alias operators: '<<' same as '<+', '>>' same as '+>'. Insert and append operation optimized with linked lists

kern/fraction-type.go

@@ -44,10 +44,11 @@ func MakeGeneratingFraction(s string) (f *FractionType, err error) {
 	if len(s) == 0 {
 		goto exit
 	}
-	if s[0] == '-' {
+	switch s[0] {
+	case '-':
 		sign = int64(-1)
 		s = s[1:]
-	} else if s[0] == '+' {
+	case '+':
 		s = s[1:]
 	}
 	//	if strings.HasSuffix(s, "()") {

kern/iterator.go

@@ -7,6 +7,7 @@ package kern
 import (
 	// "errors"
 	"fmt"
+	"slices"
 )
 
 // Operator names
@@ -50,3 +51,45 @@ func IsIterator(v any) (ok bool) {
 	_, ok = v.(Iterator)
 	return
 }
+
+type IteratorBase struct {
+	ItemIndex int64
+	ItemCount int64
+	current   any
+}
+
+func (it *IteratorBase) Current() (item any, err error) {
+	return it.current, nil
+}
+
+func (it *IteratorBase) Index() int64 {
+	return it.ItemIndex
+}
+
+func (it *IteratorBase) Count() int64 {
+	return it.ItemCount
+}
+
+func (it *IteratorBase) HasOperation(name string) bool {
+	return slices.Contains([]string{NextName, IndexName, CountName, CurrentName}, name)
+}
+
+func (it *IteratorBase) Clean() (err error) {
+	return
+}
+
+func (it *IteratorBase) Reset() (err error) {
+	it.ItemIndex = -1
+	it.ItemCount = 0
+	it.current = nil
+	return
+}
+
+func (it *IteratorBase) Increment() {
+	it.ItemIndex++
+	it.ItemCount++
+}
+
+func (it *IteratorBase) SetCurrent(v any) {
+	it.current = v
+}

kern/linked-list.go

@@ -0,0 +1,273 @@
+// simple-list project slist.go
+package kern
+
+import (
+	"fmt"
+)
+
+type ListNode struct {
+	data any
+	next *ListNode
+}
+
+func (node *ListNode) Next() *ListNode {
+	return node.next
+}
+
+func (self *ListNode) Data() any {
+	return self.data
+}
+
+type LinkedList struct {
+	count uint32
+	first *ListNode
+	last  *ListNode
+}
+
+func NewLinkedList() (list *LinkedList) {
+	list = &LinkedList{0, nil, nil}
+	return
+}
+
+func (ls *LinkedList) Len() uint32 {
+	return ls.count
+}
+
+func (ls *LinkedList) Empty() bool {
+	return ls.count == 0
+}
+
+func (ls *LinkedList) PushFront(data any) *ListNode {
+	ls.first = &ListNode{data, ls.first}
+	if ls.last == nil {
+		ls.last = ls.first
+	}
+	ls.count++
+	return ls.first
+}
+
+func (ls *LinkedList) SeqPushFront(data any) (result *LinkedList) {
+	switch seq := data.(type) {
+	case Iterator:
+		result = ls.IterPushFront(seq)
+	default:
+		ls.PushFront(data)
+		result = ls
+	}
+	return
+}
+
+func (ls *LinkedList) IterPushFront(it Iterator) *LinkedList {
+	for item, err1 := it.Next(); err1 == nil; item, err1 = it.Next() {
+		ls.PushFront(item)
+	}
+	return ls
+}
+
+func (ls *LinkedList) PushBack(data any) (node *ListNode) {
+	node = &ListNode{data, nil}
+	if ls.last != nil {
+		ls.last.next = node
+	}
+	ls.last = node
+	if ls.first == nil {
+		ls.first = node
+	}
+	ls.count++
+	return
+}
+
+func (ls *LinkedList) SeqPushBack(data any) (result *LinkedList) {
+	switch seq := data.(type) {
+	case Iterator:
+		result = ls.IterPushBack(seq)
+	default:
+		ls.PushBack(data)
+		result = ls
+	}
+	return
+}
+
+func (ls *LinkedList) IterPushBack(it Iterator) *LinkedList {
+	for item, err1 := it.Next(); err1 == nil; item, err1 = it.Next() {
+		ls.PushBack(item)
+	}
+	return ls
+}
+
+func (ls *LinkedList) FirstNode() *ListNode {
+	return ls.first
+}
+
+func (ls *LinkedList) First() (data any, err error) {
+	if ls.first != nil {
+		data = ls.first.data
+	} else {
+		err = errorListEmpty()
+	}
+	return
+}
+
+func (ls *LinkedList) LastNode() *ListNode {
+	return ls.last
+}
+
+func (ls *LinkedList) Last() (data interface{}, err error) {
+	if ls.last != nil {
+		data = ls.last.data
+	} else {
+		err = errorListEmpty()
+	}
+	return
+}
+
+func (ls *LinkedList) NodeAt(index uint32) (node *ListNode, err error) {
+	if ls.count == 0 {
+		err = errorListEmpty()
+	} else if index > ls.count {
+		err = errorOutOfRange()
+	} else if index == ls.count-1 {
+		node = ls.last
+	} else {
+		current := ls.first
+		for pos := uint32(0); pos < index; pos++ {
+			current = current.next
+		}
+		node = current
+	}
+	return
+}
+
+func (ls *LinkedList) At(index uint32) (data interface{}, err error) {
+	node, err := ls.NodeAt(index)
+	if err == nil {
+		data = node.data
+	}
+	return
+}
+
+func (ls *LinkedList) Insert(index uint32, data interface{}) *ListNode {
+	var prev *ListNode
+
+	prev = nil
+	current := ls.first
+	for pos := uint32(0); current != nil && pos < index; pos++ {
+		prev = current
+		current = current.next
+	}
+
+	node := &ListNode{data, current}
+
+	if prev != nil {
+		prev.next = node
+	}
+
+	if ls.first == current {
+		ls.first = node
+	}
+	if node.next == nil {
+		ls.last = node
+	}
+	ls.count++
+	return node
+}
+
+func (ls *LinkedList) PushBackStringArray(items []string) {
+	for _, v := range items {
+		ls.PushBack(v)
+	}
+}
+
+// type TraverseOperator func(index uint32, elem interface{}, userData interface{}) (err error)
+
+// func (self *LinkedList) Traverse(op TraverseOperator, user_data interface{}) (err error) {
+// 	index := uint32(0)
+// 	for current := self.first; current != nil; current = current.next {
+// 		err = op(index, current.data, user_data)
+// 		if err != nil {
+// 			break
+// 		}
+// 		index++
+// 	}
+// 	return
+// }
+
+// func (self *LinkedList) Traverse2(observer Observer, abortOnError bool) (err error) {
+// 	index := uint32(0)
+// 	for current := self.first; current != nil; current = current.next {
+// 		err = observer.Observe(current, index)
+// 		if err != nil && abortOnError {
+// 			break
+// 		}
+// 		index++
+// 	}
+// 	return
+// }
+
+type EqualFunc func(current, target any) bool
+
+func (ls *LinkedList) FindFirst(eqFunc EqualFunc, targetData any) (targetNode *ListNode) {
+	for current := ls.first; current != nil && targetNode == nil; current = current.next {
+		if eqFunc(current.data, targetData) {
+			targetNode = current
+		}
+	}
+	return
+}
+
+func (ls *LinkedList) FindNext(eqFunc EqualFunc, startNode *ListNode) (targetNode *ListNode) {
+	if startNode != nil {
+		for current := startNode.next; current != nil && targetNode == nil; current = current.next {
+			if eqFunc(current.data, startNode.Data()) {
+				targetNode = current
+			}
+		}
+	}
+	return
+}
+
+// type DataFeeder func(user_data interface{}) interface{}
+// type NodeObserver func(node *ListNode, index uint32, userData interface{})
+
+// func (self *LinkedList) FeedTail(feeder DataFeeder, feederUserData interface{}, observer NodeObserver, observerUserData interface{}) (count uint32) {
+// 	count = 0
+// 	for item := feeder(feederUserData); item != nil; item = feeder(feederUserData) {
+// 		// fmt.Println("Item", count, item)
+// 		node := self.PushBack(item)
+// 		if observer != nil {
+// 			observer(node, count, observerUserData)
+// 		}
+// 		count++
+// 	}
+// 	return
+// }
+
+// func (self *LinkedList) FeedTail2(feeder Feeder, observer Observer, abortOnError bool) (count uint32, err error) {
+// 	count = 0
+// 	// item := feeder.Next()
+// 	for item, err1 := feeder.Next(); item != nil; item, err1 = feeder.Next() {
+// 		if err1 != nil {
+// 			if err == nil {
+// 				err = err1
+// 			}
+// 			if abortOnError {
+// 				break
+// 			}
+// 		}
+// 		// fmt.Println("Item", count, item)
+// 		node := self.PushBack(item)
+// 		if observer != nil {
+// 			observer.Observe(node, count)
+// 		}
+// 		count++
+// 	}
+// 	return
+// }
+
+func errorListEmpty() error {
+	return fmt.Errorf("List is empty")
+}
+
+func errorOutOfRange() error {
+	return fmt.Errorf("Out of range")
+}

kern/list-type.go

@@ -50,13 +50,13 @@ func ListFromStrings(stringList []string) (list *ListType) {
 	return
 }
 
-func (dict *ListType) ToString(opt FmtOpt) (s string) {
+func (ls *ListType) ToString(opt FmtOpt) (s string) {
 	indent := GetFormatIndent(opt)
 	flags := GetFormatFlags(opt)
 
 	var sb strings.Builder
 	sb.WriteByte('[')
-	if len(*dict) > 0 {
+	if len(*ls) > 0 {
 		innerOpt := MakeFormatOptions(flags, indent+1)
 		nest := strings.Repeat("  ", indent+1)
 
@@ -64,7 +64,7 @@ func (dict *ListType) ToString(opt FmtOpt) (s string) {
 			sb.WriteByte('\n')
 			sb.WriteString(nest)
 		}
-		for i, item := range []any(*dict) {
+		for i, item := range []any(*ls) {
 			if i > 0 {
 				if flags&MultiLine != 0 {
 					sb.WriteString(",\n")
@@ -96,11 +96,11 @@ func (dict *ListType) ToString(opt FmtOpt) (s string) {
 	return
 }
 
-func (dict *ListType) String() string {
-	return dict.ToString(0)
+func (ls *ListType) String() string {
+	return ls.ToString(0)
 }
 
-func (dict *ListType) TypeName() string {
+func (ls *ListType) TypeName() string {
 	return "list"
 }
 

operator-cat.go

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

operator-context.go

@@ -5,6 +5,8 @@
 package expr
 
 import (
+	"io"
+
 	"git.portale-stac.it/go-pkg/expr/kern"
 	"git.portale-stac.it/go-pkg/expr/scan"
 )
@@ -23,8 +25,8 @@ func newContextTerm(tk *scan.Token) (inst *scan.Term) {
 
 func evalContextValue(ctx kern.ExprContext, opTerm *scan.Term) (v any, err error) {
 	var childValue any
-
 	var sourceCtx kern.ExprContext
+
 	if len(opTerm.Children) == 0 {
 		sourceCtx = ctx
 	} else if opTerm.Children[0].Symbol() == scan.SymVariable && opTerm.Children[0].Source() == "global" {
@@ -33,6 +35,8 @@ func evalContextValue(ctx kern.ExprContext, opTerm *scan.Term) (v any, err error
 		if dc, ok := childValue.(*dataCursor); ok {
 			sourceCtx = dc.ctx
 		}
+	} else {
+		return
 	}
 
 	if sourceCtx != nil {
@@ -53,6 +57,20 @@ func evalContextValue(ctx kern.ExprContext, opTerm *scan.Term) (v any, err error
 			}
 			v = d
 		}
+	} else if childValue != nil {
+		if it, ok := childValue.(kern.Iterator); ok {
+			var item any
+			values := kern.NewListA()
+			for item, err = it.Next(); err == nil; item, err = it.Next() {
+				values.AppendItem(item)
+			}
+			if err == io.EOF {
+				err = nil
+				v = values
+			}
+		} else {
+			err = opTerm.ErrIncompatiblePrefixPostfixType(childValue)
+		}
 	} else {
 		err = opTerm.ErrIncompatiblePrefixPostfixType(childValue)
 	}

operator-filter.go

@@ -6,7 +6,6 @@ package expr
 
 import (
 	"fmt"
-	"io"
 
 	"git.portale-stac.it/go-pkg/expr/kern"
 	"git.portale-stac.it/go-pkg/expr/scan"
@@ -25,9 +24,10 @@ func newFilterTerm(tk *scan.Token) (inst *scan.Term) {
 }
 
 func evalFilter(ctx kern.ExprContext, opTerm *scan.Term) (v any, err error) {
-	var leftValue, rightValue any
+	// var leftValue, rightValue any
+	var leftValue any
 	var it kern.Iterator
-	var item any
+	// var item any
 	var ok bool
 
 	if err = opTerm.CheckOperands(); err != nil {
@@ -44,31 +44,120 @@ func evalFilter(ctx kern.ExprContext, opTerm *scan.Term) (v any, err error) {
 		}
 	}
 
-	values := kern.NewListA()
-	for item, err = it.Next(); err == nil; item, err = it.Next() {
-		ctx.SetVar("_", item)
+	// values := kern.NewListA()
+	// for item, err = it.Next(); err == nil; item, err = it.Next() {
+	// 	ctx.SetVar("_", item)
+	// 	ctx.SetVar("__", it.Index())
+	// 	ctx.SetVar("_#", it.Count())
+	// 	if rightValue, err = opTerm.Children[1].Compute(ctx); err == nil {
+	// 		if success, valid := kern.ToBool(rightValue); valid {
+	// 			if success {
+	// 				values.AppendItem(item)
+	// 			}
+	// 		} else {
+	// 			err = fmt.Errorf("filter expression must return a boolean or a castable to boolean, got %v [%T]", rightValue, rightValue)
+	// 		}
+	// 	}
+	// 	ctx.DeleteVar("_#")
+	// 	ctx.DeleteVar("__")
+	// 	ctx.DeleteVar("_")
+	// 	if err != nil {
+	// 		break
+	// 	}
+	// }
+	// if err == io.EOF {
+	// 	err = nil
+	// }
+	// v = values
+
+	v = newFilerIterator(ctx, it, opTerm.Children[1])
+	return
+}
+
+const filterIteratorType = "filter"
+
+type filterIterator struct {
+	kern.IteratorBase
+	ctx   kern.ExprContext
+	itSrc kern.Iterator
+	expr  *scan.Term
+}
+
+func newFilerIterator(ctx kern.ExprContext, itSrc kern.Iterator, filterExpr *scan.Term) (it *filterIterator) {
+	it = &filterIterator{
+		IteratorBase: kern.IteratorBase{},
+		ctx:          ctx,
+		itSrc:        itSrc,
+		expr:         filterExpr,
+	}
+	it.IteratorBase.Reset()
+	return
+}
+
+func (it *filterIterator) TypeName() string {
+	return filterIteratorType
+}
+
+func (it *filterIterator) String() string {
+	return fmt.Sprintf("$(%s %s bool-expr)", it.itSrc, filterIteratorType)
+}
+
+func (it *filterIterator) Next() (item any, err error) {
+	var attempt, result any
+
+	ctx := it.ctx
+
+	for attempt, err = it.itSrc.Next(); err == nil; attempt, err = it.itSrc.Next() {
+		ctx.SetVar("_", attempt)
 		ctx.SetVar("__", it.Index())
 		ctx.SetVar("_#", it.Count())
-		if rightValue, err = opTerm.Children[1].Compute(ctx); err == nil {
-			if success, valid := kern.ToBool(rightValue); valid {
-				if success {
-					values.AppendItem(item)
-				}
-			} else {
-				err = fmt.Errorf("filter expression must return a boolean or a castable to boolean, got %v [%T]", rightValue, rightValue)
-			}
-		}
+		result, err = it.expr.Compute(ctx)
 		ctx.DeleteVar("_#")
 		ctx.DeleteVar("__")
 		ctx.DeleteVar("_")
+
+		if err == nil {
+			if success, valid := kern.ToBool(result); valid {
+				if success {
+					item = attempt
+					break
+				}
+			} else {
+				err = fmt.Errorf("filter expression must return a boolean or a castable to boolean, got %v [%T]", result, result)
+			}
+		}
 		if err != nil {
 			break
 		}
 	}
-	if err == io.EOF {
-		err = nil
+
+	it.SetCurrent(item)
+	return
+}
+
+// func (it *filterIterator) Reset() (err error) {
+// 	err = it.itLeft.Reset()
+// 	it.IteratorBase.Reset()
+// 	return
+// }
+
+func (it *filterIterator) CallOperation(name string, args map[string]any) (v any, err error) {
+	switch name {
+	case kern.NextName:
+		v, err = it.Next()
+	// case kern.ResetName:
+	// 	err = it.Reset()
+	// case kern.CleanName:
+	// 	err = it.Clean()
+	case kern.IndexName:
+		v = it.Index()
+	case kern.CurrentName:
+		v, err = it.Current()
+	case kern.CountName:
+		v = it.Count()
+	default:
+		err = kern.ErrNoOperation(name)
 	}
-	v = values
 	return
 }
 

operator-insert.go

@@ -31,6 +31,41 @@ func newAppendTerm(tk *scan.Token) (inst *scan.Term) {
 	}
 }
 
+func prependToList(ctx kern.ExprContext, opTerm *scan.Term, leftValue, rightValue any) (result any, err error) {
+	if list, ok := rightValue.(*kern.ListType); ok {
+		var it kern.Iterator
+		if it, ok = leftValue.(kern.Iterator); !ok {
+			if it, err = NewIterator(ctx, leftValue, nil); err != nil {
+				return
+			}
+		}
+
+		ls := kern.NewLinkedList()
+		ls.SeqPushBack(it)
+
+		newList := kern.ListType(nil)
+		if newSize := len(*list) + int(ls.Len()); newSize > cap(*list) {
+			newList = make([]any, 0, newSize)
+			for node := ls.FirstNode(); node != nil; node = node.Next() {
+				newList = append(newList, node.Data())
+			}
+		}
+		for _, item := range *list {
+			newList = append(newList, item)
+		}
+		result = &newList
+
+		// ***** EVENTUALMENTE ABILITARE LA MODIFICA DELLA VARIABILE
+		// ***** CON UN OPERATORE SPECIFICO
+		// if opTerm.Children[1].Symbol() == scan.SymVariable {
+		// 	ctx.UnsafeSetVar(opTerm.Children[1].Source(), result)
+		// }
+	} else {
+		err = opTerm.ErrIncompatibleTypes(leftValue, rightValue)
+	}
+	return
+}
+
 func evalPrepend(ctx kern.ExprContext, opTerm *scan.Term) (v any, err error) {
 	var leftValue, rightValue any
 
@@ -38,13 +73,39 @@ func evalPrepend(ctx kern.ExprContext, opTerm *scan.Term) (v any, err error) {
 		return
 	}
 
-	if kern.IsList(rightValue) {
-		list, _ := rightValue.(*kern.ListType)
-		newList := append(kern.ListType{leftValue}, *list...)
-		v = &newList
-		if opTerm.Children[1].Symbol() == scan.SymVariable {
-			ctx.UnsafeSetVar(opTerm.Children[1].Source(), v)
+	v, err = prependToList(ctx, opTerm, leftValue, rightValue)
+	return
+}
+
+func appendToList(ctx kern.ExprContext, opTerm *scan.Term, leftValue, rightValue any) (result any, err error) {
+	if list, ok := leftValue.(*kern.ListType); ok {
+		var it kern.Iterator
+		if it, ok = rightValue.(kern.Iterator); !ok {
+			if it, err = NewIterator(ctx, rightValue, nil); err != nil {
+				return
 			}
+		}
+
+		ls := kern.NewLinkedList()
+		ls.SeqPushBack(it)
+
+		newList := *list
+		if newSize := len(*list) + int(ls.Len()); newSize > cap(*list) {
+			newList = make([]any, 0, newSize)
+			for _, item := range *list {
+				newList = append(newList, item)
+			}
+		}
+		for node := ls.FirstNode(); node != nil; node = node.Next() {
+			newList = append(newList, node.Data())
+		}
+		result = &newList
+
+		// ***** EVENTUALMENTE ABILITARE LA MODIFICA DELLA VARIABILE
+		// ***** CON UN OPERATORE SPECIFICO
+		// if opTerm.Children[0].Symbol() == scan.SymVariable {
+		// 	ctx.UnsafeSetVar(opTerm.Children[0].Source(), result)
+		// }
 	} else {
 		err = opTerm.ErrIncompatibleTypes(leftValue, rightValue)
 	}
@@ -58,16 +119,8 @@ func evalAppend(ctx kern.ExprContext, opTerm *scan.Term) (v any, err error) {
 		return
 	}
 
-	if kern.IsList(leftValue) {
-		list, _ := leftValue.(*kern.ListType)
-		newList := append(*list, rightValue)
-		v = &newList
-		if opTerm.Children[0].Symbol() == scan.SymVariable {
-			ctx.UnsafeSetVar(opTerm.Children[0].Source(), v)
-		}
-	} else {
-		err = opTerm.ErrIncompatibleTypes(leftValue, rightValue)
-	}
+	v, err = appendToList(ctx, opTerm, leftValue, rightValue)
+
 	return
 }
 

operator-join.go

@@ -1,73 +0,0 @@
-// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
-// All rights reserved.
-
-// operator-join.go
-package expr
-
-import (
-	"fmt"
-	"io"
-
-	"git.portale-stac.it/go-pkg/expr/kern"
-	"git.portale-stac.it/go-pkg/expr/scan"
-)
-
-//-------- join term
-
-func newJoinTerm(tk *scan.Token) (inst *scan.Term) {
-	return &scan.Term{
-		Tk:       *tk,
-		Children: make([]*scan.Term, 0, 2),
-		Position: scan.PosInfix,
-		Priority: scan.PriIterOp,
-		EvalFunc: evalJoin,
-	}
-}
-
-func evalJoin(ctx kern.ExprContext, opTerm *scan.Term) (v any, err error) {
-	var leftValue, rightValue any
-	var itLeft, itRight kern.Iterator
-	var item any
-	var ok bool
-
-	if err = opTerm.CheckOperands(); err != nil {
-		return
-	}
-
-	if leftValue, err = opTerm.Children[0].Compute(ctx); err != nil {
-		return
-	}
-
-	if rightValue, err = opTerm.Children[1].Compute(ctx); err != nil {
-		return
-	}
-
-	if itLeft, ok = leftValue.(kern.Iterator); !ok {
-		if itLeft, err = NewIterator(ctx, leftValue, nil); err != nil {
-			return nil, fmt.Errorf("left operand of JOIN must be an iterable data-source; got %s", kern.TypeName(leftValue))
-		}
-	}
-
-	if itRight, ok = rightValue.(kern.Iterator); !ok {
-		if itRight, err = NewIterator(ctx, rightValue, nil); err != nil {
-			return nil, fmt.Errorf("right operand of JOIN must be an iterable data-source; got %s", kern.TypeName(rightValue))
-		}
-	}
-
-	values := kern.NewListA()
-	for _, it := range []kern.Iterator{itLeft, itRight} {
-		for item, err = it.Next(); err == nil; item, err = it.Next() {
-			values.AppendItem(item)
-		}
-	}
-	if err == io.EOF {
-		err = nil
-	}
-	v = values
-	return
-}
-
-// init
-func init() {
-	scan.RegisterTermConstructor(scan.SymKwJoin, newJoinTerm)
-}

operator-map.go

@@ -6,7 +6,6 @@ package expr
 
 import (
 	"fmt"
-	"io"
 
 	"git.portale-stac.it/go-pkg/expr/kern"
 	"git.portale-stac.it/go-pkg/expr/scan"
@@ -25,9 +24,10 @@ func newMapTerm(tk *scan.Token) (inst *scan.Term) {
 }
 
 func evalMap(ctx kern.ExprContext, opTerm *scan.Term) (v any, err error) {
-	var leftValue, rightValue any
+	// var leftValue, rightValue any
+	var leftValue any
 	var it kern.Iterator
-	var item any
+	// var item any
 	var ok bool
 
 	if err = opTerm.CheckOperands(); err != nil {
@@ -44,27 +44,28 @@ func evalMap(ctx kern.ExprContext, opTerm *scan.Term) (v any, err error) {
 		}
 	}
 
-	values := kern.NewListA()
-	for item, err = it.Next(); err == nil; item, err = it.Next() {
-		ctx.SetVar("_", item)
-		ctx.SetVar("__", it.Index())
-		ctx.SetVar("_#", it.Count())
-		if rightValue, err = opTerm.Children[1].Compute(ctx); err == nil {
-			values.AppendItem(rightValue)
-		}
-		ctx.DeleteVar("_#")
-		ctx.DeleteVar("__")
-		ctx.DeleteVar("_")
-		if err != nil {
-			break
-		}
-	}
-	if err == io.EOF {
-		err = nil
-	}
-	if err == nil {
-		v = values
-	}
+	// values := kern.NewListA()
+	// for item, err = it.Next(); err == nil; item, err = it.Next() {
+	// 	ctx.SetVar("_", item)
+	// 	ctx.SetVar("__", it.Index())
+	// 	ctx.SetVar("_#", it.Count())
+	// 	if rightValue, err = opTerm.Children[1].Compute(ctx); err == nil {
+	// 		values.AppendItem(rightValue)
+	// 	}
+	// 	ctx.DeleteVar("_#")
+	// 	ctx.DeleteVar("__")
+	// 	ctx.DeleteVar("_")
+	// 	if err != nil {
+	// 		break
+	// 	}
+	// }
+	// if err == io.EOF {
+	// 	err = nil
+	// }
+	// if err == nil {
+	// 	v = values
+	// }
+	v, err = NewIterIter(it, ctx, opTerm.Children[1:])
 	return
 }
 

operator-shift.go

@@ -39,7 +39,9 @@ func evalRightShift(ctx kern.ExprContext, opTerm *scan.Term) (v any, err error)
 		return
 	}
 
-	v, err = bitRightShift(opTerm, leftValue, rightValue)
+	if v, err = bitRightShift(opTerm, leftValue, rightValue); err != nil {
+		v, err = prependToList(ctx, opTerm, leftValue, rightValue)
+	}
 	return
 }
 
@@ -71,7 +73,9 @@ func evalLeftShift(ctx kern.ExprContext, opTerm *scan.Term) (v any, err error) {
 		return
 	}
 
-	v, err = bitLeftShift(opTerm, leftValue, rightValue)
+	if v, err = bitLeftShift(opTerm, leftValue, rightValue); err != nil {
+		v, err = appendToList(ctx, opTerm, leftValue, rightValue)
+	}
 	return
 }
 

scan/symbol-map.go

@@ -138,6 +138,7 @@ func init() {
 		SymKwMap:     {"map", SymClassOperator, PosInfix},
 		SymKwFilter:  {"filter", SymClassOperator, PosInfix},
 		SymKwDigest:  {"digest", SymClassOperator, PosInfix},
+		SymKwCat:     {"cat", SymClassOperator, PosInfix},
 		SymKwJoin:    {"join", SymClassOperator, PosInfix},
 		SymKwGroupBy: {"groupby", SymClassOperator, PosInfix},
 		SymKwFunc:    {"func(", SymClassDeclaration, PosPrefix},

scan/symbol.go

@@ -122,6 +122,7 @@ const (
 	SymKwMap
 	SymKwFilter
 	SymKwDigest
+	SymKwCat
 	SymKwGroupBy
 	SymKwJoin
 	SymKwNil
@@ -141,6 +142,7 @@ func init() {
 		"IN":      SymKwIn,
 		"INCLUDE": SymKwInclude,
 		"MAP":     SymKwMap,
+		"CAT":     SymKwCat,
 		"FILTER":  SymKwFilter,
 		"NOT":     SymKwNot,
 		"OR":      SymKwOr,

scan/term.go

@@ -15,9 +15,9 @@ type TermPriority uint32
 const (
 	PriNone TermPriority = iota
 	PriRange
-	PriIterOp // map, filter, digest, etc
 	PriBut
 	PriAssign
+	PriIterOp // map, filter, digest, etc
 	PriInsert
 	PriOr
 	PriAnd

t_builtin-os-file_test.go

@@ -33,13 +33,24 @@ func TestFuncOs(t *testing.T) {
 		/*  19 */ {`builtin "os.file"; it=fileLineIterator("test-file.txt"); string(it)`, `$(fileLineIterator@"test-file.txt")`, nil},
 		/*  20 */ {`builtin "os.file"; handle=fileOpen("/etc/hosts"); fileClose(handle); string(handle)`, `reader`, nil},
 		/*  21 */ {`builtin "os.file"; handle=fileCreate("/tmp/dummy"); fileClose(handle); string(handle)`, `writer`, nil},
-		/*  22 */ {`builtin "os.file"; it=fileByteIterator("test-file.txt"); string(it)`, `$(fileByteIterator@"test-file.txt")`, nil},
-		/*  23 */ {`builtin ["os.file", "string"]; it=fileByteIterator("test-file.txt"); char(it++)`, `u`, nil},
-		/*  24 */ {`builtin ["os.file", "string"]; it=fileByteIterator("test-file.txt"); it++; it.reset; char(it++)`, `u`, nil},
 	}
 
 	// t.Setenv("EXPR_PATH", ".")
 
-	runTestSuiteSpec(t, section, inputs, 24)
-	// runTestSuite(t, section, inputs)
+	// runTestSuiteSpec(t, section, inputs, 24)
+	runTestSuite(t, section, inputs)
+}
+
+func TestFuncOsByteIter(t *testing.T) {
+	section := "Builtin-OS-File-Byte-Iter"
+	inputs := []inputType{
+		/*   1 */ {`builtin "os.file"; it=fileByteIterator("test-file.txt"); string(it)`, `$(fileByteIterator@"test-file.txt")`, nil},
+		/*   2 */ {`builtin ["os.file", "string"]; it=fileByteIterator("test-file.txt"); char(it++)`, `u`, nil},
+		/*   3 */ {`builtin ["os.file", "string"]; it=fileByteIterator("test-file.txt"); it++; it.reset; char(it++)`, `u`, nil},
+	}
+
+	// t.Setenv("EXPR_PATH", ".")
+
+	// runTestSuiteSpec(t, section, inputs, 24)
+	runTestSuite(t, section, inputs)
 }

t_common_test.go

@@ -23,13 +23,19 @@ func runCtxTestSuiteSpec(t *testing.T, ctx kern.ExprContext, section string, inp
 	succeeded := 0
 	failed := 0
 	for _, count := range spec {
-		good := doTest(t, ctx, section, &inputs[count-1], count)
+		index := count - 1
+		if index >= 0 && index < len(inputs) {
+			good := doTest(t, ctx, section, &inputs[index], count)
 
 			if good {
 				succeeded++
 			} else {
 				failed++
 			}
+		} else {
+			t.Errorf("%s -- test count: %d, invalid index", section, count)
+			failed++
+		}
 	}
 	t.Logf("%s -- test count: %d, succeeded: %d, failed: %d", section, len(spec), succeeded, failed)
 }

t_funcs_test.go

@@ -54,8 +54,7 @@ func TestFuncs2(t *testing.T) {
 	inputs := []inputType{
 		/*   1 */ {`sum=func(a,b){a+b}; sum(1,2)`, int64(3), nil},
 		/*   2 */ {`sum=func(a,b){a+b}; sum(1)`, nil, `sum(): too few params -- expected 2, got 1`},
-		/*   3 */ {`["1", "2", "3"] map int()`, nil, `int(): too few params -- expected 1, got 0`},
-		/*   4 */ {`builtin "iterator"; times=func(a,b){a*b}; run($(["1", "2", "3"]), times)`, nil, `operator(): missing params -- a, b`},
+		/*   3 */ {`builtin "iterator"; times=func(a,b){a*b}; run($(["1", "2", "3"]), times)`, nil, `operator(): missing params -- a, b`},
 	}
 	// runTestSuiteSpec(t, section, inputs, 4)
 	runTestSuite(t, section, inputs)

t_iter-iter_test.go

@@ -11,16 +11,16 @@ import (
 )
 
 func TestIterIterator(t *testing.T) {
-	section := "Iterator"
+	section := "Iter-Iter"
 	inputs := []inputType{
-		/*   1 */ {`it=$(4); $(it) filter ${_}==100`, kern.NewListA(), nil},
-		/*   2 */ {`it=$(4); $(it, $_) filter ${_}==100`, kern.NewListA(), nil},
+		/*   1 */ {`it=$(4); $$($(it) filter ${_}==100)`, kern.NewListA(), nil},
+		/*   2 */ {`it=$(4); $$($(it, $_) filter ${_}==100)`, kern.NewListA(), nil},
 		/*   3 */ {`it=$(4); $(it, 10+$_, last-1) digest ${_}`, int64(12), nil},
 		/*   4 */ {`f=func(n){last-n}; it=$(4); $(it, 10+$_, f(-1)) digest ${_}`, int64(14), nil},
 	}
 
-	runTestSuiteSpec(t, section, inputs, 4)
-	// runTestSuite(t, section, inputs)
+	// runTestSuiteSpec(t, section, inputs, 4)
+	runTestSuite(t, section, inputs)
 }
 
 // func TestNewIterIterator(t *testing.T) {

t_iterator_test.go

@@ -35,17 +35,62 @@ func TestIteratorParser(t *testing.T) {
 		/*  20 */ {`it=$({1:"one",2:"two",3:"three"}, "default", "value"); it++`, "one", nil},
 		/*  21 */ {`it=$({1:"one",2:"two",3:"three"}, "desc", "key"); it++`, int64(3), nil},
 		/*  22 */ {`it=$({1:"one",2:"two",3:"three"}, "asc", "item"); it++`, kern.NewList([]any{int64(1), "one"}), nil},
-		/*  23 */ {`builtin "os.file"; fileLineIterator("test-file.txt") map ${__}`, kern.NewList([]any{int64(0), int64(1)}), nil},
-		/*  24 */ {`builtin "os.file"; #(fileLineIterator("test-file.txt") filter (#${_} == 2))`, int64(0), nil},
-		/*  25 */ {`builtin "os.file"; #(fileLineIterator("test-file.txt") filter (#${_} == 3))`, int64(2), nil},
-		/*  26 */ {`#($(10) map ${_})`, int64(10), nil},
-		/*  27 */ {`#($(10,0) map ${_})`, int64(10), nil},
-		/*  28 */ {`$(10) digest ${_}`, int64(9), nil},
-		/*  29 */ {`$(10,0) digest ${_}`, int64(1), nil},
-		/*  30 */ {`$(10,0,-2) digest ${_}`, int64(2), nil},
-		/*  31 */ {`[3,4,5] map ${_#}`, kern.NewList([]any{int64(1), int64(2), int64(3)}), nil},
 	}
 
-	// runTestSuiteSpec(t, section, inputs, 10)
+	// runTestSuiteSpec(t, section, inputs, 1)
+	runTestSuite(t, section, inputs)
+}
+
+func TestFilterIterator(t *testing.T) {
+	section := "Iterator-Filter"
+	inputs := []inputType{
+		/*   1 */ {`$$([1,2,3] filter $_%2==0)`, kern.NewList([]any{int64(2)}), nil},
+		/*   2 */ {`it = [1,2,3] filter $_%2!=1; $$(it)`, kern.NewList([]any{int64(2)}), nil},
+		/*   3 */ {`builtin "os.file"; #$$(fileLineIterator("test-file.txt") filter (#${_} == 2))`, int64(0), nil},
+		/*   4 */ {`builtin "os.file"; #$$(fileLineIterator("test-file.txt") filter (#${_} == 3))`, int64(2), nil},
+	}
+
+	// runTestSuiteSpec(t, section, inputs, 2)
+	runTestSuite(t, section, inputs)
+}
+
+func TestDigestIterator(t *testing.T) {
+	section := "Iterator-Digest"
+	inputs := []inputType{
+		/*   1 */ {`$(10) digest ${_}`, int64(9), nil},
+		/*   2 */ {`$(10,0) digest ${_}`, int64(1), nil},
+		/*   3 */ {`$(10,0,-2) digest ${_}`, int64(2), nil},
+	}
+
+	// runTestSuiteSpec(t, section, inputs, 2)
+	runTestSuite(t, section, inputs)
+}
+
+func TestCatIterator(t *testing.T) {
+	section := "Iterator-Cat"
+	inputs := []inputType{
+		/*   1 */ {`$$([1] cat [])`, kern.NewList([]any{int64(1)}), nil},
+		/*   2 */ {`$$([1] cat [2])`, kern.NewList([]any{int64(1), int64(2)}), nil},
+		/*   3 */ {`$$([1] cat nil)`, kern.NewList([]any{int64(1)}), nil},
+		/*   4 */ {`$$(nil cat [2])`, kern.NewList([]any{int64(2)}), nil},
+		/*   5 */ {`$$(nil cat nil)`, kern.NewList([]any{}), nil},
+		/*   6 */ {`$$(["a","b"] cat ["x"-true])`, nil, `[1:23] left operand 'x' [string] and right operand 'true' [bool] are not compatible with operator "-"`},
+	}
+
+	// runTestSuiteSpec(t, section, inputs, 6)
+	runTestSuite(t, section, inputs)
+}
+
+func TestMapIterator(t *testing.T) {
+	section := "Iterator-Map"
+	inputs := []inputType{
+		/*   1 */ {`$$([3,4,5] map ${_#})`, kern.NewList([]any{int64(1), int64(2), int64(3)}), nil},
+		/*   2 */ {`#$$($(10) map ${_})`, int64(10), nil},
+		/*   3 */ {`#$$($(10,0) map ${_})`, int64(10), nil},
+		/*   4 */ {`builtin "os.file"; $$(fileLineIterator("test-file.txt") map ${__})`, kern.NewList([]any{int64(0), int64(1)}), nil},
+		/*   5 */ {`$$(["1", "2", "3"] map int())`, nil, `int(): too few params -- expected 1, got 0`},
+	}
+
+	// runTestSuiteSpec(t, section, inputs, 2)
 	runTestSuite(t, section, inputs)
 }

t_list_test.go

@@ -54,10 +54,13 @@ func TestListParser(t *testing.T) {
 		/*  38 */ {`[0,1,2,3,4][3:-1]`, kern.NewListA(int64(3)), nil},
 		/*  30 */ {`[0,1,2,3,4][-3:-1]`, kern.NewListA(int64(2), int64(3)), nil},
 		/*  40 */ {`[0,1,2,3,4][0:]`, kern.NewListA(int64(0), int64(1), int64(2), int64(3), int64(4)), nil},
+		/*  41 */ {`[0] << $([1,2,3,4])`, kern.NewListA(int64(0), int64(1), int64(2), int64(3), int64(4)), nil},
+		/*  42 */ {`L=[]; [1] >> L; L`, kern.NewListA(), nil},
+		/*  43 */ {`L=[]; L << [1]; L`, kern.NewListA(), nil},
 	}
 
 	// t.Setenv("EXPR_PATH", ".")
 
-	// runTestSuiteSpec(t, section, inputs, 1)
+	// runTestSuiteSpec(t, section, inputs, 42)
 	runTestSuite(t, section, inputs)
 }

t_operator_test.go

@@ -43,49 +43,35 @@ func TestOperator(t *testing.T) {
 	runTestSuite(t, section, inputs)
 }
 
-func TestOperatorMap(t *testing.T) {
-	section := "Operator-Map"
+func TestOperatorInsert(t *testing.T) {
+	section := "Operator-Insert"
 	inputs := []inputType{
-		/*   1 */ {`a=1; --a`, int64(0), nil},
-		/*   2 */ {`[1,2,3] map var("_")`, kern.NewList([]any{int64(1), int64(2), int64(3)}), nil},
-		/*   3 */ {`[1,2,3] map $_`, kern.NewList([]any{int64(1), int64(2), int64(3)}), nil},
+		/*   1 */ {`["a", "b"] << nil`, kern.NewListA("a", "b"), nil},
+		/*   2 */ {`["a", "b"] << []`, kern.NewListA("a", "b"), nil},
+		/*   3 */ {`["a", "b"] << 3`, kern.NewListA("a", "b", int64(3)), nil},
+		/*   4 */ {`3 << ["a", "b"]`, nil, `[1:5] left operand '3' [integer] and right operand '["a", "b"]' [list] are not compatible with operator "<<"`},
+		/*   5 */ {`nil >> ["a", "b"]`, kern.NewListA("a", "b"), nil},
+		/*   6 */ {`[] >> ["a", "b"]`, kern.NewListA("a", "b"), nil},
+		/*   7 */ {`["a", "b"] << $([1,2,3])`, kern.NewListA("a", "b", int64(1), int64(2), int64(3)), nil},
+		/*   8 */ {`L=["a", "b"]; L << $([1,2,3])`, kern.NewListA("a", "b", int64(1), int64(2), int64(3)), nil},
+		/*   9 */ {`L=["a", "b"]; L << $([1,2,3]); L`, kern.NewListA("a", "b", int64(1), int64(2), int64(3)), nil},
+		/*  10 */ {`L << $([1,2,3])`, nil, `undefined variable or function "L"`},
 	}
 
-	// runTestSuiteSpec(t, section, inputs, 3)
-	runTestSuite(t, section, inputs)
-}
-
-func TestOperatorFilter(t *testing.T) {
-	section := "Operator-Filter"
-	inputs := []inputType{
-		/*   1 */ {`[1,2,3,4] filter ($_ % 2 == 0)`, kern.NewList([]any{int64(2), int64(4)}), nil},
-	}
-
-	// runTestSuiteSpec(t, section, inputs, 1)
+	// runTestSuiteSpec(t, section, inputs, 9)
 	runTestSuite(t, section, inputs)
 }
 
 func TestOperatorDigest(t *testing.T) {
 	section := "Operator-Digest"
 	inputs := []inputType{
-		/*   1 */ {`max=0; [2,3,1] digest max=(($_ > max) ? {$_} :: {max})`, int64(3), nil},
+		/*   1 */ {`max=0; [2,3,1] digest (max=(($_ > max) ? {$_} :: {max}))`, int64(3), nil},
 	}
 
 	// runTestSuiteSpec(t, section, inputs, 29)
 	runTestSuite(t, section, inputs)
 }
 
-func TestOperatorJoin(t *testing.T) {
-	section := "Operator-Join"
-	inputs := []inputType{
-		/*   1 */ {`["a","b"] join ["x"]`, kern.NewList([]any{"a", "b", "x"}), nil},
-		/*   2 */ {`["a","b"] join ["x"-true]`, nil, `[1:21] left operand 'x' [string] and right operand 'true' [bool] are not compatible with operator "-"`},
-	}
-
-	// runTestSuiteSpec(t, section, inputs, 2)
-	runTestSuite(t, section, inputs)
-}
-
 func TestOperatorGroupBy(t *testing.T) {
 	section := "Operator-GroupBy"
 	inputs := []inputType{
@@ -113,6 +99,6 @@ func TestOperatorGroupBy(t *testing.T) {
 			nil},
 	}
 
-	runTestSuiteSpec(t, section, inputs, 3)
-	// runTestSuite(t, section, inputs)
+	// runTestSuiteSpec(t, section, inputs, 3)
+	runTestSuite(t, section, inputs)
 }

t_symbol_test.go

@@ -32,15 +32,15 @@ func testStringEndingWithOperator(source string) bool {
 	return scan.StringEndsWithOperator(source)
 }
 
-func testStringArrayEndingWithOperatorSpec(t *testing.T, section string, inputs []inputType, spec ...int) {
-	for i := range spec {
-		if spec[i] < 1 || spec[i] > len(inputs) {
-			t.Errorf("Invalid test spec index: %d (must be between 1 and %d)", spec[i], len(inputs))
-			continue
-		}
-		doEndingTest(t, section, inputs[spec[i]-1], spec[i]-1)
-	}
-}
+// func testStringArrayEndingWithOperatorSpec(t *testing.T, section string, inputs []inputType, spec ...int) {
+// 	for i := range spec {
+// 		if spec[i] < 1 || spec[i] > len(inputs) {
+// 			t.Errorf("Invalid test spec index: %d (must be between 1 and %d)", spec[i], len(inputs))
+// 			continue
+// 		}
+// 		doEndingTest(t, section, inputs[spec[i]-1], spec[i]-1)
+// 	}
+// }
 
 func testStringArrayEndingWithOperator(t *testing.T, section string, inputs []inputType) {
 	for i, input := range inputs {