deep list inclusion and item membership implemented

- fraction type renamed as FractionType and moved from operator-fraction.go to fraction-type.go
- ListType moved from operator-list.go to list-type.go
- all test file were renamed adding the "t_" prefix
- defined a test template in file t_temple_test.go
- new test file t_relational_test.go where relational tests are collected
- lists can now compared as set using operators <, <=, >, and >= (IMPORTANT: here = menas same content, not same list)

ast.go

@@ -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
@@ -128,7 +128,7 @@ func (self *ast) eval(ctx ExprContext, preset bool) (result any, err error) {
 		}
 		if err == nil {
 			result, err = self.root.compute(ctx)
-			ctx.setVar(ControlLastResult, result)
+			ctx.UnsafeSetVar(ControlLastResult, result)
 		}
 		// } else {
 		// 	err = errors.New("empty expression")

common-params.go

@@ -5,7 +5,26 @@
 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

@@ -5,10 +5,14 @@
 package expr
 
 const (
+	typeAny      = "any"
 	typeBoolean  = "boolean"
-	typeFloat    = "decimal"
+	typeFloat    = "float"
 	typeFraction = "fraction"
+	typeHandle   = "handle"
 	typeInt      = "integer"
+	typeItem     = "item"
 	typeNumber   = "number"
+	typePair     = "pair"
 	typeString   = "string"
 )

context-helpers.go

@@ -15,14 +15,16 @@ 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) {

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 {
-	f FuncTemplate
-}
-
-func (functor *simpleFunctor) Invoke(ctx ExprContext, name string, args []any) (result any, err error) {
-	return functor.f(ctx, name, args)
+// ---- Function Param Info
+type ExprFuncParam interface {
+	Name() string
+	Type() string
+	IsOptional() bool
+	IsRepeat() bool
+	DefaultValue() any
 }
 
 // ---- Function Info
 type ExprFunc interface {
+	Formatter
 	Name() string
 	MinArgs() int
 	MaxArgs() int
 	Functor() Functor
+	Params() []ExprFuncParam
+	ReturnType() string
 }
 
 // ----Expression Context
@@ -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
 }

doc/Expr.adoc

@@ -22,7 +22,7 @@ Expressions calculator
 
 toc::[]
 
-#TODO: Work in progress (last update on 2024/05/17, 15:47 p.m.)#
+#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.
@@ -266,10 +266,10 @@ 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]`"one" + 2` _["one2"]_
+| [blue]`+` | _concatenation_ | Join two strings or two _stringable_ values | [blue]`"one" + "two"` -> _"onetwo"_ +
+[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.
@@ -280,22 +280,22 @@ _item_ = _string-expr_ "**.**" _integer-expr_
 ====
 
 .String examples
-`>>>` [blue]`s="abc"`  [gray]_assign the string to variable s_ +
+`>>>` [blue]`s="abc"`  [gray]_// assign the string to variable s_ +
 [green]`abc` +
-`>>>` [blue]`s.1`      [gray]_char at position 1 (starting from 0)_ +
+`>>>` [blue]`s.1`      [gray]_// char at position 1 (starting from 0)_ +
 [green]`b` +
-`>>>` [blue]`s.(-1)`   [gray]_char at position -1, the rightmost one_ +
+`>>>` [blue]`s.(-1)`   [gray]_// char at position -1, the rightmost one_ +
 [green]`c` +
-`>>>` [blue]`\#s`       [gray]_number of chars_ +
+`>>>` [blue]`\#s`       [gray]_// number of chars_ +
 [gren]`3` +
-`>>>` [blue]`#"abc"`   [gray]_number of chars_ +
+`>>>` [blue]`#"abc"`   [gray]_// number of chars_ +
 [green]`3`
 
 
 === Booleans
 Boolean data type has two values only: [blue]_true_ and [blue]_false_. Relational and boolean expressions result in boolean values.
 
-.Relational operators
+.Relational operators^(*)^
 [cols="^1,^2,6,4"]
 |===
 | Symbol    | Operation     | Description               | Examples
@@ -314,6 +314,8 @@ Boolean data type has two values only: [blue]_true_ and [blue]_false_. Relationa
 [blue]`"b" \<= "b"` -> _true_
 |===
 
+^(*)^ See also the  [blue]`in` operator in the _list_ and _dictionary_ sections.
+
 
 .Boolean operators
 [cols="^2,^2,5,4"]
@@ -371,13 +373,18 @@ _non-empty-list_ = "**[**" _any-value_ {"**,**" _any-value} "**]**" +
 
 | [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]`>>` | _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_
 |===
 
 The items of array can be accessed using the dot `.` operator.
 
 .Item access syntax
 ====
-_item_ = _list-expr_ "**.**" _list-expr_
+_item_ = _list-expr_ "**.**" _integer-expr_
 ====
 
 .Items of list
@@ -394,14 +401,16 @@ _item_ = _list-expr_ "**.**" _list-expr_
 `>>>` [blue]`list.(10)` +
 [red]`Eval Error: [1:9] index 10 out of bounds` +
 `>>>` [blue]`#list` +
-[green]`3`
+[green]`3` +
+`>>>` [blue]`index=2; ["a", "b", "c", "d"].index` +
+[green]`c`
 
 
 
 === Dictionaries
-WARNING: Support for dictionaries is still ongoing.
+The _dictionary_, or _dict_, data-type is set of pairs _key/value_. It is also known as _map_ or _associative array_.
 
-The _dictionary_, or _dict_, data-type is set of pairs _key/value_. It is also known as _map_ or _associative array_. Dictionary literals are sequences of pairs separated by comma `,`; sequences are enclosed between brace brackets.
+Dictionary literals are sequences of pairs separated by comma [blue]`,` enclosed between brace brackets.
 
 .Dict literal syntax
 ====
@@ -412,11 +421,27 @@ _non-empty-dict_ = "**{**" _key-scalar_ "**:**" _any-value_ {"**,**" _key-scalar
 
 .Examples
 `>>>` [blue]`{1:"one", 2:"two"}` +
+[green]`{1: "one", 2: "two"}` +
 `>>>` [blue]`{"one":1, "two": 2}` +
-`>>>` [blue]`{"sum":1+2+3, "prod":1*2*3}`
+[green]`{"one": 1, "two": 2}` +
+`>>>` [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_ supports variables like most programming languages. A variable is an identifier with an assigned value. Variables are stored in _contexts_.
+_Expr_, like most programming languages, supports variables. A variable is an identifier with an assigned value. Variables are stored in _contexts_.
 
 .Variable literal syntax
 ====
@@ -467,12 +492,19 @@ The value of each sub-expression is stored in the automatica variable _last_.
 
 
 === [blue]`but` operator
-[blue]`but` is an infixed operator. Its operands can be expressions of any type. It evaluates the left expression first, then the right expression. The value of the right expression is the final result. Examples: [blue]`5 but 2` 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 variables 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
@@ -540,11 +572,12 @@ NOTE: These operators have a high priority, in particular higher than the operat
 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+|*ITEM*| [blue]`.` | _Infix_ | _Item_| _collection_ `"."` _key_ -> _any_
+.2+|*ITEM*| [blue]`.` | _Infix_ | _List item_| _list_ `"."` _integer_ -> _any_
+| [blue]`.` | _Infix_ | _Dict item_ | _dict_ `"."` _any_ -> _any_
 .2+|*INC*| [blue]`++` | _Postfix_ | _Post increment_| _integer-variable_ `"++"` -> _integer_
 | [blue]`++` | _Postfix_ | _Next item_ | _iterator_ `"++"` -> _any_
 .1+|*FACT*| [blue]`!` | _Postfix_ | _Factorial_| _integer_ `"!"` -> _integer_
@@ -556,24 +589,29 @@ The table below shows all supported operators by decreasing priorities.
 | [blue]`/` | _Infix_ | _Division_ | _number_ `"/"` _number_ -> _number_
 | [blue]`./` | _Infix_ | _Float-division_ | __number__ `"./"` _number_ -> _float_
 | [blue]`%` | _Infix_ | _Integer-remainder_ | _integer_ `"%"` _integer_ -> _integer_
-.5+|*SUM*| [blue]`+` | _Infix_ | _Sum_ | _number_ `"+"` _number_ -> _number_
+.6+|*SUM*| [blue]`+` | _Infix_ | _Sum_ | _number_ `"+"` _number_ -> _number_
 | [blue]`+` | _Infix_ |  _String-concat_ | (_string_\|_number_) `"+"` (_string_\|_number_) -> _string_
 | [blue]`+` | _Infix_ |  _List-join_ | _list_ `"+"` _list_ -> _list_
+| [blue]`+` | _Infix_ |  _Dict-join_ | _dict_ `"+"` _dict_ -> _dict_
 | [blue]`-` | _Infix_ | _Subtraction_ | _number_ `"-"` _number_ -> _number_
 | [blue]`-` | _Infix_ | _List-difference_ | _list_ `"-"` _list_ -> _list_
-.6+|*RELATION*| [blue]`<` | _Infix_ | _less_ | _comparable_ `"<"` _comparable_ -> _boolean_
+.8+|*RELATION*| [blue]`<` | _Infix_ | _less_ | _comparable_ `"<"` _comparable_ -> _boolean_
 | [blue]`\<=` | _Infix_ |  _less-equal_ | _comparable_ `"\<="` _comparable_ -> _boolean_
 | [blue]`>` | _Infix_ |  _greater_ | _comparable_ `">"` _comparable_ -> _boolean_
 | [blue]`>=` | _Infix_ |  _greater-equal_ | _comparable_ `">="` _comparable_ -> _boolean_
 | [blue]`==` | _Infix_ |  _equal_ | _comparable_ `"=="` _comparable_ -> _boolean_
 | [blue]`!=` | _Infix_ |  _not-equal_ | _comparable_ `"!="` _comparable_ -> _boolean_
+| [blue]`in` | _Infix_ |  _member-of-list_ | _any_ `"in"` _list_ -> _boolean_
+| [blue]`in` | _Infix_ |  _key-of-dict_ | _any_ `"in"` _dict_ -> _boolean_
 .1+|*NOT*| [blue]`not` | _Prefix_ | _not_ | `"not"` _boolean_ -> _boolean_
 .2+|*AND*| [blue]`and` | _Infix_ | _and_ | _boolean_ `"and"` _boolean_ -> _boolean_
 | [blue]`&&` | _Infix_ | _and_ | _boolean_ `"&&"` _boolean_ -> _boolean_
 .2+|*OR*| [blue]`or` | _Infix_ | _or_ | _boolean_ `"or"` _boolean_ -> _boolean_
 | [blue]`\|\|` | _Infix_ | _or_ | _boolean_ `"\|\|"` _boolean_ -> _boolean_
-.1+|*ASSIGN*| [blue]`=` | _Infix_ | _assignment_ | _identifier_ "=" _any_ -> _any_
-.1+|*BUT*| [blue]`but` | _Infix_ | _but_ | _any_ "but" _any_ -> _any_
+.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

doc/Expr.html

@@ -585,7 +585,7 @@ pre.rouge .ss {
 <div class="sectionbody">
 <!-- toc disabled -->
 <div class="paragraph">
-<p><mark>TODO: Work in progress (last update on 2024/05/17, 15:47 p.m.)</mark></p>
+<p><mark>TODO: Work in progress (last update on 2024/05/20, 06:58 a.m.)</mark></p>
 </div>
 </div>
 </div>
@@ -999,14 +999,14 @@ pre.rouge .ss {
 <td class="tableblock halign-center valign-top"><p class="tableblock"><code class="blue">+</code></p></td>
 <td class="tableblock halign-center valign-top"><p class="tableblock"><em>concatenation</em></p></td>
 <td class="tableblock halign-left valign-top"><p class="tableblock">Join two strings or two <em>stringable</em> values</p></td>
-<td class="tableblock halign-left valign-top"><p class="tableblock"><code class="blue">"one" + "two"</code> <em>["onetwo"]</em><br>
-<code class="blue">"one" + 2</code> <em>["one2"]</em></p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock"><code class="blue">"one" + "two"</code> &#8594; <em>"onetwo"</em><br>
+<code class="blue">"one" + 2</code> &#8594; <em>"one2"</em></p></td>
 </tr>
 <tr>
 <td class="tableblock halign-center valign-top"><p class="tableblock"><code class="blue">*</code></p></td>
 <td class="tableblock halign-center valign-top"><p class="tableblock"><em>repeat</em></p></td>
 <td class="tableblock halign-left valign-top"><p class="tableblock">Make <em>n</em> copy of a string</p></td>
-<td class="tableblock halign-left valign-top"><p class="tableblock"><code class="blue">"one" * 2</code> <em>["oneone"]</em></p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock"><code class="blue">"one" * 2</code> &#8594; <em>"oneone"</em></p></td>
 </tr>
 </tbody>
 </table>
@@ -1023,15 +1023,15 @@ pre.rouge .ss {
 </div>
 <div class="paragraph">
 <div class="title">String examples</div>
-<p><code>&gt;&gt;&gt;</code> <code class="blue">s="abc"</code>  <em class="gray">assign the string to variable s</em><br>
+<p><code>&gt;&gt;&gt;</code> <code class="blue">s="abc"</code>  <em class="gray">// assign the string to variable s</em><br>
 <code class="green">abc</code><br>
-<code>&gt;&gt;&gt;</code> <code class="blue">s.1</code>      <em class="gray">char at position 1 (starting from 0)</em><br>
+<code>&gt;&gt;&gt;</code> <code class="blue">s.1</code>      <em class="gray">// char at position 1 (starting from 0)</em><br>
 <code class="green">b</code><br>
-<code>&gt;&gt;&gt;</code> <code class="blue">s.(-1)</code>   <em class="gray">char at position -1, the rightmost one</em><br>
+<code>&gt;&gt;&gt;</code> <code class="blue">s.(-1)</code>   <em class="gray">// char at position -1, the rightmost one</em><br>
 <code class="green">c</code><br>
-<code>&gt;&gt;&gt;</code> <code class="blue">#s</code>       <em class="gray">number of chars</em><br>
+<code>&gt;&gt;&gt;</code> <code class="blue">#s</code>       <em class="gray">// number of chars</em><br>
 <code class="gren">3</code><br>
-<code>&gt;&gt;&gt;</code> <code class="blue">#"abc"</code>   <em class="gray">number of chars</em><br>
+<code>&gt;&gt;&gt;</code> <code class="blue">#"abc"</code>   <em class="gray">// number of chars</em><br>
 <code class="green">3</code></p>
 </div>
 </div>
@@ -1041,7 +1041,7 @@ pre.rouge .ss {
 <p>Boolean data type has two values only: <em class="blue">true</em> and <em class="blue">false</em>. Relational and boolean expressions result in boolean values.</p>
 </div>
 <table class="tableblock frame-all grid-all stretch">
-<caption class="title">Table 4. Relational operators</caption>
+<caption class="title">Table 4. Relational operators<sup>(*)</sup></caption>
 <colgroup>
 <col style="width: 7.6923%;">
 <col style="width: 15.3846%;">
@@ -1101,6 +1101,9 @@ pre.rouge .ss {
 </tr>
 </tbody>
 </table>
+<div class="paragraph">
+<p><sup>(*)</sup> See also the  <code class="blue">in</code> operator in the <em>list</em> and <em>dictionary</em> sections.</p>
+</div>
 <table class="tableblock frame-all grid-all stretch">
 <caption class="title">Table 5. Boolean operators</caption>
 <colgroup>
@@ -1227,6 +1230,31 @@ pre.rouge .ss {
 <td class="tableblock halign-left valign-top"><p class="tableblock">Left list without elements in the right list</p></td>
 <td class="tableblock halign-left valign-top"><p class="tableblock"><code class="blue">[1,2,3] - [2]</code> &#8594; <em>[1,3]</em></p></td>
 </tr>
+<tr>
+<td class="tableblock halign-center valign-top"><p class="tableblock"><code class="blue">&gt;&gt;</code></p></td>
+<td class="tableblock halign-center valign-top"><p class="tableblock"><em>Front insertion</em></p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Insert an item in front</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock"><code class="blue">0 &gt;&gt; [1,2]</code> &#8594; <em>[0,1,2]</em></p></td>
+</tr>
+<tr>
+<td class="tableblock halign-center valign-top"><p class="tableblock"><code class="blue">&lt;&lt;</code></p></td>
+<td class="tableblock halign-center valign-top"><p class="tableblock"><em>Back insertion</em></p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Insert an item at end</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock"><code class="blue">[1,2] &lt;&lt; 3</code> &#8594; <em>[1,2,3]</em></p></td>
+</tr>
+<tr>
+<td class="tableblock halign-center valign-top"><p class="tableblock"><code class="blue">.</code></p></td>
+<td class="tableblock halign-center valign-top"><p class="tableblock"><em>List item</em></p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Item at given position</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock"><code class="blue">[1,2.3].1</code> &#8594; <em>2</em></p></td>
+</tr>
+<tr>
+<td class="tableblock halign-center valign-top"><p class="tableblock"><code class="blue">in</code></p></td>
+<td class="tableblock halign-center valign-top"><p class="tableblock"><em>Item in list</em></p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">True if item is in list</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock"><code class="blue">2 in [1,2,3]</code> &#8594; <em>true</em><br>
+<code class="blue">6 in [1,2,3]</code> &#8594; <em>false</em></p></td>
+</tr>
 </tbody>
 </table>
 <div class="paragraph">
@@ -1236,7 +1264,7 @@ pre.rouge .ss {
 <div class="title">Example 6. Item access syntax</div>
 <div class="content">
 <div class="paragraph">
-<p><em>item</em> = <em>list-expr</em> "<strong>.</strong>" <em>list-expr</em></p>
+<p><em>item</em> = <em>list-expr</em> "<strong>.</strong>" <em>integer-expr</em></p>
 </div>
 </div>
 </div>
@@ -1255,25 +1283,18 @@ pre.rouge .ss {
 <code>&gt;&gt;&gt;</code> <code class="blue">list.(10)</code><br>
 <code class="red">Eval Error: [1:9] index 10 out of bounds</code><br>
 <code>&gt;&gt;&gt;</code> <code class="blue">#list</code><br>
-<code class="green">3</code></p>
+<code class="green">3</code><br>
+<code>&gt;&gt;&gt;</code> <code class="blue">index=2; ["a", "b", "c", "d"].index</code><br>
+<code class="green">c</code></p>
 </div>
 </div>
 <div class="sect2">
 <h3 id="_dictionaries"><a class="anchor" href="#_dictionaries"></a><a class="link" href="#_dictionaries">2.5. Dictionaries</a></h3>
-<div class="admonitionblock warning">
-<table>
-<tr>
-<td class="icon">
-<i class="fa icon-warning" title="Warning"></i>
-</td>
-<td class="content">
-Support for dictionaries is still ongoing.
-</td>
-</tr>
-</table>
+<div class="paragraph">
+<p>The <em>dictionary</em>, or <em>dict</em>, data-type is set of pairs <em>key/value</em>. It is also known as <em>map</em> or <em>associative array</em>.</p>
 </div>
 <div class="paragraph">
-<p>The <em>dictionary</em>, or <em>dict</em>, data-type is set of pairs <em>key/value</em>. It is also known as <em>map</em> or <em>associative array</em>. Dictionary literals are sequences of pairs separated by comma <code>,</code>; sequences are enclosed between brace brackets.</p>
+<p>Dictionary literals are sequences of pairs separated by comma <code class="blue">,</code> enclosed between brace brackets.</p>
 </div>
 <div class="exampleblock">
 <div class="title">Example 7. Dict literal syntax</div>
@@ -1288,9 +1309,50 @@ Support for dictionaries is still ongoing.
 <div class="paragraph">
 <div class="title">Examples</div>
 <p><code>&gt;&gt;&gt;</code> <code class="blue">{1:"one", 2:"two"}</code><br>
+<code class="green">{1: "one", 2: "two"}</code><br>
 <code>&gt;&gt;&gt;</code> <code class="blue">{"one":1, "two": 2}</code><br>
-<code>&gt;&gt;&gt;</code> <code class="blue">{"sum":1+2+3, "prod":1*2*3}</code></p>
+<code class="green">{"one": 1, "two": 2}</code><br>
+<code>&gt;&gt;&gt;</code> <code class="blue">{"sum":1+2+3, "prod":1*2*3}</code><br>
+<code class="green">{"sum": 6, "prod": 6}</code></p>
 </div>
+<table class="tableblock frame-all grid-all stretch">
+<caption class="title">Table 7. Dict operators</caption>
+<colgroup>
+<col style="width: 15.3846%;">
+<col style="width: 15.3846%;">
+<col style="width: 30.7692%;">
+<col style="width: 38.4616%;">
+</colgroup>
+<thead>
+<tr>
+<th class="tableblock halign-center valign-top">Symbol</th>
+<th class="tableblock halign-center valign-top">Operation</th>
+<th class="tableblock halign-left valign-top">Description</th>
+<th class="tableblock halign-left valign-top">Examples</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td class="tableblock halign-center valign-top"><p class="tableblock"><code class="blue">+</code></p></td>
+<td class="tableblock halign-center valign-top"><p class="tableblock"><em>Join</em></p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Joins two dicts</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock"><code class="blue">{1:"one"}+{6:"six"}</code> &#8594; <em>{1: "one", 6: "six"}</em></p></td>
+</tr>
+<tr>
+<td class="tableblock halign-center valign-top"><p class="tableblock"><code class="blue">.</code></p></td>
+<td class="tableblock halign-center valign-top"><p class="tableblock"><em>Dict item value</em></p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">Item value of given key</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock"><code class="blue">{"one":1, "two":2}."two"</code> &#8594; <em>2</em></p></td>
+</tr>
+<tr>
+<td class="tableblock halign-center valign-top"><p class="tableblock"><code class="blue">in</code></p></td>
+<td class="tableblock halign-center valign-top"><p class="tableblock"><em>Key in dict</em></p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">True if key is in dict</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock"><code class="blue">"one" in {"one":1, "two":2}</code> &#8594; <em>true</em><br>
+<code class="blue">"six" in {"one":1, "two":2}</code> &#8594; <em>false</em></p></td>
+</tr>
+</tbody>
+</table>
 </div>
 </div>
 </div>
@@ -1298,7 +1360,7 @@ Support for dictionaries is still ongoing.
 <h2 id="_variables"><a class="anchor" href="#_variables"></a><a class="link" href="#_variables">3. Variables</a></h2>
 <div class="sectionbody">
 <div class="paragraph">
-<p><em>Expr</em> supports variables like most programming languages. A variable is an identifier with an assigned value. Variables are stored in <em>contexts</em>.</p>
+<p><em>Expr</em>, like most programming languages, supports variables. A variable is an identifier with an assigned value. Variables are stored in <em>contexts</em>.</p>
 </div>
 <div class="exampleblock">
 <div class="title">Example 8. Variable literal syntax</div>
@@ -1393,17 +1455,26 @@ Technically <code class="blue">;</code> is not treated as a real operator. It ac
 <div class="sect2">
 <h3 id="_but_operator"><a class="anchor" href="#_but_operator"></a><a class="link" href="#_but_operator">4.2. <code class="blue">but</code> operator</a></h3>
 <div class="paragraph">
-<p><code class="blue">but</code> is an infixed operator. Its operands can be expressions of any type. It evaluates the left expression first, then the right expression. The value of the right expression is the final result. Examples: <code class="blue">5 but 2</code> returns 2, <code class="blue">x=2*3 but x-1</code> returns 5.</p>
+<p><code class="blue">but</code> 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.</p>
 </div>
 <div class="paragraph">
-<p><code class="blue">but</code> is very similar to <code class="blue">;</code>. The only difference is that <code class="blue">;</code> can&#8217;t be used inside parenthesis <code class="blue">(</code> and <code class="blue">)</code>.</p>
+<div class="title">Examples</div>
+<p><code class="blue">5 but 2</code><br>
+<code class="green">2</code><br>
+<code class="blue">x=2*3 but x-1</code><br>
+<code class="green">5</code>.</p>
+</div>
+<div class="paragraph">
+<p><code class="blue">but</code> behavior is very similar to <code class="blue">;</code>. The only difference is that <code class="blue">;</code> is not a true operator and can&#8217;t be used inside parenthesis <code class="blue">(</code> and <code class="blue">)</code>.</p>
 </div>
 </div>
 <div class="sect2">
 <h3 id="_assignment_operator"><a class="anchor" href="#_assignment_operator"></a><a class="link" href="#_assignment_operator">4.3. Assignment operator <code class="blue">=</code></a></h3>
 <div class="paragraph">
-<p>The assignment operator <code class="blue">=</code> is used to define variables in the evaluation context or to change their value (see <em>ExprContext</em>).
-The value on the left side of <code class="blue">=</code> must be an identifier. The value on the right side can be any expression and it becomes the result of the assignment operation.</p>
+<p>The assignment operator <code class="blue">=</code> is used to define variables or to change their value in the evaluation context (see <em>ExprContext</em>).</p>
+</div>
+<div class="paragraph">
+<p>The value on the left side of <code class="blue">=</code> must be an identifier. The value on the right side can be any expression and it becomes the result of the assignment operation.</p>
 </div>
 <div class="paragraph">
 <div class="title">Example</div>
@@ -1509,13 +1580,13 @@ These operators have a high priority, in particular higher than the operator <co
 <p>The table below shows all supported operators by decreasing priorities.</p>
 </div>
 <table class="tableblock frame-all grid-all stretch">
-<caption class="title">Table 7. Operators priorities</caption>
+<caption class="title">Table 8. Operators priorities</caption>
 <colgroup>
-<col style="width: 12.5%;">
-<col style="width: 12.5%;">
-<col style="width: 12.5%;">
-<col style="width: 31.25%;">
-<col style="width: 31.25%;">
+<col style="width: 11.7647%;">
+<col style="width: 11.7647%;">
+<col style="width: 11.7647%;">
+<col style="width: 29.4117%;">
+<col style="width: 35.2942%;">
 </colgroup>
 <thead>
 <tr>
@@ -1528,11 +1599,17 @@ These operators have a high priority, in particular higher than the operator <co
 </thead>
 <tbody>
 <tr>
-<td class="tableblock halign-center valign-top"><p class="tableblock"><strong>ITEM</strong></p></td>
+<td class="tableblock halign-center valign-top" rowspan="2"><p class="tableblock"><strong>ITEM</strong></p></td>
 <td class="tableblock halign-center valign-top"><p class="tableblock"><code class="blue">.</code></p></td>
 <td class="tableblock halign-center valign-top"><p class="tableblock"><em>Infix</em></p></td>
-<td class="tableblock halign-center valign-top"><p class="tableblock"><em>Item</em></p></td>
-<td class="tableblock halign-center valign-top"><p class="tableblock"><em>collection</em> <code>"."</code> <em>key</em> &#8594; <em>any</em></p></td>
+<td class="tableblock halign-center valign-top"><p class="tableblock"><em>List item</em></p></td>
+<td class="tableblock halign-center valign-top"><p class="tableblock"><em>list</em> <code>"."</code> <em>integer</em> &#8594; <em>any</em></p></td>
+</tr>
+<tr>
+<td class="tableblock halign-center valign-top"><p class="tableblock"><code class="blue">.</code></p></td>
+<td class="tableblock halign-center valign-top"><p class="tableblock"><em>Infix</em></p></td>
+<td class="tableblock halign-center valign-top"><p class="tableblock"><em>Dict item</em></p></td>
+<td class="tableblock halign-center valign-top"><p class="tableblock"><em>dict</em> <code>""</code> <em>any</em> &#8594; <em>any</em></p></td>
 </tr>
 <tr>
 <td class="tableblock halign-center valign-top" rowspan="2"><p class="tableblock"><strong>INC</strong></p></td>
@@ -1605,7 +1682,7 @@ These operators have a high priority, in particular higher than the operator <co
 <td class="tableblock halign-center valign-top"><p class="tableblock"><em>integer</em> <code>"%"</code> <em>integer</em> &#8594; <em>integer</em></p></td>
 </tr>
 <tr>
-<td class="tableblock halign-center valign-top" rowspan="5"><p class="tableblock"><strong>SUM</strong></p></td>
+<td class="tableblock halign-center valign-top" rowspan="6"><p class="tableblock"><strong>SUM</strong></p></td>
 <td class="tableblock halign-center valign-top"><p class="tableblock"><code class="blue">+</code></p></td>
 <td class="tableblock halign-center valign-top"><p class="tableblock"><em>Infix</em></p></td>
 <td class="tableblock halign-center valign-top"><p class="tableblock"><em>Sum</em></p></td>
@@ -1624,6 +1701,12 @@ These operators have a high priority, in particular higher than the operator <co
 <td class="tableblock halign-center valign-top"><p class="tableblock"><em>list</em> <code>"+"</code> <em>list</em> &#8594; <em>list</em></p></td>
 </tr>
 <tr>
+<td class="tableblock halign-center valign-top"><p class="tableblock"><code class="blue">+</code></p></td>
+<td class="tableblock halign-center valign-top"><p class="tableblock"><em>Infix</em></p></td>
+<td class="tableblock halign-center valign-top"><p class="tableblock"><em>Dict-join</em></p></td>
+<td class="tableblock halign-center valign-top"><p class="tableblock"><em>dict</em> <code>"+"</code> <em>dict</em> &#8594; <em>dict</em></p></td>
+</tr>
+<tr>
 <td class="tableblock halign-center valign-top"><p class="tableblock"><code class="blue">-</code></p></td>
 <td class="tableblock halign-center valign-top"><p class="tableblock"><em>Infix</em></p></td>
 <td class="tableblock halign-center valign-top"><p class="tableblock"><em>Subtraction</em></p></td>
@@ -1636,7 +1719,7 @@ These operators have a high priority, in particular higher than the operator <co
 <td class="tableblock halign-center valign-top"><p class="tableblock"><em>list</em> <code>"-"</code> <em>list</em> &#8594; <em>list</em></p></td>
 </tr>
 <tr>
-<td class="tableblock halign-center valign-top" rowspan="6"><p class="tableblock"><strong>RELATION</strong></p></td>
+<td class="tableblock halign-center valign-top" rowspan="8"><p class="tableblock"><strong>RELATION</strong></p></td>
 <td class="tableblock halign-center valign-top"><p class="tableblock"><code class="blue">&lt;</code></p></td>
 <td class="tableblock halign-center valign-top"><p class="tableblock"><em>Infix</em></p></td>
 <td class="tableblock halign-center valign-top"><p class="tableblock"><em>less</em></p></td>
@@ -1673,6 +1756,18 @@ These operators have a high priority, in particular higher than the operator <co
 <td class="tableblock halign-center valign-top"><p class="tableblock"><em>comparable</em> <code>"!="</code> <em>comparable</em> &#8594; <em>boolean</em></p></td>
 </tr>
 <tr>
+<td class="tableblock halign-center valign-top"><p class="tableblock"><code class="blue">in</code></p></td>
+<td class="tableblock halign-center valign-top"><p class="tableblock"><em>Infix</em></p></td>
+<td class="tableblock halign-center valign-top"><p class="tableblock"><em>member-of-list</em></p></td>
+<td class="tableblock halign-center valign-top"><p class="tableblock"><em>any</em> <code>"in"</code> <em>list</em> &#8594; <em>boolean</em></p></td>
+</tr>
+<tr>
+<td class="tableblock halign-center valign-top"><p class="tableblock"><code class="blue">in</code></p></td>
+<td class="tableblock halign-center valign-top"><p class="tableblock"><em>Infix</em></p></td>
+<td class="tableblock halign-center valign-top"><p class="tableblock"><em>key-of-dict</em></p></td>
+<td class="tableblock halign-center valign-top"><p class="tableblock"><em>any</em> <code>"in"</code> <em>dict</em> &#8594; <em>boolean</em></p></td>
+</tr>
+<tr>
 <td class="tableblock halign-center valign-top"><p class="tableblock"><strong>NOT</strong></p></td>
 <td class="tableblock halign-center valign-top"><p class="tableblock"><code class="blue">not</code></p></td>
 <td class="tableblock halign-center valign-top"><p class="tableblock"><em>Prefix</em></p></td>
@@ -1706,13 +1801,25 @@ These operators have a high priority, in particular higher than the operator <co
 <td class="tableblock halign-center valign-top"><p class="tableblock"><em>boolean</em> <code>"||"</code> <em>boolean</em> &#8594; <em>boolean</em></p></td>
 </tr>
 <tr>
-<td class="tableblock halign-center valign-top"><p class="tableblock"><strong>ASSIGN</strong></p></td>
+<td class="tableblock halign-center valign-top" rowspan="3"><p class="tableblock"><strong>ASSIGN</strong></p></td>
 <td class="tableblock halign-center valign-top"><p class="tableblock"><code class="blue">=</code></p></td>
 <td class="tableblock halign-center valign-top"><p class="tableblock"><em>Infix</em></p></td>
 <td class="tableblock halign-center valign-top"><p class="tableblock"><em>assignment</em></p></td>
 <td class="tableblock halign-center valign-top"><p class="tableblock"><em>identifier</em> "=" <em>any</em> &#8594; <em>any</em></p></td>
 </tr>
 <tr>
+<td class="tableblock halign-center valign-top"><p class="tableblock"><code class="blue">&gt;&gt;</code></p></td>
+<td class="tableblock halign-center valign-top"><p class="tableblock"><em>Infix</em></p></td>
+<td class="tableblock halign-center valign-top"><p class="tableblock"><em>front-insert</em></p></td>
+<td class="tableblock halign-center valign-top"><p class="tableblock"><em>any</em> "&gt;&gt;" <em>list</em> &#8594; <em>list</em></p></td>
+</tr>
+<tr>
+<td class="tableblock halign-center valign-top"><p class="tableblock"><code class="blue">&lt;&lt;</code></p></td>
+<td class="tableblock halign-center valign-top"><p class="tableblock"><em>Infix</em></p></td>
+<td class="tableblock halign-center valign-top"><p class="tableblock"><em>back-insert</em></p></td>
+<td class="tableblock halign-center valign-top"><p class="tableblock"><em>list</em> "&lt;&lt;" <em>any</em> &#8594; <em>list</em></p></td>
+</tr>
+<tr>
 <td class="tableblock halign-center valign-top"><p class="tableblock"><strong>BUT</strong></p></td>
 <td class="tableblock halign-center valign-top"><p class="tableblock"><code class="blue">but</code></p></td>
 <td class="tableblock halign-center valign-top"><p class="tableblock"><em>Infix</em></p></td>
@@ -1767,7 +1874,7 @@ These operators have a high priority, in particular higher than the operator <co
 </div>
 <div id="footer">
 <div id="footer-text">
-Last updated 2024-05-17 15:47:29 +0200
+Last updated 2024-05-20 09:40:23 +0200
 </div>
 </div>
 </body>

formatter.go

@@ -4,17 +4,62 @@
 // 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
+}

fraction-type.go

@@ -0,0 +1,401 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// fraction-type.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 FractionType struct {
+	num, den int64
+}
+
+func newFraction(num, den int64) *FractionType {
+	num, den = simplifyIntegers(num, den)
+	return &FractionType{num, den}
+}
+
+func float64ToFraction(f float64) (fract *FractionType, 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 *FractionType, 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 *FractionType) toFloat() float64 {
+	return float64(f.num) / float64(f.den)
+}
+
+func (f *FractionType) String() string {
+	return f.ToString(0)
+}
+
+func (f *FractionType) ToString(opt FmtOpt) string {
+	var sb strings.Builder
+	if opt&MultiLine == 0 {
+		sb.WriteString(fmt.Sprintf("%d|%d", f.num, f.den))
+	} 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 *FractionType) TypeName() string {
+	return "fraction"
+}
+
+// -------- fraction utility functions
+
+// greatest common divider
+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
+}
+
+// lower common multiple
+func lcm(a, b int64) (l int64) {
+	g := gcd(a, b)
+	l = a * b / g
+	return
+}
+
+// Sum two fractions
+func sumFract(f1, f2 *FractionType) (sum *FractionType) {
+	m := lcm(f1.den, f2.den)
+	sum = newFraction(f1.num*(m/f1.den)+f2.num*(m/f2.den), m)
+	return
+}
+
+// Multiply two fractions
+func mulFract(f1, f2 *FractionType) (prod *FractionType) {
+	prod = newFraction(f1.num*f2.num, f1.den*f2.den)
+	return
+}
+
+func anyToFract(v any) (f *FractionType, err error) {
+	var ok bool
+	if f, ok = v.(*FractionType); !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 *FractionType, 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 *FractionType
+	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
+}
+
+// Returns
+//
+//		 <0 if af1 < af2
+//		 =0 if af1 == af2
+//		 >0 if af1 > af2
+//	 err if af1 or af2 is not convertible to fraction
+func cmpAnyFract(af1, af2 any) (result int, err error) {
+	var f1, f2 *FractionType
+	if f1, f2, err = anyPairToFract(af1, af2); err != nil {
+		return
+	}
+	result = cmpFract(f1, f2)
+	return
+}
+
+// Returns
+//
+//	<0 if af1 < af2
+//	=0 if af1 == af2
+//	>0 if af1 > af2
+func cmpFract(f1, f2 *FractionType) (result int) {
+	f2.num = -f2.num
+	f := sumFract(f1, f2)
+	if f.num < 0 {
+		result = -1
+	} else if f.num > 0 {
+		result = 1
+	} else {
+		result = 0
+	}
+	return
+}
+
+func subAnyFract(af1, af2 any) (sum any, err error) {
+	var f1, f2 *FractionType
+	if f1, f2, err = anyPairToFract(af1, af2); err != nil {
+		return
+	}
+	f2.num = -f2.num
+	f := sumFract(f1, f2)
+	if f.num == 0 {
+		sum = 0
+	} else {
+		sum = simplifyFraction(f)
+	}
+	return
+}
+
+func mulAnyFract(af1, af2 any) (prod any, err error) {
+	var f1, f2 *FractionType
+	if f1, f2, err = anyPairToFract(af1, af2); err != nil {
+		return
+	}
+	if f1.num == 0 || f2.num == 0 {
+		prod = 0
+	} else {
+		f := &FractionType{f1.num * f2.num, f1.den * f2.den}
+		prod = simplifyFraction(f)
+	}
+	return
+}
+
+func divAnyFract(af1, af2 any) (quot any, err error) {
+	var f1, f2 *FractionType
+	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 := &FractionType{f1.num * f2.den, f1.den * f2.num}
+		quot = simplifyFraction(f)
+	}
+	return
+}
+
+func simplifyFraction(f *FractionType) (v any) {
+	f.num, f.den = simplifyIntegers(f.num, f.den)
+	if f.den == 1 {
+		v = f.num
+	} else {
+		v = &FractionType{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) *FractionType {
+	return &FractionType{n, 1}
+}
+
+func isFraction(v any) (ok bool) {
+	_, ok = v.(*FractionType)
+	return ok
+}

func-base.go

@@ -54,6 +54,24 @@ func isDictionaryFunc(ctx ExprContext, name string, args []any) (result any, err
 	return
 }
 
+func boolFunc(ctx ExprContext, name string, args []any) (result any, err error) {
+	switch v := args[0].(type) {
+	case int64:
+		result = (v != 0)
+	case *FractionType:
+		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:
@@ -94,7 +112,7 @@ func decFunc(ctx ExprContext, name string, args []any) (result any, err error) {
 		if f, err = strconv.ParseFloat(v, 64); err == nil {
 			result = f
 		}
-	case *fraction:
+	case *FractionType:
 		result = v.toFloat()
 	default:
 		err = errCantConvert(name, v, "float")
@@ -119,10 +137,6 @@ func fractFunc(ctx ExprContext, name string, args []any) (result any, err error)
 		}
 	case float64:
 		result, err = float64ToFraction(v)
-		// var n, d int64
-		// if n, d, err = float64ToFraction(v); err == nil {
-		//	result = newFraction(n, d)
-		// }
 	case bool:
 		if v {
 			result = newFraction(1, 1)
@@ -131,17 +145,7 @@ func fractFunc(ctx ExprContext, name string, args []any) (result any, err error)
 		}
 	case string:
 		result, err = makeGeneratingFraction(v)
-		// var f float64
-		// // TODO temporary implementation
-		// if f, err = strconv.ParseFloat(v, 64); err == nil {
-		// 	var n, d int64
-		// 	if n, d, err = float64ToFraction(f); err == nil {
-		// 		result = newFraction(n, d)
-		// 	}
-		// } else {
-		// 	errors.New("convertion from string to float is ongoing")
-		// }
-	case *fraction:
+	case *FractionType:
 		result = v
 	default:
 		err = errCantConvert(name, v, "float")
@@ -154,20 +158,27 @@ func iteratorFunc(ctx ExprContext, name string, args []any) (result any, err err
 }
 
 func ImportBuiltinsFuncs(ctx ExprContext) {
-	ctx.RegisterFunc("isNil", &simpleFunctor{f: isNilFunc}, 1, 1)
-	ctx.RegisterFunc("isInt", &simpleFunctor{f: isIntFunc}, 1, 1)
-	ctx.RegisterFunc("isFloat", &simpleFunctor{f: isFloatFunc}, 1, 1)
-	ctx.RegisterFunc("isBool", &simpleFunctor{f: isBoolFunc}, 1, 1)
-	ctx.RegisterFunc("isString", &simpleFunctor{f: isStringFunc}, 1, 1)
-	ctx.RegisterFunc("isFraction", &simpleFunctor{f: isFractionFunc}, 1, 1)
-	ctx.RegisterFunc("isFract", &simpleFunctor{f: isFractionFunc}, 1, 1)
-	ctx.RegisterFunc("isRational", &simpleFunctor{f: isRationalFunc}, 1, 1)
-	ctx.RegisterFunc("isList", &simpleFunctor{f: isListFunc}, 1, 1)
-	ctx.RegisterFunc("isDictionary", &simpleFunctor{f: isDictionaryFunc}, 1, 1)
-	ctx.RegisterFunc("isDict", &simpleFunctor{f: isDictionaryFunc}, 1, 1)
-	ctx.RegisterFunc("int", &simpleFunctor{f: intFunc}, 1, 1)
-	ctx.RegisterFunc("dec", &simpleFunctor{f: decFunc}, 1, 1)
-	ctx.RegisterFunc("fract", &simpleFunctor{f: fractFunc}, 1, 2)
+	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() {

func-import.go

@@ -137,8 +137,12 @@ 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("importAll", &simpleFunctor{f: importAllFunc}, 1, -1)
+	ctx.RegisterFunc("import", newGolangFunctor(importFunc), typeAny, []ExprFuncParam{
+		newFuncParamFlag(typeFilepath, pfRepeat),
+	})
+	ctx.RegisterFunc("importAll", newGolangFunctor(importAllFunc), typeAny, []ExprFuncParam{
+		newFuncParamFlag(typeFilepath, pfRepeat),
+	})
 }
 
 func init() {

func-math.go

@@ -21,7 +21,7 @@ func doAdd(ctx ExprContext, name string, it Iterator, count, level int) (result
 	var sumAsFloat, sumAsFract bool
 	var floatSum float64 = 0.0
 	var intSum int64 = 0
-	var fractSum *fraction
+	var fractSum *FractionType
 	var v any
 
 	level++
@@ -61,9 +61,9 @@ func doAdd(ctx ExprContext, name string, it Iterator, count, level int) (result
 		if sumAsFloat {
 			floatSum += numAsFloat(v)
 		} else if sumAsFract {
-			var item *fraction
+			var item *FractionType
 			var ok bool
-			if item, ok = v.(*fraction); !ok {
+			if item, ok = v.(*FractionType); !ok {
 				iv, _ := v.(int64)
 				item = newFraction(iv, 1)
 			}
@@ -95,7 +95,7 @@ func doMul(ctx ExprContext, name string, it Iterator, count, level int) (result
 	var mulAsFloat, mulAsFract bool
 	var floatProd float64 = 1.0
 	var intProd int64 = 1
-	var fractProd *fraction
+	var fractProd *FractionType
 	var v any
 
 	level++
@@ -136,9 +136,9 @@ func doMul(ctx ExprContext, name string, it Iterator, count, level int) (result
 		if mulAsFloat {
 			floatProd *= numAsFloat(v)
 		} else if mulAsFract {
-			var item *fraction
+			var item *FractionType
 			var ok bool
-			if item, ok = v.(*fraction); !ok {
+			if item, ok = v.(*FractionType); !ok {
 				iv, _ := v.(int64)
 				item = newFraction(iv, 1)
 			}
@@ -167,8 +167,13 @@ func mulFunc(ctx ExprContext, name string, args []any) (result any, err error) {
 }
 
 func ImportMathFuncs(ctx ExprContext) {
-	ctx.RegisterFunc("add", &simpleFunctor{f: addFunc}, 0, -1)
-	ctx.RegisterFunc("mul", &simpleFunctor{f: mulFunc}, 0, -1)
+	ctx.RegisterFunc("add", &golangFunctor{f: addFunc}, typeNumber, []ExprFuncParam{
+		newFuncParamFlagDef(paramValue, pfOptional|pfRepeat, 0),
+	})
+
+	ctx.RegisterFunc("mul", &golangFunctor{f: mulFunc}, typeNumber, []ExprFuncParam{
+		newFuncParamFlagDef(paramValue, pfOptional|pfRepeat, 1),
+	})
 }
 
 func init() {

func-os.go

@@ -158,12 +158,26 @@ 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("appendFile", &simpleFunctor{f: appendFileFunc}, 1, 1)
-	ctx.RegisterFunc("createFile", &simpleFunctor{f: createFileFunc}, 1, 1)
-	ctx.RegisterFunc("writeFile", &simpleFunctor{f: writeFileFunc}, 1, -1)
-	ctx.RegisterFunc("readFile", &simpleFunctor{f: readFileFunc}, 1, 2)
-	ctx.RegisterFunc("closeFile", &simpleFunctor{f: closeFileFunc}, 1, 1)
+	ctx.RegisterFunc("openFile", newGolangFunctor(openFileFunc), typeHandle, []ExprFuncParam{
+		newFuncParam(typeFilepath),
+	})
+	ctx.RegisterFunc("appendFile", newGolangFunctor(appendFileFunc), typeHandle, []ExprFuncParam{
+		newFuncParam(typeFilepath),
+	})
+	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() {

func-string.go

@@ -33,9 +33,9 @@ func doJoinStr(funcName string, sep string, it Iterator) (result any, err error)
 }
 
 func joinStrFunc(ctx ExprContext, name string, args []any) (result any, err error) {
-//	if len(args) < 1 {
-//		return nil, errMissingRequiredParameter(name, paramSeparator)
-//	}
+	//	if len(args) < 1 {
+	//		return nil, errMissingRequiredParameter(name, paramSeparator)
+	//	}
 	if sep, ok := args[0].(string); ok {
 		if len(args) == 1 {
 			result = ""
@@ -62,9 +62,6 @@ func subStrFunc(ctx ExprContext, name string, args []any) (result any, err error
 	var source string
 	var ok bool
 
-//	if len(args) < 1 {
-//		return nil, errMissingRequiredParameter(name, paramSource)
-//	}
 	if source, ok = args[0].(string); !ok {
 		return nil, errWrongParamType(name, paramSource, typeString, args[0])
 	}
@@ -93,9 +90,6 @@ func trimStrFunc(ctx ExprContext, name string, args []any) (result any, err erro
 	var source string
 	var ok bool
 
-//	if len(args) < 1 {
-//		return nil, errMissingRequiredParameter(name, paramSource)
-//	}
 	if source, ok = args[0].(string); !ok {
 		return nil, errWrongParamType(name, paramSource, typeString, args[0])
 	}
@@ -108,9 +102,7 @@ func startsWithStrFunc(ctx ExprContext, name string, args []any) (result any, er
 	var ok bool
 
 	result = false
-//	if len(args) < 1 {
-//		return result, errMissingRequiredParameter(name, paramSource)
-//	}
+
 	if source, ok = args[0].(string); !ok {
 		return result, errWrongParamType(name, paramSource, typeString, args[0])
 	}
@@ -133,9 +125,7 @@ func endsWithStrFunc(ctx ExprContext, name string, args []any) (result any, err
 	var ok bool
 
 	result = false
-//	if len(args) < 1 {
-//		return result, errMissingRequiredParameter(name, paramSource)
-//	}
+
 	if source, ok = args[0].(string); !ok {
 		return result, errWrongParamType(name, paramSource, typeString, args[0])
 	}
@@ -159,9 +149,6 @@ func splitStrFunc(ctx ExprContext, name string, args []any) (result any, err err
 	var parts []string
 	var ok bool
 
-//	if len(args) < 1 {
-//		return result, errMissingRequiredParameter(name, paramSource)
-//	}
 	if source, ok = args[0].(string); !ok {
 		return result, errWrongParamType(name, paramSource, typeString, args[0])
 	}
@@ -196,12 +183,36 @@ func splitStrFunc(ctx ExprContext, name string, args []any) (result any, err err
 
 // Import above functions in the context
 func ImportStringFuncs(ctx ExprContext) {
-	ctx.RegisterFunc("joinStr", &simpleFunctor{f: joinStrFunc}, 1, -1)
-	ctx.RegisterFunc("subStr", &simpleFunctor{f: subStrFunc}, 1, -1)
-	ctx.RegisterFunc("splitStr", &simpleFunctor{f: splitStrFunc}, 2, -1)
-	ctx.RegisterFunc("trimStr", &simpleFunctor{f: trimStrFunc}, 1, -1)
-	ctx.RegisterFunc("startsWithStr", &simpleFunctor{f: startsWithStrFunc}, 2, -1)
-	ctx.RegisterFunc("endsWithStr", &simpleFunctor{f: endsWithStrFunc}, 2, -1)
+	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.

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

@@ -6,7 +6,7 @@ package expr
 
 import "path/filepath"
 
-var globalCtx *SimpleFuncStore
+var globalCtx *SimpleStore
 
 func ImportInContext(name string) (exists bool) {
 	var mod *module
@@ -50,5 +50,6 @@ func GetFuncInfo(ctx ExprContext, name string) (item ExprFunc, exists bool, owne
 }
 
 func init() {
-	globalCtx = NewSimpleFuncStore()
+	globalCtx = NewSimpleStore()
+	ImportBuiltinsFuncs(globalCtx)
 }

helpers.go

@@ -34,12 +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}
-				ctx.RegisterFunc(arg.Name, functor, 0, -1)
+				functor := newGolangFunctor(f)
+				// 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)
 			}

list-type.go

@@ -0,0 +1,149 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// list-type.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
+}
+
+func (ls *ListType) contains(t *ListType) (answer bool) {
+	if len(*ls) >= len(*t) {
+		answer = true
+		for _, item := range *t {
+			if answer = ls.indexDeepSameCmp(item) >= 0; !answer {
+				break
+			}
+		}
+	}
+	return
+}
+
+func (list *ListType) indexDeepSameCmp(target any) (index int) {
+	var eq bool
+	var err error
+	index = -1
+	for i, item := range *list {
+		if eq, err = deepSame(item, target, sameContent); err != nil {
+			break
+		} else if eq {
+			index = i
+			break
+		}
+	}
+	return
+}
+
+func sameContent(a, b any) (same bool, err error) {
+	la, _ := a.(*ListType)
+	lb, _ := b.(*ListType)
+	if len(*la) == len(*lb) {
+		same = true
+		for _, item := range *la {
+			if pos := lb.indexDeepSameCmp(item); pos < 0 {
+				same = false
+				break
+			}
+		}
+	}
+	return
+}
+
+func deepSame(a, b any, deepCmp deepFuncTemplate) (eq bool, err error) {
+	if isNumOrFract(a) && isNumOrFract(b) {
+		if IsNumber(a) && IsNumber(b) {
+			if IsInteger(a) && IsInteger(b) {
+				li, _ := a.(int64)
+				ri, _ := b.(int64)
+				eq = li == ri
+			} else {
+				eq = numAsFloat(a) == numAsFloat(b)
+			}
+		} else {
+			var cmp int
+			if cmp, err = cmpAnyFract(a, b); err == nil {
+				eq = cmp == 0
+			}
+		}
+	} else if deepCmp != nil && IsList(a) && IsList(b) {
+		eq, err = deepCmp(a, b)
+	} else {
+		eq = reflect.DeepEqual(a, b)
+	}
+
+	return
+}

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 {
-		v, err = expr.eval(ctx, false)
+	if expr, ok := self.value().(*term); ok {
+		v, err = expr.compute(ctx)
 	} else {
 		err = fmt.Errorf("expression expected, got %T", self.value())
 	}

operand-func.go

@@ -31,7 +31,8 @@ func checkFunctionCall(ctx ExprContext, name string, params []any) (err error) {
 			err = errTooMuchParams(info.MaxArgs(), len(params))
 		}
 		if err == nil && owner != ctx {
-			ctx.RegisterFunc(name, info.Functor(), info.MinArgs(), info.MaxArgs())
+			// ctx.RegisterFunc(name, info.Functor(), info.MinArgs(), info.MaxArgs())
+			ctx.RegisterFuncInfo(info)
 		}
 	} else {
 		err = fmt.Errorf("unknown function %s()", name)
@@ -75,27 +76,30 @@ func newFuncDefTerm(tk *Token, args []*term) *term {
 
 // -------- eval func def
 // TODO
-type funcDefFunctor struct {
-	params []string
-	expr   Expr
-}
+// type funcDefFunctor struct {
+// 	params []string
+// 	expr   Expr
+// }
 
-func (functor *funcDefFunctor) 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 functor, ok := arg.(Functor); ok {
-				ctx.RegisterFunc(p, functor, 0, -1)
-			} else {
-				ctx.setVar(p, arg)
-			}
-		} else {
-			ctx.setVar(p, nil)
-		}
-	}
-	result, err = functor.expr.eval(ctx, false)
-	return
-}
+// func (funcDef *funcDefFunctor) Invoke(ctx ExprContext, name string, args []any) (result any, err error) {
+// 	for i, p := range funcDef.params {
+// 		if i < len(args) {
+// 			arg := args[i]
+// 			if functor, ok := arg.(Functor); ok {
+// 				// ctx.RegisterFunc(p, functor, 0, -1)
+// 				ctx.RegisterFunc2(p, functor, typeAny, []ExprFuncParam{
+// 					newFuncParam(paramValue),
+// 				})
+// 			} else {
+// 				ctx.UnsafeSetVar(p, arg)
+// 			}
+// 		} else {
+// 			ctx.UnsafeSetVar(p, nil)
+// 		}
+// 	}
+// 	result, err = funcDef.expr.eval(ctx, false)
+// 	return
+// }
 
 func evalFuncDef(ctx ExprContext, self *term) (v any, err error) {
 	bodySpec := self.value()
@@ -104,10 +108,11 @@ func evalFuncDef(ctx ExprContext, self *term) (v any, err error) {
 		for _, param := range self.children {
 			paramList = append(paramList, param.source())
 		}
-		v = &funcDefFunctor{
-			params: paramList,
-			expr:   expr,
-		}
+		v = newExprFunctor(expr, paramList)
+		// v = &funcDefFunctor{
+		// 	params: paramList,
+		// 	expr:   expr,
+		// }
 	} else {
 		err = errors.New("invalid function definition: the body specification must be an expression")
 	}

operand-iterator.go

@@ -66,14 +66,16 @@ func evalFirstChild(ctx ExprContext, self *term) (value any, err error) {
 }
 
 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.(map[any]any); ok {
+	if dictAny, ok := firstChildValue.(*DictType); ok {
 		requiredFields := []string{currentName, nextName}
 		fieldsMask := 0b11
 		foundFields := 0
 		ds = make(map[string]Functor)
-		for keyAny, item := range dictAny {
+		for keyAny, item := range *dictAny {
 			if key, ok := keyAny.(string); ok {
-				if functor, ok := item.(*funcDefFunctor); ok {
+				//if functor, ok := item.(*funcDefFunctor); ok {
+				if functor, ok := item.(Functor); ok {
 					ds[key] = functor
 					if index := slices.Index(requiredFields, key); index >= 0 {
 						foundFields |= 1 << index

operand-list.go

@@ -4,83 +4,14 @@
 // operand-list.go
 package expr
 
-import (
-	"fmt"
-	"reflect"
-	"strings"
-)
-
-type ListType []any
-
-func (ls *ListType) ToString(opt FmtOpt) 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(']')
-	return sb.String()
-}
-
-func (ls *ListType) String() string {
-	return ls.ToString(0)
-}
-
-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 (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)
+	return newListTerm(0, 0, args)
 }
 
-func newListTerm(args []*term) *term {
+func newListTerm(row, col int, args []*term) *term {
 	return &term{
-		tk:       *NewValueToken(0, 0, SymList, "[]", args),
+		tk:       *NewValueToken(row, col, SymList, "[]", args),
 		parent:   nil,
 		children: nil,
 		position: posLeaf,

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,
@@ -18,6 +18,8 @@ func newVarTerm(tk *Token) *term {
 		priority: priValue,
 		evalFunc: evalVar,
 	}
+	t.tk.Sym = SymVariable
+	return t
 }
 
 // -------- eval func

operator-assign.go

@@ -22,7 +22,7 @@ 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
 	}
@@ -31,20 +31,23 @@ func evalAssign(ctx ExprContext, self *term) (v any, err error) {
 
 	if v, err = rightChild.compute(ctx); err == nil {
 		if functor, ok := v.(Functor); ok {
-			var minArgs, maxArgs int = 0, -1
-
 			funcName := rightChild.source()
-			if info, exists := ctx.GetFuncInfo(funcName); exists {
-				minArgs = info.MinArgs()
-				maxArgs = info.MaxArgs()
-			} else if funcDef, ok := functor.(*funcDefFunctor); ok {
-				l := len(funcDef.params)
-				minArgs = l
-				maxArgs = l
-			}
-			ctx.RegisterFunc(leftTerm.source(), functor, minArgs, maxArgs)
+			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 {
-			ctx.setVar(leftTerm.source(), v)
+				err = self.Errorf("unknown function %s()", funcName)
+			}
+		} else {
+			ctx.UnsafeSetVar(leftTerm.source(), v)
 		}
 	}
 	return

operator-coalesce.go

@@ -9,8 +9,6 @@ package expr
 func newNullCoalesceTerm(tk *Token) (inst *term) {
 	return &term{
 		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

@@ -20,18 +20,18 @@ 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 {
-		if formatter, ok := ctx.(Formatter); ok {
+		if formatter, ok := sourceCtx.(Formatter); ok {
 			v = formatter.ToString(0)
 		} else {
 			keys := sourceCtx.EnumVars(func(name string) bool { return name[0] != '_' })

operator-dot.go

@@ -4,8 +4,6 @@
 // operator-dot.go
 package expr
 
-import "fmt"
-
 // -------- dot term
 func newDotTerm(tk *Token) (inst *term) {
 	return &term{
@@ -17,24 +15,6 @@ 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
 
@@ -48,39 +28,8 @@ func evalDot(ctx ExprContext, self *term) (v any, err error) {
 	indexTerm := self.children[1]
 
 	switch unboxedValue := leftValue.(type) {
-	case *ListType:
-		var index int
-		array := ([]any)(*unboxedValue)
-		if index, err = verifyIndex(ctx, indexTerm, len(array)); err == nil {
-			v = array[index]
-		}
-	case string:
-		var index int
-		if index, err = verifyIndex(ctx, indexTerm, len(unboxedValue)); err == nil {
-			v = string(unboxedValue[index])
-		}
-	case map[any]any:
-		var ok bool
-		var indexValue any
-		if indexValue, err = indexTerm.compute(ctx); err == nil {
-			if v, ok = unboxedValue[indexValue]; !ok {
-				err = fmt.Errorf("key %v does not belong to the dictionary", rightValue)
-			}
-		}
-	// case *dataCursor:
-	// 	if indexTerm.symbol() == SymIdentifier {
-	// 		opName := indexTerm.source()
-	// 		if opName == resetName {
-	// 			_, err = unboxedValue.Reset()
-	// 		} else if opName == cleanName {
-	// 			_, err = unboxedValue.Clean()
-	// 		} else {
-	// 			err = indexTerm.Errorf("iterators do not support command %q", opName)
-	// 		}
-	// 		v = err == nil
-	// 	}
 	case ExtIterator:
-		if indexTerm.symbol() == SymIdentifier {
+		if indexTerm.symbol() == SymVariable /*|| indexTerm.symbol() == SymString */ {
 			opName := indexTerm.source()
 			if unboxedValue.HasOperation(opName) {
 				v, err = unboxedValue.CallOperation(opName, []any{})
@@ -88,10 +37,14 @@ func evalDot(ctx ExprContext, self *term) (v any, err error) {
 				err = indexTerm.Errorf("this iterator do not support the %q command", opName)
 				v = false
 			}
+		} else {
+			err = indexTerm.tk.ErrorExpectedGot("identifier")
 		}
 	default:
+		if rightValue, err = self.children[1].compute(ctx); err == nil {
 			err = self.errIncompatibleTypes(leftValue, rightValue)
 		}
+	}
 	return
 }
 

operator-fraction.go

@@ -9,201 +9,8 @@ package expr
 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()
-}
-
 // -------- fraction term
 func newFractionTerm(tk *Token) *term {
 	return &term{
@@ -248,168 +55,11 @@ func evalFraction(ctx ExprContext, self *term) (v any, err error) {
 	if den == 1 {
 		v = num
 	} else {
-		v = &fraction{num, den}
+		v = &FractionType{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

@@ -16,10 +16,10 @@ func newInTerm(tk *Token) (inst *term) {
 	}
 }
 
-func hasKey(d map[any]any, target any) (ok bool) {
-	_, ok = d[target]
-	return
-}
+// 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
@@ -30,10 +30,10 @@ func evalIn(ctx ExprContext, self *term) (v any, err error) {
 
 	if IsList(rightValue) {
 		list, _ := rightValue.(*ListType)
-		v = list.indexDeepCmp(leftValue) >= 0
+		v = list.indexDeepSameCmp(leftValue) >= 0
 	} else if IsDict(rightValue) {
-		d, _ := rightValue.(map[any]any)
-		v = hasKey(d, leftValue)
+		dict, _ := rightValue.(*DictType)
+		v = dict.hasKey(leftValue)
 	} else {
 		err = self.errIncompatibleTypes(leftValue, rightValue)
 	}

operator-index.go

@@ -0,0 +1,123 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// operator-index.go
+package expr
+
+// -------- index term
+func newIndexTerm(tk *Token) (inst *term) {
+	return &term{
+		tk:       *tk,
+		children: make([]*term, 0, 2),
+		position: posInfix,
+		priority: priDot,
+		evalFunc: evalIndex,
+	}
+}
+
+func verifyKey(indexTerm *term, indexList *ListType) (index any, err error) {
+	index = (*indexList)[0]
+	return
+}
+
+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 < 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 verifyRange(indexTerm *term, indexList *ListType, maxValue int) (startIndex, endIndex int, err error) {
+	v, _ := ((*indexList)[0]).(*intPair)
+	startIndex = v.a
+	endIndex = v.b
+	if startIndex < 0 && startIndex >= -maxValue {
+		startIndex = maxValue + startIndex
+	}
+	if endIndex < 0 && endIndex >= -maxValue {
+		endIndex = maxValue + endIndex + 1
+	}
+	if startIndex < 0 || startIndex > maxValue {
+		err = indexTerm.Errorf("range start-index %d is out of bounds", startIndex)
+	} else if endIndex < 0 || endIndex > maxValue {
+		err = indexTerm.Errorf("range end-index %d is out of bounds", endIndex)
+	} else if startIndex > endIndex {
+		err = indexTerm.Errorf("range start-index %d must not be greater than end-index %d", startIndex, endIndex)
+	}
+	return
+}
+
+func evalIndex(ctx ExprContext, self *term) (v any, err error) {
+	var leftValue, rightValue any
+	var indexList *ListType
+	var ok bool
+
+	if leftValue, rightValue, err = self.evalInfix(ctx); err != nil {
+		return
+	}
+
+	indexTerm := self.children[1]
+	if indexList, ok = rightValue.(*ListType); !ok {
+		err = self.Errorf("invalid index expression")
+		return
+	} else if len(*indexList) != 1 {
+		err = indexTerm.Errorf("one index only is allowed")
+		return
+	}
+
+	if IsInteger((*indexList)[0]) {
+		switch unboxedValue := leftValue.(type) {
+		case *ListType:
+			var index int
+			if index, err = verifyIndex(indexTerm, indexList, len(*unboxedValue)); err == nil {
+				v = (*unboxedValue)[index]
+			}
+		case string:
+			var index int
+			if index, err = verifyIndex(indexTerm, indexList, len(unboxedValue)); err == nil {
+				v = string(unboxedValue[index])
+			}
+		case *DictType:
+			var ok bool
+			var indexValue any
+			if indexValue, err = verifyKey(indexTerm, indexList); err == nil {
+				if v, ok = (*unboxedValue)[indexValue]; !ok {
+					err = indexTerm.Errorf("key %v does not belong to the dictionary", rightValue)
+				}
+			}
+		default:
+			err = self.errIncompatibleTypes(leftValue, rightValue)
+		}
+	} else if isIntPair((*indexList)[0]) {
+		switch unboxedValue := leftValue.(type) {
+		case *ListType:
+			var start, end int
+			if start, end, err = verifyRange(indexTerm, indexList, len(*unboxedValue)); err == nil {
+				sublist := ListType((*unboxedValue)[start:end])
+				v = &sublist
+			}
+		case string:
+			var start, end int
+			if start, end, err = verifyRange(indexTerm, indexList, len(unboxedValue)); err == nil {
+				v = unboxedValue[start:end]
+			}
+		default:
+			err = self.errIncompatibleTypes(leftValue, rightValue)
+		}
+	}
+	return
+}
+
+// init
+func init() {
+	registerTermConstructor(SymIndex, newIndexTerm)
+}

operator-insert.go

@@ -37,6 +37,9 @@ func evalInsert(ctx ExprContext, self *term) (v any, err error) {
 		list, _ := rightValue.(*ListType)
 		newList := append(ListType{leftValue}, *list...)
 		v = &newList
+		if self.children[1].symbol() == SymVariable {
+			ctx.UnsafeSetVar(self.children[1].source(), v)
+		}
 	} else {
 		err = self.errIncompatibleTypes(leftValue, rightValue)
 	}
@@ -54,12 +57,33 @@ func evalAppend(ctx ExprContext, self *term) (v any, err error) {
 		list, _ := leftValue.(*ListType)
 		newList := append(*list, rightValue)
 		v = &newList
+		if self.children[0].symbol() == SymVariable {
+			ctx.UnsafeSetVar(self.children[0].source(), v)
+		}
 	} 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-length.go

@@ -30,8 +30,9 @@ func evalLength(ctx ExprContext, self *term) (v any, err error) {
 		s, _ := childValue.(string)
 		v = int64(len(s))
 	} else if IsDict(childValue) {
-		m, _ := childValue.(map[any]any)
-		v = int64(len(m))
+		// 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)

operator-post-inc.go

@@ -25,7 +25,7 @@ func evalPostInc(ctx ExprContext, self *term) (v any, err error) {
 
 	if it, ok := childValue.(Iterator); ok {
 		v, err = it.Next()
-	} else if IsInteger(childValue) && self.children[0].symbol() == SymIdentifier {
+	} else if IsInteger(childValue) && self.children[0].symbol() == SymVariable {
 		v = childValue
 		i, _ := childValue.(int64)
 		ctx.SetVar(self.children[0].source(), i+1)

operator-range.go

@@ -0,0 +1,69 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// operator-range.go
+package expr
+
+import "fmt"
+
+// -------- range term
+type intPair struct {
+	a, b int
+}
+
+func (p *intPair) TypeName() string {
+	return typePair
+}
+
+func (p *intPair) ToString(opt FmtOpt) string {
+	return fmt.Sprintf("(%d, %d)", p.a, p.b)
+}
+
+func isIntPair(v any) bool {
+	_, ok := v.(*intPair)
+	return ok
+}
+
+func newRangeTerm(tk *Token) (inst *term) {
+	return &term{
+		tk:       *tk,
+		children: make([]*term, 0, 2),
+		position: posInfix,
+		priority: priDot,
+		evalFunc: evalRange,
+	}
+}
+
+func evalRange(ctx ExprContext, self *term) (v any, err error) {
+	var leftValue, rightValue any
+
+	// if err = self.checkOperands(); err != nil {
+	// 	return
+	// }
+	if len(self.children) == 0 {
+		leftValue = int64(0)
+		rightValue = int64(-1)
+	} else if len(self.children) == 1 {
+		if leftValue, err = self.children[0].compute(ctx); err != nil {
+			return
+		}
+		rightValue = int64(-1)
+	} else if leftValue, rightValue, err = self.evalInfix(ctx); err != nil {
+		return
+	}
+	if !(IsInteger(leftValue) && IsInteger(rightValue)) {
+		err = self.errIncompatibleTypes(leftValue, rightValue)
+		return
+	}
+
+	startIndex, _ := leftValue.(int64)
+	endIndex, _ := rightValue.(int64)
+
+	v = &intPair{int(startIndex), int(endIndex)}
+	return
+}
+
+// init
+func init() {
+	registerTermConstructor(SymColon, newRangeTerm)
+}

operator-rel.go

@@ -4,13 +4,13 @@
 // operator-rel.go
 package expr
 
+import "reflect"
+
 //-------- equal term
 
 func newEqualTerm(tk *Token) (inst *term) {
 	return &term{
 		tk:       *tk,
-		// class:    classOperator,
-		// kind:     kindBool,
 		children: make([]*term, 0, 2),
 		position: posInfix,
 		priority: priRelational,
@@ -18,6 +18,33 @@ func newEqualTerm(tk *Token) (inst *term) {
 	}
 }
 
+type deepFuncTemplate func(a, b any) (eq bool, err error)
+
+func equals(a, b any, deepCmp deepFuncTemplate) (eq bool, err error) {
+	if isNumOrFract(a) && isNumOrFract(b) {
+		if IsNumber(a) && IsNumber(b) {
+			if IsInteger(a) && IsInteger(b) {
+				li, _ := a.(int64)
+				ri, _ := b.(int64)
+				eq = li == ri
+			} else {
+				eq = numAsFloat(a) == numAsFloat(b)
+			}
+		} else {
+			var cmp int
+			if cmp, err = cmpAnyFract(a, b); err == nil {
+				eq = cmp == 0
+			}
+		}
+	} else if deepCmp != nil && IsList(a) && IsList(b) {
+		eq, err = deepCmp(a, b)
+	} else {
+		eq = reflect.DeepEqual(a, b)
+	}
+
+	return
+}
+
 func evalEqual(ctx ExprContext, self *term) (v any, err error) {
 	var leftValue, rightValue any
 
@@ -25,21 +52,7 @@ func evalEqual(ctx ExprContext, self *term) (v any, err error) {
 		return
 	}
 
-	if IsNumber(leftValue) && IsNumber(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) {
-		ls, _ := leftValue.(string)
-		rs, _ := rightValue.(string)
-		v = ls == rs
-	} else {
-		err = self.errIncompatibleTypes(leftValue, rightValue)
-	}
+	v, err = equals(leftValue, rightValue, nil)
 	return
 }
 
@@ -48,8 +61,6 @@ func evalEqual(ctx ExprContext, self *term) (v any, err error) {
 func newNotEqualTerm(tk *Token) (inst *term) {
 	return &term{
 		tk:       *tk,
-		// class:    classOperator,
-		// kind:     kindBool,
 		children: make([]*term, 0, 2),
 		position: posInfix,
 		priority: priRelational,
@@ -65,38 +76,11 @@ func evalNotEqual(ctx ExprContext, self *term) (v any, err error) {
 	return
 }
 
-// func evalNotEqual(ctx exprContext, self *term) (v any, err error) {
-// 	var leftValue, rightValue any
-
-// 	if leftValue, rightValue, err = self.evalInfix(ctx); err != nil {
-// 		return
-// 	}
-
-// 	if isNumber(leftValue) && isNumber(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) {
-// 		ls, _ := leftValue.(string)
-// 		rs, _ := rightValue.(string)
-// 		v = ls != rs
-// 	} else {
-// 		err = self.errIncompatibleTypes(leftValue, rightValue)
-// 	}
-// 	return
-// }
-
 //-------- less term
 
 func newLessTerm(tk *Token) (inst *term) {
 	return &term{
 		tk:       *tk,
-		// class:    classOperator,
-		// kind:     kindBool,
 		children: make([]*term, 0, 2),
 		position: posInfix,
 		priority: priRelational,
@@ -104,28 +88,44 @@ func newLessTerm(tk *Token) (inst *term) {
 	}
 }
 
+func lessThan(self *term, a, b any) (isLess bool, err error) {
+	if isNumOrFract(a) && isNumOrFract(b) {
+		if IsNumber(a) && IsNumber(b) {
+			if IsInteger(a) && IsInteger(b) {
+				li, _ := a.(int64)
+				ri, _ := b.(int64)
+				isLess = li < ri
+			} else {
+				isLess = numAsFloat(a) < numAsFloat(b)
+			}
+		} else {
+			var cmp int
+			if cmp, err = cmpAnyFract(a, b); err == nil {
+				isLess = cmp < 0
+			}
+		}
+	} else if IsString(a) && IsString(b) {
+		ls, _ := a.(string)
+		rs, _ := b.(string)
+		isLess = ls < rs
+		// Inclusion test
+	} else if IsList(a) && IsList(b) {
+		aList, _ := a.(*ListType)
+		bList, _ := b.(*ListType)
+		isLess = len(*aList) < len(*bList) && bList.contains(aList)
+	} else {
+		err = self.errIncompatibleTypes(a, b)
+	}
+	return
+}
+
 func evalLess(ctx ExprContext, self *term) (v any, err error) {
 	var leftValue, rightValue any
 
 	if leftValue, rightValue, err = self.evalInfix(ctx); err != nil {
 		return
 	}
-
-	if IsNumber(leftValue) && IsNumber(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) {
-		ls, _ := leftValue.(string)
-		rs, _ := rightValue.(string)
-		v = ls < rs
-	} else {
-		err = self.errIncompatibleTypes(leftValue, rightValue)
-	}
+	v, err = lessThan(self, leftValue, rightValue)
 	return
 }
 
@@ -141,6 +141,19 @@ func newLessEqualTerm(tk *Token) (inst *term) {
 	}
 }
 
+func lessThanOrEqual(self *term, a, b any) (isLessEq bool, err error) {
+	if isLessEq, err = lessThan(self, a, b); err == nil {
+		if !isLessEq {
+			if IsList(a) && IsList(b) {
+				isLessEq, err = sameContent(a, b)
+			} else {
+				isLessEq, err = equals(a, b, nil)
+			}
+		}
+	}
+	return
+}
+
 func evalLessEqual(ctx ExprContext, self *term) (v any, err error) {
 	var leftValue, rightValue any
 
@@ -148,21 +161,8 @@ func evalLessEqual(ctx ExprContext, self *term) (v any, err error) {
 		return
 	}
 
-	if IsNumber(leftValue) && IsNumber(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) {
-		ls, _ := leftValue.(string)
-		rs, _ := rightValue.(string)
-		v = ls <= rs
-	} else {
-		err = self.errIncompatibleTypes(leftValue, rightValue)
-	}
+	v, err = lessThanOrEqual(self, leftValue, rightValue)
+
 	return
 }
 
@@ -171,8 +171,6 @@ func evalLessEqual(ctx ExprContext, self *term) (v any, err error) {
 func newGreaterTerm(tk *Token) (inst *term) {
 	return &term{
 		tk:       *tk,
-		// class:    classOperator,
-		// kind:     kindBool,
 		children: make([]*term, 0, 2),
 		position: posInfix,
 		priority: priRelational,
@@ -181,10 +179,13 @@ func newGreaterTerm(tk *Token) (inst *term) {
 }
 
 func evalGreater(ctx ExprContext, self *term) (v any, err error) {
-	if v, err = evalLessEqual(ctx, self); err == nil {
-		b, _ := toBool(v)
-		v = !b
+	var leftValue, rightValue any
+
+	if leftValue, rightValue, err = self.evalInfix(ctx); err != nil {
+		return
 	}
+
+	v, err = lessThan(self, rightValue, leftValue)
 	return
 }
 
@@ -193,8 +194,6 @@ func evalGreater(ctx ExprContext, self *term) (v any, err error) {
 func newGreaterEqualTerm(tk *Token) (inst *term) {
 	return &term{
 		tk:       *tk,
-		// class:    classOperator,
-		// kind:     kindBool,
 		children: make([]*term, 0, 2),
 		position: posInfix,
 		priority: priRelational,
@@ -203,10 +202,13 @@ func newGreaterEqualTerm(tk *Token) (inst *term) {
 }
 
 func evalGreaterEqual(ctx ExprContext, self *term) (v any, err error) {
-	if v, err = evalLess(ctx, self); err == nil {
-		b, _ := toBool(v)
-		v = !b
+	var leftValue, rightValue any
+
+	if leftValue, rightValue, err = self.evalInfix(ctx); err != nil {
+		return
 	}
+
+	v, err = lessThanOrEqual(self, rightValue, leftValue)
 	return
 }
 

operator-sum.go

@@ -38,15 +38,11 @@ func evalPlus(ctx ExprContext, self *term) (v any, err error) {
 			rightInt, _ := rightValue.(int64)
 			v = leftInt + rightInt
 		}
-	} else if IsList(leftValue) || IsList(rightValue) {
+	} else if IsList(leftValue) && IsList(rightValue) {
 		var leftList, rightList *ListType
-		var ok bool
-		if leftList, ok = leftValue.(*ListType); !ok {
-			leftList = &ListType{leftValue}
-		}
-		if rightList, ok = rightValue.(*ListType); !ok {
-			rightList = &ListType{rightValue}
-		}
+		leftList, _ = leftValue.(*ListType)
+		rightList, _ = rightValue.(*ListType)
+
 		sumList := make(ListType, 0, len(*leftList)+len(*rightList))
 		for _, item := range *leftList {
 			sumList = append(sumList, item)
@@ -55,19 +51,17 @@ func evalPlus(ctx ExprContext, self *term) (v any, err error) {
 			sumList = append(sumList, item)
 		}
 		v = &sumList
-	} else if isFraction(leftValue) || isFraction(rightValue) {
+	} 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.(map[any]any)
-		rightDict, _ := rightValue.(map[any]any)
-		c := CloneMap(leftDict)
-		for key, value := range rightDict {
-			c[key] = value
-		}
+		leftDict, _ := leftValue.(*DictType)
+		rightDict, _ := rightValue.(*DictType)
+		c := leftDict.clone()
+		c.merge(rightDict)
 		v = c
 	} else {
 		err = self.errIncompatibleTypes(leftValue, rightValue)

parser.go

@@ -154,15 +154,34 @@ func (self *parser) parseFuncDef(scanner *scanner) (tree *term, err error) {
 	return
 }
 
-func (self *parser) parseList(scanner *scanner, allowVarRef bool) (subtree *term, err error) {
+func (self *parser) parseList(scanner *scanner, parsingIndeces bool, allowVarRef bool) (subtree *term, err error) {
+	r, c := scanner.lastPos()
 	args := make([]*term, 0)
 	lastSym := SymUnknown
 	itemExpected := false
 	for lastSym != SymClosedSquare && lastSym != SymEos {
 		var subTree *ast
+		zeroRequired := scanner.current.Sym == SymColon
 		if subTree, err = self.parseItem(scanner, allowVarRef, SymComma, SymClosedSquare); err == nil {
-			if subTree.root != nil {
-				args = append(args, subTree.root)
+			root := subTree.root
+			if root != nil {
+				if !parsingIndeces && root.symbol() == SymColon {
+					err = root.Errorf("unexpected range expression")
+					break
+				}
+				args = append(args, root)
+				if parsingIndeces && root.symbol() == SymColon && zeroRequired { //len(root.children) == 0 {
+					if len(root.children) == 1 {
+						root.children = append(root.children, root.children[0])
+					} else if len(root.children) > 1 {
+						err = root.Errorf("invalid range specification")
+						break
+					}
+					zeroTk := NewValueToken(root.tk.row, root.tk.col, SymInteger, "0", int64(0))
+					zeroTerm := newTerm(zeroTk)
+					zeroTerm.setParent(root)
+					root.children[0] = zeroTerm
+				}
 			} else if itemExpected {
 				prev := scanner.Previous()
 				err = prev.ErrorExpectedGot("list-item")
@@ -175,11 +194,10 @@ func (self *parser) parseList(scanner *scanner, allowVarRef bool) (subtree *term
 		itemExpected = lastSym == SymComma
 	}
 	if err == nil {
-		// TODO Check arguments
 		if lastSym != SymClosedSquare {
 			err = scanner.Previous().ErrorExpectedGot("]")
 		} else {
-			subtree = newListTerm(args)
+			subtree = newListTerm(r, c, args)
 		}
 	}
 	return
@@ -277,6 +295,7 @@ func (self *parser) parseDictionary(scanner *scanner, allowVarRef bool) (subtree
 			err = scanner.Previous().ErrorExpectedGot("}")
 		} else {
 			subtree = newDictTerm(args)
+			// subtree = newMapTerm(args)
 		}
 	}
 	return
@@ -293,14 +312,14 @@ func (self *parser) parseSelectorCase(scanner *scanner, allowVarRef bool, defaul
 			err = tk.Errorf("case list in default clause")
 			return
 		}
-		if filterList, err = self.parseList(scanner, allowVarRef); err != nil {
+		if filterList, err = self.parseList(scanner, false, allowVarRef); err != nil {
 			return
 		}
 		tk = scanner.Next()
 		startRow = tk.row
 		startCol = tk.col
 	} else if !defaultCase {
-		filterList = newListTerm(make([]*term, 0))
+		filterList = newListTerm(startRow, startCol, make([]*term, 0))
 	}
 
 	if tk.Sym == SymOpenBrace {
@@ -351,6 +370,14 @@ func (self *parser) Parse(scanner *scanner, termSymbols ...Symbol) (tree *ast, e
 	return self.parseGeneral(scanner, true, false, termSymbols...)
 }
 
+func couldBeACollection(t *term) bool {
+	var sym = SymUnknown
+	if t != nil {
+		sym = t.symbol()
+	}
+	return sym == SymList || sym == SymString || sym == SymDict || sym == SymExpression || sym == SymVariable
+}
+
 func (self *parser) parseGeneral(scanner *scanner, allowForest bool, allowVarRef bool, termSymbols ...Symbol) (tree *ast, err error) {
 	var selectorTerm *term = nil
 	var currentTerm *term = nil
@@ -389,7 +416,7 @@ 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:
@@ -400,16 +427,29 @@ func (self *parser) parseGeneral(scanner *scanner, allowForest bool, allowVarRef
 			}
 		case SymOpenSquare:
 			var listTerm *term
-			if listTerm, err = self.parseList(scanner, allowVarRef); err == nil {
+			parsingIndeces := couldBeACollection(currentTerm)
+			if listTerm, err = self.parseList(scanner, parsingIndeces, allowVarRef); err == nil {
+				if parsingIndeces {
+					indexTk := NewToken(listTerm.tk.row, listTerm.tk.col, SymIndex, listTerm.source())
+					indexTerm := newTerm(indexTk)
+					if err = tree.addTerm(indexTerm); err == nil {
 						err = tree.addTerm(listTerm)
+					}
+				} else {
+					err = tree.addTerm(listTerm)
+				}
 				currentTerm = listTerm
 			}
 		case SymOpenBrace:
+			if currentTerm != nil && currentTerm.symbol() == SymColon {
+				err = currentTerm.Errorf(`selector-case outside of a selector context`)
+			} else {
 				var mapTerm *term
 				if mapTerm, err = self.parseDictionary(scanner, allowVarRef); err == nil {
 					err = tree.addTerm(mapTerm)
 					currentTerm = mapTerm
 				}
+			}
 		case SymEqual:
 			if err = checkPrevSymbol(lastSym, SymIdentifier, tk); err == nil {
 				currentTerm, err = tree.addToken2(tk)
@@ -438,15 +478,17 @@ func (self *parser) parseGeneral(scanner *scanner, allowForest bool, allowVarRef
 			}
 		case SymColon, SymDoubleColon:
 			var caseTerm *term
-			if selectorTerm == nil {
-				err = tk.Errorf("selector-case outside of a selector context")
-			} else if caseTerm, err = self.parseSelectorCase(scanner, allowVarRef, tk.Sym == SymDoubleColon); err == nil {
+			if selectorTerm != nil {
+				if caseTerm, err = self.parseSelectorCase(scanner, allowVarRef, tk.Sym == SymDoubleColon); err == nil {
 					addSelectorCase(selectorTerm, caseTerm)
 					currentTerm = caseTerm
 					if tk.Sym == SymDoubleColon {
 						selectorTerm = nil
 					}
 				}
+			} else {
+				currentTerm, err = tree.addToken2(tk)
+			}
 		default:
 			currentTerm, err = tree.addToken2(tk)
 		}

scanner.go

@@ -74,6 +74,14 @@ func (self *scanner) unreadChar() (err error) {
 	return
 }
 
+func (self *scanner) lastPos() (r, c int) {
+	if self.prev != nil {
+		r = self.prev.row
+		c = self.prev.col
+	}
+	return
+}
+
 func (self *scanner) Previous() *Token {
 	return self.prev
 }

simple-func-store.go

@@ -1,142 +0,0 @@
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
-// All rights reserved.
-
-// simple-func-store.go
-package expr
-
-import (
-	"fmt"
-	"strings"
-)
-
-type SimpleFuncStore struct {
-	SimpleVarStore
-	funcStore map[string]*funcInfo
-}
-
-type funcInfo struct {
-	name    string
-	minArgs int
-	maxArgs int
-	functor Functor
-}
-
-func (info *funcInfo) ToString(opt FmtOpt) string {
-	var sb strings.Builder
-	var i int
-	sb.WriteString("func(")
-	for i = 0; i < info.minArgs; i++ {
-		if i > 0 {
-			sb.WriteString(", ")
-		}
-		sb.WriteString(fmt.Sprintf("arg%d", i+1))
-	}
-	for ; i < info.maxArgs; i++ {
-		sb.WriteString(fmt.Sprintf("arg%d", i+1))
-	}
-	if info.maxArgs < 0 {
-		if info.minArgs > 0 {
-			sb.WriteString(", ")
-		}
-		sb.WriteString("...")
-	}
-	sb.WriteString(") {...}")
-	return sb.String()
-}
-
-func (info *funcInfo) Name() string {
-	return info.name
-}
-
-func (info *funcInfo) MinArgs() int {
-	return info.minArgs
-}
-
-func (info *funcInfo) MaxArgs() int {
-	return info.maxArgs
-}
-
-func (info *funcInfo) Functor() Functor {
-	return info.functor
-}
-
-func 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
-	for _, name := range ctx.EnumFuncs(func(name string) bool { return true }) {
-		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) 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.bak

@@ -36,7 +36,7 @@ func (ctx *SimpleVarStore) GetVar(varName string) (v any, exists bool) {
 	return
 }
 
-func (ctx *SimpleVarStore) setVar(varName string, value any) {
+func (ctx *SimpleVarStore) UnsafeSetVar(varName string, value any) {
 	// fmt.Printf("[%p] setVar(%v, %v)\n", ctx, varName, value)
 	ctx.varStore[varName] = value
 }
@@ -72,7 +72,12 @@ 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) 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) {
@@ -98,8 +103,8 @@ func varsCtxToBuilder(sb *strings.Builder, ctx ExprContext, indent int) {
 			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 if _, ok = value.(map[any]any); ok {
+			// 	sb.WriteString("dict{}")
 		} else {
 			sb.WriteString(fmt.Sprintf("%v", value))
 		}

symbol.go

@@ -72,6 +72,7 @@ const (
 	SymIdentifier
 	SymBool
 	SymInteger
+	SymVariable
 	SymFloat
 	SymFraction
 	SymString
@@ -84,6 +85,7 @@ const (
 	SymFuncDef
 	SymList
 	SymDict
+	SymIndex
 	SymExpression
 	SymSelector     // <selector> ::= <expr> "?" <selector-case> {":" <selector-case>} ["::" <default-selector-case>]
 	SymSelectorCase // <selector-case> ::= [<list>] "{" <multi-expr> "}"

t_ast_test.go

@@ -1,7 +1,7 @@
 // Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
 // All rights reserved.
 
-// ast_test.go
+// t_ast_test.go
 package expr
 
 import (

t_dict_test.go

@@ -1,7 +1,7 @@
 // Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
 // All rights reserved.
 
-// dict_test.go
+// t_dict_test.go
 package expr
 
 import (
@@ -24,7 +24,7 @@ func TestDictParser(t *testing.T) {
 		/*  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},
+		/*  4 */ {`{1:"one",2:"two",3:"three"}[3]`, "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},
@@ -42,7 +42,7 @@ func TestDictParser(t *testing.T) {
 		var gotResult any
 		var gotErr error
 
-		ctx := NewSimpleFuncStore()
+		ctx := NewSimpleStore()
 		ctx.SetVar("var1", int64(123))
 		ctx.SetVar("var2", "abc")
 		ImportMathFuncs(ctx)
@@ -102,3 +102,49 @@ func TestDictParser(t *testing.T) {
 	}
 	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)
+	}
+}

t_expr_test.go

@@ -1,7 +1,7 @@
 // Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
 // All rights reserved.
 
-// expr_test.go
+// t_expr_test.go
 package expr
 
 import (
@@ -22,7 +22,7 @@ func TestExpr(t *testing.T) {
 		/*   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},
-		/*   10 */ {`
+		/*   6 */ {`
 		ds={
 			"init":func(end){@end=end; @current=0 but true},
 			"current":func(){current},
@@ -44,7 +44,7 @@ func TestExpr(t *testing.T) {
 		var gotResult any
 		var gotErr error
 
-		ctx := NewSimpleFuncStore()
+		ctx := NewSimpleStore()
 		// ImportMathFuncs(ctx)
 		// ImportImportFunc(ctx)
 		ImportOsFuncs(ctx)

t_funcs_test.go

@@ -1,7 +1,7 @@
 // Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
 // All rights reserved.
 
-// funcs_test.go
+// t_funcs_test.go
 package expr
 
 import (
@@ -76,14 +76,41 @@ func TestFuncs(t *testing.T) {
 		/*  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)`)},
-		/*  65 */ {`dec()`, nil, errors.New(`too few params -- expected 1, got 0`)},
-		/*  66 */ {`dec(1,2,3)`, nil, errors.New(`too much params -- expected 1, got 3`)},
-		/*  67 */ {`builtin "string"; joinStr()`, nil, errors.New(`too few params -- expected 1 or more, got 0`)},
-		// /*  64 */ {`string(true)`, "true", nil},
+		/*  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},*/
 	}
 
 	t.Setenv("EXPR_PATH", ".")
 
-	//parserTest(t, "Func", inputs[54:55])
+	// parserTestSpec(t, "Func", inputs, 69)
 	parserTest(t, "Func", inputs)
 }

t_graph_test.go

@@ -1,10 +1,7 @@
 // Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
 // All rights reserved.
 
-// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
-// All rights reserved.
-
-// graph_test.go
+// t_graph_test.go
 package expr
 
 import (

t_helpers_test.go

@@ -1,7 +1,7 @@
 // Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
 // All rights reserved.
 
-// helpers_test.go
+// t_helpers_test.go
 package expr
 
 import (
@@ -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)

t_index_test.go

@@ -0,0 +1,27 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// t_index_test.go
+package expr
+
+import (
+	"errors"
+	"testing"
+)
+
+func TestCollections(t *testing.T) {
+	section := "Collection"
+	inputs := []inputType{
+		/*   1 */ {`"abcdef"[1:3]`, "bc", nil},
+		/*   2 */ {`"abcdef"[:3]`, "abc", nil},
+		/*   3 */ {`"abcdef"[1:]`, "bcdef", nil},
+		/*   4 */ {`"abcdef"[:]`, "abcdef", nil},
+		// /*   5 */ {`[0,1,2,3,4][:]`, ListType{int64(0), int64(1), int64(2), int64(3), int64(4)}, nil},
+		/*   5 */ {`"abcdef"[1:2:3]`, nil, errors.New(`[1:14] left operand '(1, 2)' [pair] and right operand '3' [integer] are not compatible with operator ":"`)},
+	}
+
+	t.Setenv("EXPR_PATH", ".")
+
+	// parserTestSpec(t, section, inputs, 5)
+	parserTest(t, section, inputs)
+}

t_iterator_test.go

@@ -1,7 +1,7 @@
 // Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
 // All rights reserved.
 
-// iterator_test.go
+// t_iterator_test.go
 package expr
 
 import "testing"

t_list_test.go

@@ -1,7 +1,7 @@
 // Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
 // All rights reserved.
 
-// list_test.go
+// t_list_test.go
 package expr
 
 import (
@@ -33,14 +33,19 @@ func TestListParser(t *testing.T) {
 		/*  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`)},
+		/*  14 */ {`[1,2,3][1]`, int64(2), nil},
+		/*  15 */ {`ls=[1,2,3] but ls[1]`, int64(2), nil},
+		/*  16 */ {`ls=[1,2,3] but ls[-1]`, int64(3), nil},
+		/*  17 */ {`list=["one","two","three"]; list[10]`, nil, errors.New(`[1:34] index 10 out of bounds`)},
 		/*  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},
+		/*  24 */ {`["a","b","c","d"][1]`, "b", nil},
+		/*  25 */ {`["a","b","c","d"][1,1]`, nil, errors.New(`[1:19] one index only is allowed`)},
+		/*  26 */ {`[0,1,2,3,4][:]`, ListType{int64(0), int64(1), int64(2), int64(3), int64(4)}, 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},
@@ -58,9 +63,7 @@ func TestListParser(t *testing.T) {
 		var gotResult any
 		var gotErr error
 
-		ctx := NewSimpleFuncStore()
-		// ctx.SetVar("var1", int64(123))
-		// ctx.SetVar("var2", "abc")
+		ctx := NewSimpleStore()
 		ImportMathFuncs(ctx)
 		parser := NewParser(ctx)
 

t_parser_test.go

@@ -1,7 +1,7 @@
 // Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
 // All rights reserved.
 
-// parser_test.go
+// t_parser_test.go
 package expr
 
 import (
@@ -98,7 +98,7 @@ func TestGeneralParser(t *testing.T) {
 		/*  77 */ {`5 % 2`, int64(1), nil},
 		/*  78 */ {`5 % (-2)`, int64(1), nil},
 		/*  79 */ {`-5 % 2`, int64(-1), nil},
-		/*  80 */ {`5 % 2.0`, nil, errors.New(`[1:4] left operand '5' [int64] and right operand '2' [float64] are not compatible with operator "%"`)},
+		/*  80 */ {`5 % 2.0`, nil, errors.New(`[1:4] left operand '5' [integer] and right operand '2' [float] are not compatible with operator "%"`)},
 		/*  81 */ {`"a" < "b" AND NOT (2 < 1)`, true, nil},
 		/*  82 */ {`"a" < "b" AND NOT (2 == 1)`, true, nil},
 		/*  83 */ {`"a" < "b" AND ~ 2 == 1`, true, nil},
@@ -137,7 +137,7 @@ func TestGeneralParser(t *testing.T) {
 		/* 116 */ {`null`, nil, errors.New(`undefined variable or function "null"`)},
 		/* 117 */ {`{"key"}`, nil, errors.New(`[1:8] expected ":", got "}"`)},
 		/* 118 */ {`{"key":}`, nil, errors.New(`[1:9] expected "dictionary-value", got "}"`)},
-		/* 119 */ {`{}`, map[any]any{}, nil},
+		/* 119 */ {`{}`, &DictType{}, nil},
 		/* 120 */ {`1|2`, newFraction(1, 2), nil},
 		/* 121 */ {`1|2 + 1`, newFraction(3, 2), nil},
 		/* 122 */ {`1|2 - 1`, newFraction(-1, 2), nil},
@@ -163,46 +163,32 @@ func TestGeneralParser(t *testing.T) {
 	}
 
 	// t.Setenv("EXPR_PATH", ".")
+	// parserTestSpec(t, "General", inputs, 102)
 	parserTest(t, "General", 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 {
-		var expr Expr
-		var gotResult any
-		var gotErr error
-
-		ctx := NewSimpleFuncStore()
-		parser := NewParser(ctx)
-
-		logTest(t, i+1, 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]", 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
-			}
-		}
-
+		good := doTest(t, section, &input, i+1)
 		if good {
 			succeeded++
 		} else {
@@ -212,6 +198,40 @@ func parserTest(t *testing.T, section string, inputs []inputType) {
 	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.Logf("[+]%s nr %3d -- %q  --> %v", section, n, source, wantResult)

t_relational_test.go

@@ -0,0 +1,52 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// t_template_test.go
+package expr
+
+import (
+	"testing"
+)
+
+func TestRelational(t *testing.T) {
+	section := "Relational"
+	inputs := []inputType{
+		/*   1 */ {`1 == 3-2`, true, nil},
+		/*   2 */ {`"a" == "a"`, true, nil},
+		/*   3 */ {`true == false`, false, nil},
+		/*   4 */ {`1.0 == 3.0-2`, true, nil},
+		/*   5 */ {`[1,2] == [2,1]`, false, nil},
+		/*   6 */ {`1 != 3-2`, false, nil},
+		/*   7 */ {`"a" != "a"`, false, nil},
+		/*   8 */ {`true != false`, true, nil},
+		/*   9 */ {`1.0 != 3.0-2`, false, nil},
+		/*  10 */ {`[1,2] != [2,1]`, true, nil},
+		/*  11 */ {`1|2 == 1|3`, false, nil},
+		/*  12 */ {`1|2 != 1|3`, true, nil},
+		/*  13 */ {`1|2 == 4|8`, true, nil},
+		/*  14 */ {`1 < 8`, true, nil},
+		/*  15 */ {`1 <= 8`, true, nil},
+		/*  16 */ {`"a" < "b"`, true, nil},
+		/*  17 */ {`"a" <= "b"`, true, nil},
+		/*  18 */ {`1.0 < 8`, true, nil},
+		/*  19 */ {`1.0 <= 8`, true, nil},
+		/*  20 */ {`1.0 <= 1.0`, true, nil},
+		/*  21 */ {`1.0 == 1`, true, nil},
+		/*  22 */ {`1|2 < 1|3`, false, nil},
+		/*  23 */ {`1|2 <= 1|3`, false, nil},
+		/*  24 */ {`1|2 > 1|3`, true, nil},
+		/*  25 */ {`1|2 >= 1|3`, true, nil},
+		/*  26 */ {`[1,2,3] > [2]`, true, nil},
+		/*  27 */ {`[1,2,3] > [9]`, false, nil},
+		/*  28 */ {`[1,2,3] >= [6]`, false, nil},
+		/*  29 */ {`[1,2,3] >= [2,6]`, false, nil},
+		/*  30 */ {`[1,[2,3],4] > [[3,2]]`, true, nil},
+		/*  31 */ {`[1,[2,[3,4]],5] > [[[4,3],2]]`, true, nil},
+		/*  32 */ {`[[4,3],2] IN [1,[2,[3,4]],5]`, true, nil},
+	}
+
+	// t.Setenv("EXPR_PATH", ".")
+
+	// parserTestSpec(t, section, inputs, 31)
+	parserTest(t, section, inputs)
+}

t_scanner_test.go

@@ -1,7 +1,7 @@
 // Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
 // All rights reserved.
 
-// scanner_test.go
+// t_scanner_test.go
 package expr
 
 import (

t_strings_test.go

@@ -1,7 +1,7 @@
 // Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
 // All rights reserved.
 
-// strings_test.go
+// t_strings_test.go
 package expr
 
 import (
@@ -14,8 +14,8 @@ func TestStringsParser(t *testing.T) {
 		/*  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},
+		/*  5 */ {`"abc"[1]`, `b`, nil},
+		/*  6 */ {`#"abc"`, int64(3), nil},
 	}
 	parserTest(t, "String", inputs)
 }

t_template_test.go

@@ -0,0 +1,21 @@
+// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// t_template_test.go
+package expr
+
+import (
+	"testing"
+)
+
+func TestSomething(t *testing.T) {
+	section := "Something"
+	inputs := []inputType{
+		/*   1 */ {`1`, int64(1), nil},
+	}
+
+	// t.Setenv("EXPR_PATH", ".")
+
+	// parserTestSpec(t, section, inputs, 1)
+	parserTest(t, section, inputs)
+}

t_term_test.go

@@ -1,7 +1,7 @@
 // Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
 // All rights reserved.
 
-// term_test.go
+// t_term_test.go
 package expr
 
 import (

t_token_test.go

@@ -1,7 +1,7 @@
 // Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
 // All rights reserved.
 
-// token_test.go
+// t_token_test.go
 package expr
 
 import (

t_utils_test.go

@@ -1,7 +1,7 @@
 // Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
 // All rights reserved.
 
-// utils_test.go
+// t_utils_test.go
 package expr
 
 import (

term.go

@@ -12,6 +12,7 @@ type termPriority uint32
 
 const (
 	priNone termPriority = iota
+	priRange
 	priBut
 	priAssign
 	priOr
@@ -161,10 +162,14 @@ func (self *term) toInt(computedValue any, valueDescription string) (i int, err
 }
 
 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",
-		leftValue, leftValue,
-		rightValue, rightValue,
+		"left operand '%s' [%s] and right operand '%s' [%s] are not compatible with operator %q",
+		leftText, leftType,
+		rightText, rightType,
 		self.source())
 }
 

utils.go

@@ -35,17 +35,17 @@ func IsList(v any) (ok bool) {
 }
 
 func IsDict(v any) (ok bool) {
-	_, ok = v.(map[any]any)
+	_, ok = v.(*DictType)
 	return ok
 }
 
 func IsFract(v any) (ok bool) {
-	_, ok = v.(*fraction)
+	_, ok = v.(*FractionType)
 	return ok
 }
 
 func IsRational(v any) (ok bool) {
-	if _, ok = v.(*fraction); !ok {
+	if _, ok = v.(*FractionType); !ok {
 		_, ok = v.(int64)
 	}
 	return ok
@@ -76,7 +76,7 @@ func isIterator(v any) (ok bool) {
 func numAsFloat(v any) (f float64) {
 	var ok bool
 	if f, ok = v.(float64); !ok {
-		if fract, ok := v.(*fraction); ok {
+		if fract, ok := v.(*FractionType); ok {
 			f = fract.toFloat()
 		} else {
 			i, _ := v.(int64)
@@ -147,6 +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
 }
 
@@ -203,3 +209,11 @@ func toInt(value any, description string) (i int, err error) {
 	}
 	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
+}