContext, self *term) (v any, err error) {
 		for _, param := range self.children {
 			paramList = append(paramList, param.source())
 		}
-		v = &funcDefFunctor{
+		v = newExprFunctor(expr, paramList)
-			params: paramList,
+		// v = &funcDefFunctor{
-			expr:   expr,
+		// 	params: paramList,
-		}
+		// 	expr:   expr,
+		// }
 	} else {
 		err = errors.New("invalid function definition: the body specification must be an expression")
 	}

operand-iterator.go

@@ -6,11 +6,13 @@ package expr
 
 import (
 	"fmt"
+	"slices"
+	"strings"
 )
 
 // -------- iterator term
 
-func newIteratorTerm(tk *Token, dsTerm *term, args []*term) *term {
+func newDsIteratorTerm(tk *Token, dsTerm *term, args []*term) *term {
 	tk.Sym = SymIterator
 
 	children := make([]*term, 0, 1+len(args))
@@ -26,6 +28,18 @@ func newIteratorTerm(tk *Token, dsTerm *term, args []*term) *term {
 	}
 }
 
+func newIteratorTerm(tk *Token, args []*term) *term {
+	tk.Sym = SymIterator
+	return &term{
+		tk:       *tk,
+		parent:   nil,
+		children: args,
+		position: posLeaf,
+		priority: priValue,
+		evalFunc: evalIterator,
+	}
+}
+
 // -------- eval iterator
 
 func evalTermArray(ctx ExprContext, a []*term) (values []any, err error) {
@@ -41,64 +55,132 @@ func evalTermArray(ctx ExprContext, a []*term) (values []any, err error) {
 	return
 }
 
-func getDataSourceDict(ctx ExprContext, self *term) (ds map[string]Functor, err error) {
+func evalFirstChild(ctx ExprContext, self *term) (value any, err error) {
-	var value any
 	if len(self.children) < 1 || self.children[0] == nil {
 		err = self.Errorf("missing the data-source parameter")
 		return
 	}
 
-	if value, err = self.children[0].compute(ctx); err != nil {
+	value, err = self.children[0].compute(ctx)
-		return
+	return
-	}
+}
 
-	if dictAny, ok := value.(map[any]any); ok {
+func getDataSourceDict(ctx ExprContext, self *term, firstChildValue any) (ds map[string]Functor, err error) {
+	// if dictAny, ok := firstChildValue.(map[any]any); ok {
+	if dictAny, ok := firstChildValue.(*DictType); ok {
+		requiredFields := []string{currentName, nextName}
+		fieldsMask := 0b11
+		foundFields := 0
 		ds = make(map[string]Functor)
-		for _, k := range []string{initName, currentName, nextName} {
+		for keyAny, item := range *dictAny {
-			if item, exists := dictAny[k]; exists && item != nil {
+			if key, ok := keyAny.(string); ok {
-				if functor, ok := item.(*funcDefFunctor); ok {
+				//if functor, ok := item.(*funcDefFunctor); ok {
-					ds[k] = functor
+				if functor, ok := item.(Functor); ok {
+					ds[key] = functor
+					if index := slices.Index(requiredFields, key); index >= 0 {
+						foundFields |= 1 << index
+					}
 				}
-			} else if k != initName {
-				err = fmt.Errorf("the data-source must provide a non-nil %q operator", k)
-				break
 			}
 		}
-	} else {
+		// check required functions
-		err = self.Errorf("the first param (data-source) of an iterator must be a dict, not a %T", value)
+		if foundFields != fieldsMask {
+			missingFields := make([]string, 0, len(requiredFields))
+			for index, field := range requiredFields {
+				if (foundFields & (1 << index)) == 0 {
+					missingFields = append(missingFields, field)
+				}
+			}
+			err = fmt.Errorf("the data-source must provide a non-nil %q operator(s)", strings.Join(missingFields, ", "))
+		}
 	}
 	return
 }
 
 func evalIterator(ctx ExprContext, self *term) (v any, err error) {
+	var firstChildValue any
 	var ds map[string]Functor
 
-	if ds, err = getDataSourceDict(ctx, self); err != nil {
+	if firstChildValue, err = evalFirstChild(ctx, self); err != nil {
 		return
 	}
 
-	dc := newDataCursor(ctx)
+	if ds, err = getDataSourceDict(ctx, self, firstChildValue); err != nil {
-
+		return
-	if initFunc, exists := ds[initName]; exists && initFunc != nil {
-		var args []any
-		if len(self.children) > 1 {
-			if args, err = evalTermArray(ctx, self.children[1:]); err != nil {
-				return
-			}
-		} else {
-			args = []any{}
-		}
-
-		initCtx := dc.ctx.Clone()
-		if dc.resource, err = initFunc.Invoke(initCtx, initName, args); err != nil {
-			return
-		}
-		exportObjects(dc.ctx, initCtx)
 	}
 
-	dc.nextFunc, _ = ds[nextName]
+	if ds != nil {
-	dc.currentFunc, _ = ds[currentName]
+		dc := newDataCursor(ctx, ds)
-	v = dc
+		if initFunc, exists := ds[initName]; exists && initFunc != nil {
+			var args []any
+			if len(self.children) > 1 {
+				if args, err = evalTermArray(ctx, self.children[1:]); err != nil {
+					return
+				}
+			} else {
+				args = []any{}
+			}
 
+			initCtx := dc.ctx.Clone()
+			if dc.resource, err = initFunc.Invoke(initCtx, initName, args); err != nil {
+				return
+			}
+			exportObjects(dc.ctx, initCtx)
+		}
+
+		dc.nextFunc, _ = ds[nextName]
+		dc.currentFunc, _ = ds[currentName]
+		dc.cleanFunc, _ = ds[cleanName]
+		dc.resetFunc, _ = ds[resetName]
+
+		v = dc
+	} else if list, ok := firstChildValue.(*ListType); ok {
+		var args []any
+		if args, err = evalSibling(ctx, self.children, nil); err == nil {
+			v = NewListIterator(list, args)
+		}
+	} else {
+		var list []any
+		if list, err = evalSibling(ctx, self.children, firstChildValue); err == nil {
+			v = NewArrayIterator(list)
+		}
+	}
+	return
+}
+
+// func evalChildren(ctx ExprContext, terms []*term, firstChildValue any) (list *ListType, err error) {
+// 	items := make(ListType, len(terms))
+// 	for i, tree := range terms {
+// 		var param any
+// 		if i == 0 && firstChildValue != nil {
+// 			param = firstChildValue
+// 		} else if param, err = tree.compute(ctx); err != nil {
+// 			break
+// 		}
+// 		items[i] = param
+// 	}
+// 	if err == nil {
+// 		list = &items
+// 	}
+// 	return
+// }
+
+func evalSibling(ctx ExprContext, terms []*term, firstChildValue any) (list []any, err error) {
+	items := make([]any, 0, len(terms))
+	for i, tree := range terms {
+		var param any
+		if i == 0 {
+			if firstChildValue == nil {
+				continue
+			}
+			param = firstChildValue
+		} else if param, err = tree.compute(ctx); err != nil {
+			break
+		}
+		items = append(items, param)
+	}
+	if err == nil {
+		list = items
+	}
 	return
 }

operand-list.go

@@ -4,6 +4,83 @@
 // operand-list.go
 package expr
 
+import (
+	"fmt"
+	"reflect"
+	"strings"
+)
+
+type ListType []any
+
+func newListA(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
+		}
+		list = &ls
+	}
+	return
+}
+
+func (ls *ListType) ToString(opt FmtOpt) (s string) {
+	var sb strings.Builder
+	sb.WriteByte('[')
+	if len(*ls) > 0 {
+		if opt&MultiLine != 0 {
+			sb.WriteString("\n  ")
+		}
+		for i, item := range []any(*ls) {
+			if i > 0 {
+				if opt&MultiLine != 0 {
+					sb.WriteString(",\n  ")
+				} else {
+					sb.WriteString(", ")
+				}
+			}
+			if s, ok := item.(string); ok {
+				sb.WriteByte('"')
+				sb.WriteString(s)
+				sb.WriteByte('"')
+			} else {
+				sb.WriteString(fmt.Sprintf("%v", item))
+			}
+		}
+		if opt&MultiLine != 0 {
+			sb.WriteByte('\n')
+		}
+	}
+	sb.WriteByte(']')
+	s = sb.String()
+	if opt&Truncate != 0 && len(s) > TruncateSize {
+		s = TruncateString(s)
+	}
+	return
+}
+
+func (ls *ListType) String() string {
+	return ls.ToString(0)
+}
+
+func (ls *ListType) TypeName() string {
+	return "list"
+}
+
+func (list *ListType) indexDeepCmp(target any) (index int) {
+	index = -1
+	for i, item := range *list {
+		if reflect.DeepEqual(item, target) {
+			index = i
+			break
+		}
+	}
+	return
+}
+
 // -------- list term
 func newListTermA(args ...*term) *term {
 	return newListTerm(args)
@@ -23,7 +100,7 @@ func newListTerm(args []*term) *term {
 // -------- list func
 func evalList(ctx ExprContext, self *term) (v any, err error) {
 	list, _ := self.value().([]*term)
-	items := make([]any, len(list))
+	items := make(ListType, len(list))
 	for i, tree := range list {
 		var param any
 		if param, err = tree.compute(ctx); err != nil {
@@ -32,35 +109,7 @@ func evalList(ctx ExprContext, self *term) (v any, err error) {
 		items[i] = param
 	}
 	if err == nil {
-		v = items
+		v = &items
 	}
 	return
 }
-
-// // -------- list term
-// func newListTerm(args []*term) *term {
-// 	return &term{
-// 		tk:       *NewToken(0, 0, SymList, "[]"),
-// 		parent:   nil,
-// 		children: args,
-// 		position: posLeaf,
-// 		priority: priValue,
-// 		evalFunc: evalList,
-// 	}
-// }
-
-// // -------- list func
-// func evalList(ctx ExprContext, self *term) (v any, err error) {
-// 	items := make([]any, len(self.children))
-// 	for i, tree := range self.children {
-// 		var param any
-// 		if param, err = tree.compute(ctx); err != nil {
-// 			break
-// 		}
-// 		items[i] = param
-// 	}
-// 	if err == nil {
-// 		v = items
-// 	}
-// 	return
-// }

operand-literal.go

@@ -0,0 +1,33 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// operand-literal.go
+package expr
+
+// -------- literal term
+func newLiteralTerm(tk *Token) *term {
+	return &term{
+		tk:       *tk,
+		parent:   nil,
+		children: nil,
+		position: posLeaf,
+		priority: priValue,
+		evalFunc: evalLiteral,
+	}
+}
+
+// -------- eval func
+func evalLiteral(ctx ExprContext, self *term) (v any, err error) {
+	v = self.tk.Value
+	return
+}
+
+// init
+func init() {
+	registerTermConstructor(SymString, newLiteralTerm)
+	registerTermConstructor(SymInteger, newLiteralTerm)
+	registerTermConstructor(SymFloat, newLiteralTerm)
+	registerTermConstructor(SymFraction, newLiteralTerm)
+	registerTermConstructor(SymBool, newLiteralTerm)
+	registerTermConstructor(SymKwNil, newLiteralTerm)
+}

operand-var.go

@@ -8,7 +8,7 @@ import "fmt"
 
 // -------- variable term
 func newVarTerm(tk *Token) *term {
-	return &term{
+	t := &term{
 		tk: *tk,
 		// class:    classVar,
 		// kind:     kindUnknown,
@@ -18,14 +18,16 @@ func newVarTerm(tk *Token) *term {
 		priority: priValue,
 		evalFunc: evalVar,
 	}
+	t.tk.Sym = SymVariable
+	return t
 }
 
 // -------- eval func
 func evalVar(ctx ExprContext, self *term) (v any, err error) {
 	var exists bool
 	name := self.source()
-	if v, exists = ctx.GetVar(name); !exists {
+	if v, exists = GetVar(ctx, name); !exists {
-		if info, exists := ctx.GetFuncInfo(name); exists {
+		if info, exists, _ := GetFuncInfo(ctx, name); exists {
 			v = info.Functor()
 		} else {
 			err = fmt.Errorf("undefined variable or function %q", name)

operator-assign.go

@@ -1,5 +1,5 @@
 // Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
-// All rights reserved.
+// All rights reserightChilded.
 
 // operator-assign.go
 package expr
@@ -22,16 +22,32 @@ func evalAssign(ctx ExprContext, self *term) (v any, err error) {
 	}
 
 	leftTerm := self.children[0]
-	if leftTerm.tk.Sym != SymIdentifier {
+	if leftTerm.tk.Sym != SymVariable {
 		err = leftTerm.tk.Errorf("left operand of %q must be a variable", self.tk.source)
 		return
 	}
 
-	if v, err = self.children[1].compute(ctx); err == nil {
+	rightChild := self.children[1]
+
+	if v, err = rightChild.compute(ctx); err == nil {
 		if functor, ok := v.(Functor); ok {
-			ctx.RegisterFunc(leftTerm.source(), functor, 0, -1)
+			funcName := rightChild.source()
+			if info, exists, _ := GetFuncInfo(ctx, funcName); exists {
+				// ctx.RegisterFuncInfo(info)
+				ctx.RegisterFunc(leftTerm.source(), info.Functor(), info.ReturnType(), info.Params())
+			} else if funcDef, ok := functor.(*exprFunctor); ok {
+				paramSpecs := ForAll(funcDef.params, newFuncParam)
+				// paramCount := len(funcDef.params)
+				// paramSpecs := make([]ExprFuncParam, paramCount)
+				// for i := range paramSpecs {
+				// 	paramSpecs[i] = newFuncParam(funcDef.params[i])
+				// }
+				ctx.RegisterFunc(leftTerm.source(), functor, typeAny, paramSpecs)
+			} else {
+				err = self.Errorf("unknown function %s()", funcName)
+			}
 		} else {
-			ctx.setVar(leftTerm.source(), v)
+			ctx.UnsafeSetVar(leftTerm.source(), v)
 		}
 	}
 	return

operator-builtin.go

@@ -1,9 +1,11 @@
 // Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
 // All rights reserved.
 
-// operator-length.go
+// operator-builtin.go
 package expr
 
+import "io"
+
 //-------- builtin term
 
 func newBuiltinTerm(tk *Token) (inst *term) {
@@ -17,36 +19,38 @@ func newBuiltinTerm(tk *Token) (inst *term) {
 }
 
 func evalBuiltin(ctx ExprContext, self *term) (v any, err error) {
-	var rightValue any
+	var childValue any
 
-	if rightValue, err = self.evalPrefix(ctx); err != nil {
+	if childValue, err = self.evalPrefix(ctx); err != nil {
 		return
 	}
 
 	count := 0
-	if isList(rightValue) {
+	if IsString(childValue) {
-		list, _ := rightValue.([]any)
+		module, _ := childValue.(string)
-		for i, moduleSpec := range list {
+		count, err = ImportInContextByGlobPattern(module)
+	} else {
+		var moduleSpec any
+		it := NewAnyIterator(childValue)
+		for moduleSpec, err = it.Next(); err == nil; moduleSpec, err = it.Next() {
 			if module, ok := moduleSpec.(string); ok {
-				if ImportInContext(ctx, module) {
+				if ImportInContext(module) {
 					count++
 				} else {
 					err = self.Errorf("unknown module %q", module)
 					break
 				}
 			} else {
-				err = self.Errorf("expected string at item nr %d, got %T", i+1, moduleSpec)
+				err = self.Errorf("expected string at item nr %d, got %T", it.Index()+1, moduleSpec)
 				break
 			}
 		}
-	} else if isString(rightValue) {
+		if err == io.EOF {
-		module, _ := rightValue.(string)
+			err = nil
-		count, err = ImportInContextByGlobPattern(ctx, module)
+		}
-	} else {
-		err = self.errIncompatibleType(rightValue)
 	}
 	if err == nil {
-		v = count
+		v = int64(count)
 	}
 	return
 }

operator-coalesce.go

@@ -8,9 +8,7 @@ package expr
 
 func newNullCoalesceTerm(tk *Token) (inst *term) {
 	return &term{
-		tk: *tk,
+		tk:       *tk,
-		// class:    classOperator,
-		// kind:     kindUnknown,
 		children: make([]*term, 0, 2),
 		position: posInfix,
 		priority: priCoalesce,
@@ -26,7 +24,7 @@ func evalNullCoalesce(ctx ExprContext, self *term) (v any, err error) {
 	}
 
 	leftTerm := self.children[0]
-	if leftTerm.tk.Sym != SymIdentifier {
+	if leftTerm.tk.Sym != SymVariable {
 		err = leftTerm.Errorf("left operand of %q must be a variable", self.tk.source)
 		return
 	}
@@ -34,11 +32,7 @@ func evalNullCoalesce(ctx ExprContext, self *term) (v any, err error) {
 	if leftValue, exists := ctx.GetVar(leftTerm.source()); exists {
 		v = leftValue
 	} else if rightValue, err = self.children[1].compute(ctx); err == nil {
-		// if _, ok := rightValue.(Functor); ok {
-		// 	err = errCoalesceNoFunc(self.children[1])
-		// } else {
 		v = rightValue
-		// }
 	}
 	return
 }
@@ -63,7 +57,7 @@ func evalAssignCoalesce(ctx ExprContext, self *term) (v any, err error) {
 	}
 
 	leftTerm := self.children[0]
-	if leftTerm.tk.Sym != SymIdentifier {
+	if leftTerm.tk.Sym != SymVariable {
 		err = leftTerm.Errorf("left operand of %q must be a variable", self.tk.source)
 		return
 	}
@@ -72,20 +66,18 @@ func evalAssignCoalesce(ctx ExprContext, self *term) (v any, err error) {
 		v = leftValue
 	} else if rightValue, err = self.children[1].compute(ctx); err == nil {
 		if functor, ok := rightValue.(Functor); ok {
-			ctx.RegisterFunc(leftTerm.source(), functor, 0, -1)
+			//ctx.RegisterFunc(leftTerm.source(), functor, 0, -1)
+			ctx.RegisterFunc(leftTerm.source(), functor, typeAny, []ExprFuncParam{
+				newFuncParamFlag(paramValue, pfOptional|pfRepeat),
+			})
 		} else {
 			v = rightValue
-			ctx.setVar(leftTerm.source(), rightValue)
+			ctx.UnsafeSetVar(leftTerm.source(), rightValue)
 		}
 	}
 	return
 }
 
-// utils
-// func errCoalesceNoFunc(t *term) error {
-// 	return t.Errorf("the right operand of a coalescing operation cannot be a function definition")
-// }
-
 // init
 func init() {
 	registerTermConstructor(SymDoubleQuestion, newNullCoalesceTerm)

operator-context.go

@@ -11,7 +11,7 @@ func newContextTerm(tk *Token) (inst *term) {
 		tk:       *tk,
 		children: make([]*term, 0, 1),
 		position: posPrefix,
-		priority: priPrePost,
+		priority: priIncDec,
 		evalFunc: evalContextValue,
 	}
 }
@@ -20,23 +20,31 @@ func evalContextValue(ctx ExprContext, self *term) (v any, err error) {
 	var childValue any
 
 	var sourceCtx ExprContext
-	if len(self.children) == 0 {
+	if self.children == nil || len(self.children) == 0 {
 		sourceCtx = ctx
+	} else if self.children[0].symbol() == SymVariable && self.children[0].source() == "global" {
+		sourceCtx = globalCtx
 	} else if childValue, err = self.evalPrefix(ctx); err == nil {
 		if dc, ok := childValue.(*dataCursor); ok {
 			sourceCtx = dc.ctx
 		}
-	} else {
-		return
 	}
 
 	if sourceCtx != nil {
-		keys := sourceCtx.EnumVars(func(name string) bool { return name[0] != '_' })
+		if formatter, ok := sourceCtx.(Formatter); ok {
-		d := make(map[string]any)
+			v = formatter.ToString(0)
-		for _, key := range keys {
+		} else {
-			d[key], _ = sourceCtx.GetVar(key)
+			keys := sourceCtx.EnumVars(func(name string) bool { return name[0] != '_' })
+			d := make(map[string]any)
+			for _, key := range keys {
+				d[key], _ = sourceCtx.GetVar(key)
+			}
+			keys = sourceCtx.EnumFuncs(func(name string) bool { return true })
+			for _, key := range keys {
+				d[key], _ = sourceCtx.GetFuncInfo(key)
+			}
+			v = d
 		}
-		v = d
 	} else {
 		err = self.errIncompatibleType(childValue)
 	}

operator-dot.go

@@ -17,50 +17,67 @@ func newDotTerm(tk *Token) (inst *term) {
 	}
 }
 
+func verifyIndex(ctx ExprContext, indexTerm *term, maxValue int) (index int, err error) {
+	var v int
+	var indexValue any
+	if indexValue, err = indexTerm.compute(ctx); err == nil {
+		if v, err = indexTerm.toInt(indexValue, "index expression value must be integer"); err == nil {
+			if v < 0 && v >= -maxValue {
+				v = maxValue + v
+			}
+			if v >= 0 && v < maxValue {
+				index = v
+			} else {
+				err = indexTerm.Errorf("index %d out of bounds", v)
+			}
+		}
+	}
+	return
+}
+
 func evalDot(ctx ExprContext, self *term) (v any, err error) {
 	var leftValue, rightValue any
 
-	if leftValue, rightValue, err = self.evalInfix(ctx); err != nil {
+	if err = self.checkOperands(); err != nil {
+		return
+	}
+	if leftValue, err = self.children[0].compute(ctx); err != nil {
 		return
 	}
 
 	indexTerm := self.children[1]
 
-	if isList(leftValue) {
+	switch unboxedValue := leftValue.(type) {
+	case *ListType:
 		var index int
-		if index, err = indexTerm.toInt(rightValue, "index expression value must be integer"); err != nil {
+		array := ([]any)(*unboxedValue)
-			return
+		if index, err = verifyIndex(ctx, indexTerm, len(array)); err == nil {
+			v = array[index]
 		}
-
+	case string:
-		list, _ := leftValue.([]any)
-		if index >= 0 && index < len(list) {
-			v = list[index]
-		} else if index >= -len(list) {
-			v = list[len(list)+index]
-		} else {
-			err = indexTerm.Errorf("index %v out of bounds", index)
-		}
-	} else if isString(leftValue) {
 		var index int
-		if index, err = indexTerm.toInt(rightValue, "index expression value must be integer"); err != nil {
+		if index, err = verifyIndex(ctx, indexTerm, len(unboxedValue)); err == nil {
-			return
+			v = string(unboxedValue[index])
 		}
-
+	case *DictType:
-		s, _ := leftValue.(string)
-		if index >= 0 && index < len(s) {
-			v = string(s[index])
-		} else if index >= -len(s) {
-			v = string(s[len(s)+index])
-		} else {
-			err = indexTerm.Errorf("index %v out of bounds", index)
-		}
-	} else if isDict(leftValue) {
 		var ok bool
-		d, _ := leftValue.(map[any]any)
+		var indexValue any
-		if v, ok = d[rightValue]; !ok {
+		if indexValue, err = indexTerm.compute(ctx); err == nil {
-			err = fmt.Errorf("key %v does not belong to the dictionary", rightValue)
+			if v, ok = (*unboxedValue)[indexValue]; !ok {
+				err = fmt.Errorf("key %v does not belong to the dictionary", rightValue)
+			}
 		}
-	} else {
+	case ExtIterator:
+		if indexTerm.symbol() == SymVariable {
+			opName := indexTerm.source()
+			if unboxedValue.HasOperation(opName) {
+				v, err = unboxedValue.CallOperation(opName, []any{})
+			} else {
+				err = indexTerm.Errorf("this iterator do not support the %q command", opName)
+				v = false
+			}
+		}
+	default:
 		err = self.errIncompatibleTypes(leftValue, rightValue)
 	}
 	return

operator-fact.go

@@ -25,7 +25,7 @@ func evalFact(ctx ExprContext, self *term) (v any, err error) {
 		return
 	}
 
-	if isInteger(leftValue) {
+	if IsInteger(leftValue) {
 		if i, _ := leftValue.(int64); i >= 0 {
 			f := int64(1)
 			for k := int64(1); k <= i; k++ {

operator-fraction.go

@@ -0,0 +1,420 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// operand-fraction.go
+package expr
+
+//https://www.youmath.it/lezioni/algebra-elementare/lezioni-di-algebra-e-aritmetica-per-scuole-medie/553-dalle-frazioni-a-numeri-decimali.html
+
+import (
+	"errors"
+	"fmt"
+	"math"
+	"strconv"
+	"strings"
+)
+
+type fraction struct {
+	num, den int64
+}
+
+func newFraction(num, den int64) *fraction {
+	/*	if den < 0 {
+		den = -den
+		num = -num
+	}*/
+	num, den = simplifyIntegers(num, den)
+	return &fraction{num, den}
+}
+
+func float64ToFraction(f float64) (fract *fraction, err error) {
+	var sign string
+	intPart, decPart := math.Modf(f)
+	if decPart < 0.0 {
+		sign = "-"
+		intPart = -intPart
+		decPart = -decPart
+	}
+	dec := fmt.Sprintf("%.12f", decPart)
+	s := fmt.Sprintf("%s%.f%s", sign, intPart, dec[1:])
+	// fmt.Printf("S: '%s'\n",s)
+	return makeGeneratingFraction(s)
+}
+
+// Based on https://cs.opensource.google/go/go/+/refs/tags/go1.22.3:src/math/big/rat.go;l=39
+/*
+func _float64ToFraction(f float64) (num, den int64, err error) {
+	const expMask = 1<<11 - 1
+	bits := math.Float64bits(f)
+	mantissa := bits & (1<<52 - 1)
+	exp := int((bits >> 52) & expMask)
+	switch exp {
+	case expMask: // non-finite
+		err = errors.New("infite")
+		return
+	case 0: // denormal
+		exp -= 1022
+	default: // normal
+		mantissa |= 1 << 52
+		exp -= 1023
+	}
+
+	shift := 52 - exp
+
+	// Optimization (?): partially pre-normalise.
+	for mantissa&1 == 0 && shift > 0 {
+		mantissa >>= 1
+		shift--
+	}
+
+	if f < 0 {
+		num = -int64(mantissa)
+	} else {
+		num = int64(mantissa)
+	}
+	den = int64(1)
+
+	if shift > 0 {
+		den = den << shift
+	} else {
+		num = num << (-shift)
+	}
+	return
+}
+*/
+
+func makeGeneratingFraction(s string) (f *fraction, err error) {
+	var num, den int64
+	var sign int64 = 1
+	var parts []string
+	if len(s) == 0 {
+		goto exit
+	}
+	if s[0] == '-' {
+		sign = int64(-1)
+		s = s[1:]
+	} else if s[0] == '+' {
+		s = s[1:]
+	}
+	if strings.HasSuffix(s, "()") {
+		s = s[0 : len(s)-2]
+	}
+	parts = strings.SplitN(s, ".", 2)
+	if num, err = strconv.ParseInt(parts[0], 10, 64); err != nil {
+		return
+	}
+	if len(parts) == 1 {
+		f = newFraction(sign*num, 1)
+	} else if len(parts) == 2 {
+		subParts := strings.SplitN(parts[1], "(", 2)
+		if len(subParts) == 1 {
+			den = 1
+			dec := parts[1]
+			lsd := len(dec)
+			for i := lsd - 1; i >= 0 && dec[i] == '0'; i-- {
+				lsd--
+			}
+			for _, c := range dec[0:lsd] {
+				if c < '0' || c > '9' {
+					return nil, errExpectedGot("fract", "digit", c)
+				}
+				num = num*10 + int64(c-'0')
+				den = den * 10
+			}
+			f = newFraction(sign*num, den)
+		} else if len(subParts) == 2 {
+			sub := num
+			mul := int64(1)
+			for _, c := range subParts[0] {
+				if c < '0' || c > '9' {
+					return nil, errExpectedGot("fract", "digit", c)
+				}
+				num = num*10 + int64(c-'0')
+				sub = sub*10 + int64(c-'0')
+				mul *= 10
+			}
+			if len(subParts) == 2 {
+				if s[len(s)-1] != ')' {
+					goto exit
+				}
+				p := subParts[1][0 : len(subParts[1])-1]
+				for _, c := range p {
+					if c < '0' || c > '9' {
+						return nil, errExpectedGot("fract", "digit", c)
+					}
+					num = num*10 + int64(c-'0')
+					den = den*10 + 9
+				}
+				den *= mul
+			}
+			num -= sub
+			f = newFraction(sign*num, den)
+		}
+	}
+exit:
+	if f == nil {
+		err = errors.New("bad syntax")
+	}
+	return
+}
+
+func (f *fraction) toFloat() float64 {
+	return float64(f.num) / float64(f.den)
+}
+
+func (f *fraction) String() string {
+	return f.ToString(0)
+}
+
+func (f *fraction) ToString(opt FmtOpt) string {
+	var sb strings.Builder
+	if opt&MultiLine == 0 {
+		sb.WriteString(fmt.Sprintf("%d|%d", f.num, f.den))
+	} else {
+		var s, num string
+		if f.num < 0 && opt&TTY == 0 {
+			num = strconv.FormatInt(-f.num, 10)
+			s = "-"
+		} else {
+			num = strconv.FormatInt(f.num, 10)
+		}
+		den := strconv.FormatInt(f.den, 10)
+		size := max(len(num), len(den))
+		if opt&TTY != 0 {
+			sb.WriteString(fmt.Sprintf("\x1b[4m%[1]*s\x1b[0m\n", -size, fmt.Sprintf("%[1]*s", (size+len(num))/2, s+num)))
+		} else {
+			if len(s) > 0 {
+				sb.WriteString("  ")
+			}
+			sb.WriteString(fmt.Sprintf("%[1]*s", -size, fmt.Sprintf("%[1]*s", (size+len(num))/2, num)))
+			sb.WriteByte('\n')
+			if len(s) > 0 {
+				sb.WriteString(s)
+				sb.WriteByte(' ')
+			}
+			sb.WriteString(strings.Repeat("-", size))
+			sb.WriteByte('\n')
+			if len(s) > 0 {
+				sb.WriteString("  ")
+			}
+		}
+		sb.WriteString(fmt.Sprintf("%[1]*s", -size, fmt.Sprintf("%[1]*s", (size+len(den))/2, den)))
+	}
+
+	return sb.String()
+}
+
+func (f *fraction) TypeName() string {
+	return "fraction"
+}
+
+// -------- fraction term
+func newFractionTerm(tk *Token) *term {
+	return &term{
+		tk:       *tk,
+		parent:   nil,
+		children: make([]*term, 0, 2),
+		position: posInfix,
+		priority: priFraction,
+		evalFunc: evalFraction,
+	}
+}
+
+// -------- eval func
+func evalFraction(ctx ExprContext, self *term) (v any, err error) {
+	var numValue, denValue any
+	var num, den int64
+	var ok bool
+
+	if numValue, denValue, err = self.evalInfix(ctx); err != nil {
+		return
+	}
+	if num, ok = numValue.(int64); !ok {
+		err = fmt.Errorf("numerator must be integer, got %T (%v)", numValue, numValue)
+		return
+	}
+	if den, ok = denValue.(int64); !ok {
+		err = fmt.Errorf("denominator must be integer, got %T (%v)", denValue, denValue)
+		return
+	}
+	if den == 0 {
+		err = errors.New("division by zero")
+		return
+	}
+
+	if den < 0 {
+		den = -den
+		num = -num
+	}
+	g := gcd(num, den)
+	num = num / g
+	den = den / g
+	if den == 1 {
+		v = num
+	} else {
+		v = &fraction{num, den}
+	}
+	return
+}
+
+func gcd(a, b int64) (g int64) {
+	if a < 0 {
+		a = -a
+	}
+	if b < 0 {
+		b = -b
+	}
+	if a < b {
+		a, b = b, a
+	}
+	r := a % b
+	for r > 0 {
+		a, b = b, r
+		r = a % b
+	}
+	g = b
+	return
+}
+
+func lcm(a, b int64) (l int64) {
+	g := gcd(a, b)
+	l = a * b / g
+	return
+}
+
+func sumFract(f1, f2 *fraction) (sum *fraction) {
+	m := lcm(f1.den, f2.den)
+	sum = newFraction(f1.num*(m/f1.den)+f2.num*(m/f2.den), m)
+	return
+}
+
+func mulFract(f1, f2 *fraction) (prod *fraction) {
+	prod = newFraction(f1.num*f2.num, f1.den*f2.den)
+	return
+}
+
+func anyToFract(v any) (f *fraction, err error) {
+	var ok bool
+	if f, ok = v.(*fraction); !ok {
+		if n, ok := v.(int64); ok {
+			f = intToFraction(n)
+		}
+	}
+	if f == nil {
+		err = errExpectedGot("fract", typeFraction, v)
+	}
+	return
+}
+
+func anyPairToFract(v1, v2 any) (f1, f2 *fraction, err error) {
+	if f1, err = anyToFract(v1); err != nil {
+		return
+	}
+	if f2, err = anyToFract(v2); err != nil {
+		return
+	}
+	return
+}
+
+func sumAnyFract(af1, af2 any) (sum any, err error) {
+	var f1, f2 *fraction
+	if f1, f2, err = anyPairToFract(af1, af2); err != nil {
+		return
+	}
+	f := sumFract(f1, f2)
+	if f.num == 0 {
+		sum = 0
+	} else {
+		sum = simplifyFraction(f)
+	}
+	return
+}
+
+func subAnyFract(af1, af2 any) (sum any, err error) {
+	var f1, f2 *fraction
+	if f1, f2, err = anyPairToFract(af1, af2); err != nil {
+		return
+	}
+	f2.num = -f2.num
+	f := sumFract(f1, f2)
+	if f.num == 0 {
+		sum = 0
+	} else {
+		sum = simplifyFraction(f)
+	}
+	return
+}
+
+func mulAnyFract(af1, af2 any) (prod any, err error) {
+	var f1, f2 *fraction
+	if f1, f2, err = anyPairToFract(af1, af2); err != nil {
+		return
+	}
+	if f1.num == 0 || f2.num == 0 {
+		prod = 0
+	} else {
+		f := &fraction{f1.num * f2.num, f1.den * f2.den}
+		prod = simplifyFraction(f)
+	}
+	return
+}
+
+func divAnyFract(af1, af2 any) (quot any, err error) {
+	var f1, f2 *fraction
+	if f1, f2, err = anyPairToFract(af1, af2); err != nil {
+		return
+	}
+	if f2.num == 0 {
+		err = errors.New("division by zero")
+		return
+		return
+	}
+	if f1.num == 0 || f2.den == 0 {
+		quot = 0
+	} else {
+		f := &fraction{f1.num * f2.den, f1.den * f2.num}
+		quot = simplifyFraction(f)
+	}
+	return
+}
+
+func simplifyFraction(f *fraction) (v any) {
+	f.num, f.den = simplifyIntegers(f.num, f.den)
+	if f.den == 1 {
+		v = f.num
+	} else {
+		v = &fraction{f.num, f.den}
+	}
+	return v
+}
+
+func simplifyIntegers(num, den int64) (a, b int64) {
+	if num == 0 {
+		return 0, 1
+	}
+	if den == 0 {
+		panic("fraction with denominator == 0")
+	}
+	if den < 0 {
+		den = -den
+		num = -num
+	}
+	g := gcd(num, den)
+	a = num / g
+	b = den / g
+	return
+}
+
+func intToFraction(n int64) *fraction {
+	return &fraction{n, 1}
+}
+
+func isFraction(v any) (ok bool) {
+	_, ok = v.(*fraction)
+	return ok
+}
+
+// init
+func init() {
+	registerTermConstructor(SymVertBar, newFractionTerm)
+}

operator-in.go

@@ -0,0 +1,46 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// operator-in.go
+package expr
+
+//-------- in term
+
+func newInTerm(tk *Token) (inst *term) {
+	return &term{
+		tk:       *tk,
+		children: make([]*term, 0, 2),
+		position: posInfix,
+		priority: priRelational,
+		evalFunc: evalIn,
+	}
+}
+
+// func hasKey(d map[any]any, target any) (ok bool) {
+// 	_, ok = d[target]
+// 	return
+// }
+
+func evalIn(ctx ExprContext, self *term) (v any, err error) {
+	var leftValue, rightValue any
+
+	if leftValue, rightValue, err = self.evalInfix(ctx); err != nil {
+		return
+	}
+
+	if IsList(rightValue) {
+		list, _ := rightValue.(*ListType)
+		v = list.indexDeepCmp(leftValue) >= 0
+	} else if IsDict(rightValue) {
+		dict, _ := rightValue.(*DictType)
+		v = dict.hasKey(leftValue)
+	} else {
+		err = self.errIncompatibleTypes(leftValue, rightValue)
+	}
+	return
+}
+
+// init
+func init() {
+	registerTermConstructor(SymKwIn, newInTerm)
+}

operator-include.go

@@ -0,0 +1,57 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// operator-include.go
+package expr
+
+//-------- include term
+
+func newIncludeTerm(tk *Token) (inst *term) {
+	return &term{
+		tk:       *tk,
+		children: make([]*term, 0, 1),
+		position: posPrefix,
+		priority: priSign,
+		evalFunc: evalInclude,
+	}
+}
+
+func evalInclude(ctx ExprContext, self *term) (v any, err error) {
+	var childValue any
+
+	if childValue, err = self.evalPrefix(ctx); err != nil {
+		return
+	}
+
+	count := 0
+	if IsList(childValue) {
+		list, _ := childValue.([]any)
+		for i, filePathSpec := range list {
+			if filePath, ok := filePathSpec.(string); ok {
+				if v, err = EvalFile(ctx, filePath); err == nil {
+					count++
+				} else {
+					err = self.Errorf("can't load file %q", filePath)
+					break
+				}
+			} else {
+				err = self.Errorf("expected string at item nr %d, got %T", i+1, filePathSpec)
+				break
+			}
+		}
+	} else if IsString(childValue) {
+		filePath, _ := childValue.(string)
+		v, err = EvalFile(ctx, filePath)
+	} else {
+		err = self.errIncompatibleType(childValue)
+	}
+	if err == nil {
+		v = count
+	}
+	return
+}
+
+// init
+func init() {
+	registerTermConstructor(SymKwInclude, newIncludeTerm)
+}

operator-insert.go

@@ -33,9 +33,13 @@ func evalInsert(ctx ExprContext, self *term) (v any, err error) {
 		return
 	}
 
-	if isList(rightValue) {
+	if IsList(rightValue) {
-		list, _ := rightValue.([]any)
+		list, _ := rightValue.(*ListType)
-		v = append([]any{leftValue}, list...)
+		newList := append(ListType{leftValue}, *list...)
+		v = &newList
+		if self.children[1].symbol() == SymVariable {
+			ctx.UnsafeSetVar(self.children[1].source(), v)
+		}
 	} else {
 		err = self.errIncompatibleTypes(leftValue, rightValue)
 	}
@@ -49,15 +53,37 @@ func evalAppend(ctx ExprContext, self *term) (v any, err error) {
 		return
 	}
 
-	if isList(leftValue) {
+	if IsList(leftValue) {
-		list, _ := leftValue.([]any)
+		list, _ := leftValue.(*ListType)
-		v = append(list, rightValue)
+		newList := append(*list, rightValue)
+		v = &newList
+		if self.children[0].symbol() == SymVariable {
+			ctx.UnsafeSetVar(self.children[0].source(), v)
+		}
 	} else {
 		err = self.errIncompatibleTypes(leftValue, rightValue)
 	}
 	return
 }
 
+// func evalAssignAppend(ctx ExprContext, self *term) (v any, err error) {
+// 	var leftValue, rightValue any
+
+// 	if leftValue, rightValue, err = self.evalInfix(ctx); err != nil {
+// 		return
+// 	}
+
+// 	if IsList(leftValue) {
+// 		list, _ := leftValue.(*ListType)
+// 		newList := append(*list, rightValue)
+// 		v = &newList
+// 		if
+// 	} else {
+// 		err = self.errIncompatibleTypes(leftValue, rightValue)
+// 	}
+// 	return
+// }
+
 // init
 func init() {
 	registerTermConstructor(SymInsert, newInsertTerm)

operator-iter-value.go

@@ -4,7 +4,6 @@
 // operator-iter-value.go
 package expr
 
-
 //-------- iter value term
 
 func newIterValueTerm(tk *Token) (inst *term) {
@@ -18,16 +17,16 @@ func newIterValueTerm(tk *Token) (inst *term) {
 }
 
 func evalIterValue(ctx ExprContext, self *term) (v any, err error) {
-	var leftValue any
+	var childValue any
 
-	if leftValue, err = self.evalPrefix(ctx); err != nil {
+	if childValue, err = self.evalPrefix(ctx); err != nil {
 		return
 	}
 
-	if dc, ok := leftValue.(*dataCursor); ok {
+	if it, ok := childValue.(Iterator); ok {
-		v, err = dc.Current()
+		v, err = it.Current()
 	} else {
-		err = self.errIncompatibleType(leftValue)
+		err = self.errIncompatibleType(childValue)
 	}
 	return
 }

operator-length.go

@@ -17,22 +17,31 @@ func newLengthTerm(tk *Token) (inst *term) {
 }
 
 func evalLength(ctx ExprContext, self *term) (v any, err error) {
-	var rightValue any
+	var childValue any
 
-	if rightValue, err = self.evalPrefix(ctx); err != nil {
+	if childValue, err = self.evalPrefix(ctx); err != nil {
 		return
 	}
 
-	if isList(rightValue) {
+	if IsList(childValue) {
-		list, _ := rightValue.([]any)
+		ls, _ := childValue.(*ListType)
-		v = len(list)
+		v = int64(len(*ls))
-	} else if isString(rightValue) {
+	} else if IsString(childValue) {
-		s, _ := rightValue.(string)
+		s, _ := childValue.(string)
-		v = len(s)
+		v = int64(len(s))
-	} else if it, ok := rightValue.(Iterator); ok {
+	} else if IsDict(childValue) {
-		v = it.Index()
+		// m, _ := childValue.(map[any]any)
+		m, _ := childValue.(*DictType)
+		v = int64(len(*m))
+	} else if it, ok := childValue.(Iterator); ok {
+		if extIt, ok := childValue.(ExtIterator); ok && extIt.HasOperation(countName) {
+			count, _ := extIt.CallOperation(countName, nil)
+			v, _ = toInt(count, "")
+		} else {
+			v = int64(it.Index() + 1)
+		}
 	} else {
-		err = self.errIncompatibleType(rightValue)
+		err = self.errIncompatibleType(childValue)
 	}
 	return
 }

operator-post-inc.go

@@ -12,25 +12,25 @@ func newPostIncTerm(tk *Token) *term {
 		parent:   nil,
 		children: make([]*term, 0, 1),
 		position: posPostfix,
-		priority: priPrePost,
+		priority: priIncDec,
 		evalFunc: evalPostInc,
 	}
 }
 
 func evalPostInc(ctx ExprContext, self *term) (v any, err error) {
-	var leftValue any
+	var childValue any
-	if leftValue, err = self.evalPrefix(ctx); err != nil {
+	if childValue, err = self.evalPrefix(ctx); err != nil {
 		return
 	}
 
-	if dc, ok := leftValue.(*dataCursor); ok {
+	if it, ok := childValue.(Iterator); ok {
-		v, err = dc.Next()
+		v, err = it.Next()
-	} else if isInteger(leftValue) && self.children[0].symbol() == SymIdentifier {
+	} else if IsInteger(childValue) && self.children[0].symbol() == SymVariable {
-		v = leftValue
+		v = childValue
-		i, _ := leftValue.(int64)
+		i, _ := childValue.(int64)
 		ctx.SetVar(self.children[0].source(), i+1)
 	} else {
-		self.errIncompatibleType(leftValue)
+		err = self.errIncompatibleType(childValue)
 	}
 	return
 }

operator-prod.go

@@ -30,13 +30,15 @@ func evalMultiply(ctx ExprContext, self *term) (v any, err error) {
 		return
 	}
 
-	if isString(leftValue) && isInteger(rightValue) {
+	if IsString(leftValue) && IsInteger(rightValue) {
 		s, _ := leftValue.(string)
 		n, _ := rightValue.(int64)
 		v = strings.Repeat(s, int(n))
-	} else if isNumber(leftValue) && isNumber(rightValue) {
+	} else if isNumOrFract(leftValue) && isNumOrFract(rightValue) {
-		if isFloat(leftValue) || isFloat(rightValue) {
+		if IsFloat(leftValue) || IsFloat(rightValue) {
 			v = numAsFloat(leftValue) * numAsFloat(rightValue)
+		} else if isFraction(leftValue) || isFraction(rightValue) {
+			v, err = mulAnyFract(leftValue, rightValue)
 		} else {
 			leftInt, _ := leftValue.(int64)
 			rightInt, _ := rightValue.(int64)
@@ -69,14 +71,16 @@ func evalDivide(ctx ExprContext, self *term) (v any, err error) {
 		return
 	}
 
-	if isNumber(leftValue) && isNumber(rightValue) {
+	if isNumOrFract(leftValue) && isNumOrFract(rightValue) {
-		if isFloat(leftValue) || isFloat(rightValue) {
+		if IsFloat(leftValue) || IsFloat(rightValue) {
 			d := numAsFloat(rightValue)
 			if d == 0.0 {
 				err = errors.New("division by zero")
 			} else {
 				v = numAsFloat(leftValue) / d
 			}
+		} else if isFraction(leftValue) || isFraction(rightValue) {
+			v, err = divAnyFract(leftValue, rightValue)
 		} else {
 			leftInt, _ := leftValue.(int64)
 			if rightInt, _ := rightValue.(int64); rightInt == 0 {
@@ -110,7 +114,7 @@ func evalDivideAsFloat(ctx ExprContext, self *term) (v any, err error) {
 		return
 	}
 
-	if isNumber(leftValue) && isNumber(rightValue) {
+	if isNumOrFract(leftValue) && isNumOrFract(rightValue) {
 		d := numAsFloat(rightValue)
 		if d == 0.0 {
 			err = errors.New("division by zero")
@@ -144,7 +148,7 @@ func evalReminder(ctx ExprContext, self *term) (v any, err error) {
 		return
 	}
 
-	if isInteger(leftValue) && isInteger(rightValue) {
+	if IsInteger(leftValue) && IsInteger(rightValue) {
 		rightInt, _ := rightValue.(int64)
 		if rightInt == 0 {
 			err = errors.New("division by zero")

operator-rel.go

@@ -25,15 +25,15 @@ func evalEqual(ctx ExprContext, self *term) (v any, err error) {
 		return
 	}
 
-	if isNumber(leftValue) && isNumber(rightValue) {
+	if IsNumber(leftValue) && IsNumber(rightValue) {
-		if isInteger(leftValue) && isInteger(rightValue) {
+		if IsInteger(leftValue) && IsInteger(rightValue) {
 			li, _ := leftValue.(int64)
 			ri, _ := rightValue.(int64)
 			v = li == ri
 		} else {
 			v = numAsFloat(leftValue) == numAsFloat(rightValue)
 		}
-	} else if isString(leftValue) && isString(rightValue) {
+	} else if IsString(leftValue) && IsString(rightValue) {
 		ls, _ := leftValue.(string)
 		rs, _ := rightValue.(string)
 		v = ls == rs
@@ -111,15 +111,15 @@ func evalLess(ctx ExprContext, self *term) (v any, err error) {
 		return
 	}
 
-	if isNumber(leftValue) && isNumber(rightValue) {
+	if IsNumber(leftValue) && IsNumber(rightValue) {
-		if isInteger(leftValue) && isInteger(rightValue) {
+		if IsInteger(leftValue) && IsInteger(rightValue) {
 			li, _ := leftValue.(int64)
 			ri, _ := rightValue.(int64)
 			v = li < ri
 		} else {
 			v = numAsFloat(leftValue) < numAsFloat(rightValue)
 		}
-	} else if isString(leftValue) && isString(rightValue) {
+	} else if IsString(leftValue) && IsString(rightValue) {
 		ls, _ := leftValue.(string)
 		rs, _ := rightValue.(string)
 		v = ls < rs
@@ -148,15 +148,15 @@ func evalLessEqual(ctx ExprContext, self *term) (v any, err error) {
 		return
 	}
 
-	if isNumber(leftValue) && isNumber(rightValue) {
+	if IsNumber(leftValue) && IsNumber(rightValue) {
-		if isInteger(leftValue) && isInteger(rightValue) {
+		if IsInteger(leftValue) && IsInteger(rightValue) {
 			li, _ := leftValue.(int64)
 			ri, _ := rightValue.(int64)
 			v = li <= ri
 		} else {
 			v = numAsFloat(leftValue) <= numAsFloat(rightValue)
 		}
-	} else if isString(leftValue) && isString(rightValue) {
+	} else if IsString(leftValue) && IsString(rightValue) {
 		ls, _ := leftValue.(string)
 		rs, _ := rightValue.(string)
 		v = ls <= rs

operator-sign.go

@@ -35,14 +35,14 @@ func evalSign(ctx ExprContext, self *term) (v any, err error) {
 		return
 	}
 
-	if isFloat(rightValue) {
+	if IsFloat(rightValue) {
 		if self.tk.Sym == SymChangeSign {
 			f, _ := rightValue.(float64)
 			v = -f
 		} else {
 			v = rightValue
 		}
-	} else if isInteger(rightValue) {
+	} else if IsInteger(rightValue) {
 		if self.tk.Sym == SymChangeSign {
 			i, _ := rightValue.(int64)
 			v = -i

operator-sum.go

@@ -28,33 +28,58 @@ func evalPlus(ctx ExprContext, self *term) (v any, err error) {
 		return
 	}
 
-	if (isString(leftValue) && isNumberString(rightValue)) || (isString(rightValue) && isNumberString(leftValue)) {
+	if (IsString(leftValue) && isNumberString(rightValue)) || (IsString(rightValue) && isNumberString(leftValue)) {
 		v = fmt.Sprintf("%v%v", leftValue, rightValue)
-	} else if isNumber(leftValue) && isNumber(rightValue) {
+	} else if IsNumber(leftValue) && IsNumber(rightValue) {
-		if isFloat(leftValue) || isFloat(rightValue) {
+		if IsFloat(leftValue) || IsFloat(rightValue) {
 			v = numAsFloat(leftValue) + numAsFloat(rightValue)
 		} else {
 			leftInt, _ := leftValue.(int64)
 			rightInt, _ := rightValue.(int64)
 			v = leftInt + rightInt
 		}
-	} else if isList(leftValue) || isList(rightValue) {
+		// } else if IsList(leftValue) || IsList(rightValue) {
-		var leftList, rightList []any
+		// 	var leftList, rightList *ListType
-		var ok bool
+		// 	var ok bool
-		if leftList, ok = leftValue.([]any); !ok {
+		// 	if leftList, ok = leftValue.(*ListType); !ok {
-			leftList = []any{leftValue}
+		// 		leftList = &ListType{leftValue}
-		}
+		// 	}
-		if rightList, ok = rightValue.([]any); !ok {
+		// 	if rightList, ok = rightValue.(*ListType); !ok {
-			rightList = []any{rightValue}
+		// 		rightList = &ListType{rightValue}
-		}
+		// 	}
-		sumList := make([]any, 0, len(leftList)+len(rightList))
+		// 	sumList := make(ListType, 0, len(*leftList)+len(*rightList))
-		for _, item := range leftList {
+		// 	for _, item := range *leftList {
+		// 		sumList = append(sumList, item)
+		// 	}
+		// 	for _, item := range *rightList {
+		// 		sumList = append(sumList, item)
+		// 	}
+		// 	v = &sumList
+	} else if IsList(leftValue) && IsList(rightValue) {
+		var leftList, rightList *ListType
+		leftList, _ = leftValue.(*ListType)
+		rightList, _ = rightValue.(*ListType)
+
+		sumList := make(ListType, 0, len(*leftList)+len(*rightList))
+		for _, item := range *leftList {
 			sumList = append(sumList, item)
 		}
-		for _, item := range rightList {
+		for _, item := range *rightList {
 			sumList = append(sumList, item)
 		}
-		v = sumList
+		v = &sumList
+	} else if (isFraction(leftValue) && IsNumber(rightValue)) || (isFraction(rightValue) && IsNumber(leftValue)) {
+		if IsFloat(leftValue) || IsFloat(rightValue) {
+			v = numAsFloat(leftValue) + numAsFloat(rightValue)
+		} else {
+			v, err = sumAnyFract(leftValue, rightValue)
+		}
+	} else if IsDict(leftValue) && IsDict(rightValue) {
+		leftDict, _ := leftValue.(*DictType)
+		rightDict, _ := rightValue.(*DictType)
+		c := leftDict.clone()
+		c.merge(rightDict)
+		v = c
 	} else {
 		err = self.errIncompatibleTypes(leftValue, rightValue)
 	}
@@ -80,24 +105,26 @@ func evalMinus(ctx ExprContext, self *term) (v any, err error) {
 		return
 	}
 
-	if isNumber(leftValue) && isNumber(rightValue) {
+	if isNumOrFract(leftValue) && isNumOrFract(rightValue) {
-		if isFloat(leftValue) || isFloat(rightValue) {
+		if IsFloat(leftValue) || IsFloat(rightValue) {
 			v = numAsFloat(leftValue) - numAsFloat(rightValue)
+		} else if isFraction(leftValue) || isFraction(rightValue) {
+			v, err = subAnyFract(leftValue, rightValue)
 		} else {
 			leftInt, _ := leftValue.(int64)
 			rightInt, _ := rightValue.(int64)
 			v = leftInt - rightInt
 		}
-	} else if isList(leftValue) && isList(rightValue) {
+	} else if IsList(leftValue) && IsList(rightValue) {
-		leftList, _ := leftValue.([]any)
+		leftList, _ := leftValue.(*ListType)
-		rightList, _ := rightValue.([]any)
+		rightList, _ := rightValue.(*ListType)
-		diffList := make([]any, 0, len(leftList)-len(rightList))
+		diffList := make(ListType, 0, len(*leftList)-len(*rightList))
-		for _, item := range leftList {
+		for _, item := range *leftList {
-			if slices.Index(rightList, item) < 0 {
+			if slices.Index(*rightList, item) < 0 {
 				diffList = append(diffList, item)
 			}
 		}
-		v = diffList
+		v = &diffList
 	} else {
 		err = self.errIncompatibleTypes(leftValue, rightValue)
 	}

parser.go

@@ -62,30 +62,45 @@ func (self *parser) parseFuncCall(scanner *scanner, allowVarRef bool, tk *Token)
 // 	// Example: "add = func(x,y) {x+y}
 // 	var body *ast
 // 	args := make([]*term, 0)
-// 	tk := scanner.Next()
+// 	lastSym := SymUnknown
-// 	for tk.Sym != SymClosedRound && tk.Sym != SymEos {
+// 	itemExpected := false
-// 		if tk.Sym == SymIdentifier {
+// 	tk := scanner.Previous()
-// 			t := newTerm(tk, nil)
+// 	for lastSym != SymClosedRound && lastSym != SymEos {
-// 			args = append(args, t)
+// 		var subTree *ast
+// 		if subTree, err = self.parseItem(scanner, true, SymComma, SymClosedRound); err == nil {
+// 			if subTree.root != nil {
+// 				if subTree.root.symbol() == SymIdentifier {
+// 					args = append(args, subTree.root)
+// 				} else {
+// 					err = tk.ErrorExpectedGotString("param-name", subTree.root.String())
+// 				}
+// 			} else if itemExpected {
+// 				prev := scanner.Previous()
+// 				err = prev.ErrorExpectedGot("function-param")
+// 				break
+// 			}
 // 		} else {
-// 			err = tk.Errorf("invalid param %q, variable identifier expected", tk.source)
 // 			break
 // 		}
-// 		tk = scanner.Next()
+// 		lastSym = scanner.Previous().Sym
+// 		itemExpected = lastSym == SymComma
 // 	}
-// 	if err == nil && tk.Sym != SymClosedRound {
+
-// 		err = tk.Errorf("unterminate function params list")
+// 	if err == nil && lastSym != SymClosedRound {
+// 		err = tk.ErrorExpectedGot(")")
 // 	}
 // 	if err == nil {
 // 		tk = scanner.Next()
 // 		if tk.Sym == SymOpenBrace {
 // 			body, err = self.parseGeneral(scanner, true, true, SymClosedBrace)
+// 		} else {
+// 			err = tk.ErrorExpectedGot("{")
 // 		}
 // 	}
 // 	if err == nil {
 // 		// TODO Check arguments
 // 		if scanner.Previous().Sym != SymClosedBrace {
-// 			err = scanner.Previous().Errorf("not properly terminated function body")
+// 			err = scanner.Previous().ErrorExpectedGot("}")
 // 		} else {
 // 			tk = scanner.makeValueToken(SymExpression, "", body)
 // 			tree = newFuncDefTerm(tk, args)
@@ -102,20 +117,14 @@ func (self *parser) parseFuncDef(scanner *scanner) (tree *term, err error) {
 	itemExpected := false
 	tk := scanner.Previous()
 	for lastSym != SymClosedRound && lastSym != SymEos {
-		var subTree *ast
+		tk = scanner.Next()
-		if subTree, err = self.parseItem(scanner, true, SymComma, SymClosedRound); err == nil {
+		if tk.IsSymbol(SymIdentifier) {
-			if subTree.root != nil {
+			param := newTerm(tk)
-				if subTree.root.symbol() == SymIdentifier {
+			args = append(args, param)
-					args = append(args, subTree.root)
+			tk = scanner.Next()
-				} else {
+		} else if itemExpected {
-					err = tk.Errorf("exptected identifier, got %q", subTree.root)
+			prev := scanner.Previous()
-				}
+			err = prev.ErrorExpectedGot("function-param")
-			} else if itemExpected {
-				prev := scanner.Previous()
-				err = prev.Errorf("expected function parameter, got %q", prev)
-				break
-			}
-		} else {
 			break
 		}
 		lastSym = scanner.Previous().Sym
@@ -123,18 +132,20 @@ func (self *parser) parseFuncDef(scanner *scanner) (tree *term, err error) {
 	}
 
 	if err == nil && lastSym != SymClosedRound {
-		err = tk.Errorf("unterminated function parameters list")
+		err = tk.ErrorExpectedGot(")")
 	}
 	if err == nil {
 		tk = scanner.Next()
-		if tk.Sym == SymOpenBrace {
+		if tk.IsSymbol(SymOpenBrace) {
 			body, err = self.parseGeneral(scanner, true, true, SymClosedBrace)
+		} else {
+			err = tk.ErrorExpectedGot("{")
 		}
 	}
 	if err == nil {
 		// TODO Check arguments
 		if scanner.Previous().Sym != SymClosedBrace {
-			err = scanner.Previous().Errorf("not properly terminated function body")
+			err = scanner.Previous().ErrorExpectedGot("}")
 		} else {
 			tk = scanner.makeValueToken(SymExpression, "", body)
 			tree = newFuncDefTerm(tk, args)
@@ -154,7 +165,7 @@ func (self *parser) parseList(scanner *scanner, allowVarRef bool) (subtree *term
 				args = append(args, subTree.root)
 			} else if itemExpected {
 				prev := scanner.Previous()
-				err = prev.Errorf("expected list item, got %q", prev)
+				err = prev.ErrorExpectedGot("list-item")
 				break
 			}
 		} else {
@@ -166,7 +177,7 @@ func (self *parser) parseList(scanner *scanner, allowVarRef bool) (subtree *term
 	if err == nil {
 		// TODO Check arguments
 		if lastSym != SymClosedSquare {
-			err = scanner.Previous().Errorf("unterminate items list")
+			err = scanner.Previous().ErrorExpectedGot("]")
 		} else {
 			subtree = newListTerm(args)
 		}
@@ -175,29 +186,18 @@ func (self *parser) parseList(scanner *scanner, allowVarRef bool) (subtree *term
 }
 
 func (self *parser) parseIterDef(scanner *scanner, allowVarRef bool) (subtree *term, err error) {
-	var ds *term
 	tk := scanner.Previous()
 	args := make([]*term, 0)
 	lastSym := SymUnknown
-	dsExpected := true
 	itemExpected := false
 	for lastSym != SymClosedRound && lastSym != SymEos {
 		var subTree *ast
 		if subTree, err = self.parseItem(scanner, allowVarRef, SymComma, SymClosedRound); err == nil {
 			if subTree.root != nil {
-				if dsExpected {
+				args = append(args, subTree.root)
-					if sym := subTree.root.symbol(); sym == SymDict || sym == SymIdentifier {
-						ds = subTree.root
-					} else {
-						err = subTree.root.Errorf("data-source dictionary expected, got %q", subTree.root.source())
-					}
-					dsExpected = false
-				} else {
-					args = append(args, subTree.root)
-				}
 			} else if itemExpected {
 				prev := scanner.Previous()
-				err = prev.Errorf("expected iterator argument, got %q", prev)
+				err = prev.ErrorExpectedGot("iterator-param")
 				break
 			}
 		} else {
@@ -209,11 +209,9 @@ func (self *parser) parseIterDef(scanner *scanner, allowVarRef bool) (subtree *t
 	if err == nil {
 		// TODO Check arguments
 		if lastSym != SymClosedRound {
-			err = scanner.Previous().Errorf("unterminate iterator param list")
+			err = scanner.Previous().ErrorExpectedGot(")")
-		} else if ds != nil {
-			subtree = newIteratorTerm(tk, ds, args)
 		} else {
-			tk.Errorf("missing data-source param")
+			subtree = newIteratorTerm(tk, args)
 		}
 	}
 	return
@@ -231,12 +229,13 @@ func (self *parser) parseDictKey(scanner *scanner, allowVarRef bool) (key any, e
 	if tk.Sym == SymInteger || tk.Sym == SymString {
 		tkSep := scanner.Next()
 		if tkSep.Sym != SymColon {
-			err = tkSep.Errorf("expected \":\", got %q", tkSep)
+			err = tkSep.ErrorExpectedGot(":")
 		} else {
 			key = tk.Value
 		}
 	} else {
-		err = tk.Errorf("expected dictionary key or closed brace, got %q", tk)
+		// err = tk.Errorf("expected dictionary key or closed brace, got %q", tk)
+		err = tk.ErrorExpectedGot("dictionary-key or }")
 	}
 	return
 }
@@ -254,7 +253,7 @@ func (self *parser) parseDictionary(scanner *scanner, allowVarRef bool) (subtree
 			tk := scanner.Previous()
 			lastSym = tk.Sym
 			if itemExpected {
-				err = tk.Errorf("expected dictionary key, got %q", tk)
+				err = tk.ErrorExpectedGot("dictionary-key")
 			}
 			break
 		}
@@ -263,7 +262,7 @@ func (self *parser) parseDictionary(scanner *scanner, allowVarRef bool) (subtree
 				args[key] = subTree.root
 			} else if key != nil {
 				prev := scanner.Previous()
-				err = prev.Errorf("expected dictionary value, got %q", prev)
+				err = prev.ErrorExpectedGot("dictionary-value")
 				break
 			}
 		} else {
@@ -275,9 +274,10 @@ func (self *parser) parseDictionary(scanner *scanner, allowVarRef bool) (subtree
 	if err == nil {
 		// TODO Check arguments
 		if lastSym != SymClosedBrace {
-			err = scanner.Previous().Errorf("unterminated dictionary")
+			err = scanner.Previous().ErrorExpectedGot("}")
 		} else {
 			subtree = newDictTerm(args)
+			// subtree = newMapTerm(args)
 		}
 	}
 	return
@@ -309,7 +309,7 @@ func (self *parser) parseSelectorCase(scanner *scanner, allowVarRef bool, defaul
 			return
 		}
 	} else {
-		err = tk.Errorf("selector-case expected, got %q", tk.source)
+		err = tk.ErrorExpectedGot("{")
 	}
 
 	if err == nil {
@@ -390,7 +390,7 @@ func (self *parser) parseGeneral(scanner *scanner, allowForest bool, allowVarRef
 			var subTree *ast
 			if subTree, err = self.parseGeneral(scanner, false, allowVarRef, SymClosedRound); err == nil {
 				subTree.root.priority = priValue
-				err = tree.addTerm(subTree.root)
+				err = tree.addTerm(newExprTerm(subTree.root))
 				currentTerm = subTree.root
 			}
 		case SymFuncCall:

parser_test.go

@@ -6,19 +6,18 @@ package expr
 
 import (
 	"errors"
-	"fmt"
 	"reflect"
 	"strings"
 	"testing"
 )
 
-func TestParser(t *testing.T) {
+type inputType struct {
-	type inputType struct {
+	source     string
-		source     string
+	wantResult any
-		wantResult any
+	wantErr    error
-		wantErr    error
+}
-	}
 
+func TestGeneralParser(t *testing.T) {
 	inputs := []inputType{
 		/*   1 */ {`1+/*5*/2`, int64(3), nil},
 		/*   2 */ {`3 == 4`, false, nil},
@@ -36,10 +35,10 @@ func TestParser(t *testing.T) {
 		/*  14 */ {`not true`, false, nil},
 		/*  15 */ {`true and false`, false, nil},
 		/*  16 */ {`true or false`, true, nil},
-		/*  17 */ {`"uno" + "due"`, `unodue`, nil},
+		/*  *17 */ {`"uno" + "due"`, `unodue`, nil},
-		/*  18 */ {`"uno" + 2`, `uno2`, nil},
+		/*  *18 */ {`"uno" + 2`, `uno2`, nil},
-		/*  19 */ {`"uno" + (2+1)`, `uno3`, nil},
+		/*  *19 */ {`"uno" + (2+1)`, `uno3`, nil},
-		/*  20 */ {`"uno" * (2+1)`, `unounouno`, nil},
+		/*  *20 */ {`"uno" * (2+1)`, `unounouno`, nil},
 		/*  21 */ {"1", int64(1), nil},
 		/*  22 */ {"1.5", float64(1.5), nil},
 		/*  23 */ {"1.5*2", float64(3.0), nil},
@@ -52,261 +51,127 @@ func TestParser(t *testing.T) {
 		/*  30 */ {"-(-2+1)", int64(1), nil},
 		/*  31 */ {"(1+1)*5", int64(10), nil},
 		/*  32 */ {"200 / (1+1) - 1", int64(99), nil},
-		/*  33 */ {`add(1,2,3)`, int64(6), nil},
+		/*  33 */ {`1+(1+(1+(1)+1)+1)+1`, int64(7), nil},
-		/*  34 */ {`mulX(1,2,3)`, nil, errors.New(`unknown function mulX()`)},
+		/*  34 */ {`(((1)))`, int64(1), nil},
-		/*  35 */ {`add(1+4,3+2,5*(3-2))`, int64(15), nil},
+		/*  35 */ {`var2="abc"; "uno_" + var2`, `uno_abc`, nil},
-		/*  36 */ {`add(add(1+4),3+2,5*(3-2))`, int64(15), nil},
+		/*  36 */ {`0 || 0.0 && "hello"`, false, nil},
-		/*  37 */ {`add(add(1,4),/*3+2,*/5*(3-2))`, int64(10), nil},
+		/*  37 */ {`"s" + true`, nil, errors.New(`[1:6] left operand 's' [string] and right operand 'true' [bool] are not compatible with operator "+"`)},
-		/*  38 */ {`1+(1+(1+(1)+1)+1)+1`, int64(7), nil},
+		/*  38 */ {`+false`, nil, errors.New(`[1:2] prefix/postfix operator "+" do not support operand 'false' [bool]`)},
-		/*  39 */ {`(((1)))`, int64(1), nil},
+		/*  39 */ {`false // very simple expression`, false, nil},
-		/*  40 */ {`"uno_" + var2`, `uno_abc`, nil},
+		/*  40 */ {`1 + // Missing right operator`, nil, errors.New(`[1:4] infix operator "+" requires two non-nil operands, got 1`)},
-		/*  41 */ {`0 || 0.0 && "hello"`, false, nil},
+		/*  41 */ {"", nil, nil},
-		/*  42 */ {`"s" + true`, nil, errors.New(`[1:6] left operand 's' [string] and right operand 'true' [bool] are not compatible with operator "+"`)},
+		/*  42 */ {"4!", int64(24), nil},
-		/*  43 */ {`+false`, nil, errors.New(`[1:2] prefix/postfix operator "+" do not support operand 'false' [bool]`)},
+		/*  43 */ {"(-4)!", nil, errors.New(`factorial of a negative integer (-4) is not allowed`)},
-		/*  44 */ {`false // very simple expression`, false, nil},
+		/*  44 */ {"-4!", int64(-24), nil},
-		/*  45 */ {`1 + // Missing right operator`, nil, errors.New(`[1:4] infix operator "+" requires two non-nil operands, got 1`)},
+		/*  45 */ {"1.5 < 7", true, nil},
-		/*  46 */ {"", nil, nil},
+		/*  46 */ {"1.5 > 7", false, nil},
-		/*  47 */ {"4!", int64(24), nil},
+		/*  47 */ {"1.5 <= 7", true, nil},
-		/*  48 */ {"(-4)!", nil, errors.New(`factorial of a negative integer (-4) is not allowed`)},
+		/*  48 */ {"1.5 >= 7", false, nil},
-		/*  49 */ {"-4!", int64(-24), nil},
+		/*  49 */ {"1.5 != 7", true, nil},
-		/*  50 */ {"1.5 < 7", true, nil},
+		/*  50 */ {"1.5 == 7", false, nil},
-		/*  51 */ {"1.5 > 7", false, nil},
+		/*  51 */ {`"1.5" < "7"`, true, nil},
-		/*  52 */ {"1.5 <= 7", true, nil},
+		/*  52 */ {`"1.5" > "7"`, false, nil},
-		/*  53 */ {"1.5 >= 7", false, nil},
+		/*  53 */ {`"1.5" == "7"`, false, nil},
-		/*  54 */ {"1.5 != 7", true, nil},
+		/*  54 */ {`"1.5" != "7"`, true, nil},
-		/*  55 */ {"1.5 == 7", false, nil},
+		/*  55 */ {"1.5 < ", nil, errors.New(`[1:6] infix operator "<" requires two non-nil operands, got 1`)},
-		/*  56 */ {`"1.5" < "7"`, true, nil},
+		/*  56 */ {"1.5 > ", nil, errors.New(`[1:6] infix operator ">" requires two non-nil operands, got 1`)},
-		/*  57 */ {`"1.5" > "7"`, false, nil},
+		/*  57 */ {"1.5 <= ", nil, errors.New(`[1:6] infix operator "<=" requires two non-nil operands, got 1`)},
-		/*  58 */ {`"1.5" == "7"`, false, nil},
+		/*  58 */ {"1.5 >= ", nil, errors.New(`[1:6] infix operator ">=" requires two non-nil operands, got 1`)},
-		/*  59 */ {`"1.5" != "7"`, true, nil},
+		/*  59 */ {"1.5 != ", nil, errors.New(`[1:6] infix operator "!=" requires two non-nil operands, got 1`)},
-		/*  60 */ {"1.5 < ", nil, errors.New(`[1:6] infix operator "<" requires two non-nil operands, got 1`)},
+		/*  60 */ {"1.5 == ", nil, errors.New(`[1:6] infix operator "==" requires two non-nil operands, got 1`)},
-		/*  61 */ {"1.5 > ", nil, errors.New(`[1:6] infix operator ">" requires two non-nil operands, got 1`)},
+		/*  61 */ {`"1.5" < `, nil, errors.New(`[1:8] infix operator "<" requires two non-nil operands, got 1`)},
-		/*  62 */ {"1.5 <= ", nil, errors.New(`[1:6] infix operator "<=" requires two non-nil operands, got 1`)},
+		/*  62 */ {`"1.5" > `, nil, errors.New(`[1:8] infix operator ">" requires two non-nil operands, got 1`)},
-		/*  63 */ {"1.5 >= ", nil, errors.New(`[1:6] infix operator ">=" requires two non-nil operands, got 1`)},
+		/*  63 */ {`"1.5" == `, nil, errors.New(`[1:8] infix operator "==" requires two non-nil operands, got 1`)},
-		/*  64 */ {"1.5 != ", nil, errors.New(`[1:6] infix operator "!=" requires two non-nil operands, got 1`)},
+		/*  64 */ {`"1.5" != `, nil, errors.New(`[1:8] infix operator "!=" requires two non-nil operands, got 1`)},
-		/*  65 */ {"1.5 == ", nil, errors.New(`[1:6] infix operator "==" requires two non-nil operands, got 1`)},
+		/*  65 */ {"+1.5", float64(1.5), nil},
-		/*  66 */ {`"1.5" < `, nil, errors.New(`[1:8] infix operator "<" requires two non-nil operands, got 1`)},
+		/*  66 */ {"+", nil, errors.New(`[1:2] prefix operator "+" requires one not nil operand`)},
-		/*  67 */ {`"1.5" > `, nil, errors.New(`[1:8] infix operator ">" requires two non-nil operands, got 1`)},
+		/*  67 */ {"4 / 0", nil, errors.New(`division by zero`)},
-		/*  68 */ {`"1.5" == `, nil, errors.New(`[1:8] infix operator "==" requires two non-nil operands, got 1`)},
+		/*  68 */ {"4.0 / 0", nil, errors.New(`division by zero`)},
-		/*  69 */ {`"1.5" != `, nil, errors.New(`[1:8] infix operator "!=" requires two non-nil operands, got 1`)},
+		/*  69 */ {"4.0 / \n2", float64(2.0), nil},
-		/*  70 */ {"+1.5", float64(1.5), nil},
+		/*  70 */ {`123`, int64(123), nil},
-		/*  71 */ {"+", nil, errors.New(`[1:2] prefix operator "+" requires one not nil operand`)},
+		/*  71 */ {`1.`, float64(1.0), nil},
-		/*  72 */ {"4 / 0", nil, errors.New(`division by zero`)},
+		/*  72 */ {`1.E-2`, float64(0.01), nil},
-		/*  73 */ {"4.0 / 0", nil, errors.New(`division by zero`)},
+		/*  73 */ {`1E2`, float64(100), nil},
-		/*  74 */ {"4.0 / \n2", float64(2.0), nil},
+		/*  74 */ {`1 / 2`, int64(0), nil},
-		/*  75 */ {`123`, int64(123), nil},
+		/*  75 */ {`1.0 / 2`, float64(0.5), nil},
-		/*  76 */ {`1.`, float64(1.0), nil},
+		/*  76 */ {`1 ./ 2`, float64(0.5), nil},
-		/*  77 */ {`1.E-2`, float64(0.01), nil},
+		/*  77 */ {`5 % 2`, int64(1), nil},
-		/*  78 */ {`1E2`, float64(100), nil},
+		/*  78 */ {`5 % (-2)`, int64(1), nil},
-		/*  79 */ {`1 / 2`, int64(0), nil},
+		/*  79 */ {`-5 % 2`, int64(-1), nil},
-		/*  80 */ {`1.0 / 2`, float64(0.5), nil},
+		/*  80 */ {`5 % 2.0`, nil, errors.New(`[1:4] left operand '5' [integer] and right operand '2' [float] are not compatible with operator "%"`)},
-		/*  81 */ {`1 ./ 2`, float64(0.5), nil},
+		/*  81 */ {`"a" < "b" AND NOT (2 < 1)`, true, nil},
-		/*  82 */ {`5 % 2`, int64(1), nil},
+		/*  82 */ {`"a" < "b" AND NOT (2 == 1)`, true, nil},
-		/*  83 */ {`5 % (-2)`, int64(1), nil},
+		/*  83 */ {`"a" < "b" AND ~ 2 == 1`, true, nil},
-		/*  84 */ {`-5 % 2`, int64(-1), nil},
+		/*  84 */ {`~ 2 > 1`, false, nil},
-		/*  85 */ {`5 % 2.0`, nil, errors.New(`[1:4] left operand '5' [int64] and right operand '2' [float64] are not compatible with operator "%"`)},
+		/*  85 */ {`~ true && true`, false, nil},
-		/*  86 */ {`"a" < "b" AND NOT (2 < 1)`, true, nil},
+		/*  86 */ {`~ false || true`, true, nil},
-		/*  87 */ {`"a" < "b" AND NOT (2 == 1)`, true, nil},
+		/*  87 */ {`false but true`, true, nil},
-		/*  88 */ {`"a" < "b" AND ~ 2 == 1`, true, nil},
+		/*  88 */ {`2+3 but 5*2`, int64(10), nil},
-		/*  89 */ {`~ 2 > 1`, false, nil},
+		/*  89 */ {`x=2`, int64(2), nil},
-		/*  90 */ {`~ true && true`, false, nil},
+		/*  90 */ {`x=2 but x*10`, int64(20), nil},
-		/*  91 */ {`~ false || true`, true, nil},
+		/*  91 */ {`false and true`, false, nil},
-		/*  92 */ {`false but true`, true, nil},
+		/*  92 */ {`false and (x==2)`, false, nil},
-		/*  93 */ {`2+3 but 5*2`, int64(10), nil},
+		/*  93 */ {`false and (x=2 but x==2) or x==2`, nil, errors.New(`undefined variable or function "x"`)},
-		/*  94 */ {`add(1,2) but var2`, "abc", nil},
+		/*  94 */ {`false or true`, true, nil},
-		/*  95 */ {`x=2`, int64(2), nil},
+		/*  95 */ {`false or (x==2)`, nil, errors.New(`undefined variable or function "x"`)},
-		/*  96 */ {`x=2 but x*10`, int64(20), nil},
+		/*  96 */ {`a=5; a`, int64(5), nil},
-		/*  97 */ {`false and true`, false, nil},
+		/*  97 */ {`2=5`, nil, errors.New(`assign operator ("=") must be preceded by a variable`)},
-		/*  98 */ {`false and (x==2)`, false, nil},
+		/*  98 */ {`2+a=5`, nil, errors.New(`[1:3] left operand of "=" must be a variable`)},
-		/*  99 */ {`false and (x=2 but x==2) or x==2`, nil, errors.New(`undefined variable or function "x"`)},
+		/*  99 */ {`2+(a=5)`, int64(7), nil},
-		/* 100 */ {`false or true`, true, nil},
+		/* 100 */ {`x ?? "default"`, "default", nil},
-		/* 101 */ {`false or (x==2)`, nil, errors.New(`undefined variable or function "x"`)},
+		/* 101 */ {`x="hello"; x ?? "default"`, "hello", nil},
-		/* 102 */ {`a=5; a`, int64(5), nil},
+		/* 102 */ {`y=x ?? func(){4}; y()`, int64(4), nil},
-		/* 103 */ {`a=5; b=2; add(a, b*3)`, int64(11), nil},
+		/* 103 */ {`x ?= "default"; x`, "default", nil},
-		/* 104 */ {`2=5`, nil, errors.New(`assign operator ("=") must be preceded by a variable`)},
+		/* 104 */ {`x="hello"; x ?= "default"; x`, "hello", nil},
-		/* 105 */ {`2+a=5`, nil, errors.New(`[1:3] left operand of "=" must be a variable`)},
+		/* 105 */ {`1 ? {"a"} : {"b"}`, "b", nil},
-		/* 106 */ {`2+(a=5)`, int64(7), nil},
+		/* 106 */ {`10 ? {"a"} : {"b"} :: {"c"}`, "c", nil},
-		/* 107 */ {`two=func(){2}; two()`, int64(2), nil},
+		/* 107 */ {`10 ? {"a"} :[true, 2+8] {"b"} :: {"c"}`, "b", nil},
-		/* 108 */ {`double=func(x) {2*x}; (double(3))`, int64(6), nil},
+		/* 108 */ {`10 ? {"a"} :[true, 2+8] {"b"} ::[10] {"c"}`, nil, errors.New(`[1:34] case list in default clause`)},
-		/* 109 */ {`double=func(x){2*x}; double(3)`, int64(6), nil},
+		/* 109 */ {`10 ? {"a"} :[10] {x="b" but x} :: {"c"}`, "b", nil},
-		/* 110 */ {`double=func(x){2*x}; a=5; double(3+a) + 1`, int64(17), nil},
+		/* 110 */ {`10 ? {"a"} :[10] {x="b"; x} :: {"c"}`, "b", nil},
-		/* 111 */ {`double=func(x){2*x}; a=5; two=func() {2}; (double(3+a) + 1) * two()`, int64(34), nil},
+		/* 111 */ {`10 ? {"a"} : {"b"}`, nil, errors.New(`[1:3] no case catches the value (10) of the selection expression`)},
-		/* 112 */ {`import("./test-funcs.expr"); (double(3+a) + 1) * two()`, int64(34), nil},
+		/* 112 */ {`10 ? {"a"} :: {"b"} : {"c"}`, nil, errors.New(`[1:22] selector-case outside of a selector context`)},
-		/* 113 */ {`import("test-funcs.expr"); (double(3+a) + 1) * two()`, int64(34), nil},
+		/* 113 */ {`1 ? {"a"} : {"b"} ? ["a"] {"A"} :["b"] {"B"}`, "B", nil},
-		/* 114 */ {`x ?? "default"`, "default", nil},
+		/* 114 */ {`2 + 1 ? {"a"} : {"b"} * 3`, "2bbb", nil},
-		/* 115 */ {`x="hello"; x ?? "default"`, "hello", nil},
+		/* 115 */ {`nil`, nil, nil},
-		/* 116 */ {`y=x ?? func(){4}; y()`, int64(4), nil},
+		/* 116 */ {`null`, nil, errors.New(`undefined variable or function "null"`)},
-		/* 117 */ {`x ?= "default"; x`, "default", nil},
+		/* 117 */ {`{"key"}`, nil, errors.New(`[1:8] expected ":", got "}"`)},
-		/* 118 */ {`x="hello"; x ?= "default"; x`, "hello", nil},
+		/* 118 */ {`{"key":}`, nil, errors.New(`[1:9] expected "dictionary-value", got "}"`)},
-		/* 119 */ {`@x="hello"; @x`, nil, errors.New(`[1:3] variable references are not allowed in top level expressions: "@x"`)},
+		/* 119 */ {`{}`, &DictType{}, nil},
-		/* 120 */ {`f=func(){@x="hello"}; f(); x`, "hello", nil},
+		/* 120 */ {`1|2`, newFraction(1, 2), nil},
-		/* 121 */ {`f=func(@y){@y=@y+1}; f(2); y`, int64(3), nil},
+		/* 121 */ {`1|2 + 1`, newFraction(3, 2), nil},
-		/* 122 */ {`f=func(@y){g=func(){@x=5}; @y=@y+g()}; f(2); y+x`, nil, errors.New(`undefined variable or function "x"`)},
+		/* 122 */ {`1|2 - 1`, newFraction(-1, 2), nil},
-		/* 123 */ {`f=func(@y){g=func(){@x=5}; @z=g(); @y=@y+@z}; f(2); y+z`, int64(12), nil},
+		/* 123 */ {`1|2 * 1`, newFraction(1, 2), nil},
-		/* 124 */ {`f=func(@y){g=func(){@x=5}; g(); @z=x; @y=@y+@z}; f(2); y+z`, int64(12), nil},
+		/* 124 */ {`1|2 * 2|3`, newFraction(2, 6), nil},
-		/* 125 */ {`f=func(@y){g=func(){@x=5}; g(); @z=x; @x=@y+@z}; f(2); y+x`, int64(9), nil},
+		/* 125 */ {`1|2 / 2|3`, newFraction(3, 4), nil},
-		/* 126 */ {`include("./test-funcs.expr"); six()`, int64(6), nil},
+		/* 126 */ {`builtin "math.arith"; add(1,2,3)`, int64(6), nil},
-		/* 127 */ {`import("./sample-export-all.expr"); six()`, int64(6), nil},
+		/* 127 */ {`builtin "math.arith"; mulX(1,2,3)`, nil, errors.New(`unknown function mulX()`)},
-		/* 128 */ {`1 ? {"a"} : {"b"}`, "b", nil},
+		/* 128 */ {`builtin "math.arith"; add(1+4,3+2,5*(3-2))`, int64(15), nil},
-		/* 129 */ {`10 ? {"a"} : {"b"} :: {"c"}`, "c", nil},
+		/* 129 */ {`builtin "math.arith"; add(add(1+4),3+2,5*(3-2))`, int64(15), nil},
-		/* 130 */ {`10 ? {"a"} :[true, 2+8] {"b"} :: {"c"}`, "b", nil},
+		/* 130 */ {`builtin "math.arith"; add(add(1,4),/*3+2,*/5*(3-2))`, int64(10), nil},
-		/* 131 */ {`10 ? {"a"} :[true, 2+8] {"b"} ::[10] {"c"}`, nil, errors.New(`[1:34] case list in default clause`)},
+		/* 131 */ {`builtin "math.arith"; a=5; b=2; add(a, b*3)`, int64(11), nil},
-		/* 132 */ {`10 ? {"a"} :[10] {x="b" but x} :: {"c"}`, "b", nil},
+		/* 132 */ {`builtin "math.arith"; var2="abc"; add(1,2) but var2`, "abc", nil},
-		/* 133 */ {`10 ? {"a"} :[10] {x="b"; x} :: {"c"}`, "b", nil},
+		/* 133 */ {`builtin "math.arith"; add(1|2, 2|3)`, newFraction(7, 6), nil},
-		/* 134 */ {`10 ? {"a"} : {"b"}`, nil, errors.New(`[1:3] no case catches the value (10) of the selection expression`)},
+		/* 134 */ {`builtin "math.arith"; add(1|2, 1.0, 2)`, float64(3.5), nil},
-		/* 135 */ {`10 ? {"a"} :: {"b"} : {"c"}`, nil, errors.New(`[1:22] selector-case outside of a selector context`)},
+		/* 135 */ {`builtin "math.arith"; mul(1|2, 2|3)`, newFraction(2, 6), nil},
-		/* 136 */ {`1 ? {"a"} : {"b"} ? ["a"] {"A"} :["b"] {"B"}`, "B", nil},
+		/* 136 */ {`builtin "math.arith"; mul(1|2, 1.0, 2)`, float64(1.0), nil},
-		/* 137 */ {`2 + 1 ? {"a"} : {"b"} * 3`, "2bbb", nil},
+		/* 137 */ {`builtin "os.file"`, int64(1), nil},
-		/* 138 */ {`nil`, nil, nil},
+		/* 138 */ {`v=10; v++; v`, int64(11), nil},
-		/* 139 */ {`null`, nil, errors.New(`undefined variable or function "null"`)},
+		/* 139 */ {`1+1|2+0.5`, float64(2), nil},
-		/* 140 */ {`{"key"}`, nil, errors.New(`[1:8] expected ":", got "}"`)},
+		/* 140 */ {`1.2()`, newFraction(6, 5), nil},
-		/* 141 */ {`{"key":}`, nil, errors.New(`[1:9] expected dictionary value, got "}"`)},
+		/* 141 */ {`1|(2-2)`, nil, errors.New(`division by zero`)},
-		/* 142 */ {`{}`, map[any]any{}, nil},
-		/* 144 */ //{`3^2`, int64(9), nil},
 	}
-	check_env_expr_path := 113
 
-	succeeded := 0
+	// t.Setenv("EXPR_PATH", ".")
-	failed := 0
+	// parserTestSpec(t, "General", inputs, 102)
-
+	parserTest(t, "General", inputs)
-	// inputs1 := []inputType{
-	// 	/* 140 */ {`ds={}; $(ds)`, nil, nil},
-	// }
-
-	for i, input := range inputs {
-		var expr Expr
-		var gotResult any
-		var gotErr error
-
-		ctx := NewSimpleFuncStore()
-		ctx.SetVar("var1", int64(123))
-		ctx.SetVar("var2", "abc")
-		ImportMathFuncs(ctx)
-		ImportImportFuncs(ctx)
-		parser := NewParser(ctx)
-
-		logTest(t, i+1, input.source, input.wantResult, input.wantErr)
-
-		r := strings.NewReader(input.source)
-		scanner := NewScanner(r, DefaultTranslations())
-
-		good := true
-		if expr, gotErr = parser.Parse(scanner); gotErr == nil {
-			gotResult, gotErr = expr.Eval(ctx)
-		}
-
-		eq := reflect.DeepEqual(gotResult, input.wantResult)
-
-		if !eq /*gotResult != input.wantResult*/ {
-			t.Errorf("%d: %q -> result = %v [%T], want %v [%T]", i+1, input.source, gotResult, gotResult, input.wantResult, input.wantResult)
-			good = false
-		}
-
-		if gotErr != input.wantErr {
-			if input.wantErr == nil || gotErr == nil || (gotErr.Error() != input.wantErr.Error()) {
-				t.Errorf("%d: %q -> err = <%v>, want <%v>", i+1, input.source, gotErr, input.wantErr)
-				good = false
-			}
-		}
-
-		if good {
-			succeeded++
-		} else {
-			failed++
-			if i+1 == check_env_expr_path {
-				t.Logf(`NOTICE: Test nr %d requires EXPR_PATH="."`, check_env_expr_path)
-			}
-		}
-	}
-	t.Log(fmt.Sprintf("test count: %d, succeeded count: %d, failed count: %d", len(inputs), succeeded, failed))
 }
 
-func TestListParser(t *testing.T) {
+func parserTestSpec(t *testing.T, section string, inputs []inputType, spec ...int) {
-	type inputType struct {
-		source     string
-		wantResult any
-		wantErr    error
-	}
-
-	inputs := []inputType{
-		/*  1 */ {`[]`, []any{}, nil},
-		/*  2 */ {`[1,2,3]`, []any{int64(1), int64(2), int64(3)}, nil},
-		/*  3 */ {`[1,2,"hello"]`, []any{int64(1), int64(2), "hello"}, nil},
-		/*  4 */ {`[1+2, not true, "hello"]`, []any{int64(3), false, "hello"}, nil},
-		/*  5 */ {`[1,2]+[3]`, []any{int64(1), int64(2), int64(3)}, nil},
-		/*  6 */ {`[1,4,3,2]-[3]`, []any{int64(1), int64(4), int64(2)}, nil},
-		/*  7 */ {`add([1,4,3,2])`, int64(10), nil},
-		/*  8 */ {`add([1,[2,2],3,2])`, int64(10), nil},
-		/*  9 */ {`mul([1,4,3.0,2])`, float64(24.0), nil},
-		/* 10 */ {`add([1,"hello"])`, nil, errors.New(`add(): param nr 2 has wrong type string, number expected`)},
-		/* 11 */ {`[a=1,b=2,c=3] but a+b+c`, int64(6), nil},
-		// /*  8 */ {`[int(x)|x=csv("test.csv",1,all(),1)]`, []any{int64(10), int64(40), int64(20)}, nil},
-		// /*  9 */ {`sum(@[int(x)|x=csv("test.csv",1,all(),1)])`, []any{int64(10), int64(40), int64(20)}, nil},
-	}
-
 	succeeded := 0
 	failed := 0
-
+	for _, count := range spec {
-	// inputs1 := []inputType{
+		good := doTest(t, section, &inputs[count-1], count)
-	// 	/*  7 */ {`add([1,4,3,2])`, int64(10), nil},
-	// }
-
-	for i, input := range inputs {
-		var expr *ast
-		var gotResult any
-		var gotErr error
-
-		ctx := NewSimpleFuncStore()
-		ctx.SetVar("var1", int64(123))
-		ctx.SetVar("var2", "abc")
-		ImportMathFuncs(ctx)
-		parser := NewParser(ctx)
-
-		logTest(t, i+1, input.source, input.wantResult, input.wantErr)
-
-		r := strings.NewReader(input.source)
-		scanner := NewScanner(r, DefaultTranslations())
-
-		good := true
-		if expr, gotErr = parser.Parse(scanner); gotErr == nil {
-			gotResult, gotErr = expr.Eval(ctx)
-		}
-
-		if (gotResult == nil && input.wantResult != nil) || (gotResult != nil && input.wantResult == nil) {
-			t.Errorf("%d: %q -> result = %v [%T], want %v [%T]", i+1, input.source, gotResult, gotResult, input.wantResult, input.wantResult)
-			good = false
-		}
-
-		if gotList, okGot := gotResult.([]any); okGot {
-			if wantList, okWant := input.wantResult.([]any); okWant {
-				if (gotList == nil && wantList != nil) || (gotList != nil && wantList == nil) {
-					t.Errorf("%d: %q -> result = %v [%T], want %v [%T]", i+1, input.source, gotResult, gotResult, input.wantResult, input.wantResult)
-					good = false
-				} else {
-					equal := len(gotList) == len(wantList)
-					if equal {
-						for i, gotItem := range gotList {
-							wantItem := wantList[i]
-							equal = gotItem == wantItem
-							if !equal {
-								break
-							}
-						}
-					}
-					if !equal {
-						t.Errorf("%d: %q -> result = %v [%T], want %v [%T]", i+1, input.source, gotResult, gotResult, input.wantResult, input.wantResult)
-						good = false
-					}
-				}
-			}
-		}
-
-		if gotErr != input.wantErr {
-			if input.wantErr == nil || gotErr == nil || (gotErr.Error() != input.wantErr.Error()) {
-				t.Errorf("%d: %q  -> err = <%v>, want <%v>", i+1, input.source, gotErr, input.wantErr)
-				good = false
-			}
-		}
 
 		if good {
 			succeeded++
@@ -314,13 +179,63 @@ func TestListParser(t *testing.T) {
 			failed++
 		}
 	}
-	t.Log(fmt.Sprintf("test count: %d, succeeded count: %d, failed count: %d", len(inputs), succeeded, failed))
+	t.Logf("%s -- test count: %d, succeeded: %d, failed: %d", section, len(spec), succeeded, failed)
 }
 
-func logTest(t *testing.T, n int, source string, wantResult any, wantErr error) {
+func parserTest(t *testing.T, section string, inputs []inputType) {
+
+	succeeded := 0
+	failed := 0
+
+	for i, input := range inputs {
+		good := doTest(t, section, &input, i+1)
+		if good {
+			succeeded++
+		} else {
+			failed++
+		}
+	}
+	t.Logf("%s -- test count: %d, succeeded: %d, failed: %d", section, len(inputs), succeeded, failed)
+}
+
+func doTest(t *testing.T, section string, input *inputType, count int) (good bool) {
+	var expr Expr
+	var gotResult any
+	var gotErr error
+
+	ctx := NewSimpleStore()
+	parser := NewParser(ctx)
+
+	logTest(t, count, section, input.source, input.wantResult, input.wantErr)
+
+	r := strings.NewReader(input.source)
+	scanner := NewScanner(r, DefaultTranslations())
+
+	good = true
+	if expr, gotErr = parser.Parse(scanner); gotErr == nil {
+		gotResult, gotErr = expr.Eval(ctx)
+	}
+
+	eq := reflect.DeepEqual(gotResult, input.wantResult)
+
+	if !eq /*gotResult != input.wantResult*/ {
+		t.Errorf("%d: %q -> result = %v [%T], want = %v [%T]", count, input.source, gotResult, gotResult, input.wantResult, input.wantResult)
+		good = false
+	}
+
+	if gotErr != input.wantErr {
+		if input.wantErr == nil || gotErr == nil || (gotErr.Error() != input.wantErr.Error()) {
+			t.Errorf("%d: %q -> got-err = <%v>, expected-err = <%v>", count, input.source, gotErr, input.wantErr)
+			good = false
+		}
+	}
+	return
+}
+
+func logTest(t *testing.T, n int, section, source string, wantResult any, wantErr error) {
 	if wantErr == nil {
-		t.Log(fmt.Sprintf("[+]Test nr %3d -- %q  --> %v", n, source, wantResult))
+		t.Logf("[+]%s nr %3d -- %q  --> %v", section, n, source, wantResult)
 	} else {
-		t.Log(fmt.Sprintf("[-]Test nr %3d -- %q  --> %v", n, source, wantErr))
+		t.Logf("[-]%s nr %3d -- %q  --> %v", section, n, source, wantErr)
 	}
 }

scanner.go

@@ -160,6 +160,12 @@ func (self *scanner) fetchNextToken() (tk *Token) {
 			//} else if next == '/' {
 			if next, _ := self.peek(); next == '/' {
 				tk = self.moveOn(SymDotSlash, ch, next)
+			} else if next == '.' {
+				if next1, _ := self.peek(); next1 == '.' {
+					tk = self.moveOn(SymTripleDot, ch, next, next1)
+				} else {
+					tk = self.moveOn(SymDoubleDot, ch, next)
+				}
 			} else {
 				tk = self.makeToken(SymDot, ch)
 			}
@@ -379,20 +385,37 @@ func (self *scanner) parseNumber(firstCh byte) (tk *Token) {
 				}
 			}
 		}
-		if err == nil && (ch == 'e' || ch == 'E') {
+		if err == nil {
-			sym = SymFloat
+			if ch == 'e' || ch == 'E' {
-			sb.WriteByte(ch)
+				sym = SymFloat
-			if ch, err = self.readChar(); err == nil {
+				sb.WriteByte(ch)
-				if ch == '+' || ch == '-' {
+				if ch, err = self.readChar(); err == nil {
-					sb.WriteByte(ch)
+					if ch == '+' || ch == '-' {
-					ch, err = self.readChar()
-				}
-				if ch >= '0' && ch <= '9' {
-					for ; err == nil && (ch >= '0' && ch <= '9'); ch, err = self.readChar() {
 						sb.WriteByte(ch)
+						ch, err = self.readChar()
+					}
+					if ch >= '0' && ch <= '9' {
+						for ; err == nil && (ch >= '0' && ch <= '9'); ch, err = self.readChar() {
+							sb.WriteByte(ch)
+						}
+					} else {
+						err = fmt.Errorf("[%d:%d] expected integer exponent, got %c", self.row, self.column, ch)
+					}
+				}
+			} else if ch == '(' {
+				sym = SymFraction
+				sb.WriteByte(ch)
+				ch, err = self.readChar()
+				for ; err == nil && (ch >= '0' && ch <= '9'); ch, err = self.readChar() {
+					sb.WriteByte(ch)
+				}
+				if err == nil {
+					if ch != ')' {
+						err = fmt.Errorf("[%d:%d] expected ')', got '%c'", self.row, self.column, ch)
+					} else {
+						sb.WriteByte(ch)
+						_, err = self.readChar()
 					}
-				} else {
-					err = errors.New("expected integer exponent")
 				}
 			}
 		}
@@ -406,6 +429,8 @@ func (self *scanner) parseNumber(firstCh byte) (tk *Token) {
 		txt := sb.String()
 		if sym == SymFloat {
 			value, err = strconv.ParseFloat(txt, 64)
+		} else if sym == SymFraction {
+			value, err = makeGeneratingFraction(txt)
 		} else {
 			value, err = strconv.ParseInt(txt, numBase, 64)
 		}

scanner_test.go

@@ -7,6 +7,7 @@ package expr
 import (
 	"errors"
 	"fmt"
+	"reflect"
 	"strings"
 	"testing"
 )
@@ -55,15 +56,18 @@ func TestScanner(t *testing.T) {
 		/* 33 */ {`(`, SymOpenRound, nil, nil},
 		/* 34 */ {`)`, SymClosedRound, nil, nil},
 		/* 35 */ {`1E+2`, SymFloat, float64(100), nil},
-		/* 36 */ {`1E+x`, SymError, errors.New("expected integer exponent"), nil},
+		/* 36 */ {`1E+x`, SymError, errors.New("[1:5] expected integer exponent, got x"), nil},
 		/* 37 */ {`$`, SymDollar, nil, nil},
 		/* 38 */ {`\`, SymError, errors.New("incomplete escape sequence"), nil},
 		/* 39 */ {`"string"`, SymString, "string", nil},
-		/* 39 */ {`identifier`, SymIdentifier, "identifier", nil},
+		/* 40 */ {`identifier`, SymIdentifier, "identifier", nil},
+		/* 41 */ {`1.2(3)`, SymFraction, newFraction(37, 30), nil},
 	}
 
 	for i, input := range inputs {
-
+		// if i != 40 {
+		// 	continue
+		// }
 		if input.wantErr == nil {
 			t.Log(fmt.Sprintf("[+]Test nr %2d -- %q", i+1, input.source))
 		} else {
@@ -75,7 +79,8 @@ func TestScanner(t *testing.T) {
 
 		if tk := scanner.Next(); tk == nil {
 			t.Errorf("%d: %q -> got = (nil), want %v (value %v [%T])", i+1, input.source, input.wantSym, input.wantValue, input.wantValue)
-		} else if tk.Sym != input.wantSym || tk.Value != input.wantValue {
+			// } else if tk.Sym != input.wantSym || tk.Value != input.wantValue {
+		} else if tk.Sym != input.wantSym || !reflect.DeepEqual(tk.Value, input.wantValue) {
 			if tk.Sym == SymError && input.wantSym == tk.Sym {
 				if tkErr, tkOk := tk.Value.(error); tkOk {
 					if inputErr, inputOk := input.wantValue.(error); inputOk {
@@ -86,7 +91,7 @@ func TestScanner(t *testing.T) {
 					}
 				}
 			} else {
-				t.Errorf("%d: %q -> got = %v (value=%v [%T), want %v (value=%v [%T)", i+1,
+				t.Errorf("%d: %q -> got = %v (value=%v [%T]), want %v (value=%v [%T])", i+1,
 					input.source, tk.Sym, tk.Value, tk.Value, input.wantSym, input.wantValue, input.wantValue)
 			}
 		}

simple-func-store.go

@@ -1,84 +0,0 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
-// All rights reserved.
-
-// simple-func-store.go
-package expr
-
-import "fmt"
-
-type SimpleFuncStore struct {
-	SimpleVarStore
-	funcStore map[string]*funcInfo
-}
-
-type funcInfo struct {
-	name    string
-	minArgs int
-	maxArgs int
-	functor Functor
-}
-
-func (info *funcInfo) Name() string {
-	return info.name
-}
-
-func (info *funcInfo) MinArgs() int {
-	return info.minArgs
-}
-
-func (info *funcInfo) MaxArgs() int {
-	return info.maxArgs
-}
-
-func (info *funcInfo) Functor() Functor {
-	return info.functor
-}
-
-func NewSimpleFuncStore() *SimpleFuncStore {
-	ctx := &SimpleFuncStore{
-		SimpleVarStore: SimpleVarStore{varStore: make(map[string]any)},
-		funcStore:      make(map[string]*funcInfo),
-	}
-	ImportBuiltinsFuncs(ctx)
-	return ctx
-}
-
-func (ctx *SimpleFuncStore) Clone() ExprContext {
-	return &SimpleFuncStore{
-		SimpleVarStore: SimpleVarStore{varStore: CloneMap(ctx.varStore)},
-		funcStore:      CloneMap(ctx.funcStore),
-	}
-}
-
-func (ctx *SimpleFuncStore) GetFuncInfo(name string) (info ExprFunc, exists bool) {
-	info, exists = ctx.funcStore[name]
-	return
-}
-
-func (ctx *SimpleFuncStore) RegisterFunc(name string, functor Functor, minArgs, maxArgs int) {
-	ctx.funcStore[name] = &funcInfo{name: name, minArgs: minArgs, maxArgs: maxArgs, functor: functor}
-}
-
-func (ctx *SimpleFuncStore) EnumFuncs(acceptor func(name string) (accept bool)) (funcNames []string) {
-	funcNames = make([]string, 0)
-	for name := range ctx.funcStore {
-		if acceptor != nil {
-			if acceptor(name) {
-				funcNames = append(funcNames, name)
-			}
-		} else {
-			funcNames = append(funcNames, name)
-		}
-	}
-	return
-}
-
-func (ctx *SimpleFuncStore) Call(name string, args []any) (result any, err error) {
-	if info, exists := ctx.funcStore[name]; exists {
-		functor := info.functor
-		result, err = functor.Invoke(ctx, name, args)
-	} else {
-		err = fmt.Errorf("unknown function %s()", name)
-	}
-	return
-}

simple-func-store.go.bak

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

simple-store.go

@@ -0,0 +1,173 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// simple-store.go
+package expr
+
+import (
+	"fmt"
+	"slices"
+	"strings"
+)
+
+type SimpleStore struct {
+	varStore  map[string]any
+	funcStore map[string]*funcInfo
+}
+
+func NewSimpleStore() *SimpleStore {
+	ctx := &SimpleStore{
+		varStore:  make(map[string]any),
+		funcStore: make(map[string]*funcInfo),
+	}
+	//ImportBuiltinsFuncs(ctx)
+	return ctx
+}
+
+func (ctx *SimpleStore) Clone() ExprContext {
+	return &SimpleStore{
+		varStore:  CloneFilteredMap(ctx.varStore, func(name string) bool { return name[0] != '@' }),
+		funcStore: CloneFilteredMap(ctx.funcStore, func(name string) bool { return name[0] != '@' }),
+	}
+}
+
+func varsCtxToBuilder(sb *strings.Builder, ctx ExprContext, indent int) {
+	sb.WriteString("vars: {\n")
+	first := true
+	for _, name := range ctx.EnumVars(func(name string) bool { return name[0] != '_' }) {
+		if first {
+			first = false
+		} else {
+			sb.WriteByte(',')
+			sb.WriteByte('\n')
+		}
+
+		value, _ := ctx.GetVar(name)
+		sb.WriteString(strings.Repeat("\t", indent+1))
+		sb.WriteString(name)
+		sb.WriteString(": ")
+		if f, ok := value.(Formatter); ok {
+			sb.WriteString(f.ToString(0))
+		} else if _, ok = value.(Functor); ok {
+			sb.WriteString("func(){}")
+			// } else if _, ok = value.(map[any]any); ok {
+			// 	sb.WriteString("dict{}")
+		} else {
+			sb.WriteString(fmt.Sprintf("%v", value))
+		}
+	}
+	sb.WriteString(strings.Repeat("\t", indent))
+	sb.WriteString("\n}\n")
+}
+
+func varsCtxToString(ctx ExprContext, indent int) string {
+	var sb strings.Builder
+	varsCtxToBuilder(&sb, ctx, indent)
+	return sb.String()
+}
+
+func funcsCtxToBuilder(sb *strings.Builder, ctx ExprContext, indent int) {
+	sb.WriteString("funcs: {\n")
+	first := true
+	names := ctx.EnumFuncs(func(name string) bool { return true })
+	slices.Sort(names)
+	for _, name := range names {
+		if first {
+			first = false
+		} else {
+			sb.WriteByte(',')
+			sb.WriteByte('\n')
+		}
+		value, _ := ctx.GetFuncInfo(name)
+		sb.WriteString(strings.Repeat("\t", indent+1))
+		sb.WriteString(name)
+		//sb.WriteString("=")
+		if formatter, ok := value.(Formatter); ok {
+			sb.WriteString(formatter.ToString(0))
+		} else {
+			sb.WriteString(fmt.Sprintf("%v", value))
+		}
+	}
+	sb.WriteString("\n}\n")
+}
+
+func (ctx *SimpleStore) ToString(opt FmtOpt) string {
+	var sb strings.Builder
+	varsCtxToBuilder(&sb, ctx, 0)
+	funcsCtxToBuilder(&sb, ctx, 0)
+	return sb.String()
+}
+
+func (ctx *SimpleStore) GetVar(varName string) (v any, exists bool) {
+	v, exists = ctx.varStore[varName]
+	return
+}
+
+func (ctx *SimpleStore) UnsafeSetVar(varName string, value any) {
+	// fmt.Printf("[%p] setVar(%v, %v)\n", ctx, varName, value)
+	ctx.varStore[varName] = value
+}
+
+func (ctx *SimpleStore) SetVar(varName string, value any) {
+	// fmt.Printf("[%p] SetVar(%v, %v)\n", ctx, varName, value)
+	if allowedValue, ok := fromGenericAny(value); ok {
+		ctx.varStore[varName] = allowedValue
+	} else {
+		panic(fmt.Errorf("unsupported type %T of value %v", value, value))
+	}
+}
+
+func (ctx *SimpleStore) EnumVars(acceptor func(name string) (accept bool)) (varNames []string) {
+	varNames = make([]string, 0)
+	for name := range ctx.varStore {
+		if acceptor != nil {
+			if acceptor(name) {
+				varNames = append(varNames, name)
+			}
+		} else {
+			varNames = append(varNames, name)
+		}
+	}
+	return
+}
+
+func (ctx *SimpleStore) GetFuncInfo(name string) (info ExprFunc, exists bool) {
+	info, exists = ctx.funcStore[name]
+	return
+}
+
+func (ctx *SimpleStore) RegisterFuncInfo(info ExprFunc) {
+	ctx.funcStore[info.Name()], _ = info.(*funcInfo)
+}
+
+func (ctx *SimpleStore) RegisterFunc(name string, functor Functor, returnType string, params []ExprFuncParam) (err error) {
+	var info *funcInfo
+	if info, err = newFuncInfo(name, functor, returnType, params); err == nil {
+		ctx.funcStore[name] = info
+	}
+	return
+}
+
+func (ctx *SimpleStore) EnumFuncs(acceptor func(name string) (accept bool)) (funcNames []string) {
+	funcNames = make([]string, 0)
+	for name := range ctx.funcStore {
+		if acceptor != nil {
+			if acceptor(name) {
+				funcNames = append(funcNames, name)
+			}
+		} else {
+			funcNames = append(funcNames, name)
+		}
+	}
+	return
+}
+
+func (ctx *SimpleStore) Call(name string, args []any) (result any, err error) {
+	if info, exists := ctx.funcStore[name]; exists {
+		functor := info.functor
+		result, err = functor.Invoke(ctx, name, args)
+	} else {
+		err = fmt.Errorf("unknown function %s()", name)
+	}
+	return
+}

simple-var-store.go

@@ -1,70 +0,0 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
-// All rights reserved.
-
-// simple-var-store.go
-package expr
-
-import "fmt"
-
-type SimpleVarStore struct {
-	varStore map[string]any
-}
-
-func NewSimpleVarStore() *SimpleVarStore {
-	return &SimpleVarStore{
-		varStore: make(map[string]any),
-	}
-}
-
-func (ctx *SimpleVarStore) Clone() (clone ExprContext) {
-	clone = &SimpleVarStore{
-		varStore: CloneMap(ctx.varStore),
-	}
-	return clone
-}
-
-func (ctx *SimpleVarStore) GetVar(varName string) (v any, exists bool) {
-	v, exists = ctx.varStore[varName]
-	return
-}
-
-func (ctx *SimpleVarStore) setVar(varName string, value any) {
-	ctx.varStore[varName] = value
-}
-
-func (ctx *SimpleVarStore) SetVar(varName string, value any) {
-	if allowedValue, ok := fromGenericAny(value); ok {
-		ctx.varStore[varName] = allowedValue
-	} else {
-		panic(fmt.Errorf("unsupported type %T of value %v", value, value))
-	}
-}
-
-func (ctx *SimpleVarStore) EnumVars(acceptor func(name string) (accept bool)) (varNames []string) {
-	varNames = make([]string, 0)
-	for name := range ctx.varStore {
-		if acceptor != nil {
-			if acceptor(name) {
-				varNames = append(varNames, name)
-			}
-		} else {
-			varNames = append(varNames, name)
-		}
-	}
-	return
-}
-
-func (ctx *SimpleVarStore) GetFuncInfo(name string) (f ExprFunc, exists bool) {
-	return
-}
-
-func (ctx *SimpleVarStore) Call(name string, args []any) (result any, err error) {
-	return
-}
-
-func (ctx *SimpleVarStore) RegisterFunc(name string, functor Functor, minArgs, maxArgs int) {
-}
-
-func (ctx *SimpleVarStore) EnumFuncs(acceptor func(name string) (accept bool)) (funcNames []string) {
-	return
-}

simple-var-store.go.bak

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

strings_test.go

@@ -0,0 +1,21 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// strings_test.go
+package expr
+
+import (
+	"testing"
+)
+
+func TestStringsParser(t *testing.T) {
+	inputs := []inputType{
+		/*  1 */ {`"uno" + "due"`, `unodue`, nil},
+		/*  2 */ {`"uno" + 2`, `uno2`, nil},
+		/*  3 */ {`"uno" + (2+1)`, `uno3`, nil},
+		/*  4 */ {`"uno" * (2+1)`, `unounouno`, nil},
+		/*  5 */ {`"abc".1`, `b`, nil},
+		/*  5 */ {`#"abc"`, int64(3), nil},
+	}
+	parserTest(t, "String", inputs)
+}

symbol.go

@@ -33,7 +33,7 @@ const (
 	SymBackTick                          //  22: '`'
 	SymExclamation                       //  23: '!'
 	SymQuestion                          //  24: '?'
-	SymAmpersand                         //  25: '&&'
+	SymAmpersand                         //  25: '&'
 	SymDoubleAmpersand                   //  26: '&&'
 	SymPercent                           //  27: '%'
 	SymAt                                //  28: '@'
@@ -64,13 +64,17 @@ const (
 	SymCaret                             //  53: '^'
 	SymDollarRound                       //  54: '$('
 	SymOpenClosedRound                   //  55: '()'
-	SymDoubleDollar                      //  56: '$$
+	SymDoubleDollar                      //  56: '$$'
+	SymDoubleDot                         //  57: '..'
+	SymTripleDot                         //  58: '...'
 	SymChangeSign
 	SymUnchangeSign
 	SymIdentifier
 	SymBool
 	SymInteger
+	SymVariable
 	SymFloat
+	SymFraction
 	SymString
 	SymIterator
 	SymOr
@@ -96,6 +100,8 @@ const (
 	SymKwBut
 	SymKwFunc
 	SymKwBuiltin
+	SymKwIn
+	SymKwInclude
 	SymKwNil
 )
 
@@ -108,6 +114,8 @@ func init() {
 		"BUILTIN": SymKwBuiltin,
 		"BUT":     SymKwBut,
 		"FUNC":    SymKwFunc,
+		"IN":      SymKwIn,
+		"INCLUDE": SymKwInclude,
 		"NOT":     SymKwNot,
 		"OR":      SymKwOr,
 		"NIL":     SymKwNil,

term-constuctor-registry.go

@@ -17,11 +17,10 @@ func registerTermConstructor(sym Symbol, constructor termContructor) {
 	constructorRegistry[sym] = constructor
 }
 
-func newTerm(tk *Token, parent *term) (inst *term) {
+func newTerm(tk *Token) (inst *term) {
 	if constructorRegistry != nil {
 		if construct, exists := constructorRegistry[tk.Sym]; exists {
 			inst = construct(tk)
-			inst.setParent(parent)
 		}
 	}
 	return

term.go

@@ -20,12 +20,13 @@ const (
 	priRelational
 	priSum
 	priProduct
+	priFraction
 	priSelector
 	priSign
 	priFact
 	priIterValue
 	priCoalesce
-	priPrePost
+	priIncDec
 	priDot
 	priValue
 )
@@ -154,16 +155,20 @@ func (self *term) toInt(computedValue any, valueDescription string) (i int, err
 	if index64, ok := computedValue.(int64); ok {
 		i = int(index64)
 	} else {
-		err = self.Errorf("%s, got %T", valueDescription, computedValue)
+		err = self.Errorf("%s, got %T (%v)", valueDescription, computedValue, computedValue)
 	}
 	return
 }
 
 func (self *term) errIncompatibleTypes(leftValue, rightValue any) error {
+	leftType := getTypeName(leftValue)
+	leftText := getFormatted(leftValue, Truncate)
+	rightType := getTypeName(rightValue)
+	rightText := getFormatted(rightValue, Truncate)
 	return self.tk.Errorf(
-		"left operand '%v' [%T] and right operand '%v' [%T] are not compatible with operator %q",
+		"left operand '%s' [%s] and right operand '%s' [%s] are not compatible with operator %q",
-		leftValue, leftValue,
+		leftText, leftType,
-		rightValue, rightValue,
+		rightText, rightType,
 		self.source())
 }
 
@@ -217,9 +222,9 @@ func (self *term) evalInfix(ctx ExprContext) (leftValue, rightValue any, err err
 	return
 }
 
-func (self *term) evalPrefix(ctx ExprContext) (rightValue any, err error) {
+func (self *term) evalPrefix(ctx ExprContext) (childValue any, err error) {
 	if err = self.checkOperands(); err == nil {
-		rightValue, err = self.children[0].compute(ctx)
+		childValue, err = self.children[0].compute(ctx)
 	}
 	return
 }

term_test.go

@@ -31,6 +31,7 @@ func TestGetRoom(t *testing.T) {
 		t.Errorf("err: got <%v>, want <nil>", gotErr)
 	}
 }
+
 func TestGetChildrenCount(t *testing.T) {
 	tk1 := NewValueToken(0, 0, SymInteger, "100", 100)
 

token.go

@@ -46,7 +46,7 @@ func NewValueToken(row, col int, sym Symbol, source string, value any) *Token {
 
 func NewErrorToken(row, col int, err error) *Token {
 	if err == io.EOF {
-		return NewToken(row, col, SymEos, "")
+		return NewToken(row, col, SymEos, "<EOF>")
 	}
 	return NewValueToken(row, col, SymError, fmt.Sprintf("[%d:%d]", row, col), err)
 }
@@ -63,6 +63,10 @@ func (tk *Token) IsTerm(termSymbols []Symbol) bool {
 	return tk.IsEos() || tk.IsError() || (termSymbols != nil && slices.Index(termSymbols, tk.Sym) >= 0)
 }
 
+func (tk *Token) IsSymbol(sym Symbol) bool {
+	return tk.Sym == sym
+}
+
 func (self *Token) Errorf(template string, args ...any) (err error) {
 	err = fmt.Errorf(fmt.Sprintf("[%d:%d] ", self.row, self.col)+template, args...)
 	return
@@ -81,3 +85,13 @@ func (self *Token) Errors(msg string) (err error) {
 	err = fmt.Errorf("[%d:%d] %v", self.row, self.col, msg)
 	return
 }
+
+func (self *Token) ErrorExpectedGot(symbol string) (err error) {
+	err = fmt.Errorf("[%d:%d] expected %q, got %q", self.row, self.col, symbol, self)
+	return
+}
+
+func (self *Token) ErrorExpectedGotString(symbol, got string) (err error) {
+	err = fmt.Errorf("[%d:%d] expected %q, got %q", self.row, self.col, symbol, got)
+	return
+}

tools/func-bolerplate.bash

@@ -0,0 +1,71 @@
+#!/usr/bin/env bash
+
+if [ $# -lt 2 ]; then
+	echo >&2 "Usage: $(basename "${0}") <module-name> <func-name>..."
+	exit 1
+fi
+
+MODULE_NAME=${1,,}
+GO_FILE="func-${MODULE_NAME//[-.]/_}.go"
+
+shift
+FUNC_LIST=
+i=0
+for name; do
+	if [ ${i} -gt 0 ]; then
+		if [ $((i+1)) -eq $# ]; then
+			FUNC_LIST+=" and "
+		else
+			FUNC_LIST+=", "
+		fi
+	fi
+	FUNC_LIST+="${name}()"
+	((i++))
+done
+
+cat > "${GO_FILE}" <<EOF
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// func-${MODULE_NAME}.go
+package expr
+
+import (
+)
+
+
+// --- Start of function definitions
+
+$(
+for name; do
+	cat <<IEOF
+func ${name}Func(ctx ExprContext, name string, args []any) (result any, err error) {
+        return
+}
+
+IEOF
+
+done
+)
+
+// --- End of function definitions
+
+// Import above functions in the context
+func Import${MODULE_NAME^}Funcs(ctx ExprContext) {
+$(
+for name; do
+        cat <<IEOF
+        ctx.RegisterFunc("${name}", &simpleFunctor{f: ${name}Func}, 1, -1)
+IEOF
+
+done
+)
+}
+
+// Register the import function in the import-register.
+// That will allow to import all function of this module by the "builtin" operator."
+func init() {
+	registerImport("${MODULE_NAME}", Import${name}Funcs, "The \"${MODULE_NAME}\" module implements the ${FUNC_LIST} function(s)")
+}
+EOF
+

utils.go

@@ -4,46 +4,84 @@
 // utils.go
 package expr
 
-import "reflect"
+import (
+	"fmt"
+	"reflect"
+)
 
-func isString(v any) (ok bool) {
+func IsString(v any) (ok bool) {
 	_, ok = v.(string)
 	return ok
 }
 
-func isInteger(v any) (ok bool) {
+func IsInteger(v any) (ok bool) {
 	_, ok = v.(int64)
 	return ok
 }
 
-func isFloat(v any) (ok bool) {
+func IsFloat(v any) (ok bool) {
 	_, ok = v.(float64)
 	return ok
 }
 
-func isList(v any) (ok bool) {
+func IsBool(v any) (ok bool) {
-	_, ok = v.([]any)
+	_, ok = v.(bool)
 	return ok
 }
 
-func isDict(v any) (ok bool) {
+func IsList(v any) (ok bool) {
-	_, ok = v.(map[any]any)
+	_, ok = v.(*ListType)
 	return ok
 }
 
-func isNumber(v any) (ok bool) {
+func IsDict(v any) (ok bool) {
-	return isFloat(v) || isInteger(v)
+	_, ok = v.(*DictType)
+	return ok
+}
+
+func IsFract(v any) (ok bool) {
+	_, ok = v.(*fraction)
+	return ok
+}
+
+func IsRational(v any) (ok bool) {
+	if _, ok = v.(*fraction); !ok {
+		_, 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)
+	return IsString(v) || IsNumber(v)
+}
+
+func isFunctor(v any) (ok bool) {
+	_, ok = v.(Functor)
+	return
+}
+
+func isIterator(v any) (ok bool) {
+	_, ok = v.(Iterator)
+	return
 }
 
 func numAsFloat(v any) (f float64) {
 	var ok bool
 	if f, ok = v.(float64); !ok {
-		i, _ := v.(int64)
+		if fract, ok := v.(*fraction); ok {
-		f = float64(i)
+			f = fract.toFloat()
+		} else {
+			i, _ := v.(int64)
+			f = float64(i)
+		}
 	}
 	return
 }
@@ -109,6 +147,12 @@ func fromGenericAny(v any) (exprAny any, ok bool) {
 	if exprAny, ok = anyFloat(v); ok {
 		return
 	}
+	if exprAny, ok = v.(*DictType); ok {
+		return
+	}
+	if exprAny, ok = v.(*ListType); ok {
+		return
+	}
 	return
 }
 
@@ -136,3 +180,40 @@ func CloneMap[K comparable, V any](source map[K]V) map[K]V {
 	dest := make(map[K]V, len(source))
 	return CopyMap(dest, source)
 }
+
+func CopyFilteredMap[K comparable, V any](dest, source map[K]V, filter func(key K) (accept bool)) map[K]V {
+	// fmt.Printf("--- Clone with filter %p\n", filter)
+	if filter == nil {
+		return CopyMap(dest, source)
+	} else {
+		for k, v := range source {
+			if filter(k) {
+				// fmt.Printf("\tClone var %q\n", k)
+				dest[k] = v
+			}
+		}
+	}
+	return dest
+}
+
+func CloneFilteredMap[K comparable, V any](source map[K]V, filter func(key K) (accept bool)) map[K]V {
+	dest := make(map[K]V, len(source))
+	return CopyFilteredMap(dest, source, filter)
+}
+
+func toInt(value any, description string) (i int, err error) {
+	if valueInt64, ok := value.(int64); ok {
+		i = int(valueInt64)
+	} else {
+		err = fmt.Errorf("%s expected integer, got %T (%v)", description, value, value)
+	}
+	return
+}
+
+func ForAll[T, V any](ts []T, fn func(T) V) []V {
+	result := make([]V, len(ts))
+	for i, t := range ts {
+		result[i] = fn(t)
+	}
+	return result
+}

utils_test.go

@@ -0,0 +1,139 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// utils_test.go
+package expr
+
+import (
+	"errors"
+	"testing"
+)
+
+func TestIsString(t *testing.T) {
+	count := 0
+	succeeded := 0
+	failed := 0
+
+	count++
+	if !IsBool(true) {
+		t.Errorf("%d: IsBool(true) -> result = false, want true", count)
+		failed++
+	} else {
+		succeeded++
+	}
+
+	count++
+	if !IsString("abc") {
+		t.Errorf("%d: IsString(\"abc\") -> result = false, want true", count)
+		failed++
+	} else {
+		succeeded++
+	}
+
+	count++
+	if !IsInteger(int64(123)) {
+		t.Errorf("%d: IsInteger(123) -> result = false, want true", count)
+		failed++
+	} else {
+		succeeded++
+	}
+
+	count++
+	if !IsFloat(1.23) {
+		t.Errorf("%d: IsFloat(1.23) -> result = false, want true", count)
+		failed++
+	} else {
+		succeeded++
+	}
+
+	count++
+	if !IsFloat(numAsFloat(123)) {
+		t.Errorf("%d: IsFloat(numAsFloat(123)) -> result = false, want true", count)
+		failed++
+	} else {
+		succeeded++
+	}
+
+	count++
+	b, ok := toBool(true)
+	if !(ok && b) {
+		t.Errorf("%d: toBool(true) b=%v, ok=%v -> result = false, want true", count, b, ok)
+		failed++
+	} else {
+		succeeded++
+	}
+
+	count++
+	b, ok = toBool("abc")
+	if !(ok && b) {
+		t.Errorf("%d: toBool(\"abc\") b=%v, ok=%v -> result = false, want true", count, b, ok)
+		failed++
+	} else {
+		succeeded++
+	}
+
+	t.Logf("test count: %d, succeeded count: %d, failed count: %d", count, succeeded, failed)
+}
+
+func TestToIntOk(t *testing.T) {
+	source := int64(64)
+	wantValue := int(64)
+	wantErr := error(nil)
+
+	gotValue, gotErr := toInt(source, "test")
+
+	if gotErr != nil || gotValue != wantValue {
+		t.Errorf("toInt(%v, \"test\") gotValue=%v, gotErr=%v -> wantValue=%v, wantErr=%v",
+			source, gotValue, gotErr, wantValue, wantErr)
+	}
+}
+
+func TestToIntErr(t *testing.T) {
+	source := uint64(64)
+	wantValue := 0
+	wantErr := errors.New(`test expected integer, got uint64 (64)`)
+
+	gotValue, gotErr := toInt(source, "test")
+
+	if gotErr.Error() != wantErr.Error() || gotValue != wantValue {
+		t.Errorf("toInt(%v, \"test\") gotValue=%v, gotErr=%v -> wantValue=%v, wantErr=%v",
+			source, gotValue, gotErr, wantValue, wantErr)
+	}
+}
+
+func TestAnyInteger(t *testing.T) {
+	type inputType struct {
+		source    any
+		wantValue int64
+		wantOk    bool
+	}
+	section := "utils.anyInteger"
+
+	inputs := []inputType{
+		/*  1 */ {int8(-8), int64(-8), true},
+		/*  2 */ {int16(-16), int64(-16), true},
+		/*  3 */ {int32(-32), int64(-32), true},
+		/*  4 */ {int64(-64), int64(-64), true},
+		/*  5 */ {uint8(8), int64(8), true},
+		/*  6 */ {uint16(16), int64(16), true},
+		/*  7 */ {uint32(32), int64(32), true},
+		/*  8 */ {uint64(64), int64(64), true},
+		/*  9 */ {int(-1), int64(-1), true},
+		/* 10 */ {true, 0, false},
+	}
+
+	succeeded := 0
+	failed := 0
+
+	for i, input := range inputs {
+		gotValue, gotOk := anyInteger(input.source)
+		if gotOk != input.wantOk || gotValue != input.wantValue {
+			t.Errorf("%d: anyInteger(%v) -> gotOk = %t, wantOk = %t; gotValue = %v, wantValue = %v",
+				i+1, input.source, gotOk, input.wantOk, gotValue, input.wantValue)
+			failed++
+		} else {
+			succeeded++
+		}
+	}
+	t.Logf("%s -- test count: %d, succeeded: %d, failed: %d", section, len(inputs), succeeded, failed)
+}