tests improved

If _stdout is nil, they write to os.Stdout

bind-expr-functions.go

@@ -17,19 +17,31 @@ type exprFunctor struct {
 // }
 
 func newExprFunctor(e Expr, params []ExprFuncParam, ctx ExprContext) *exprFunctor {
-	return &exprFunctor{expr: e, params: params, defCtx: ctx}
+	var defCtx ExprContext
+	if ctx != nil {
+//		if ctx.GetParent() != nil {
+//			defCtx = ctx.Clone()
+//			defCtx.SetParent(ctx)
+//		} else {
+			defCtx = ctx
+//		}
+	}
+	return &exprFunctor{expr: e, params: params, defCtx: defCtx}
+}
+
+func (functor *exprFunctor) GetDefinitionContext() ExprContext {
+	return functor.defCtx
 }
 
 func (functor *exprFunctor) Invoke(ctx ExprContext, name string, args []any) (result any, err error) {
-	if functor.defCtx != nil {
+	// if functor.defCtx != nil {
-		ctx.Merge(functor.defCtx)
+	// 	ctx.Merge(functor.defCtx)
-	}
+	// }
 
 	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)
 				paramSpecs := funcArg.GetParams()
 				ctx.RegisterFunc(p.Name(), funcArg, TypeAny, paramSpecs)
 			} else {
@@ -42,17 +54,3 @@ func (functor *exprFunctor) Invoke(ctx ExprContext, name string, args []any) (re
 	result, err = functor.expr.Eval(ctx)
 	return
 }
-
-func CallExprFunction(parentCtx ExprContext, funcName string, params ...any) (v any, err error) {
-	ctx := cloneContext(parentCtx)
-	ctx.SetParent(parentCtx)
-
-	if err == nil {
-		if err = checkFunctionCall(ctx, funcName, &params); err == nil {
-			if v, err = ctx.Call(funcName, params); err == nil {
-				exportObjects(parentCtx, ctx)
-			}
-		}
-	}
-	return
-}

builtin-base.go

@@ -5,6 +5,7 @@
 package expr
 
 import (
+	"fmt"
 	"math"
 	"strconv"
 )
@@ -120,6 +121,32 @@ func decFunc(ctx ExprContext, name string, args []any) (result any, err error) {
 	return
 }
 
+func stringFunc(ctx ExprContext, name string, args []any) (result any, err error) {
+	switch v := args[0].(type) {
+	case int64:
+		result = strconv.FormatInt(v, 10)
+	case float64:
+		result = strconv.FormatFloat(v, 'g', -1, 64)
+	case bool:
+		if v {
+			result = "true"
+		} else {
+			result = "false"
+		}
+	case string:
+		result = v
+	case *FractionType:
+		result = v.ToString(0)
+	case Formatter:
+		result = v.ToString(0)
+	case fmt.Stringer:
+		result = v.String()
+	default:
+		err = ErrCantConvert(name, v, "string")
+	}
+	return
+}
+
 func fractFunc(ctx ExprContext, name string, args []any) (result any, err error) {
 	switch v := args[0].(type) {
 	case int64:
@@ -175,6 +202,7 @@ func ImportBuiltinsFuncs(ctx ExprContext) {
 	ctx.RegisterFunc("bool", NewGolangFunctor(boolFunc), TypeBoolean, anyParams)
 	ctx.RegisterFunc("int", NewGolangFunctor(intFunc), TypeInt, anyParams)
 	ctx.RegisterFunc("dec", NewGolangFunctor(decFunc), TypeFloat, anyParams)
+	ctx.RegisterFunc("string", NewGolangFunctor(stringFunc), TypeString, anyParams)
 	ctx.RegisterFunc("fract", NewGolangFunctor(fractFunc), TypeFraction, []ExprFuncParam{
 		NewFuncParam(ParamValue),
 		NewFuncParamFlagDef("denominator", PfDefault, 1),

builtin-fmt.go

@@ -4,11 +4,26 @@
 // builtin-fmt.go
 package expr
 
-import "fmt"
+import (
+	"fmt"
+	"io"
+	"os"
+)
+
+func getStdout(ctx ExprContext) io.Writer {
+	var w io.Writer
+	if wany, exists := ctx.GetVar(ControlStdout); exists && wany != nil {
+		w, _ = wany.(io.Writer)
+	}
+	if w == nil {
+		w = os.Stdout
+	}
+	return w
+}
 
 func printFunc(ctx ExprContext, name string, args []any) (result any, err error) {
 	var n int
-	if n, err = fmt.Print(args...); err == nil {
+	if n, err = fmt.Fprint(getStdout(ctx), args...); err == nil {
 		result = int64(n)
 	}
 	return
@@ -16,7 +31,7 @@ func printFunc(ctx ExprContext, name string, args []any) (result any, err error)
 
 func printLnFunc(ctx ExprContext, name string, args []any) (result any, err error) {
 	var n int
-	if n, err = fmt.Println(args...); err == nil {
+	if n, err = fmt.Fprintln(getStdout(ctx), args...); err == nil {
 		result = int64(n)
 	}
 	return

builtin-os-file.go

@@ -68,7 +68,7 @@ func createFileFunc(ctx ExprContext, name string, args []any) (result any, err e
 			result = &osWriter{fh: fh, writer: bufio.NewWriter(fh)}
 		}
 	} else {
-		err = errMissingFilePath("createFile")
+		err = errMissingFilePath(name)
 	}
 	return
 }
@@ -80,7 +80,7 @@ func openFileFunc(ctx ExprContext, name string, args []any) (result any, err err
 			result = &osReader{fh: fh, reader: bufio.NewReader(fh)}
 		}
 	} else {
-		err = errMissingFilePath("openFile")
+		err = errMissingFilePath(name)
 	}
 	return
 }
@@ -92,7 +92,7 @@ func appendFileFunc(ctx ExprContext, name string, args []any) (result any, err e
 			result = &osWriter{fh: fh, writer: bufio.NewWriter(fh)}
 		}
 	} else {
-		err = errMissingFilePath("appendFile")
+		err = errMissingFilePath(name)
 	}
 	return
 }
@@ -118,13 +118,13 @@ func closeFileFunc(ctx ExprContext, name string, args []any) (result any, err er
 		}
 	}
 	if err == nil && (handle == nil || invalidFileHandle != nil) {
-		err = errInvalidFileHandle("closeFileFunc", handle)
+		err = errInvalidFileHandle(name, handle)
 	}
 	result = err == nil
 	return
 }
 
-func writeFileFunc(ctx ExprContext, name string, args []any) (result any, err error) {
+func fileWriteTextFunc(ctx ExprContext, name string, args []any) (result any, err error) {
 	var handle osHandle
 	var invalidFileHandle any
 	var ok bool
@@ -142,12 +142,12 @@ func writeFileFunc(ctx ExprContext, name string, args []any) (result any, err er
 	}
 
 	if err == nil && (handle == nil || invalidFileHandle != nil) {
-		err = errInvalidFileHandle("writeFileFunc", invalidFileHandle)
+		err = errInvalidFileHandle(name, invalidFileHandle)
 	}
 	return
 }
 
-func readFileFunc(ctx ExprContext, name string, args []any) (result any, err error) {
+func fileReadTextFunc(ctx ExprContext, name string, args []any) (result any, err error) {
 	var handle osHandle
 	var invalidFileHandle any
 	var ok bool
@@ -165,23 +165,50 @@ func readFileFunc(ctx ExprContext, name string, args []any) (result any, err err
 				limit = s[0]
 			}
 
-			if v, err = r.reader.ReadString(limit); err == nil {
+			v, err = r.reader.ReadString(limit)
-				if len(v) > 0 && v[len(v)-1] == limit {
+			if err == io.EOF {
+				err = nil
+			}
+			if len(v) > 0 {
+				if v[len(v)-1] == limit {
 					result = v[0 : len(v)-1]
 				} else {
 					result = v
 				}
 			}
-			if err == io.EOF {
-				err = nil
-			}
 		} else {
 			invalidFileHandle = handle
 		}
 	}
 
 	if err == nil && (handle == nil || invalidFileHandle != nil) {
-		err = errInvalidFileHandle("readFileFunc", invalidFileHandle)
+		err = errInvalidFileHandle(name, invalidFileHandle)
+	}
+	return
+}
+
+func fileReadTextAllFunc(ctx ExprContext, name string, args []any) (result any, err error) {
+	var handle osHandle
+	var invalidFileHandle any
+	var ok bool
+
+	result = nil
+	if handle, ok = args[0].(osHandle); !ok || args[0] == nil {
+		invalidFileHandle = args[0]
+	}
+
+	if handle != nil {
+		if r, ok := handle.(*osReader); ok {
+			var b []byte
+			b, err = io.ReadAll(r.reader)
+			result = string(b)
+		} else {
+			invalidFileHandle = handle
+		}
+	}
+
+	if err == nil && (handle == nil || invalidFileHandle != nil) {
+		err = errInvalidFileHandle(name, invalidFileHandle)
 	}
 	return
 }
@@ -190,21 +217,30 @@ func ImportOsFuncs(ctx ExprContext) {
 	ctx.RegisterFunc("fileOpen", NewGolangFunctor(openFileFunc), TypeHandle, []ExprFuncParam{
 		NewFuncParam(ParamFilepath),
 	})
+
 	ctx.RegisterFunc("fileAppend", NewGolangFunctor(appendFileFunc), TypeHandle, []ExprFuncParam{
 		NewFuncParam(ParamFilepath),
 	})
+
 	ctx.RegisterFunc("fileCreate", NewGolangFunctor(createFileFunc), TypeHandle, []ExprFuncParam{
 		NewFuncParam(ParamFilepath),
 	})
-	ctx.RegisterFunc("fileWrite", NewGolangFunctor(writeFileFunc), TypeInt, []ExprFuncParam{
+
+	ctx.RegisterFunc("fileClose", NewGolangFunctor(closeFileFunc), TypeBoolean, []ExprFuncParam{
+		NewFuncParam(TypeHandle),
+	})
+
+	ctx.RegisterFunc("fileWriteText", NewGolangFunctor(fileWriteTextFunc), TypeInt, []ExprFuncParam{
 		NewFuncParam(TypeHandle),
 		NewFuncParamFlagDef(TypeItem, PfDefault|PfRepeat, ""),
 	})
-	ctx.RegisterFunc("fileRead", NewGolangFunctor(readFileFunc), TypeString, []ExprFuncParam{
+
+	ctx.RegisterFunc("fileReadText", NewGolangFunctor(fileReadTextFunc), TypeString, []ExprFuncParam{
 		NewFuncParam(TypeHandle),
 		NewFuncParamFlagDef("limitCh", PfDefault, "\n"),
 	})
-	ctx.RegisterFunc("fileClose", NewGolangFunctor(closeFileFunc), TypeBoolean, []ExprFuncParam{
+
+	ctx.RegisterFunc("fileReadTextAll", NewGolangFunctor(fileReadTextAllFunc), TypeString, []ExprFuncParam{
 		NewFuncParam(TypeHandle),
 	})
 }

builtin-string.go

@@ -66,11 +66,11 @@ func subStrFunc(ctx ExprContext, name string, args []any) (result any, err error
 		return nil, ErrWrongParamType(name, ParamSource, TypeString, args[0])
 	}
 
-	if start, err = ToInt(args[1], name+"()"); err != nil {
+	if start, err = ToGoInt(args[1], name+"()"); err != nil {
 		return
 	}
 
-	if count, err = ToInt(args[2], name+"()"); err != nil {
+	if count, err = ToGoInt(args[2], name+"()"); err != nil {
 		return
 	}
 

common-errors.go

@@ -36,15 +36,15 @@ func ErrFuncDivisionByZero(funcName string) error {
 	return fmt.Errorf("%s(): division by zero", funcName)
 }
 
-func ErrDivisionByZero() error {
+// func ErrDivisionByZero() error {
-	return fmt.Errorf("division by zero")
+// 	return fmt.Errorf("division by zero")
-}
+// }
 
 // --- Parameter errors
 
-func ErrMissingRequiredParameter(funcName, paramName string) error {
+// func ErrMissingRequiredParameter(funcName, paramName string) error {
-	return fmt.Errorf("%s(): missing required parameter %q", funcName, paramName)
+// 	return fmt.Errorf("%s(): missing required parameter %q", funcName, paramName)
-}
+// }
 
 func ErrInvalidParameterValue(funcName, paramName string, paramValue any) error {
 	return fmt.Errorf("%s(): invalid value %s (%v) for parameter %q", funcName, TypeName(paramValue), paramValue, paramName)

common-params.go

@@ -15,7 +15,13 @@ const (
 	ParamStart     = "start"
 	ParamEnd       = "end"
 	ParamValue     = "value"
+	ParamName      = "name"
 	ParamEllipsis  = "..."
 	ParamFilepath  = "filepath"
 	ParamDirpath   = "dirpath"
 )
+
+// to be moved in its own source file
+const (
+	ConstLastIndex = 0xFFFF_FFFF
+)

context-helpers.go

@@ -41,3 +41,9 @@ func exportObjects(destCtx, sourceCtx ExprContext) {
 		}
 	}
 }
+
+func exportObjectsToParent(sourceCtx ExprContext) {
+	if parentCtx := sourceCtx.GetParent(); parentCtx != nil {
+		exportObjects(parentCtx, sourceCtx)
+	}
+}

context.go

@@ -10,6 +10,7 @@ type Functor interface {
 	SetFunc(info ExprFunc)
 	GetFunc() ExprFunc
 	GetParams() []ExprFuncParam
+	GetDefinitionContext() ExprContext
 }
 
 // ---- Function Param Info
@@ -31,22 +32,24 @@ type ExprFunc interface {
 	Functor() Functor
 	Params() []ExprFuncParam
 	ReturnType() string
+	PrepareCall(parentCtx ExprContext, name string, varParams *[]any) (ctx ExprContext, err error)
+	AllocContext(parentCtx ExprContext) (ctx ExprContext)
 }
 
 // ----Expression Context
 type ExprContext interface {
 	Clone() ExprContext
-	Merge(ctx ExprContext)
+	// Merge(ctx ExprContext)
 	SetParent(ctx ExprContext)
 	GetParent() (ctx ExprContext)
 	GetVar(varName string) (value any, exists bool)
+	GetLast() any
 	SetVar(varName string, value any)
 	UnsafeSetVar(varName string, value any)
 	EnumVars(func(name string) (accept bool)) (varNames []string)
 	EnumFuncs(func(name string) (accept bool)) (funcNames []string)
 	GetFuncInfo(name string) (item ExprFunc, exists bool)
 	Call(name string, args []any) (result any, err error)
-	// RegisterFunc(name string, f Functor, minArgs, maxArgs int)
 	RegisterFuncInfo(info ExprFunc)
 	RegisterFunc(name string, f Functor, returnType string, param []ExprFuncParam) error
 }

control.go

@@ -11,6 +11,7 @@ const (
 	ControlBoolShortcut  = "_bool_shortcut"
 	ControlSearchPath    = "_search_path"
 	ControlParentContext = "_parent_context"
+	ControlStdout        = "_stdout"
 )
 
 // Other control variables
@@ -23,11 +24,17 @@ const (
 	init_search_path = "~/.local/lib/go-pkg/expr:/usr/local/lib/go-pkg/expr:/usr/lib/go-pkg/expr"
 )
 
+func SetCtrl(ctx ExprContext, name string, value any) (current any) {
+	current, _ = ctx.GetVar(name)
+	ctx.UnsafeSetVar(name, value)
+	return
+}
+
 func initDefaultVars(ctx ExprContext) {
 	if _, exists := ctx.GetVar(ControlPreset); exists {
 		return
 	}
-	ctx.SetVar(ControlPreset, true)
+	ctx.UnsafeSetVar(ControlPreset, true)
-	ctx.SetVar(ControlBoolShortcut, true)
+	ctx.UnsafeSetVar(ControlBoolShortcut, true)
-	ctx.SetVar(ControlSearchPath, init_search_path)
+	ctx.UnsafeSetVar(ControlSearchPath, init_search_path)
 }

doc/Expr.adoc

@@ -9,6 +9,7 @@ Expressions calculator
 :icons: font
 :icon-set: fi
 :numbered:
+:data-uri:
 //:table-caption: Tabella
 //:figure-caption: Diagramma
 :docinfo1:
@@ -19,21 +20,52 @@ Expressions calculator
 :rouge-style: gruvbox
 // :rouge-style: colorful
 //:rouge-style: monokay
+// Work around to manage double-column in back-tick quotes
+:2c: ::
 
 toc::[]
 
-#TODO: Work in progress (last update on 2024/06/02, 08:18 a.m.)#
+#TODO: Work in progress (last update on 2024/06/21, 05:40 a.m.)#
 
 == Expr
 _Expr_ is a GO package capable of analysing, interpreting and calculating expressions.
 
+
 === Concepts and terminology
-#TODO#
+
+Expressions are texts containing sequences of operations represented by a syntax very similar to that of most programming languages. _Expr_ package provides these macro functions:
+
+* *_Scanner_* -- Its input is a text. It scans expression text characters to produce a flow of logical symbol and related attributes, aka tokens.
+* *_Parser_* -- Parser input is the token flow coming from the scanner. It analyses the token flow verifyng if it complies with the _Expr_ syntax. If that is the case, the Parser generates the Abstract Syntax Tree (AST). This is tree data structure that represents the components of an expressions and how they are related one each other.
+* *_Calculator_*. Its input is the AST. It computes the parsed expression contained in the AST and returns the result or an error.
 
 image::expression-diagram.png[]
 
+==== Variables
+_Expr_ supports variables. The result of an expression can be stored in a variable and reused in other espressions simply specifying the name of the variable as an operand.
+
+==== Multi-expression
+An input text valid for _Expr_ can contain more than an expression. Expressions are separated by [blue]`;` (semicolon). When an input contains two or more expressions it is called _multi-expression_.
+
+_Expr_ parses and computes each expression of a multi-espression, from the left to the right. If all expressions are computed without errors, it only returns the value of the last, the right most.
+
+The result of each expression of a multi-expression is stored in an automatic variable named _last_. In this way, each expression can refer to the result of the previous one without the need to assign that value to a new dedicated variable.
+
+==== Calculation context
+All objects, such as variables and functions, created during the calculation of an expression are stored in a memory called _context_.
+
+The expression context is analogous to the stack-frame of other programming languages. When a function is called, a new context is allocated to store local definitions.
+
+Function contexts are created by cloning the calling context. More details on this topic are given later in this document.
+
+_Expr_ creates and keeps a inner _global context_ where it stores imported functions, either from builtin or plugin modules. To perform calculations, the calling program must provide its own context; this is the _main context_. All calculations take place in this context. As mentioned eralier, when a function is called, a new context is created by cloning the calling context. The createt context can be called _function context_.
+
+Imported functions are registerd in the _global context_. When an expression first calls an imported function, that function is linked to the current context; this can be the _main context_ or a _function context_.
+
 === `dev-expr` test tool
-`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.
+Before we begin to describe the syntax of _Expr_, it is worth introducing _dev-expr_ because it will be used to show many examples of expressions.
+
+`dev-expr` is a simple program that can be used to evaluate expressions interactively. As its name suggests, it was created for testing purpose.  In fact, in additon to the automatic verification test suite based on the Go test framework, `dev-expr` provided an important aid for quickly testing of new features during their development.
 
 `dev-expr` can work as a _REPL_, _**R**ead-**E**xecute-**P**rint-**L**oop_, or it can process expression acquired from files or standard input.
 
@@ -47,11 +79,10 @@ Here are some examples of execution.
 # 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)
+dev-expr -- Expressions calculator v1.10.0(build 14),2024/06/17 (celestino.amoroso@portale-stac.it)
-	Based on the Expr package v0.10.0
+	Based on the Expr package v0.19.0
 	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
@@ -61,6 +92,7 @@ expr -- Expressions calculator v1.7.1(build 2),2024/05/16 (celestino.amoroso@por
         help -- Show command list
           ml -- Enable/Disable multi-line output
         mods -- List builtin modules
+      output -- Enable/Disable printing expression results. Options 'on', 'off', 'status'
 
 --- Command line options:
     -b <builtin>       Import builtin modules.
@@ -70,10 +102,11 @@ expr -- Expressions calculator v1.7.1(build 2),2024/05/16 (celestino.amoroso@por
     -i                 Force REPL operation when all -e occurences have been processed
     -h, --help, help   Show this help menu
     -m, --modules      List all builtin modules
+    --noout            Disable printing of expression results
     -p                 Print prefix form
     -t                 Print tree form <2>
-
+    -v, --version      Show program version
->>> 
+>>>
 ----
 
 <1> Only available for single fraction values
@@ -83,8 +116,8 @@ expr -- Expressions calculator v1.7.1(build 2),2024/05/16 (celestino.amoroso@por
 [source,shell]
 ----
 [user]$ ./dev-expr
-expr -- Expressions calculator v1.7.1(build 2),2024/05/16 (celestino.amoroso@portale-stac.it)
+dev-expr -- Expressions calculator v1.10.0(build 14),2024/06/17 (celestino.amoroso@portale-stac.it)
-	Based on the Expr package v0.10.0
+	Based on the Expr package v0.19.0
 	Type help to get the list of available commands
 	See also https://git.portale-stac.it/go-pkg/expr/src/branch/main/README.adoc
 
@@ -101,21 +134,21 @@ expr -- Expressions calculator v1.7.1(build 2),2024/05/16 (celestino.amoroso@por
 7
 -
 6
->>> 1+2 but 5|2+0.5 <4>
+>>> 4+2 but 5|2+0.5 <4>
 3
->>> 1+2; 5|2+0.5 <5>
+>>> 4+2; 5|2+0.5 <5>
 3
 >>>
 ----
 
-<1> Number bases: 0x = hexadecimal, 0o = octal, 0b = binary.
+<1> Number bases: 0x = _hexadecimal_, 0o = _octal_, 0b = _binary_.
-<2> Fractions: numerator | denominator.
+<2> Fractions: _numerator_ | _denominator_.
 <3> Activate multi-line output of fractions.
 <4> But operator, see <<_but_operator>>.
 <5> Multi-expression: the same result of the previous single expression but this it is obtained with two separated calculations.
 
 == Data types
-_Expr_ supports numerical, string, relational, boolean expressions, and mixed-type lists.
+_Expr_ has its type system which is a subset of Golang's type system. It supports numerical, string, relational, boolean expressions, and mixed-type lists and maps.
 
 === Numbers
 _Expr_ supports three type of numbers:
@@ -155,7 +188,7 @@ Value range: *-9223372036854775808* to *9223372036854775807*
 | [blue]`*` | _product_     | Multiply two values       | [blue]`-1 * 2` -> -2
 | [blue]`/` | _Division_    | Divide the left value by the right one^(*)^ | [blue]`-10 / 2` -> 5
 | [blue]`%` | _Modulo_      | Remainder of the integer division | [blue]`5 % 2` -> 1
-|=== 
+|===
 
 ^(*)^ See also the _float division_ [blue]`./` below.
 
@@ -173,15 +206,20 @@ _dec-seq_ = _see-integer-literal-syntax_
 
 .Examples
 `>>>` [blue]`1.0` +
-[green]`1` +
+[green]`1`
+
 `>>>` [blue]`0.123` +
-[green]`0.123` +
+[green]`0.123`
+
 `>>>` [blue]`4.5e+3` +
-[green]`4500` +
+[green]`4500`
+
 `>>>` [blue]`4.5E-33` +
-[green]`4.5e-33` +
+[green]`4.5e-33`
+
 `>>>` [blue]`4.5E-3` +
-[green]`0.0045` +
+[green]`0.0045`
+
 `>>>` [blue]`4.5E10` +
 [green]`4.5e+10`
 
@@ -211,35 +249,43 @@ _digit-seq_ = _see-integer-literal-syntax_
 ====
 
 .Examples
-// [source,go]
-// ----
 `>>>` [blue]`1 | 2` +
-[green]`1|2` +
+[green]`1|2`
+
 `>>>` [blue]`4|6`  [gray]_// Fractions are always reduced to their lowest terms_ +
-[green]`2|3` +
+[green]`2|3`
+
 `>>>` [blue]`1|2 + 2|3` +
-[green]`7|6` +
+[green]`7|6`
+
 `>>>` [blue]`1|2 * 2|3` +
-[green]`1|3` +
+[green]`1|3`
+
 `>>>` [blue]`1|2 / 1|3` +
-[green]`3|2` +
+[green]`3|2`
+
 `>>>` [blue]`1|2 ./ 1|3` [gray]_// Force decimal division_ +
-[green]`1.5` +
+[green]`1.5`
+
 `>>>` [blue]`-1|2` +
-[green]`-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_ +
+[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` +
+[green]`11|2`
+
 `>>>` [blue]`4 - 1|2` +
-[green]`7|2` +
+[green]`7|2`
+
 `>>>` [blue]`1.0 + 1|2` +
 [green]`1.5`
 
@@ -250,12 +296,15 @@ Strings are character sequences enclosed between two double quote [blue]`"`.
 
 .Examples
 `>>>` [blue]`"I'm a string"` +
-[green]`I'm a string` +
+[green]`I'm a string`
+
 `>>>` [blue]`"123abc?!"` +
-[green]`123abc?!` +
+[green]`123abc?!`
+
 `>>>` [blue]`"123\nabc"` +
 [green]`123` +
-[green]`abc` +
+[green]`abc`
+
 `>>>` [blue]`"123\tabc"` +
 [green]`123{nbsp}{nbsp}{nbsp}{nbsp}abc`
 
@@ -272,25 +321,36 @@ Some arithmetic operators can also be used with strings.
 | [blue]`*` | _repeat_ | Make _n_ copy of a string  | [blue]`"one" * 2` -> _"oneone"_
 |===
 
-The items of strings can be accessed using the dot `.` operator.
+The items of strings can be accessed using the square `[]` operator.
 
 .Item access syntax
 ====
-_item_ = _string-expr_ "**.**" _integer-expr_
+*_item_* = _string-expr_ "**[**" _integer-expr_ "**]**"
+====
+
+.Sub-string syntax
+====
+*_sub-string_* = _string-expr_ "**[**" _integer-expr_ "**:**" _integer-expr_ "**]**"
 ====
 
 .String examples
-`>>>` [blue]`s="abc"`  [gray]_// assign the string to variable s_ +
+`>>>` [blue]`s="abcd"`  [gray]_// assign the string to variable s_ +
-[green]`abc` +
+[green]`"abcd"`
-`>>>` [blue]`s.1`      [gray]_// char at position 1 (starting from 0)_ +
+
-[green]`b` +
+`>>>` [blue]`s[1]`      [gray]_// char at position 1 (starting from 0)_ +
-`>>>` [blue]`s.(-1)`   [gray]_// char at position -1, the rightmost one_ +
+[green]`"b"`
-[green]`c` +
+
+`>>>` [blue]`s.[-1]`    [gray]_// char at position -1, the rightmost one_ +
+[green]`"d"`
+
 `>>>` [blue]`\#s`       [gray]_// number of chars_ +
-[gren]`3` +
+[gren]`4`
-`>>>` [blue]`#"abc"`   [gray]_// number of chars_ +
+
+`>>>` [blue]`#"abc"`    [gray]_// number of chars_ +
 [green]`3`
 
+`>>>` [blue]`s[1:3]`    [gray]_// chars from position 1 to position 3 excluded_ +
+[grean]`"bc"`
 
 === Booleans
 Boolean data type has two values only: [blue]_true_ and [blue]_false_. Relational and boolean expressions result in boolean values.
@@ -334,14 +394,16 @@ Boolean data type has two values only: [blue]_true_ and [blue]_false_. Relationa
 
 [CAUTION]
 ====
-Currently, boolean operations are evaluated using _short cut evaluation_. This means that, if the left expression of the [blue]`and` and [blue]`or` operators is sufficient to establish the result of the whole operation, the right expression would not evaluated at all.
+Currently, boolean operations are evaluated using _short cut evaluation_. This means that, if the left expression of the [blue]`and` and [blue]`or` operators is sufficient to establish the result of the whole operation, the right expression would not be evaluated at all.
-
 .Example
 [source,go]
 ----
 2 > (a=1) or (a=8) > 0; a // <1>
 ----
 <1> This multi-expression returns _1_ because in the first expression the left value of [blue]`or` is _true_ and as a conseguence its right value is not computed. Therefore the _a_ variable only receives the integer _1_.
+
+
+TIP: `dev-expr` provides the _ctrl()_ function that allows to change this behaviour.
 ====
 
 === Lists
@@ -356,13 +418,17 @@ _non-empty-list_ = "**[**" _any-value_ {"**,**" _any-value} "**]**" +
 
 .Examples
 `>>>` [blue]`[1,2,3]`                     [gray]_// List of integers_ +
-[green]`[1, 2, 3]` +
+[green]`[1, 2, 3]`
+
 `>>>` [blue]`["one", "two", "three"]`     [gray]_// List of strings_ +
-[green]`["one", "two", "three"]` +
+[green]`["one", "two", "three"]`
+
 `>>>` [blue]`["one", 2, false, 4.1]`      [gray]_// List of mixed-types_ +
-[green]`["one", 2, false, 4.1]` +
+[green]`["one", 2, false, 4.1]`
+
 `>>>` [blue]`["one"+1, 2.0*(9-2)]`        [gray]_// List of expressions_ +
-[green]`["one1", 14]` +
+[green]`["one1", 14]`
+
 `>>>` [blue]`[ [1,"one"], [2,"two"]]`     [gray]_// List of lists_ +
 [green]`[[1, "one"], [2, "two"]]`
 
@@ -375,37 +441,52 @@ _non-empty-list_ = "**[**" _any-value_ {"**,**" _any-value} "**]**" +
 | [blue]`-` | _Difference_ | Left list without elements in the right list  | [blue]`[1,2,3] - [2]` -> _[1,3]_
 | [blue]`>>` | _Front insertion_ | Insert an item in front | [blue]`0 >> [1,2]` -> _[0,1,2]_
 | [blue]`<<` | _Back insertion_ | Insert an item at end | [blue]`[1,2] << 3` -> _[1,2,3]_
-| [blue]`.` | _List item_ | Item at given position | [blue]`[1,2.3].1` -> _2_
+| [blue]`[]` | _Item at index_ | Item at given position | [blue]`[1,2,3][1]` -> _2_
 | [blue]`in` | _Item in list_ | True if item is in list | [blue]`2 in [1,2,3]` -> _true_ +
 [blue]`6 in [1,2,3]` -> _false_
 |===
 
-The items of array can be accessed using the dot `.` operator.
+Array's items can be accessed using the index `[]` operator.
 
 .Item access syntax
 ====
-_item_ = _list-expr_ "**.**" _integer-expr_
+*_item_* = _list-expr_ "**[**" _integer-expr_ "**]**"
+====
+
+.Sub-array (or slice of array) syntax
+====
+*_slice_* = _string-expr_ "**[**" _integer-expr_ "**:**" _integer-expr_ "**]**"
 ====
 
 .Items of list
 `>>>` [blue]`[1,2,3].1` +
-[green]`2` +
+[green]`2`
+
 `>>>` [blue]`list=[1,2,3]; list.1` +
-[green]`2` +
+[green]`2`
+
 `>>>` [blue]`["one","two","three"].1` +
-[green]`two` +
+[green]`two`
+
 `>>>` [blue]`list=["one","two","three"]; list.(2-1)` +
-[green]`two` +
+[green]`two`
+
 `>>>` [blue]`list.(-1)` +
-[green]`three` +
+[green]`three`
+
 `>>>` [blue]`list.(10)` +
-[red]`Eval Error: [1:9] index 10 out of bounds` +
+[red]`Eval Error: [1:9] index 10 out of bounds`
+
 `>>>` [blue]`#list` +
-[green]`3` +
+[green]`3`
-`>>>` [blue]`index=2; ["a", "b", "c", "d"].index` +
+
+`>>>` [blue]`index=2; ["a", "b", "c", "d"][index]` +
 [green]`c`
 
 
+`>>>` [blue]`["a", "b", "c", "d"][2:]` +
+[green]`["c", "d"]`
+
 
 === Dictionaries
 The _dictionary_, or _dict_, data-type is set of pairs _key/value_. It is also known as _map_ or _associative array_.
@@ -419,14 +500,11 @@ _empty-dict_ = "**{}**" +
 _non-empty-dict_ = "**{**" _key-scalar_ "**:**" _any-value_ {"**,**" _key-scalar_ "**:**" _any-value} "**}**" +
 ====
 
-.Examples
-`>>>` [blue]`{1:"one", 2:"two"}` +
-[green]`{1: "one", 2: "two"}` +
-`>>>` [blue]`{"one":1, "two": 2}` +
-[green]`{"one": 1, "two": 2}` +
-`>>>` [blue]`{"sum":1+2+3, "prod":1*2*3}` +
-[green]`{"sum": 6, "prod": 6}`
 
+.Item access syntax
+====
+*_item_* = _dict-expr_ "**[**" _key-expr_ "**]**"
+====
 
 .Dict operators
 [cols="^2,^2,4,5"]
@@ -434,11 +512,27 @@ _non-empty-dict_ = "**{**" _key-scalar_ "**:**" _any-value_ {"**,**" _key-scalar
 | Symbol    | Operation     | Description               | Examples
 
 | [blue]`+` | _Join_ | Joins two dicts | [blue]`{1:"one"}+{6:"six"}` -> _{1: "one", 6: "six"}_
-| [blue]`.` | _Dict item value_ | Item value of given key | [blue]`{"one":1, "two":2}."two"` -> _2_
+| [blue]`[]` | _Dict item value_ | Item value of given key | [blue]`{"one":1, "two":2}["two"]` -> _2_
 | [blue]`in` | _Key in dict_ | True if key is in dict | [blue]`"one" in {"one":1, "two":2}` -> _true_ +
 [blue]`"six" in {"one":1, "two":2}` -> _false_
 |===
 
+.Examples
+`>>>` [blue]`{1:"one", 2:"two"}` +
+[green]`{1: "one", 2: "two"}`
+
+`>>>` [blue]`{"one":1, "two": 2}` +
+[green]`{"one": 1, "two": 2}`
+
+`>>>` [blue]`{"sum":1+2+3, "prod":1*2*3}` +
+[green]`{"sum": 6, "prod": 6}`
+
+`>>>` [blue]`{"one":1, "two":2}["two"]` +
+[green]`2`
+
+`>>>` [blue]`d={"one":1, "two":2}; d["six"]=6; d` +
+[green]`{"two": 2, "one": 1, "six": 6}`
+
 
 == Variables
 _Expr_, like most programming languages, supports variables. A variable is an identifier with an assigned value. Variables are stored in _contexts_.
@@ -454,17 +548,23 @@ NOTE: The assign operator [blue]`=` returns the value assigned to the variable.
 
 .Examples
 `>>>` [blue]`a=1` +
-[green]`1` +
+[green]`1`
+
 `>>>` [blue]`a_b=1+2` +
-[green]`1+2` +
+[green]`1+2`
+
 `>>>` [blue]`a_b` +
-[green]`3` +
+[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 = 5.2 * (9-3)`  [gray]_// The assigned value has the typical approximation error of the float data-type_ +
+[green]`31.200000000000003`
+
 `>>>` [blue]`x = 1; y = 2*x` +
-[green]`2` +
+[green]`2`
+
 `>>>` [blue]`_a=2` +
-[red]`Parse Error: [1:2] unexpected token "_"` +
+[red]`Parse Error: [1:2] unexpected token "_"`
+
 `>>>` [blue]`1=2` +
 [red]`Parse Error: assign operator ("=") must be preceded by a variable`
 
@@ -474,6 +574,11 @@ NOTE: The assign operator [blue]`=` returns the value assigned to the variable.
 === [blue]`;` operator
 The semicolon operator [blue]`;` is an infixed pseudo-operator. It evaluates the left expression first and then the right expression. The value of the latter is the final result.
 
+.Mult-expression syntax
+====
+*_multi-expression_* = _expression_ {"**;**" _expression_ }
+====
+
 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.
@@ -532,38 +637,47 @@ The [blue]`:` symbol (colon) is the separator of the selector-cases. Note that i
 
 .Examples
 `>>>` [blue]`1 ? {"a"} : {"b"}` +
-[green]`b` +
+[green]`b`
-`>>>` [blue]`10 ? {"a"} : {"b"} :: {"c"}` +
+
-[green]`c' +
+`>>>` [blue]`10 ? {"a"} : {"b"} {2c} {"c"}` +
-[green]`>>>` [blue]`10 ? {"a"} :[true, 2+8] {"b"} :: {"c"}` +
+[green]`c`
-[green]`b` +
+
-`>>>` [blue]`10 ? {"a"} :[true, 2+8] {"b"} ::[10] {"c"}` +
+`>>>` [blue]`10 ? {"a"} :[true, 2+8] {"b"} {2c} {"c"}` +
-[red]`Parse Error: [1:34] case list in default clause` +
+[green]`b`
-[green]`>>>` [blue]`10 ? {"a"} :[10] {x="b" but x} :: {"c"}` +
+
-[green]`b` +
+`>>>` [blue]`10 ? {"a"} :[true, 2+8] {"b"} {2c} [10] {"c"}` +
-`>>>` [blue]`10 ? {"a"} :[10] {x="b"; x} :: {"c"}` +
+[red]`Parse Error: [1:34] case list in default clause`
-[green]`b` +
+
+`>>>` [blue]`10 ? {"a"} :[10] {x="b" but x} {2c} {"c"}` +
+[green]`b`
+
+`>>>` [blue]`10 ? {"a"} :[10] {x="b"; x} {2c} {"c"}` +
+[green]`b`
+
 `>>>` [blue]`10 ? {"a"} : {"b"}` +
 [red]`Eval Error: [1:3] no case catches the value (10) of the selection expression`
 
 
 === Variable default value [blue]`??` and [blue]`?=`
-The left operand of these two operators must be a variable. The right operator can be any expression. They return the value of the variable if this is define; otherwise they return the value of the right expression.
+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 defined; otherwise they return the value of the right expression.
 
-IMPORTANT: If the left variable is defined, the right expression is not evuated at all.
+IMPORTANT: If the left variable is defined, the right expression is not evaluated at all.
 
-The [blue]`??` do not change the status of the left variable.
+The [blue]`??` operator do not change the status of the left variable.
 
 The [blue]`?=` assigns the calculated value of the right expression to the left variable.
 
 .Examples
-`>>>` [blue]`var ?? (1+2)`'
+`>>>` [blue]`var ?? (1+2)`' +
-[green]`3` +
+[green]`3`
+
 `>>>` [blue]`var` +
-[red]`Eval Error: undefined variable or function "var"` +
+[red]`Eval Error: undefined variable or function "var"`
+
 `>>>` [blue]`var ?= (1+2)` +
-[green]`3` +
+[green]`3`
-`>>>` [blue]`var` +
+
+`>>>` [blue]`var`
 [green]`3`
 
 NOTE: These operators have a high priority, in particular higher than the operator [blue]`=`.
@@ -576,57 +690,87 @@ The table below shows all supported operators by decreasing priorities.
 |===
 | Priority | Operators     | Position | Operation | Operands and results
 
-.2+|*ITEM*| [blue]`.` | _Infix_ | _List item_| _list_ `"."` _integer_ -> _any_
+.2+|*ITEM*| [blue]`[`...`]` | _Postfix_ | _List item_| _list_ `[`  _integer_ `]` -> _any_
-| [blue]`.` | _Infix_ | _Dict item_ | _dict_ `"."` _any_ -> _any_
+| [blue]`[`...`]` | _Postfix_ | _Dict item_ | _dict_ `[` _any_ `]` -> _any_
-.2+|*INC*| [blue]`++` | _Postfix_ | _Post increment_| _integer-variable_ `"++"` -> _integer_
+.2+|*INC*| [blue]`++` | _Postfix_ | _Post increment_| _integer-variable_ `++` -> _integer_
-| [blue]`++` | _Postfix_ | _Next item_ | _iterator_ `"++"` -> _any_
+| [blue]`++` | _Postfix_ | _Next item_ | _iterator_ `++` -> _any_
-.1+|*FACT*| [blue]`!` | _Postfix_ | _Factorial_| _integer_ `"!"` -> _integer_
+.2+|*DEFAULT*| [blue]`??` | _Infix_ | _Default value_| _variable_ `??` _any-expr_ -> _any_
-.3+|*SIGN*| [blue]`+`, [blue]`-` | _Prefix_ | _Change-sign_| (`"+"`\|`"-"`) _number_ -> _number_
+| [blue]`?=` | _Infix_ | _Default/assign value_| _variable_ `?=` _any-expr_ -> _any_
-| [blue]`#` | _Prefix_ | _Lenght-of_ | `"#"` _collection_ -> _integer_
+.1+| *ITER*^1^| [blue]`()` | _Prefix_ | _Iterator value_ | `()` _iterator_ -> _any_
-| [blue]`#` | _Prefix_ | _Size-of_ | `"#"` _iterator_ -> _integer_
+.1+|*FACT*| [blue]`!` | _Postfix_ | _Factorial_| _integer_ `!` -> _integer_
-.5+|*PROD*| [blue]`*` | _Infix_ | _Product_ | _number_ `"*"` _number_ -> _number_
+.3+|*SIGN*| [blue]`+`, [blue]`-` | _Prefix_ | _Change-sign_| (`+`\|`-`) _number_ -> _number_
-| [blue]`*` | _Infix_ | _String-repeat_ | _string_ `"*"` _integer_ -> _string_
+| [blue]`#` | _Prefix_ | _Lenght-of_ | `#` _collection_ -> _integer_
-| [blue]`/` | _Infix_ | _Division_ | _number_ `"/"` _number_ -> _number_
+| [blue]`#` | _Prefix_ | _Size-of_ | `#` _iterator_ -> _integer_
-| [blue]`./` | _Infix_ | _Float-division_ | __number__ `"./"` _number_ -> _float_
+.2+|*SELECT*| [blue]`? : ::` | _Multi-Infix_ | _Case-Selector_ | _any-expr_ `?` _case-list_ _case-expr_ `:` _case-list_ _case-expr_ ... `::` _default-expr_ -> _any_
-| [blue]`%` | _Infix_ | _Integer-remainder_ | _integer_ `"%"` _integer_ -> _integer_
+| [blue]`? : ::` | _Multi-Infix_ | _Index-Selector_ | _int-expr_ `?` _case-expr_ `:` _case-expr_ ... `::` _default-expr_ -> _any_
-.6+|*SUM*| [blue]`+` | _Infix_ | _Sum_ | _number_ `"+"` _number_ -> _number_
+.1+|*FRACT*| [blue]`\|` | _Infix_ | _Fraction_ | _integer_ `\|` _integer_ -> _fraction_
-| [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_ |  _Dict-join_ | _dict_ `"+"` _dict_ -> _dict_
+| [blue]`/` | _Infix_ | _Division_ | _number_ `/` _number_ -> _number_
-| [blue]`-` | _Infix_ | _Subtraction_ | _number_ `"-"` _number_ -> _number_
+| [blue]`./` | _Infix_ | _Float-division_ | __number__ `./` _number_ -> _float_
-| [blue]`-` | _Infix_ | _List-difference_ | _list_ `"-"` _list_ -> _list_
+| [blue]`%` | _Infix_ | _Integer-remainder_ | _integer_ `%` _integer_ -> _integer_
-.8+|*RELATION*| [blue]`<` | _Infix_ | _less_ | _comparable_ `"<"` _comparable_ -> _boolean_
+.6+|*SUM*| [blue]`+` | _Infix_ | _Sum_ | _number_ `+` _number_ -> _number_
-| [blue]`\<=` | _Infix_ |  _less-equal_ | _comparable_ `"\<="` _comparable_ -> _boolean_
+| [blue]`+` | _Infix_ |  _String-concat_ | (_string_\|_number_) `+` (_string_\|_number_) -> _string_
-| [blue]`>` | _Infix_ |  _greater_ | _comparable_ `">"` _comparable_ -> _boolean_
+| [blue]`+` | _Infix_ |  _List-join_ | _list_ `+` _list_ -> _list_
-| [blue]`>=` | _Infix_ |  _greater-equal_ | _comparable_ `">="` _comparable_ -> _boolean_
+| [blue]`+` | _Infix_ |  _Dict-join_ | _dict_ `+` _dict_ -> _dict_
-| [blue]`==` | _Infix_ |  _equal_ | _comparable_ `"=="` _comparable_ -> _boolean_
+| [blue]`-` | _Infix_ | _Subtraction_ | _number_ `-` _number_ -> _number_
-| [blue]`!=` | _Infix_ |  _not-equal_ | _comparable_ `"!="` _comparable_ -> _boolean_
+| [blue]`-` | _Infix_ | _List-difference_ | _list_ `-` _list_ -> _list_
-| [blue]`in` | _Infix_ |  _member-of-list_ | _any_ `"in"` _list_ -> _boolean_
+.8+|*RELATION*| [blue]`<` | _Infix_ | _Less_ | _comparable_ `<` _comparable_ -> _boolean_
-| [blue]`in` | _Infix_ |  _key-of-dict_ | _any_ `"in"` _dict_ -> _boolean_
+| [blue]`\<=` | _Infix_ |  _less-equal_ | _comparable_ `\<=` _comparable_ -> _boolean_
-.1+|*NOT*| [blue]`not` | _Prefix_ | _not_ | `"not"` _boolean_ -> _boolean_
+| [blue]`>` | _Infix_ |  _Greater_ | _comparable_ `>` _comparable_ -> _boolean_
-.2+|*AND*| [blue]`and` | _Infix_ | _and_ | _boolean_ `"and"` _boolean_ -> _boolean_
+| [blue]`>=` | _Infix_ |  _Greater-equal_ | _comparable_ `>=` _comparable_ -> _boolean_
-| [blue]`&&` | _Infix_ | _and_ | _boolean_ `"&&"` _boolean_ -> _boolean_
+| [blue]`==` | _Infix_ |  _Equal_ | _comparable_ `==` _comparable_ -> _boolean_
-.2+|*OR*| [blue]`or` | _Infix_ | _or_ | _boolean_ `"or"` _boolean_ -> _boolean_
+| [blue]`!=` | _Infix_ |  _Not-equal_ | _comparable_ `!=` _comparable_ -> _boolean_
-| [blue]`\|\|` | _Infix_ | _or_ | _boolean_ `"\|\|"` _boolean_ -> _boolean_
+| [blue]`in` | _Infix_ |  _Member-of-list_ | _any_ `in` _list_ -> _boolean_
-.3+|*ASSIGN*| [blue]`=` | _Infix_ | _assignment_ | _identifier_ "=" _any_ -> _any_
+| [blue]`in` | _Infix_ |  _Key-of-dict_ | _any_ `in` _dict_ -> _boolean_
-| [blue]`>>` | _Infix_ | _front-insert_ | _any_ ">>" _list_ -> _list_
+.1+|*NOT*| [blue]`not` | _Prefix_ | _Not_ | `not` _boolean_ -> _boolean_
-| [blue]`<<` | _Infix_ | _back-insert_ | _list_ "<<" _any_ -> _list_
+.2+|*AND*| [blue]`and` | _Infix_ | _And_ | _boolean_ `and` _boolean_ -> _boolean_
- .1+|*BUT*| [blue]`but` | _Infix_ | _but_ | _any_ "but" _any_ -> _any_
+| [blue]`&&` | _Infix_ | _And_ | _boolean_ `&&` _boolean_ -> _boolean_
+.2+|*OR*| [blue]`or` | _Infix_ | _Or_ | _boolean_ `or` _boolean_ -> _boolean_
+| [blue]`\|\|` | _Infix_ | _Or_ | _boolean_ `\|\|` _boolean_ -> _boolean_
+.3+|*ASSIGN*| [blue]`=` | _Infix_ | _Assignment_ | _identifier_ `=` _any_ -> _any_
+| [blue]`>>` | _Infix_ | _Front-insert_ | _any_ `>>` _list_ -> _list_
+| [blue]`<<` | _Infix_ | _Back-insert_ | _list_ `<<` _any_ -> _list_
+.1+|*BUT*| [blue]`but` | _Infix_ | _But_ | _any_ `but` _any_ -> _any_
+.1+|*RANGE*| [blue]`:` | _Infix_ | _Index-range_ | _integer_ `:` _integer_ -> _integer-pair_
 |===
 
+^1^ Experimental
+
+
 == Functions
 Functions in _Expr_ are very similar to functions available in many programming languages. Actually, _Expr_ supports two types of function, _expr-functions_ and _go-functions_.
 
 * _expr-functions_ are defined using _Expr_'s syntax. They can be passed as arguments to other functions and can be returned from functions. Moreover, they bind themselves to the defining context, thus becoming closures.
 * _go-functions_ are regular Golang functions callable from _Expr_ expressions. They are defined in Golang source files called _modules_ and compiled within the _Expr_ package. To make Golang functions available in _Expr_ contextes, it is required to _import_ the module in which they are defined.
 
-In _Expr_ functions compute values in a local context (scope) that do not make effects on the calling context. This is the normal behavior. Using the reference operator [blue]`@` it is possibile to export local definition to the calling context.
+
+=== _Expr_ function definition
+A function is identified and referenced by its name. It can have zero or more parameter. _Expr_ functions also support optional parameters.
+
+. Expr's function definition syntax
+====
+*_function-definition_* = _identifier_ "**=**"  "**func(**" [_param-list_] "**)**"  "**{**" _multi-expression_ "**}**"
+_param_list_ = _required-param-list_ [ "**,**" _optional-param-list_ ]
+_required-param-list_ = _identifier_ { "**,**" _identifier_ }
+_optional-param-list_ = _optional-parm_ { "**,**" _optional-param_ }
+_optional-param_ = _identifier_ "**=**" _any-expr_
+====
+
+.Examples
+#TODO#
+
+=== _Golang_ function definition
+Description of how to define Golan functions and how to bind them to _Expr_ are topics treated in another document that I'll write, one day, maybe.
 
 === Function calls
 #TODO: function calls operations#
 
-=== Function definitions
+Functions compute values in a local context (scope) that do not make effects on the calling context. This is the normal behavior. Using the reference operator [blue]`@` it is possibile to export local definition to the calling context.
-#TODO: function definitions operations#
+
+
+== Iterators
+#TODO: function calls operations#
 
 == Builtins
 #TODO: builtins#
@@ -637,4 +781,7 @@ In _Expr_ functions compute values in a local context (scope) that do not make e
 [blue]_import([grey]#<source-file>#)_ loads the multi-expression contained in the specified source and returns its value.
 
 
+== Plugins
+#TODO: plugins#
+
 

function.go

@@ -21,7 +21,7 @@ func (functor *baseFunctor) ToString(opt FmtOpt) (s string) {
 	if functor.info != nil {
 		s = functor.info.ToString(opt)
 	} else {
-		s = "func() {}"
+		s = "func(){}"
 	}
 	return s
 }
@@ -42,6 +42,10 @@ func (functor *baseFunctor) GetFunc() ExprFunc {
 	return functor.info
 }
 
+func (functor *baseFunctor) GetDefinitionContext() ExprContext {
+	return nil
+}
+
 // ---- Function Parameters
 type paramFlags uint16
 
@@ -94,13 +98,15 @@ func (param *funcParamInfo) DefaultValue() any {
 }
 
 // --- Functions
+
+// funcInfo implements ExprFunc
 type funcInfo struct {
-	name       string
+	name         string
-	minArgs    int
+	minArgs      int
-	maxArgs    int
+	maxArgs      int
-	functor    Functor
+	functor      Functor
-	params     []ExprFuncParam
+	formalParams []ExprFuncParam
-	returnType string
+	returnType   string
 }
 
 func newFuncInfo(name string, functor Functor, returnType string, params []ExprFuncParam) (info *funcInfo, err error) {
@@ -126,18 +132,18 @@ func newFuncInfo(name string, functor Functor, returnType string, params []ExprF
 		}
 	}
 	info = &funcInfo{
-		name: name, minArgs: minArgs, maxArgs: maxArgs, functor: functor, returnType: returnType, params: params,
+		name: name, minArgs: minArgs, maxArgs: maxArgs, functor: functor, returnType: returnType, formalParams: params,
 	}
 	functor.SetFunc(info)
 	return info, nil
 }
 
-func newUnnamedFuncInfo(functor Functor, returnType string, params []ExprFuncParam) (info *funcInfo, err error) {
+// func newUnnamedFuncInfo(functor Functor, returnType string, params []ExprFuncParam) (info *funcInfo, err error) {
-	return newFuncInfo("unnamed", functor, returnType, params)
+// 	return newFuncInfo("unnamed", functor, returnType, params)
-}
+// }
 
 func (info *funcInfo) Params() []ExprFuncParam {
-	return info.params
+	return info.formalParams
 }
 
 func (info *funcInfo) ReturnType() string {
@@ -152,8 +158,8 @@ func (info *funcInfo) ToString(opt FmtOpt) string {
 		sb.WriteString(info.Name())
 	}
 	sb.WriteByte('(')
-	if info.params != nil {
+	if info.formalParams != nil {
-		for i, p := range info.params {
+		for i, p := range info.formalParams {
 			if i > 0 {
 				sb.WriteString(", ")
 			}
@@ -180,7 +186,7 @@ func (info *funcInfo) ToString(opt FmtOpt) string {
 	} else {
 		sb.WriteString(TypeAny)
 	}
-	sb.WriteString(" {}")
+	sb.WriteString("{}")
 	return sb.String()
 }
 
@@ -199,3 +205,53 @@ func (info *funcInfo) MaxArgs() int {
 func (info *funcInfo) Functor() Functor {
 	return info.functor
 }
+
+func (info *funcInfo) AllocContext(parentCtx ExprContext) (ctx ExprContext) {
+	if defCtx := info.functor.GetDefinitionContext(); defCtx != nil {
+		ctx = defCtx.Clone()
+		ctx.SetParent(defCtx)
+	} else {
+		ctx = parentCtx.Clone()
+		ctx.SetParent(parentCtx)
+	}
+	return
+}
+
+func (info *funcInfo) PrepareCall(parentCtx ExprContext, name string, varActualParams *[]any) (ctx ExprContext, err error) {
+	passedCount := len(*varActualParams)
+	if info.MinArgs() > passedCount {
+		err = ErrTooFewParams(name, info.MinArgs(), info.MaxArgs(), passedCount)
+	}
+
+	for i := passedCount; i < len(info.formalParams); i++ {
+		p := info.formalParams[i]
+		if !p.IsDefault() {
+			break
+		}
+		*varActualParams = append(*varActualParams, p.DefaultValue())
+	}
+	if err == nil && info.MaxArgs() >= 0 && info.MaxArgs() < len(*varActualParams) {
+		err = ErrTooMuchParams(name, info.MaxArgs(), len(*varActualParams))
+	}
+
+	if err == nil {
+		ctx = info.AllocContext(parentCtx)
+	}
+	return
+}
+
+// ----- Call a function ---
+
+func CallFunction(parentCtx ExprContext, name string, actualParams []any) (result any, err error) {
+	if info, exists, _ := GetFuncInfo(parentCtx, name); exists {
+		var ctx ExprContext
+		if ctx, err = info.PrepareCall(parentCtx, name, &actualParams); err == nil {
+			functor := info.Functor()
+			result, err = functor.Invoke(ctx, name, actualParams)
+			exportObjectsToParent(ctx)
+		}
+	} else {
+		err = fmt.Errorf("unknown function %s()", name)
+	}
+	return
+}

iter-list.go

@@ -26,21 +26,21 @@ func NewListIterator(list *ListType, args []any) (it *ListIterator) {
 	}
 	it = &ListIterator{a: list, count: 0, index: -1, start: 0, stop: listLen - 1, step: 1}
 	if argc >= 1 {
-		if i, err := ToInt(args[0], "start index"); err == nil {
+		if i, err := ToGoInt(args[0], "start index"); err == nil {
 			if i < 0 {
 				i = listLen + i
 			}
 			it.start = i
 		}
 		if argc >= 2 {
-			if i, err := ToInt(args[1], "stop index"); err == nil {
+			if i, err := ToGoInt(args[1], "stop index"); err == nil {
 				if i < 0 {
 					i = listLen + i
 				}
 				it.stop = i
 			}
 			if argc >= 3 {
-				if i, err := ToInt(args[2], "step"); err == nil {
+				if i, err := ToGoInt(args[2], "step"); err == nil {
 					if i < 0 {
 						i = -i
 					}

operand-func.go

@@ -6,7 +6,6 @@ package expr
 
 import (
 	"errors"
-	"fmt"
 )
 
 // -------- function call term
@@ -22,35 +21,7 @@ func newFuncCallTerm(tk *Token, args []*term) *term {
 }
 
 // -------- eval func call
-func checkFunctionCall(ctx ExprContext, name string, varParams *[]any) (err error) {
+func evalFuncCall(ctx ExprContext, self *term) (v any, err error) {
-	if info, exists, owner := GetFuncInfo(ctx, name); exists {
-		passedCount := len(*varParams)
-		if info.MinArgs() > passedCount {
-			err = ErrTooFewParams(name, info.MinArgs(), info.MaxArgs(), passedCount)
-		}
-		for i, p := range info.Params() {
-			if i >= passedCount {
-				if !p.IsDefault() {
-					break
-				}
-				*varParams = append(*varParams, p.DefaultValue())
-			}
-		}
-		if err == nil && info.MaxArgs() >= 0 && info.MaxArgs() < len(*varParams) {
-			err = ErrTooMuchParams(name, info.MaxArgs(), len(*varParams))
-		}
-		if err == nil && owner != ctx {
-			ctx.RegisterFuncInfo(info)
-		}
-	} else {
-		err = fmt.Errorf("unknown function %s()", name)
-	}
-	return
-}
-
-func evalFuncCall(parentCtx ExprContext, self *term) (v any, err error) {
-	ctx := cloneContext(parentCtx)
-	ctx.SetParent(parentCtx)
 	name, _ := self.tk.Value.(string)
 	params := make([]any, len(self.children), len(self.children)+5)
 	for i, tree := range self.children {
@@ -62,11 +33,7 @@ func evalFuncCall(parentCtx ExprContext, self *term) (v any, err error) {
 	}
 
 	if err == nil {
-		if err = checkFunctionCall(ctx, name, &params); err == nil {
+		v, err = CallFunction(ctx, name, params)
-			if v, err = ctx.Call(name, params); err == nil {
-				exportObjects(parentCtx, ctx)
-			}
-		}
 	}
 	return
 }

operator-bool.go

@@ -37,9 +37,7 @@ func evalNot(ctx ExprContext, self *term) (v any, err error) {
 
 func newAndTerm(tk *Token) (inst *term) {
 	return &term{
-		tk: *tk,
+		tk:       *tk,
-		// class:    classOperator,
-		// kind:     kindBool,
 		children: make([]*term, 0, 2),
 		position: posInfix,
 		priority: priAnd,
@@ -88,7 +86,7 @@ func evalAndWithShortcut(ctx ExprContext, self *term) (v any, err error) {
 	}
 
 	if leftBool, lok := ToBool(leftValue); !lok {
-		err = fmt.Errorf("got %T as left operand type of 'and' operator, it must be bool", leftBool)
+		err = fmt.Errorf("got %s as left operand type of 'AND' operator, it must be bool", TypeName(leftValue))
 		return
 	} else if !leftBool {
 		v = false
@@ -106,9 +104,7 @@ func evalAndWithShortcut(ctx ExprContext, self *term) (v any, err error) {
 
 func newOrTerm(tk *Token) (inst *term) {
 	return &term{
-		tk: *tk,
+		tk:       *tk,
-		// class:    classOperator,
-		// kind:     kindBool,
 		children: make([]*term, 0, 2),
 		position: posInfix,
 		priority: priOr,
@@ -157,7 +153,7 @@ func evalOrWithShortcut(ctx ExprContext, self *term) (v any, err error) {
 	}
 
 	if leftBool, lok := ToBool(leftValue); !lok {
-		err = fmt.Errorf("got %T as left operand type of 'or' operator, it must be bool", leftBool)
+		err = fmt.Errorf("got %s as left operand type of 'OR' operator, it must be bool", TypeName(leftValue))
 		return
 	} else if leftBool {
 		v = true

operator-index.go

@@ -23,7 +23,7 @@ func verifyKey(indexTerm *term, indexList *ListType) (index any, err error) {
 func verifyIndex(indexTerm *term, indexList *ListType, maxValue int) (index int, err error) {
 	var v int
 
-	if v, err = ToInt((*indexList)[0], "index expression"); err == nil {
+	if v, err = ToGoInt((*indexList)[0], "index expression"); err == nil {
 		if v < 0 && v >= -maxValue {
 			v = maxValue + v
 		}
@@ -40,11 +40,14 @@ func verifyRange(indexTerm *term, indexList *ListType, maxValue int) (startIndex
 	v, _ := ((*indexList)[0]).(*intPair)
 	startIndex = v.a
 	endIndex = v.b
+	if endIndex == ConstLastIndex {
+		endIndex = maxValue
+	}
 	if startIndex < 0 && startIndex >= -maxValue {
 		startIndex = maxValue + startIndex
 	}
 	if endIndex < 0 && endIndex >= -maxValue {
-		endIndex = maxValue + endIndex + 1
+		endIndex = maxValue + endIndex
 	}
 	if startIndex < 0 || startIndex > maxValue {
 		err = indexTerm.Errorf("range start-index %d is out of bounds", startIndex)
@@ -87,13 +90,14 @@ func evalIndex(ctx ExprContext, self *term) (v any, err error) {
 				v = string(unboxedValue[index])
 			}
 		case *DictType:
-			var ok bool
+/* 			var ok bool
 			var indexValue any
 			if indexValue, err = verifyKey(indexTerm, indexList); err == nil {
 				if v, ok = (*unboxedValue)[indexValue]; !ok {
 					err = indexTerm.Errorf("key %v does not belong to the dictionary", rightValue)
 				}
-			}
+			} */
+			v, err = getDictItem(unboxedValue, indexTerm, indexList, rightValue)
 		default:
 			err = self.errIncompatibleTypes(leftValue, rightValue)
 		}
@@ -113,6 +117,29 @@ func evalIndex(ctx ExprContext, self *term) (v any, err error) {
 		default:
 			err = self.errIncompatibleTypes(leftValue, rightValue)
 		}
+	} else if IsDict(leftValue) {
+		d := leftValue.(*DictType)
+
+		/* 		var ok bool
+		   		var indexValue any
+		   		if indexValue, err = verifyKey(indexTerm, indexList); err == nil {
+		   			if v, ok = (*d)[indexValue]; !ok {
+		   				err = indexTerm.Errorf("key %v does not belong to the dictionary", rightValue)
+		   			}
+		   		}*/
+		v, err = getDictItem(d, indexTerm, indexList, rightValue)
+	}
+	return
+}
+
+func getDictItem(d *DictType, indexTerm *term, indexList *ListType, rightValue any) (v any, err error) {
+	var ok bool
+	var indexValue any
+
+	if indexValue, err = verifyKey(indexTerm, indexList); err == nil {
+		if v, ok = (*d)[indexValue]; !ok {
+			err = indexTerm.Errorf("key %v does not belong to the dictionary", rightValue)
+		}
 	}
 	return
 }

operator-length.go

@@ -36,7 +36,7 @@ func evalLength(ctx ExprContext, self *term) (v any, err error) {
 	} else if it, ok := childValue.(Iterator); ok {
 		if extIt, ok := childValue.(ExtIterator); ok && extIt.HasOperation(countName) {
 			count, _ := extIt.CallOperation(countName, nil)
-			v, _ = ToInt(count, "")
+			v, _ = ToGoInt(count, "")
 		} else {
 			v = int64(it.Index() + 1)
 		}

operator-range.go

@@ -29,7 +29,7 @@ func newRangeTerm(tk *Token) (inst *term) {
 		tk:       *tk,
 		children: make([]*term, 0, 2),
 		position: posInfix,
-		priority: priDot,
+		priority: priRange,
 		evalFunc: evalRange,
 	}
 }
@@ -47,7 +47,7 @@ func evalRange(ctx ExprContext, self *term) (v any, err error) {
 		if leftValue, err = self.children[0].compute(ctx); err != nil {
 			return
 		}
-		rightValue = int64(-1)
+		rightValue = int64(ConstLastIndex)
 	} else if leftValue, rightValue, err = self.evalInfix(ctx); err != nil {
 		return
 	}

parser.go

@@ -325,6 +325,14 @@ func couldBeACollection(t *term) bool {
 	return sym == SymList || sym == SymString || sym == SymDict || sym == SymExpression || sym == SymVariable
 }
 
+// func areSymbolsOutOfCtx(tk *Token, ctxTerm *term, syms ...Symbol) bool {
+// 	var areOut = false
+// 	if ctxTerm != nil {
+// 		areOut = tk.IsOneOf(syms)
+// 	}
+// 	return areOut
+// }
+
 func (self *parser) parseGeneral(scanner *scanner, allowForest bool, allowVarRef bool, termSymbols ...Symbol) (tree *ast, err error) {
 	var selectorTerm *term = nil
 	var currentTerm *term = nil
@@ -332,7 +340,7 @@ func (self *parser) parseGeneral(scanner *scanner, allowForest bool, allowVarRef
 	tree = NewAst()
 	firstToken := true
 	// lastSym := SymUnknown
-	for tk = scanner.Next(); err == nil && tk != nil && !tk.IsTerm(termSymbols); tk = scanner.Next() {
+	for tk = scanner.Next(); err == nil && tk != nil && !tk.IsTerm(termSymbols); /*&& !areSymbolsOutOfCtx(tk, selectorTerm, SymColon, SymDoubleColon)*/ tk = scanner.Next() {
 		if tk.Sym == SymComment {
 			continue
 		}
@@ -438,6 +446,10 @@ func (self *parser) parseGeneral(scanner *scanner, allowForest bool, allowVarRef
 			} else {
 				currentTerm, err = tree.addToken2(tk)
 			}
+			if tk.IsSymbol(SymColon) {
+				// Colon outside a selector term acts like a separator
+				firstToken = true
+			}
 		default:
 			currentTerm, err = tree.addToken2(tk)
 		}

plugins.go

@@ -6,7 +6,9 @@ package expr
 
 import (
 	"fmt"
+	"os"
 	"plugin"
+	"strings"
 )
 
 var pluginRegister map[string]*plugin.Plugin
@@ -25,6 +27,17 @@ func pluginExists(name string) (exists bool) {
 	return
 }
 
+func makePluginName(name string) (decorated string) {
+	var template string
+	if execName, err := os.Executable(); err != nil || strings.Index(execName, "debug") < 0 {
+		template = "expr-%s-plugin.so"
+	} else {
+		template = "expr-%s-plugin.so.debug"
+	}
+	decorated = fmt.Sprintf(template, name)
+	return
+}
+
 func importPlugin( /*ctx ExprContext,*/ dirList []string, name string) (err error) {
 	var filePath string
 	var p *plugin.Plugin
@@ -33,7 +46,7 @@ func importPlugin( /*ctx ExprContext,*/ dirList []string, name string) (err erro
 	var importFunc func(ExprContext)
 	var ok bool
 
-	decoratedName := fmt.Sprintf("expr-%s-plugin.so", name)
+	decoratedName := makePluginName(name)
 
 	if filePath, err = makeFilepath(decoratedName, dirList); err != nil {
 		return

simple-store.go

@@ -7,7 +7,7 @@ package expr
 import (
 	"fmt"
 	"slices"
-//	"strings"
+	// "strings"
 )
 
 type SimpleStore struct {
@@ -36,87 +36,21 @@ func (ctx *SimpleStore) GetParent() ExprContext {
 }
 
 func (ctx *SimpleStore) Clone() ExprContext {
-	return &SimpleStore{
+	clone := &SimpleStore{
 		varStore:  CloneFilteredMap(ctx.varStore, filterRefName),
 		funcStore: CloneFilteredMap(ctx.funcStore, filterRefName),
 	}
+	return clone
 }
 
-func (ctx *SimpleStore) Merge(src ExprContext) {
+// func (ctx *SimpleStore) Merge(src ExprContext) {
-	for _, name := range src.EnumVars(filterRefName) {
+// 	for _, name := range src.EnumVars(filterRefName) {
-		ctx.varStore[name], _ = src.GetVar(name)
+// 		ctx.varStore[name], _ = src.GetVar(name)
-	}
+// 	}
-	for _, name := range src.EnumFuncs(filterRefName) {
+// 	for _, name := range src.EnumFuncs(filterRefName) {
-		ctx.funcStore[name], _ = src.GetFuncInfo(name)
+// 		ctx.funcStore[name], _ = src.GetFuncInfo(name)
-	}
+// 	}
-}
+// }
-/*
-func varsCtxToBuilder(sb *strings.Builder, ctx ExprContext, indent int) {
-	sb.WriteString("vars: {\n")
-	first := true
-	for _, name := range ctx.EnumVars(nil) {
-		if first {
-			first = false
-		} else {
-			sb.WriteByte(',')
-			sb.WriteByte('\n')
-		}
-
-		value, _ := ctx.GetVar(name)
-		sb.WriteString(strings.Repeat("\t", indent+1))
-		sb.WriteString(name)
-		sb.WriteString(": ")
-		if f, ok := value.(Formatter); ok {
-			sb.WriteString(f.ToString(0))
-		} else if _, ok = value.(Functor); ok {
-			sb.WriteString("func(){}")
-			// } else if _, ok = value.(map[any]any); ok {
-			// 	sb.WriteString("dict{}")
-		} else {
-			sb.WriteString(fmt.Sprintf("%v", value))
-		}
-	}
-	sb.WriteString(strings.Repeat("\t", indent))
-	sb.WriteString("\n}")
-}
-
-func varsCtxToString(ctx ExprContext, indent int) string {
-	var sb strings.Builder
-	varsCtxToBuilder(&sb, ctx, indent)
-	return sb.String()
-}
-
-func funcsCtxToBuilder(sb *strings.Builder, ctx ExprContext, indent int) {
-	sb.WriteString("funcs: {\n")
-	first := true
-	names := ctx.EnumFuncs(func(name string) bool { return true })
-	slices.Sort(names)
-	for _, name := range names {
-		if first {
-			first = false
-		} else {
-			sb.WriteByte(',')
-			sb.WriteByte('\n')
-		}
-		value, _ := ctx.GetFuncInfo(name)
-		sb.WriteString(strings.Repeat("\t", indent+1))
-		if formatter, ok := value.(Formatter); ok {
-			sb.WriteString(formatter.ToString(0))
-		} else {
-			sb.WriteString(fmt.Sprintf("%v", value))
-		}
-	}
-	sb.WriteString("\n}")
-}
-
-func (ctx *SimpleStore) ToString(opt FmtOpt) string {
-	var sb strings.Builder
-	varsCtxToBuilder(&sb, ctx, 0)
-	sb.WriteByte('\n')
-	funcsCtxToBuilder(&sb, ctx, 0)
-	return sb.String()
-}
-*/
 
 func (ctx *SimpleStore) ToString(opt FmtOpt) string {
 	dict := ctx.ToDict()
@@ -165,6 +99,11 @@ func (ctx *SimpleStore) GetVar(varName string) (v any, exists bool) {
 	return
 }
 
+func (ctx *SimpleStore) GetLast() (v any) {
+	v = ctx.varStore["last"]
+	return
+}
+
 func (ctx *SimpleStore) UnsafeSetVar(varName string, value any) {
 	// fmt.Printf("[%p] setVar(%v, %v)\n", ctx, varName, value)
 	ctx.varStore[varName] = value

t_bool_test.go

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

t_builtin-base_test.go

@@ -63,5 +63,5 @@ func TestFuncBase(t *testing.T) {
 	t.Setenv("EXPR_PATH", ".")
 
 	// parserTestSpec(t, section, inputs, 2)
-	parserTest(t, section, inputs)
+	runTestSuite(t, section, inputs)
 }

t_builtin-fmt_test.go

@@ -0,0 +1,48 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// t_builtin-fmt.go
+package expr
+
+import (
+	// "errors"
+	"bytes"
+	"fmt"
+	"testing"
+)
+
+func TestFuncFmt(t *testing.T) {
+	section := "Builtin-Fmt"
+
+	inputs := []inputType{
+		/*   1 */ {`builtin "fmt"; print("ciao")`, int64(4), nil},
+		/*   2 */ {`builtin "fmt"; println(" ciao")`, int64(6), nil},
+	}
+
+	//t.Setenv("EXPR_PATH", ".")
+
+	// runTestSuiteSpec(t, section, inputs, 19)
+	runTestSuite(t, section, inputs)
+}
+
+func TestFmt(t *testing.T) {
+	section := "Builtin-Fmt"
+
+	text := "ciao mondo"
+	inputs := []inputType{
+		/*   1 */ {fmt.Sprintf(`println("%s")`, text), int64(11), nil},
+	}
+
+	// t.Setenv("EXPR_PATH", ".")
+
+	var b bytes.Buffer
+	ctx := NewSimpleStore()
+	currentStdout := SetCtrl(ctx, ControlStdout, &b)
+
+	runCtxTestSuite(t, ctx, section, inputs)
+
+	SetCtrl(ctx, ControlStdout, currentStdout)
+	if b.String() != text+"\n" {
+		t.Errorf("println(): Got: %q, Want: %q", b.String(), text+"\n")
+	}
+}

t_builtin-import_test.go

@@ -20,5 +20,5 @@ func TestFuncImport(t *testing.T) {
 	t.Setenv("EXPR_PATH", "test-resources")
 
 	// parserTestSpec(t, section, inputs, 69)
-	parserTest(t, section, inputs)
+	runTestSuite(t, section, inputs)
 }

t_builtin-math-arith_test.go

@@ -25,5 +25,5 @@ func TestFuncMathArith(t *testing.T) {
 	// t.Setenv("EXPR_PATH", ".")
 
 	// parserTestSpec(t, section, inputs, 69)
-	parserTest(t, section, inputs)
+	runTestSuite(t, section, inputs)
 }

t_builtin-os-file_test.go

@@ -16,14 +16,21 @@ func TestFuncOs(t *testing.T) {
 		/*   2 */ {`builtin "os.file"; handle=fileOpen("/etc/hosts"); fileClose(handle)`, true, nil},
 		/*   3 */ {`builtin "os.file"; handle=fileOpen("/etc/hostsX")`, nil, errors.New(`open /etc/hostsX: no such file or directory`)},
 		/*   4 */ {`builtin "os.file"; handle=fileCreate("/tmp/dummy"); fileClose(handle)`, true, nil},
-		/*   5 */ {`builtin "os.file"; handle=fileAppend("/tmp/dummy"); fileWrite(handle, "bye-bye"); fileClose(handle)`, true, nil},
+		/*   5 */ {`builtin "os.file"; handle=fileAppend("/tmp/dummy"); fileWriteText(handle, "bye-bye"); fileClose(handle)`, true, nil},
-		/*   6 */ {`builtin "os.file"; handle=fileOpen("/tmp/dummy"); word=fileRead(handle, "-"); fileClose(handle);word`, "bye", nil},
+		/*   6 */ {`builtin "os.file"; handle=fileOpen("/tmp/dummy"); word=fileReadText(handle, "-"); fileClose(handle);word`, "bye", nil},
-		/*   7 */ {`builtin "os.file"; word=fileRead(nil, "-")`, nil, errors.New(`readFileFunc(): invalid file handle`)},
+		/*   7 */ {`builtin "os.file"; word=fileReadText(nil, "-")`, nil, errors.New(`fileReadText(): invalid file handle`)},
-		/*   7 */ {`builtin "os.file"; fileWrite(nil, "bye")`, nil, errors.New(`writeFileFunc(): invalid file handle`)},
+		/*   8 */ {`builtin "os.file"; fileWriteText(nil, "bye")`, nil, errors.New(`fileWriteText(): invalid file handle`)},
+		/*   9 */ {`builtin "os.file"; handle=fileOpen()`, nil, errors.New(`fileOpen(): too few params -- expected 1, got 0`)},
+		/*  10 */ {`builtin "os.file"; handle=fileOpen(123)`, nil, errors.New(`fileOpen(): missing or invalid file path`)},
+		/*  11 */ {`builtin "os.file"; handle=fileCreate(123)`, nil, errors.New(`fileCreate(): missing or invalid file path`)},
+		/*  12 */ {`builtin "os.file"; handle=fileAppend(123)`, nil, errors.New(`fileAppend(): missing or invalid file path`)},
+		/*  13 */ {`builtin "os.file"; handle=fileClose(123)`, nil, errors.New(`fileClose(): invalid file handle`)},
+		/*  14 */ {`builtin "os.file"; handle=fileOpen("/tmp/dummy"); c=fileReadTextAll(handle); fileClose(handle); c`, "bye-bye", nil},
+		/*  15 */ {`builtin "os.file"; c=fileReadTextAll(123)`, nil, errors.New(`fileReadTextAll(): invalid file handle 123 [int64]`)},
 	}
 
 	// t.Setenv("EXPR_PATH", ".")
 
 	// parserTestSpec(t, section, inputs, 69)
-	parserTest(t, section, inputs)
+	runTestSuite(t, section, inputs)
 }

t_builtin-string_test.go

@@ -64,6 +64,6 @@ func TestFuncString(t *testing.T) {
 
 	//t.Setenv("EXPR_PATH", ".")
 
-	// parserTestSpec(t, section, inputs, 19)
+	// runTestSuiteSpec(t, section, inputs, 19)
-	parserTest(t, section, inputs)
+	runTestSuite(t, section, inputs)
 }

t_common_test.go

@@ -0,0 +1,113 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// t_common_test.go
+package expr
+
+import (
+	"reflect"
+	"strings"
+	"testing"
+)
+
+type inputType struct {
+	source     string
+	wantResult any
+	wantErr    error
+}
+
+func runCtxTestSuiteSpec(t *testing.T, ctx ExprContext, section string, inputs []inputType, spec ...int) {
+	succeeded := 0
+	failed := 0
+	for _, count := range spec {
+		good := doTest(t, ctx, section, &inputs[count-1], count)
+
+		if good {
+			succeeded++
+		} else {
+			failed++
+		}
+	}
+	t.Logf("%s -- test count: %d, succeeded: %d, failed: %d", section, len(spec), succeeded, failed)
+}
+
+func runTestSuiteSpec(t *testing.T, section string, inputs []inputType, spec ...int) {
+	runCtxTestSuiteSpec(t, nil, section, inputs, spec...)
+}
+
+func runCtxTestSuite(t *testing.T, ctx ExprContext, section string, inputs []inputType) {
+
+	succeeded := 0
+	failed := 0
+
+	for i, input := range inputs {
+		good := doTest(t, ctx, section, &input, i+1)
+		if good {
+			succeeded++
+		} else {
+			failed++
+		}
+	}
+	t.Logf("%s -- test count: %d, succeeded: %d, failed: %d", section, len(inputs), succeeded, failed)
+}
+func runTestSuite(t *testing.T, section string, inputs []inputType) {
+	runCtxTestSuite(t, nil, section, inputs)
+/*
+	succeeded := 0
+	failed := 0
+
+	for i, input := range inputs {
+		good := doTest(t, nil, 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, ctx ExprContext, section string, input *inputType, count int) (good bool) {
+	var expr Expr
+	var gotResult any
+	var gotErr error
+
+	parser := NewParser()
+	if ctx == nil {
+		ctx = NewSimpleStore()
+	}
+
+	logTest(t, count, section, input.source, input.wantResult, input.wantErr)
+
+	r := strings.NewReader(input.source)
+	scanner := NewScanner(r, DefaultTranslations())
+
+	good = true
+	if expr, gotErr = parser.Parse(scanner); gotErr == nil {
+		gotResult, gotErr = expr.Eval(ctx)
+	}
+
+	eq := reflect.DeepEqual(gotResult, input.wantResult)
+
+	if !eq /*gotResult != input.wantResult*/ {
+		t.Errorf("%d: %q -> result = %v [%s], want = %v [%s]", count, input.source, gotResult, TypeName(gotResult), input.wantResult, TypeName(input.wantResult))
+		good = false
+	}
+
+	if gotErr != input.wantErr {
+		if input.wantErr == nil || gotErr == nil || (gotErr.Error() != input.wantErr.Error()) {
+			t.Errorf("%d: %q -> got-err = <%v>, expected-err = <%v>", count, input.source, gotErr, input.wantErr)
+			good = false
+		}
+	}
+	return
+}
+
+func logTest(t *testing.T, n int, section, source string, wantResult any, wantErr error) {
+	if wantErr == nil {
+		t.Logf("[+]%s nr %3d -- %q  --> %v", section, n, source, wantResult)
+	} else {
+		t.Logf("[-]%s nr %3d -- %q  --> %v", section, n, source, wantErr)
+	}
+}

t_dict_test.go

@@ -31,6 +31,7 @@ func TestDictParser(t *testing.T) {
 		/*  8 */ {`D={"a":1, "b":2}; D["a"]=9; D`, map[any]any{"a": 9, "b": 2}, nil},
 		/*  9 */ {`D={"a":1, "b":2}; D["z"]=9; D`, map[any]any{"z": 9, "a": 1, "b": 2}, nil},
 		/* 10 */ {`D={"a":1, "b":2}; D[nil]=9`, nil, errors.New(`[1:21] index/key is nil`)},
+		/* 11 */ {`D={"a":1, "b":2}; D["a"]`, int64(1), nil},
 	}
 
 	succeeded := 0

t_expr_test.go

@@ -14,7 +14,7 @@ func TestExpr(t *testing.T) {
 	inputs := []inputType{
 		/*   1 */ {`0?{}`, nil, nil},
 		/*   2 */ {`fact=func(n){(n)?{1}::{n*fact(n-1)}}; fact(5)`, int64(120), nil},
-		/*   3 */ {`builtin "os.file"; f=fileOpen("test-file.txt"); line=fileRead(f); fileClose(f); line`, "uno", nil},
+		/*   3 */ {`builtin "os.file"; f=fileOpen("test-file.txt"); line=fileReadText(f); fileClose(f); line`, "uno", nil},
 		/*   4 */ {`mynot=func(v){int(v)?{true}::{false}}; mynot(0)`, true, nil},
 		/*   5 */ {`1 ? {1} : [1+0] {3*(1+1)}`, int64(6), nil},
 		/*   6 */ {`
@@ -33,5 +33,5 @@ func TestExpr(t *testing.T) {
 	// t.Setenv("EXPR_PATH", ".")
 
 	// parserTestSpec(t, section, inputs, 3)
-	parserTest(t, section, inputs)
+	runTestSuite(t, section, inputs)
 }

t_fractions_test.go

@@ -34,7 +34,7 @@ func TestFractionsParser(t *testing.T) {
 		/*  20 */ {`fract("1a")`, (*FractionType)(nil), errors.New(`strconv.ParseInt: parsing "1a": invalid syntax`)},
 		/*  21 */ {`fract(1,0)`, nil, errors.New(`fract(): division by zero`)},
 	}
-	parserTest(t, section, inputs)
+	runTestSuite(t, section, inputs)
 }
 
 func TestFractionToStringSimple(t *testing.T) {

t_funcs_test.go

@@ -29,13 +29,15 @@ func TestFuncs(t *testing.T) {
 		/*  15 */ {`f=func(x,n=2){x+n}; f(3)`, int64(5), nil},
 		/*  16 */ {`f=func(x,n=2,y){x+n}`, nil, errors.New(`[1:16] can't mix default and non-default parameters`)},
 		/*  17 */ {`f=func(x,n){1}; f(3,4,)`, nil, errors.New(`[1:24] expected "function-param-value", got ")"`)},
+		/*  18 */ {`factory=func(base){func(){@base=base+1}}; inc10=factory(10); inc5=factory(5); inc10(); inc5(); inc10()`, int64(12), nil},
+		/*  19 */ {`f=func(a,y=1,z="sos"){}; string(f)`, `f(a, y=1, z="sos"):any{}`, nil},
 		// /*  18 */ {`f=func(a){a*2}`, nil, errors.New(`[1:24] expected "function-param-value", got ")"`)},
 	}
 
 	// t.Setenv("EXPR_PATH", ".")
 
-	// parserTestSpec(t, section, inputs, 17)
+	// runTestSuiteSpec(t, section, inputs, 17)
-	parserTest(t, section, inputs)
+	runTestSuite(t, section, inputs)
 }
 
 func dummy(ctx ExprContext, name string, args []any) (result any, err error) {
@@ -44,7 +46,7 @@ func dummy(ctx ExprContext, name string, args []any) (result any, err error) {
 
 func TestFunctionToStringSimple(t *testing.T) {
 	source := NewGolangFunctor(dummy)
-	want := "func() {}"
+	want := "func(){}"
 	got := source.ToString(0)
 	if got != want {
 		t.Errorf(`(func() -> result = %v [%T], want = %v [%T]`, got, got, want, want)

t_index_test.go

@@ -23,5 +23,5 @@ func TestCollections(t *testing.T) {
 	t.Setenv("EXPR_PATH", ".")
 
 	// parserTestSpec(t, section, inputs, 5)
-	parserTest(t, section, inputs)
+	runTestSuite(t, section, inputs)
 }

t_iterator_test.go

@@ -14,13 +14,13 @@ func TestIteratorParser(t *testing.T) {
 		/*   4 */ {`include "test-resources/iterator.expr"; it=$(ds,3); it++; it++; it.reset; ()it`, int64(0), nil},
 		/*   5 */ {`builtin "math.arith"; include "test-resources/iterator.expr"; it=$(ds,3); add(it)`, int64(6), nil},
 		/*   6 */ {`builtin "math.arith"; include "test-resources/iterator.expr"; it=$(ds,3); mul(it)`, int64(0), nil},
-		/*   7 */ {`builtin "math.arith"; include "test-resources/file-reader.expr"; it=$(ds,"int.list"); mul(it)`, int64(12000), nil},
+		/*   7 */ {`builtin "math.arith"; include "test-resources/file-reader.expr"; it=$(ds,"test-resources/int.list"); mul(it)`, int64(12000), nil},
-		/*   8 */ {`include "test-resources/file-reader.expr"; it=$(ds,"int.list"); it++; it.index`, int64(0), nil},
+		/*   8 */ {`include "test-resources/file-reader.expr"; it=$(ds,"test-resources/int.list"); it++; it.index`, int64(0), nil},
-		/*  10 */ {`include "test-resources/file-reader.expr"; it=$(ds,"int.list"); it.clean`, true, nil},
+		/*  10 */ {`include "test-resources/file-reader.expr"; it=$(ds,"test-resources/int.list"); it.clean`, true, nil},
 		/*  11 */ {`it=$(1,2,3); it++`, int64(1), nil},
 	}
 	// inputs1 := []inputType{
 	// 	/*   1 */ {`0?{}`, nil, nil},
 	// }
-	parserTest(t, "Iterator", inputs)
+	runTestSuite(t, "Iterator", inputs)
 }

t_list_test.go

@@ -49,12 +49,14 @@ func TestListParser(t *testing.T) {
 		/*  35 */ {`L=[1,2]; L[5]=9; L`, nil, errors.New(`index 5 out of bounds (0, 1)`)},
 		/*  36 */ {`L=[1,2]; L[]=9; L`, nil, errors.New(`[1:12] index/key specification expected, got [] [list]`)},
 		/*  37 */ {`L=[1,2]; L[nil]=9;`, nil, errors.New(`[1:12] index/key is nil`)},
-		// /*  8 */ {`[int(x)|x=csv("test.csv",1,all(),1)]`, []any{int64(10), int64(40), int64(20)}, nil},
+		/*  38 */ {`[0,1,2,3,4][2:3]`, newListA(int64(2)), nil},
-		// /*  9 */ {`sum(@[int(x)|x=csv("test.csv",1,all(),1)])`, []any{int64(10), int64(40), int64(20)}, nil},
+		/*  39 */ {`[0,1,2,3,4][3:-1]`, newListA(int64(3)), nil},
+		/*  40 */ {`[0,1,2,3,4][-3:-1]`, newListA(int64(2), int64(3)), nil},
+		/*  41 */ {`[0,1,2,3,4][0:]`, newListA(int64(0), int64(1), int64(2), int64(3), int64(4)), nil},
 	}
 
 	// t.Setenv("EXPR_PATH", ".")
 
 	// parserTestSpec(t, section, inputs, 17)
-	parserTest(t, section, inputs)
+	runTestSuite(t, section, inputs)
 }

t_parser_test.go

@@ -6,17 +6,9 @@ package expr
 
 import (
 	"errors"
-	"reflect"
-	"strings"
 	"testing"
 )
 
-type inputType struct {
-	source     string
-	wantResult any
-	wantErr    error
-}
-
 func TestGeneralParser(t *testing.T) {
 	section := "Parser"
 
@@ -148,78 +140,5 @@ func TestGeneralParser(t *testing.T) {
 
 	// t.Setenv("EXPR_PATH", ".")
 	// parserTestSpec(t, section, inputs, 102)
-	parserTest(t, section, inputs)
+	runTestSuite(t, section, inputs)
-}
-
-func parserTestSpec(t *testing.T, section string, inputs []inputType, spec ...int) {
-	succeeded := 0
-	failed := 0
-	for _, count := range spec {
-		good := doTest(t, section, &inputs[count-1], count)
-
-		if good {
-			succeeded++
-		} else {
-			failed++
-		}
-	}
-	t.Logf("%s -- test count: %d, succeeded: %d, failed: %d", section, len(spec), succeeded, failed)
-}
-
-func parserTest(t *testing.T, section string, inputs []inputType) {
-
-	succeeded := 0
-	failed := 0
-
-	for i, input := range inputs {
-		good := doTest(t, section, &input, i+1)
-		if good {
-			succeeded++
-		} else {
-			failed++
-		}
-	}
-	t.Logf("%s -- test count: %d, succeeded: %d, failed: %d", section, len(inputs), succeeded, failed)
-}
-
-func doTest(t *testing.T, section string, input *inputType, count int) (good bool) {
-	var expr Expr
-	var gotResult any
-	var gotErr error
-
-	ctx := NewSimpleStore()
-	parser := NewParser()
-
-	logTest(t, count, section, input.source, input.wantResult, input.wantErr)
-
-	r := strings.NewReader(input.source)
-	scanner := NewScanner(r, DefaultTranslations())
-
-	good = true
-	if expr, gotErr = parser.Parse(scanner); gotErr == nil {
-		gotResult, gotErr = expr.Eval(ctx)
-	}
-
-	eq := reflect.DeepEqual(gotResult, input.wantResult)
-
-	if !eq /*gotResult != input.wantResult*/ {
-		t.Errorf("%d: %q -> result = %v [%s], want = %v [%s]", count, input.source, gotResult, TypeName(gotResult), input.wantResult, TypeName(input.wantResult))
-		good = false
-	}
-
-	if gotErr != input.wantErr {
-		if input.wantErr == nil || gotErr == nil || (gotErr.Error() != input.wantErr.Error()) {
-			t.Errorf("%d: %q -> got-err = <%v>, expected-err = <%v>", count, input.source, gotErr, input.wantErr)
-			good = false
-		}
-	}
-	return
-}
-
-func logTest(t *testing.T, n int, section, source string, wantResult any, wantErr error) {
-	if wantErr == nil {
-		t.Logf("[+]%s nr %3d -- %q  --> %v", section, n, source, wantResult)
-	} else {
-		t.Logf("[-]%s nr %3d -- %q  --> %v", section, n, source, wantErr)
-	}
 }

t_plugin_test.go

@@ -0,0 +1,31 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// t_plugin_test.go
+package expr
+
+import (
+	"testing"
+)
+
+func _TestImportPlugin(t *testing.T) {
+	if err := importPlugin([]string{"test-resources"}, "json"); err != nil {
+		t.Errorf("importPlugin() failed: %v", err)
+	}
+}
+
+func TestPluginExists(t *testing.T) {
+	name := "json"
+	exists := pluginExists(name)
+	t.Logf("pluginExists(%v): %v", name, exists)
+
+}
+
+func TestMakePluginName(t *testing.T) {
+	name := "json"
+	want := "expr-" + name + "-plugin.so"
+
+	if got := makePluginName(name); got != want {
+		t.Errorf("makePluginName(%q) failed: Got: %q, Want: %q", name, got, want)
+	}
+}

t_relational_test.go

@@ -48,5 +48,5 @@ func TestRelational(t *testing.T) {
 	// t.Setenv("EXPR_PATH", ".")
 
 	// parserTestSpec(t, section, inputs, 31)
-	parserTest(t, section, inputs)
+	runTestSuite(t, section, inputs)
 }

t_strings_test.go

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

t_template_test.go

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

t_utils_test.go

@@ -6,6 +6,7 @@ package expr
 
 import (
 	"errors"
+	"reflect"
 	"testing"
 )
 
@@ -97,7 +98,7 @@ func TestToIntOk(t *testing.T) {
 	wantValue := int(64)
 	wantErr := error(nil)
 
-	gotValue, gotErr := ToInt(source, "test")
+	gotValue, gotErr := ToGoInt(source, "test")
 
 	if gotErr != nil || gotValue != wantValue {
 		t.Errorf("toInt(%v, \"test\") gotValue=%v, gotErr=%v -> wantValue=%v, wantErr=%v",
@@ -110,7 +111,7 @@ func TestToIntErr(t *testing.T) {
 	wantValue := 0
 	wantErr := errors.New(`test expected integer, got uint64 (64)`)
 
-	gotValue, gotErr := ToInt(source, "test")
+	gotValue, gotErr := ToGoInt(source, "test")
 
 	if gotErr.Error() != wantErr.Error() || gotValue != wantValue {
 		t.Errorf("toInt(%v, \"test\") gotValue=%v, gotErr=%v -> wantValue=%v, wantErr=%v",
@@ -154,3 +155,12 @@ func TestAnyInteger(t *testing.T) {
 	}
 	t.Logf("%s -- test count: %d, succeeded: %d, failed: %d", section, len(inputs), succeeded, failed)
 }
+
+func TestCopyMap(t *testing.T) {
+	source := map[string]int{"one": 1, "two": 2, "three": 3}
+	dest := make(map[string]int)
+	result := CopyMap(dest, source)
+	if !reflect.DeepEqual(result, source) {
+		t.Errorf("utils.CopyMap() failed")
+	}
+}

test-resources/file-reader.expr

@@ -1,23 +1,22 @@
 builtin ["os.file", "base"];
 
 readInt=func(fh){
-	line=fileRead(fh);
+	line=fileReadText(fh);
 	line ? [nil] {nil} :: {int(line)}
 };
 
 ds={
 	"init":func(filename){
 		fh=fileOpen(filename);
-		fh ? [nil] {nil} :: { @current=readInt(fh); @prev=@current };
+		fh ? [nil] {nil} :: { @current=readInt(fh) };
 		fh
 	},
 	"current":func(){
-		prev
+		current
 	},
 	"next":func(fh){
-		current ? 
+		@current=readInt(fh);
-			[nil] {current}
+		current
-			:: {@prev=current; @current=readInt(fh) but current}
 	},
 	"clean":func(fh){
 		fileClose(fh)
@@ -25,9 +24,9 @@ ds={
 }
 
 //;f=$(ds, "int.list")
-/*
+
-;f++
+//;f++
-;f++
+//;f++
-;f++
+//;f++
-*/
+//*/
 //;add(f)

token.go

@@ -60,7 +60,11 @@ func (tk *Token) IsError() bool {
 }
 
 func (tk *Token) IsTerm(termSymbols []Symbol) bool {
-	return tk.IsEos() || tk.IsError() || (termSymbols != nil && slices.Index(termSymbols, tk.Sym) >= 0)
+	return tk.IsEos() || tk.IsError() || tk.IsOneOf(termSymbols)
+}
+
+func (tk *Token) IsOneOf(termSymbols []Symbol) bool {
+	return termSymbols != nil && slices.Index(termSymbols, tk.Sym) >= 0
 }
 
 func (tk *Token) IsSymbol(sym Symbol) bool {

utils.go

@@ -135,23 +135,25 @@ func anyInteger(v any) (i int64, ok bool) {
 }
 
 func fromGenericAny(v any) (exprAny any, ok bool) {
-	if exprAny, ok = v.(bool); ok {
+	if v != nil {
-		return
+		if exprAny, ok = v.(bool); ok {
-	}
+			return
-	if exprAny, ok = v.(string); ok {
+		}
-		return
+		if exprAny, ok = v.(string); ok {
-	}
+			return
-	if exprAny, ok = anyInteger(v); ok {
+		}
-		return
+		if exprAny, ok = anyInteger(v); ok {
-	}
+			return
-	if exprAny, ok = anyFloat(v); ok {
+		}
-		return
+		if exprAny, ok = anyFloat(v); ok {
-	}
+			return
-	if exprAny, ok = v.(*DictType); ok {
+		}
-		return
+		if exprAny, ok = v.(*DictType); ok {
-	}
+			return
-	if exprAny, ok = v.(*ListType); ok {
+		}
-		return
+		if exprAny, ok = v.(*ListType); ok {
+			return
+		}
 	}
 	return
 }
@@ -176,10 +178,10 @@ func CopyMap[K comparable, V any](dest, source map[K]V) map[K]V {
 	return dest
 }
 
-func CloneMap[K comparable, V any](source map[K]V) map[K]V {
+// func CloneMap[K comparable, V any](source map[K]V) map[K]V {
-	dest := make(map[K]V, len(source))
+// 	dest := make(map[K]V, len(source))
-	return CopyMap(dest, 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)
@@ -201,7 +203,7 @@ func CloneFilteredMap[K comparable, V any](source map[K]V, filter func(key K) (a
 	return CopyFilteredMap(dest, source, filter)
 }
 
-func ToInt(value any, description string) (i int, err error) {
+func ToGoInt(value any, description string) (i int, err error) {
 	if valueInt64, ok := value.(int64); ok {
 		i = int(valueInt64)
 	} else if valueInt, ok := value.(int); ok {