Doc: Fixed a lot of typos

common-type-names.go

@@ -6,6 +6,7 @@ package expr
 
 const (
 	TypeAny           = "any"
+	TypeNil           = "nil"
 	TypeBoolean       = "boolean"
 	TypeFloat         = "float"
 	TypeFraction      = "fraction"
@@ -15,6 +16,7 @@ const (
 	TypeNumber        = "number"
 	TypePair          = "pair"
 	TypeString        = "string"
+	TypeDict          = "dict"
 	TypeListOf        = "list-of-"
 	TypeListOfStrings = "list-of-strings"
 )

data-cursor.go

@@ -6,12 +6,14 @@ package expr
 
 import (
 	"io"
+	"slices"
 )
 
 type dataCursor struct {
 	ds        map[string]Functor
 	ctx       ExprContext
-	initState bool // true if no item has prodiced yet (this replace di initial Next() call in the contructor)
+	initState bool // true if no item has produced yet (this replace di initial Next() call in the contructor)
+	// cursorValid bool // true if resource is nil or if clean has not yet been called
 	index     int
 	count     int
 	current   any
@@ -26,6 +28,7 @@ func NewDataCursor(ctx ExprContext, ds map[string]Functor, resource any) (dc *da
 	dc = &dataCursor{
 		ds:        ds,
 		initState: true,
+		// cursorValid: true,
 		index:     -1,
 		count:     0,
 		current:   nil,
@@ -36,7 +39,6 @@ func NewDataCursor(ctx ExprContext, ds map[string]Functor, resource any) (dc *da
 		cleanFunc: ds[CleanName],
 		resetFunc: ds[ResetName],
 	}
-	//dc.Next()
 	return
 }
 
@@ -77,7 +79,7 @@ func (dc *dataCursor) String() string {
 }
 
 func (dc *dataCursor) HasOperation(name string) (exists bool) {
-	exists = name == IndexName
+	exists = slices.Contains([]string{CleanName, ResetName, CurrentName, IndexName}, name)
 	if !exists {
 		f, ok := dc.ds[name]
 		exists = ok && isFunctor(f)
@@ -88,63 +90,83 @@ func (dc *dataCursor) HasOperation(name string) (exists bool) {
 func (dc *dataCursor) CallOperation(name string, args map[string]any) (value any, err error) {
 	if name == IndexName {
 		value = int64(dc.Index())
+	} else if name == CleanName {
+		err = dc.Clean()
+	} else if name == ResetName {
+		err = dc.Reset()
 	} else if functor, ok := dc.ds[name]; ok && isFunctor(functor) {
-		if functor == dc.cleanFunc {
+		ctx := cloneContext(dc.ctx)
-			value, err = dc.Clean()
+		value, err = functor.InvokeNamed(ctx, name, args)
-		} else if functor == dc.resetFunc {
+		exportObjects(dc.ctx, ctx)
-			value, err = dc.Reset()
-		} else {
-			ctx := cloneContext(dc.ctx)
-			value, err = functor.InvokeNamed(ctx, name, args)
-			exportObjects(dc.ctx, ctx)
-		}
 	} else {
 		err = errNoOperation(name)
 	}
 	return
 }
 
-func (dc *dataCursor) Reset() (success bool, err error) {
+// func (dc *dataCursor) Reset() (err error) {
+// 	if dc.resetFunc != nil {
+// 		if dc.resource != nil {
+// 			ctx := cloneContext(dc.ctx)
+// 			actualParams := bindActualParams(dc.resetFunc, []any{dc.resource})
+// 			_, err = dc.resetFunc.InvokeNamed(ctx, ResetName, actualParams)
+// 			exportObjects(dc.ctx, ctx)
+// 			dc.index = -1
+// 			dc.count = 0
+// 			dc.initState = true
+// 			dc.current = nil
+// 			dc.lastErr = nil
+// 		} else {
+// 			err = errInvalidDataSource()
+// 		}
+// 	} else {
+// 		err = errNoOperation(ResetName)
+// 	}
+// 	return
+// }
+
+func (dc *dataCursor) Reset() (err error) {
 	if dc.resetFunc != nil {
-		if dc.resource != nil {
+		ctx := cloneContext(dc.ctx)
-			ctx := cloneContext(dc.ctx)
+		actualParams := bindActualParams(dc.resetFunc, []any{dc.resource})
-			actualParams := bindActualParams(dc.resetFunc, []any{dc.resource})
+		_, err = dc.resetFunc.InvokeNamed(ctx, ResetName, actualParams)
-			_, err = dc.resetFunc.InvokeNamed(ctx, ResetName, actualParams)
+		exportObjects(dc.ctx, ctx)
-			exportObjects(dc.ctx, ctx)
-			dc.index = -1
-			dc.count = 0
-			dc.initState = true
-			dc.current = nil
-			dc.lastErr = nil
-			//dc.Next()
-		} else {
-			err = errInvalidDataSource()
-		}
-	} else {
-		err = errNoOperation(ResetName)
 	}
-	success = err == nil
+	dc.index = -1
+	dc.count = 0
+	dc.initState = true
+	dc.current = nil
+	dc.lastErr = nil
 	return
 }
 
-func (dc *dataCursor) Clean() (success bool, err error) {
+func (dc *dataCursor) Clean() (err error) {
 	if dc.cleanFunc != nil {
-		if dc.resource != nil {
+		ctx := cloneContext(dc.ctx)
-			ctx := cloneContext(dc.ctx)
+		actualParams := bindActualParams(dc.cleanFunc, []any{dc.resource})
-			actualParams := bindActualParams(dc.cleanFunc, []any{dc.resource})
+		_, err = dc.cleanFunc.InvokeNamed(ctx, CleanName, actualParams)
-			_, err = dc.cleanFunc.InvokeNamed(ctx, CleanName, actualParams)
+		exportObjects(dc.ctx, ctx)
-			//			dc.resource = nil
-			exportObjects(dc.ctx, ctx)
-		} else {
-			err = errInvalidDataSource()
-		}
-	} else {
-		err = errNoOperation(CleanName)
 	}
-	success = err == nil
+	dc.lastErr = io.EOF
 	return
 }
 
+// func (dc *dataCursor) Clean() (err error) {
+// 	if dc.cleanFunc != nil {
+// 		if dc.resource != nil {
+// 			ctx := cloneContext(dc.ctx)
+// 			actualParams := bindActualParams(dc.cleanFunc, []any{dc.resource})
+// 			_, err = dc.cleanFunc.InvokeNamed(ctx, CleanName, actualParams)
+// 			exportObjects(dc.ctx, ctx)
+// 		} else {
+// 			err = errInvalidDataSource()
+// 		}
+// 	} else {
+// 		err = errNoOperation(CleanName)
+// 	}
+// 	return
+// }
+
 func (dc *dataCursor) Current() (item any, err error) { // must return io.EOF at the last item
 	dc.init()
 
@@ -191,46 +213,89 @@ func (dc *dataCursor) Next() (current any, err error) { // must return io.EOF af
 		return
 	}
 	current = dc.current
-	if dc.resource != nil {
+	filter := dc.ds[FilterName]
-		filter := dc.ds[FilterName]
+	mapper := dc.ds[MapName]
-		mapper := dc.ds[MapName]
+	var item any
-		var item any
+	for item == nil && dc.lastErr == nil {
-		for item == nil && dc.lastErr == nil {
+		ctx := cloneContext(dc.ctx)
-			ctx := cloneContext(dc.ctx)
+		dc.index++
-			dc.index++
 
-			actualParams := bindActualParams(dc.nextFunc, []any{dc.resource, dc.index})
+		actualParams := bindActualParams(dc.nextFunc, []any{dc.resource, dc.index})
-			if item, dc.lastErr = dc.nextFunc.InvokeNamed(ctx, NextName, actualParams); dc.lastErr == nil {
+		if item, dc.lastErr = dc.nextFunc.InvokeNamed(ctx, NextName, actualParams); dc.lastErr == nil {
-				if item == nil {
+			if item == nil {
-					dc.lastErr = io.EOF
+				dc.lastErr = io.EOF
-				} else {
+			} else {
-					accepted := true
+				accepted := true
-					if filter != nil {
+				if filter != nil {
-						if accepted, dc.lastErr = dc.checkFilter(filter, item); dc.lastErr != nil || !accepted {
+					if accepted, dc.lastErr = dc.checkFilter(filter, item); dc.lastErr != nil || !accepted {
-							item = nil
+						item = nil
-						}
-					}
-					if accepted {
-						dc.count++
-					}
-					if item != nil && mapper != nil {
-						item, dc.lastErr = dc.mapItem(mapper, item)
 					}
 				}
+				if accepted {
+					dc.count++
+				}
+				if item != nil && mapper != nil {
+					item, dc.lastErr = dc.mapItem(mapper, item)
+				}
 			}
-			exportObjects(dc.ctx, ctx)
 		}
-		dc.current = item
+		exportObjects(dc.ctx, ctx)
-		if dc.lastErr != nil {
+	}
-			dc.index--
+	dc.current = item
-			dc.Clean()
+	if dc.lastErr != nil {
-		}
+		dc.index--
-	} else {
+		dc.Clean()
-		dc.lastErr = errInvalidDataSource()
 	}
 	return
 }
 
+// func (dc *dataCursor) Next() (current any, err error) { // must return io.EOF after the last item
+// 	if dc.initState {
+// 		dc.init()
+// 	} else if err = dc.lastErr; err != nil {
+// 		return
+// 	}
+// 	current = dc.current
+// 	if dc.resource != nil {
+// 		filter := dc.ds[FilterName]
+// 		mapper := dc.ds[MapName]
+// 		var item any
+// 		for item == nil && dc.lastErr == nil {
+// 			ctx := cloneContext(dc.ctx)
+// 			dc.index++
+
+// 			actualParams := bindActualParams(dc.nextFunc, []any{dc.resource, dc.index})
+// 			if item, dc.lastErr = dc.nextFunc.InvokeNamed(ctx, NextName, actualParams); dc.lastErr == nil {
+// 				if item == nil {
+// 					dc.lastErr = io.EOF
+// 				} else {
+// 					accepted := true
+// 					if filter != nil {
+// 						if accepted, dc.lastErr = dc.checkFilter(filter, item); dc.lastErr != nil || !accepted {
+// 							item = nil
+// 						}
+// 					}
+// 					if accepted {
+// 						dc.count++
+// 					}
+// 					if item != nil && mapper != nil {
+// 						item, dc.lastErr = dc.mapItem(mapper, item)
+// 					}
+// 				}
+// 			}
+// 			exportObjects(dc.ctx, ctx)
+// 		}
+// 		dc.current = item
+// 		if dc.lastErr != nil {
+// 			dc.index--
+// 			dc.Clean()
+// 		}
+// 	} else {
+// 		dc.lastErr = errInvalidDataSource()
+// 	}
+// 	return
+// }
+
 func (dc *dataCursor) Index() int {
 	return dc.index - 1
 }

doc/Expr.adoc

@@ -58,7 +58,7 @@ The expression context is analogous to the stack-frame of other programming lang
 
 Function contexts are created by cloning the calling context. More details on this topic are given later in this document.
 
-_Expr_ creates and keeps a inner _global context_ where it stores imported functions, either from builtin or plugin modules. To perform calculations, the calling program must provide its own context; this is the _main context_. All calculations take place in this context. As mentioned eralier, when a function is called, a new context is created by cloning the calling context. The createt context can be called _function context_.
+_Expr_ creates and keeps a inner _global context_ where it stores imported functions, either from builtin or plugin modules. To perform calculations, the calling program must provide its own context; this is the _main context_. All calculations take place in this context. As mentioned eralier, when a function is called, a new context is created by cloning the calling context. The created context can be called _function context_.
 
 Imported functions are registerd in the _global context_. When an expression first calls an imported function, that function is linked to the current context; this can be the _main context_ or a _function context_.
 
@@ -321,7 +321,7 @@ Some arithmetic operators can also be used with strings.
 | [blue]`*` | _repeat_ | Make _n_ copy of a string  | [blue]`"one" * 2` -> _"oneone"_
 |===
 
-The items of strings can be accessed using the square `[]` operator.
+The charanters in a string can be accessed using the square `[]` operator.
 
 .Item access syntax
 ====
@@ -340,10 +340,10 @@ The items of strings can be accessed using the square `[]` operator.
 `>>>` [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]`"d"`
 
-`>>>` [blue]`\#s`       [gray]_// number of chars_ +
+`>>>` [blue]`#s`       [gray]_// number of chars_ +
 [gren]`4`
 
 `>>>` [blue]`#"abc"`    [gray]_// number of chars_ +
@@ -369,9 +369,9 @@ Boolean data type has two values only: [blue]_true_ and [blue]_false_. Relationa
 | [blue]`\<=` | _Less or Equal_ | True if the left value is less than or equal to the right one | [blue]`5 \<= 2` -> _false_ +
 [blue]`"b" \<= "b"` -> _true_
 | [blue]`>` | _Greater_ | True if the left value is greater than the right one | [blue]`5 > 2` -> _true_ +
-[blue]`"a" < "b"` -> _false_
+[blue]`"a" > "b"` -> _false_
 | [blue]`>=` | _Greater or Equal_ | True if the left value is greater than or equal to the right one | [blue]`5 >= 2` -> _true_ +
-[blue]`"b" \<= "b"` -> _true_
+[blue]`"b" >= "b"` -> _true_
 |===
 
 ^(*)^ See also the  [blue]`in` operator in the _list_ and _dictionary_ sections.
@@ -388,7 +388,7 @@ Boolean data type has two values only: [blue]_true_ and [blue]_false_. Relationa
 | [blue]`AND` / [blue]`&&` | _And_ | True if both left and right values are true  | [blue]`false && true` -> _false_ +
 [blue]`"a" < "b" AND NOT (2 < 1)` -> _true_
 
-| [blue]`OR` / [blue]`\|\|` | _Or_ | True if at least one of the left and right values integers true| [blue]`false or true` -> _true_ +
+| [blue]`OR` / [blue]`\|\|` | _Or_ | True if at least one of the left and right values integers is true| [blue]`false or true` -> _true_ +
 [blue]`"a" == "b" OR (2 == 1)` -> _false_
 |===
 
@@ -413,7 +413,7 @@ _Expr_ supports list of mixed-type values, also specified by normal expressions.
 ====
 *_list_* = _empty-list_ | _non-empty-list_ +
 _empty-list_ = "**[]**" +
-_non-empty-list_ = "**[**" _any-value_ {"**,**" _any-value} "**]**" +
+_non-empty-list_ = "**[**" _any-value_ {"**,**" _any-value_} "**]**" +
 ====
 
 .Examples
@@ -459,22 +459,22 @@ Array's items can be accessed using the index `[]` operator.
 ====
 
 .Items of list
-`>>>` [blue]`[1,2,3].1` +
+`>>>` [blue]`[1,2,3][1]` +
 [green]`2`
 
-`>>>` [blue]`list=[1,2,3]; list.1` +
+`>>>` [blue]`list=[1,2,3]; list[1]` +
 [green]`2`
 
-`>>>` [blue]`["one","two","three"].1` +
+`>>>` [blue]`["one","two","three"][1]` +
 [green]`two`
 
-`>>>` [blue]`list=["one","two","three"]; list.(2-1)` +
+`>>>` [blue]`list=["one","two","three"]; list[2-1]` +
 [green]`two`
 
-`>>>` [blue]`list.(-1)` +
+`>>>` [blue]`list[-1]` +
 [green]`three`
 
-`>>>` [blue]`list.(10)` +
+`>>>` [blue]`list[10]` +
 [red]`Eval Error: [1:9] index 10 out of bounds`
 
 `>>>` [blue]`#list` +
@@ -497,7 +497,7 @@ Dictionary literals are sequences of pairs separated by comma [blue]`,` enclosed
 ====
 *_dict_* = _empty-dict_ | _non-empty-dict_ +
 _empty-dict_ = "**{}**" +
-_non-empty-dict_ = "**{**" _key-scalar_ "**:**" _any-value_ {"**,**" _key-scalar_ "**:**" _any-value} "**}**" +
+_non-empty-dict_ = "**{**" _key-scalar_ "**:**" _any-value_ {"**,**" _key-scalar_ "**:**" _any-value_} "**}**" +
 ====
 
 
@@ -551,7 +551,7 @@ NOTE: The assign operator [blue]`=` returns the value assigned to the variable.
 [green]`1`
 
 `>>>` [blue]`a_b=1+2` +
-[green]`1+2`
+[green]`3`
 
 `>>>` [blue]`a_b` +
 [green]`3`
@@ -562,7 +562,7 @@ NOTE: The assign operator [blue]`=` returns the value assigned to the variable.
 `>>>` [blue]`x = 1; y = 2*x` +
 [green]`2`
 
-`>>>` [blue]`_a=2` +
+`>>>` [blue]`\_a=2` +
 [red]`Parse Error: [1:2] unexpected token "_"`
 
 `>>>` [blue]`1=2` +
@@ -574,12 +574,12 @@ NOTE: The assign operator [blue]`=` returns the value assigned to the variable.
 === [blue]`;` operator
 The semicolon operator [blue]`;` is an infixed pseudo-operator. It evaluates the left expression first and then the right expression. The value of the latter is the final result.
 
-.Mult-expression syntax
+.Multi-expression syntax
 ====
 *_multi-expression_* = _expression_ {"**;**" _expression_ }
 ====
 
-An expression that contains [blue]`;` is called a _multi-expression_ and each component expressione is called a _sub-expression_.
+An expression that contains [blue]`;` is called a _multi-expression_ and each component expression is called a _sub-expression_.
 
 IMPORTANT: Technically [blue]`;` is not treated as a real operator. It acts as a separator in lists of expressions.
 
@@ -589,7 +589,7 @@ TIP: [blue]`;` can be used to set some variables before the final calculation.
 `>>>` [blue]`a=1; b=2; c=3; a+b+c` +
 [green]`6`
 
-The value of each sub-expression is stored in the automatica variable _last_.
+The value of each sub-expression is stored in the automatic variable _last_.
 
 .Example
 `>>>` [blue]`2+3; b=last+10; last` +
@@ -600,9 +600,10 @@ The value of each sub-expression is stored in the automatica variable _last_.
 [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` +
+`>>>` [blue]`5 but 2` +
-[green]`2` +
+[green]`2`
-[blue]`x=2*3 but x-1` +
+
+`>>>` [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]`)`.
@@ -610,17 +611,21 @@ The value of each sub-expression is stored in the automatica variable _last_.
 === Assignment operator [blue]`=`
 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.
+The value on the left side of [blue]`=` must be a variable identifier or an expression that evalutes to a variable. The value on the right side can be any expression and it becomes the result of the assignment operation.
 
-.Example
+.Examples
-`>>>` [blue]`a=15+1`
+`>>>` [blue]`a=15+1` +
 [green]`16`
 
+`>>>` [blue]`L=[1,2,3]; L[1]=5; L` +
+[green]`[1, 5, 3]`
+
 
 === Selector operator [blue]`? : ::`
 The _selector operator_ is very similar to the _switch/case/default_ statement available in many programming languages.
 
 .Selector literal Syntax
+====
 _selector-operator_ = _select-expression_ "*?*" _selector-case_ { "*:*" _selector-case_ } ["*::*" _default-multi-expression_] +
 _selector-case_ = [_match-list_] _case-value_ +
 _match-list_ = "*[*" _item_ {"*,*" _items_} "*]*" +
@@ -628,6 +633,7 @@ _item_ = _expression_ +
 _case-multi-expression_ = "*{*" _multi-expression_ "*}*" +
 _multi-expression_ = _expression_ { "*;*" _expression_ } +
 _default-multi-expression_ = _multi-expression_
+====
 
 In other words, the selector operator evaluates the _select-expression_ on the left-hand side of the [blue]`?` symbol; it then compares the result obtained with the values listed in the __match-list__'s, from left to right. If the comparision finds a match with a value in a _match-list_, the associated _case-multi-expression_ is evaluted, and its result will be the final result of the selection operation.
 
@@ -668,7 +674,7 @@ The [blue]`??` operator do not change the status of the left variable.
 The [blue]`?=` assigns the calculated value of the right expression to the left variable.
 
 .Examples
-`>>>` [blue]`var ?? (1+2)`' +
+`>>>` [blue]`var ?? (1+2)` +
 [green]`3`
 
 `>>>` [blue]`var` +
@@ -677,7 +683,7 @@ The [blue]`?=` assigns the calculated value of the right expression to the left
 `>>>` [blue]`var ?= (1+2)` +
 [green]`3`
 
-`>>>` [blue]`var`
+`>>>` [blue]`var` +
 [green]`3`
 
 NOTE: These operators have a high priority, in particular higher than the operator [blue]`=`.
@@ -739,21 +745,21 @@ The table below shows all supported operators by decreasing priorities.
 
 
 == Functions
-Functions in _Expr_ are very similar to functions available in many programming languages. Actually, _Expr_ supports two types of function, _expr-functions_ and _go-functions_.
+Functions in _Expr_ are very similar to functions available in many programming languages. Currently, _Expr_ supports two types of function, _expr-functions_ and _go-functions_.
 
 * _expr-functions_ are defined using _Expr_'s syntax. They can be passed as arguments to other functions and can be returned from functions. Moreover, they bind themselves to the defining context, thus becoming closures.
-* _go-functions_ are regular Golang functions callable from _Expr_ expressions. They are defined in Golang source files called _modules_ and compiled within the _Expr_ package. To make Golang functions available in _Expr_ contextes, it is required to _import_ the module in which they are defined.
+* _go-functions_ are regular Golang functions callable from _Expr_ expressions. They are defined in Golang source files called _modules_ and compiled within the _Expr_ package. To make Golang functions available in _Expr_ contextes, it is required to activate the builtin module or to load the plugin module in which they are defined.
 
 
 === _Expr_ function definition
 A function is identified and referenced by its name. It can have zero or more parameter. _Expr_ functions also support optional parameters.
 
-. Expr's function definition syntax
+.Expr's function definition syntax
 ====
-*_function-definition_* = _identifier_ "**=**"  "**func(**" [_param-list_] "**)**"  "**{**" _multi-expression_ "**}**"
+*_function-definition_* = _identifier_ "**=**"  "**func(**" [_param-list_] "**)**"  "**{**" _multi-expression_ "**}**" +
-_param_list_ = _required-param-list_ [ "**,**" _optional-param-list_ ]
+_param_list_ = _required-param-list_ [ "**,**" _optional-param-list_ ] +
-_required-param-list_ = _identifier_ { "**,**" _identifier_ }
+_required-param-list_ = _identifier_ { "**,**" _identifier_ } +
-_optional-param-list_ = _optional-parm_ { "**,**" _optional-param_ }
+_optional-param-list_ = _optional-parm_ { "**,**" _optional-param_ } +
 _optional-param_ = _identifier_ "**=**" _any-expr_
 ====
 

doc/Expr.html

@@ -657,7 +657,7 @@ pre.rouge .ss {
 <p>Function contexts are created by cloning the calling context. More details on this topic are given later in this document.</p>
 </div>
 <div class="paragraph">
-<p><em>Expr</em> creates and keeps a inner <em>global context</em> where it stores imported functions, either from builtin or plugin modules. To perform calculations, the calling program must provide its own context; this is the <em>main context</em>. All calculations take place in this context. As mentioned eralier, when a function is called, a new context is created by cloning the calling context. The createt context can be called <em>function context</em>.</p>
+<p><em>Expr</em> creates and keeps a inner <em>global context</em> where it stores imported functions, either from builtin or plugin modules. To perform calculations, the calling program must provide its own context; this is the <em>main context</em>. All calculations take place in this context. As mentioned eralier, when a function is called, a new context is created by cloning the calling context. The created context can be called <em>function context</em>.</p>
 </div>
 <div class="paragraph">
 <p>Imported functions are registerd in the <em>global context</em>. When an expression first calls an imported function, that function is linked to the current context; this can be the <em>main context</em> or a <em>function context</em>.</p>
@@ -1109,7 +1109,7 @@ dev-expr <span class="nt">--</span> Expressions calculator v1.10.0<span class="o
 </tbody>
 </table>
 <div class="paragraph">
-<p>The items of strings can be accessed using the square <code>[]</code> operator.</p>
+<p>The charanters in a string can be accessed using the square <code>[]</code> operator.</p>
 </div>
 <div class="exampleblock">
 <div class="title">Example 4. Item access syntax</div>
@@ -1137,11 +1137,11 @@ dev-expr <span class="nt">--</span> Expressions calculator v1.10.0<span class="o
 <code class="green">"b"</code></p>
 </div>
 <div class="paragraph">
-<p><code>&gt;&gt;&gt;</code> <code class="blue">s.[-1]</code>    <em class="gray">// char at position -1, the rightmost one</em><br>
+<p><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">"d"</code></p>
 </div>
 <div class="paragraph">
-<p><code>&gt;&gt;&gt;</code> <code class="blue">\#s</code>       <em class="gray">// number of chars</em><br>
+<p><code>&gt;&gt;&gt;</code> <code class="blue">#s</code>       <em class="gray">// number of chars</em><br>
 <code class="gren">4</code></p>
 </div>
 <div class="paragraph">
@@ -1208,14 +1208,14 @@ dev-expr <span class="nt">--</span> Expressions calculator v1.10.0<span class="o
 <td class="tableblock halign-center valign-top"><p class="tableblock"><em>Greater</em></p></td>
 <td class="tableblock halign-left valign-top"><p class="tableblock">True if the left value is greater than the right one</p></td>
 <td class="tableblock halign-left valign-top"><p class="tableblock"><code class="blue">5 &gt; 2</code> &#8594; <em>true</em><br>
-<code class="blue">"a" &lt; "b"</code> &#8594; <em>false</em></p></td>
+<code class="blue">"a" &gt; "b"</code> &#8594; <em>false</em></p></td>
 </tr>
 <tr>
 <td class="tableblock halign-center valign-top"><p class="tableblock"><code class="blue">&gt;=</code></p></td>
 <td class="tableblock halign-center valign-top"><p class="tableblock"><em>Greater or Equal</em></p></td>
 <td class="tableblock halign-left valign-top"><p class="tableblock">True if the left value is greater than or equal to the right one</p></td>
 <td class="tableblock halign-left valign-top"><p class="tableblock"><code class="blue">5 &gt;= 2</code> &#8594; <em>true</em><br>
-<code class="blue">"b" &lt;= "b"</code> &#8594; <em>true</em></p></td>
+<code class="blue">"b" &gt;= "b"</code> &#8594; <em>true</em></p></td>
 </tr>
 </tbody>
 </table>
@@ -1256,7 +1256,7 @@ dev-expr <span class="nt">--</span> Expressions calculator v1.10.0<span class="o
 <tr>
 <td class="tableblock halign-center valign-top"><p class="tableblock"><code class="blue">OR</code> / <code class="blue">||</code></p></td>
 <td class="tableblock halign-center valign-top"><p class="tableblock"><em>Or</em></p></td>
-<td class="tableblock halign-left valign-top"><p class="tableblock">True if at least one of the left and right values integers true</p></td>
+<td class="tableblock halign-left valign-top"><p class="tableblock">True if at least one of the left and right values integers is true</p></td>
 <td class="tableblock halign-left valign-top"><p class="tableblock"><code class="blue">false or true</code> &#8594; <em>true</em><br>
 <code class="blue">"a" == "b" OR (2 == 1)</code> &#8594; <em>false</em></p></td>
 </tr>
@@ -1314,7 +1314,7 @@ dev-expr <span class="nt">--</span> Expressions calculator v1.10.0<span class="o
 <div class="paragraph">
 <p><strong><em>list</em></strong> = <em>empty-list</em> | <em>non-empty-list</em><br>
 <em>empty-list</em> = "<strong>[]</strong>"<br>
-<em>non-empty-list</em> = "<strong>[</strong>" <em>any-value</em> {"<strong>,</strong>" _any-value} "<strong>]</strong>"<br></p>
+<em>non-empty-list</em> = "<strong>[</strong>" <em>any-value</em> {"<strong>,</strong>" <em>any-value</em>} "<strong>]</strong>"<br></p>
 </div>
 </div>
 </div>
@@ -1416,27 +1416,27 @@ dev-expr <span class="nt">--</span> Expressions calculator v1.10.0<span class="o
 </div>
 <div class="paragraph">
 <div class="title">Items of list</div>
-<p><code>&gt;&gt;&gt;</code> <code class="blue">[1,2,3].1</code><br>
+<p><code>&gt;&gt;&gt;</code> <code class="blue">[1,2,3][1]</code><br>
 <code class="green">2</code></p>
 </div>
 <div class="paragraph">
-<p><code>&gt;&gt;&gt;</code> <code class="blue">list=[1,2,3]; list.1</code><br>
+<p><code>&gt;&gt;&gt;</code> <code class="blue">list=[1,2,3]; list[1]</code><br>
 <code class="green">2</code></p>
 </div>
 <div class="paragraph">
-<p><code>&gt;&gt;&gt;</code> <code class="blue">["one","two","three"].1</code><br>
+<p><code>&gt;&gt;&gt;</code> <code class="blue">["one","two","three"][1]</code><br>
 <code class="green">two</code></p>
 </div>
 <div class="paragraph">
-<p><code>&gt;&gt;&gt;</code> <code class="blue">list=["one","two","three"]; list.(2-1)</code><br>
+<p><code>&gt;&gt;&gt;</code> <code class="blue">list=["one","two","three"]; list[2-1]</code><br>
 <code class="green">two</code></p>
 </div>
 <div class="paragraph">
-<p><code>&gt;&gt;&gt;</code> <code class="blue">list.(-1)</code><br>
+<p><code>&gt;&gt;&gt;</code> <code class="blue">list[-1]</code><br>
 <code class="green">three</code></p>
 </div>
 <div class="paragraph">
-<p><code>&gt;&gt;&gt;</code> <code class="blue">list.(10)</code><br>
+<p><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></p>
 </div>
 <div class="paragraph">
@@ -1466,7 +1466,7 @@ dev-expr <span class="nt">--</span> Expressions calculator v1.10.0<span class="o
 <div class="paragraph">
 <p><strong><em>dict</em></strong> = <em>empty-dict</em> | <em>non-empty-dict</em><br>
 <em>empty-dict</em> = "<strong>{}</strong>"<br>
-<em>non-empty-dict</em> = "<strong>{</strong>" <em>key-scalar</em> "<strong>:</strong>" <em>any-value</em> {"<strong>,</strong>" <em>key-scalar</em> "<strong>:</strong>" _any-value} "<strong>}</strong>"<br></p>
+<em>non-empty-dict</em> = "<strong>{</strong>" <em>key-scalar</em> "<strong>:</strong>" <em>any-value</em> {"<strong>,</strong>" <em>key-scalar</em> "<strong>:</strong>" <em>any-value</em>} "<strong>}</strong>"<br></p>
 </div>
 </div>
 </div>
@@ -1575,7 +1575,7 @@ The assign operator <code class="blue">=</code> returns the value assigned to th
 </div>
 <div class="paragraph">
 <p><code>&gt;&gt;&gt;</code> <code class="blue">a_b=1+2</code><br>
-<code class="green">1+2</code></p>
+<code class="green">3</code></p>
 </div>
 <div class="paragraph">
 <p><code>&gt;&gt;&gt;</code> <code class="blue">a_b</code><br>
@@ -1590,8 +1590,8 @@ The assign operator <code class="blue">=</code> returns the value assigned to th
 <code class="green">2</code></p>
 </div>
 <div class="paragraph">
-<p><code>&gt;&gt;&gt;</code> <code class="blue"><em>a=2</code><br>
+<p><code>&gt;&gt;&gt;</code> <code class="blue">_a=2</code><br>
-<code class="red">Parse Error: [1:2] unexpected token "</em>"</code></p>
+<code class="red">Parse Error: [1:2] unexpected token "_"</code></p>
 </div>
 <div class="paragraph">
 <p><code>&gt;&gt;&gt;</code> <code class="blue">1=2</code><br>
@@ -1608,7 +1608,7 @@ The assign operator <code class="blue">=</code> returns the value assigned to th
 <p>The semicolon operator <code class="blue">;</code> is an infixed pseudo-operator. It evaluates the left expression first and then the right expression. The value of the latter is the final result.</p>
 </div>
 <div class="exampleblock">
-<div class="title">Example 12. Mult-expression syntax</div>
+<div class="title">Example 12. Multi-expression syntax</div>
 <div class="content">
 <div class="paragraph">
 <p><strong><em>multi-expression</em></strong> = <em>expression</em> {"<strong>;</strong>" <em>expression</em> }</p>
@@ -1616,7 +1616,7 @@ The assign operator <code class="blue">=</code> returns the value assigned to th
 </div>
 </div>
 <div class="paragraph">
-<p>An expression that contains <code class="blue">;</code> is called a <em>multi-expression</em> and each component expressione is called a <em>sub-expression</em>.</p>
+<p>An expression that contains <code class="blue">;</code> is called a <em>multi-expression</em> and each component expression is called a <em>sub-expression</em>.</p>
 </div>
 <div class="admonitionblock important">
 <table>
@@ -1648,7 +1648,7 @@ Technically <code class="blue">;</code> is not treated as a real operator. It ac
 <code class="green">6</code></p>
 </div>
 <div class="paragraph">
-<p>The value of each sub-expression is stored in the automatica variable <em>last</em>.</p>
+<p>The value of each sub-expression is stored in the automatic variable <em>last</em>.</p>
 </div>
 <div class="paragraph">
 <div class="title">Example</div>
@@ -1663,9 +1663,11 @@ Technically <code class="blue">;</code> is not treated as a real operator. It ac
 </div>
 <div class="paragraph">
 <div class="title">Examples</div>
-<p><code class="blue">5 but 2</code><br>
+<p><code>&gt;&gt;&gt;</code> <code class="blue">5 but 2</code><br>
-<code class="green">2</code><br>
+<code class="green">2</code></p>
-<code class="blue">x=2*3 but x-1</code><br>
+</div>
+<div class="paragraph">
+<p><code>&gt;&gt;&gt;</code> <code class="blue">x=2*3 but x-1</code><br>
 <code class="green">5</code>.</p>
 </div>
 <div class="paragraph">
@@ -1678,21 +1680,27 @@ Technically <code class="blue">;</code> is not treated as a real operator. It ac
 <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>
+<p>The value on the left side of <code class="blue">=</code> must be a variable identifier or an expression that evalutes to a variable. 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>
+<div class="title">Examples</div>
-<p><code>&gt;&gt;&gt;</code> <code class="blue">a=15+1</code>
+<p><code>&gt;&gt;&gt;</code> <code class="blue">a=15+1</code><br>
 <code class="green">16</code></p>
 </div>
+<div class="paragraph">
+<p><code>&gt;&gt;&gt;</code> <code class="blue">L=[1,2,3]; L[1]=5; L</code><br>
+<code class="green">[1, 5, 3]</code></p>
+</div>
 </div>
 <div class="sect2">
 <h3 id="_selector_operator"><a class="anchor" href="#_selector_operator"></a><a class="link" href="#_selector_operator">4.4. Selector operator <code class="blue">? : ::</code></a></h3>
 <div class="paragraph">
 <p>The <em>selector operator</em> is very similar to the <em>switch/case/default</em> statement available in many programming languages.</p>
 </div>
+<div class="exampleblock">
+<div class="title">Example 13. Selector literal Syntax</div>
+<div class="content">
 <div class="paragraph">
-<div class="title">Selector literal Syntax</div>
 <p><em>selector-operator</em> = <em>select-expression</em> "<strong>?</strong>" <em>selector-case</em> { "<strong>:</strong>" <em>selector-case</em> } ["<strong>::</strong>" <em>default-multi-expression</em>]<br>
 <em>selector-case</em> = [<em>match-list</em>] <em>case-value</em><br>
 <em>match-list</em> = "<strong>[</strong>" <em>item</em> {"<strong>,</strong>" <em>items</em>} "<strong>]</strong>"<br>
@@ -1701,6 +1709,8 @@ Technically <code class="blue">;</code> is not treated as a real operator. It ac
 <em>multi-expression</em> = <em>expression</em> { "<strong>;</strong>" <em>expression</em> }<br>
 <em>default-multi-expression</em> = <em>multi-expression</em></p>
 </div>
+</div>
+</div>
 <div class="paragraph">
 <p>In other words, the selector operator evaluates the <em>select-expression</em> on the left-hand side of the <code class="blue">?</code> symbol; it then compares the result obtained with the values listed in the <em>match-list</em>'s, from left to right. If the comparision finds a match with a value in a <em>match-list</em>, the associated <em>case-multi-expression</em> is evaluted, and its result will be the final result of the selection operation.</p>
 </div>
@@ -1765,8 +1775,8 @@ If the left variable is defined, the right expression is not evaluated at all.
 </div>
 <div class="paragraph">
 <div class="title">Examples</div>
-<p><code>&gt;&gt;&gt;</code> <code class="blue">var ?? (1+2)&#8217;<br>
+<p><code>&gt;&gt;&gt;</code> <code class="blue">var ?? (1+2)</code><br>
-[green]`3</code></p>
+<code class="green">3</code></p>
 </div>
 <div class="paragraph">
 <p><code>&gt;&gt;&gt;</code> <code class="blue">var</code><br>
@@ -1777,7 +1787,7 @@ If the left variable is defined, the right expression is not evaluated at all.
 <code class="green">3</code></p>
 </div>
 <div class="paragraph">
-<p><code>&gt;&gt;&gt;</code> <code class="blue">var</code>
+<p><code>&gt;&gt;&gt;</code> <code class="blue">var</code><br>
 <code class="green">3</code></p>
 </div>
 <div class="admonitionblock note">
@@ -2106,7 +2116,7 @@ These operators have a high priority, in particular higher than the operator <co
 <h2 id="_functions"><a class="anchor" href="#_functions"></a><a class="link" href="#_functions">6. Functions</a></h2>
 <div class="sectionbody">
 <div class="paragraph">
-<p>Functions in <em>Expr</em> are very similar to functions available in many programming languages. Actually, <em>Expr</em> supports two types of function, <em>expr-functions</em> and <em>go-functions</em>.</p>
+<p>Functions in <em>Expr</em> are very similar to functions available in many programming languages. Currently, <em>Expr</em> supports two types of function, <em>expr-functions</em> and <em>go-functions</em>.</p>
 </div>
 <div class="ulist">
 <ul>
@@ -2114,7 +2124,7 @@ These operators have a high priority, in particular higher than the operator <co
 <p><em>expr-functions</em> are defined using <em>Expr</em>'s syntax. They can be passed as arguments to other functions and can be returned from functions. Moreover, they bind themselves to the defining context, thus becoming closures.</p>
 </li>
 <li>
-<p><em>go-functions</em> are regular Golang functions callable from <em>Expr</em> expressions. They are defined in Golang source files called <em>modules</em> and compiled within the <em>Expr</em> package. To make Golang functions available in <em>Expr</em> contextes, it is required to <em>import</em> the module in which they are defined.</p>
+<p><em>go-functions</em> are regular Golang functions callable from <em>Expr</em> expressions. They are defined in Golang source files called <em>modules</em> and compiled within the <em>Expr</em> package. To make Golang functions available in <em>Expr</em> contextes, it is required to activate the builtin module or to load the plugin module in which they are defined.</p>
 </li>
 </ul>
 </div>
@@ -2123,20 +2133,14 @@ These operators have a high priority, in particular higher than the operator <co
 <div class="paragraph">
 <p>A function is identified and referenced by its name. It can have zero or more parameter. <em>Expr</em> functions also support optional parameters.</p>
 </div>
-<div class="olist arabic">
-<ol class="arabic">
-<li>
-<p>Expr&#8217;s function definition syntax</p>
-</li>
-</ol>
-</div>
 <div class="exampleblock">
+<div class="title">Example 14. Expr&#8217;s function definition syntax</div>
 <div class="content">
 <div class="paragraph">
-<p><strong><em>function-definition</em></strong> = <em>identifier</em> "<strong>=</strong>"  "<strong>func(</strong>" [<em>param-list</em>] "<strong>)</strong>"  "<strong>{</strong>" <em>multi-expression</em> "<strong>}</strong>"
+<p><strong><em>function-definition</em></strong> = <em>identifier</em> "<strong>=</strong>"  "<strong>func(</strong>" [<em>param-list</em>] "<strong>)</strong>"  "<strong>{</strong>" <em>multi-expression</em> "<strong>}</strong>"<br>
-<em>param_list</em> = <em>required-param-list</em> [ "<strong>,</strong>" <em>optional-param-list</em> ]
+<em>param_list</em> = <em>required-param-list</em> [ "<strong>,</strong>" <em>optional-param-list</em> ]<br>
-<em>required-param-list</em> = <em>identifier</em> { "<strong>,</strong>" <em>identifier</em> }
+<em>required-param-list</em> = <em>identifier</em> { "<strong>,</strong>" <em>identifier</em> }<br>
-<em>optional-param-list</em> = <em>optional-parm</em> { "<strong>,</strong>" <em>optional-param</em> }
+<em>optional-param-list</em> = <em>optional-parm</em> { "<strong>,</strong>" <em>optional-param</em> }<br>
 <em>optional-param</em> = <em>identifier</em> "<strong>=</strong>" <em>any-expr</em></p>
 </div>
 </div>
@@ -2200,7 +2204,7 @@ These operators have a high priority, in particular higher than the operator <co
 </div>
 <div id="footer">
 <div id="footer-text">
-Last updated 2024-06-21 09:06:12 +0200
+Last updated 2024-09-12 06:56:30 +0200
 </div>
 </div>
 </body>

function.go

@@ -348,8 +348,8 @@ func CallFunctionByArgs(parentCtx ExprContext, name string, args []any) (result
 	return
 }
 
-func CallFunctionByParams(parentCtx ExprContext, name string, params map[string]any) (result any, err error) {
+func CallFunctionByParams(parentCtx ExprContext, name string, actualParams map[string]any) (result any, err error) {
-	var actualParams map[string]any
+	//var actualParams map[string]any
 	if info, exists := GetFuncInfo(parentCtx, name); exists {
 		functor := info.Functor()
 		ctx := info.AllocContext(parentCtx)

iterator.go

@@ -33,6 +33,8 @@ type Iterator interface {
 
 type ExtIterator interface {
 	Iterator
+	Reset() error
+	Clean() error
 	HasOperation(name string) bool
 	CallOperation(name string, args map[string]any) (value any, err error)
 }

list-iterator.go

@@ -99,7 +99,9 @@ func (it *ListIterator) CallOperation(name string, args map[string]any) (v any,
 	case NextName:
 		v, err = it.Next()
 	case ResetName:
-		v, err = it.Reset()
+		err = it.Reset()
+	case CleanName:
+		err = it.Clean()
 	case IndexName:
 		v = int64(it.Index())
 	case CurrentName:
@@ -147,8 +149,12 @@ func (it *ListIterator) Count() int {
 	return it.count
 }
 
-func (it *ListIterator) Reset() (bool, error) {
+func (it *ListIterator) Reset() (error) {
 	it.index = it.start - it.step
 	it.count = 0
-	return true, nil
+	return nil
+}
+
+func (it *ListIterator) Clean() (error) {
+	return nil
 }

operand-iterator.go

@@ -92,6 +92,7 @@ func evalIterator(ctx ExprContext, opTerm *term) (v any, err error) {
 
 	if ds != nil {
 		var dc *dataCursor
+		dcCtx := ctx.Clone()
 		if initFunc, exists := ds[InitName]; exists && initFunc != nil {
 			var args []any
 			var resource any
@@ -109,9 +110,10 @@ func evalIterator(ctx ExprContext, opTerm *term) (v any, err error) {
 			if resource, err = initFunc.InvokeNamed(initCtx, InitName, actualParams); err != nil {
 				return
 			}
-			dcCtx := ctx.Clone()
 			exportObjects(dcCtx, initCtx)
 			dc = NewDataCursor(dcCtx, ds, resource)
+		} else {
+			dc = NewDataCursor(dcCtx, ds, nil)
 		}
 
 		v = dc

t_iterator_test.go

@@ -17,7 +17,7 @@ func TestIteratorParser(t *testing.T) {
 		/*   6 */ {`builtin "math.arith"; include "test-resources/iterator.expr"; it=$(ds,3); mul(it)`, int64(0), nil},
 		/*   7 */ {`builtin "math.arith"; include "test-resources/file-reader.expr"; it=$(ds,"test-resources/int.list"); mul(it)`, int64(12000), nil},
 		/*   8 */ {`include "test-resources/file-reader.expr"; it=$(ds,"test-resources/int.list"); it++; it.index`, int64(0), nil},
-		/*   9 */ {`include "test-resources/file-reader.expr"; it=$(ds,"test-resources/int.list"); it.clean`, true, nil},
+		/*   9 */ {`include "test-resources/file-reader.expr"; it=$(ds,"test-resources/int.list"); it.clean`, nil, nil},
 		/*  10 */ {`it=$(1,2,3); it++`, int64(1), nil},
 		/*  11 */ {`it=$(1,2,3); it++; it.reset; it++`, int64(1), nil},
 		/*  12 */ {`it=$([1,2,3,4],1); it++`, int64(2), nil},
@@ -25,8 +25,10 @@ func TestIteratorParser(t *testing.T) {
 		/*  14 */ {`it=$([1,2,3,4],1,3,2); it++; it++;`, int64(4), nil},
 		/*  15 */ {`it=$([1,2,3,4],1,2,2); it++; it++;`, nil, `EOF`},
 		/*  16 */ {`include "test-resources/filter.expr"; it=$(ds,10); it++`, int64(2), nil},
+		/*  17 */ {`it=$({"next":func(){5}}); it++`, int64(5), nil},
+		/*  18 */ {`it=$({"next":func(){5}}); it.clean`, nil, nil},
 	}
 
-	// runTestSuiteSpec(t, section, inputs, 11)
+	//runTestSuiteSpec(t, section, inputs, 18)
 	runTestSuite(t, section, inputs)
 }