diff --git a/int-iterator.go b/int-iterator.go
index 6c7910b..434b60f 100644
--- a/int-iterator.go
+++ b/int-iterator.go
@@ -11,6 +11,7 @@ import (
 
 	"git.portale-stac.it/go-pkg/expr/kern"
 	"git.portale-stac.it/go-pkg/expr/types"
+	"git.portale-stac.it/go-pkg/expr/types/interval"
 )
 
 type IntIterator struct {
@@ -21,6 +22,16 @@ type IntIterator struct {
 	step  int64
 }
 
+func NewIntIteratorFromInterval(p *interval.IntervalType) (it *IntIterator, err error) {
+	b := p.Begin()
+	e := p.End()
+	s := p.Step()
+	if b > e {
+		s = -s
+	}
+	return NewIntIteratorA(b, e, s)
+}
+
 func NewIntIteratorA(args ...any) (it *IntIterator, err error) {
 	return NewIntIterator(args)
 }
diff --git a/operand-iterator.go b/operand-iterator.go
index 23068a5..a724d06 100644
--- a/operand-iterator.go
+++ b/operand-iterator.go
@@ -13,6 +13,7 @@ import (
 	"git.portale-stac.it/go-pkg/expr/sym"
 	"git.portale-stac.it/go-pkg/expr/types/array"
 	"git.portale-stac.it/go-pkg/expr/types/dict"
+	"git.portale-stac.it/go-pkg/expr/types/interval"
 	"git.portale-stac.it/go-pkg/expr/types/list"
 )
 
@@ -146,11 +147,13 @@ func evalIterator(ctx kern.ExprContext, opTerm *scan.Term) (v any, err error) {
 		if args, err = evalSiblings(ctx, opTerm.Children, nil); err == nil {
 			v = NewLinkedListIterator(ll, args)
 		}
-	} else if intVal, ok := firstChildValue.(int64); ok {
-		var args []any
-		if args, err = evalSiblings(ctx, opTerm.Children, intVal); err == nil {
-			v, err = NewIntIterator(args)
-		}
+	} else if intervalVal, ok := firstChildValue.(*interval.IntervalType); ok {
+		v, err = NewIntIteratorFromInterval(intervalVal)
+		// } else if intVal, ok := firstChildValue.(int64); ok {
+		// 	var args []any
+		// 	if args, err = evalSiblings(ctx, opTerm.Children, intVal); err == nil {
+		// 		v, err = NewIntIterator(args)
+		// 	}
 	} else if it, ok := firstChildValue.(kern.Iterator); ok {
 		v, err = NewIterIter(it, ctx, opTerm.Children[1:])
 	} else {
diff --git a/operand-selector-case.go b/operand-selector-case.go
index 314f23b..0bcba97 100644
--- a/operand-selector-case.go
+++ b/operand-selector-case.go
@@ -5,9 +5,6 @@
 package expr
 
 import (
-	"fmt"
-	"strings"
-
 	"git.portale-stac.it/go-pkg/expr/kern"
 	"git.portale-stac.it/go-pkg/expr/scan"
 	"git.portale-stac.it/go-pkg/expr/sym"
@@ -20,17 +17,17 @@ type selectorCase struct {
 	caseExpr   kern.Expr
 }
 
-func (sc *selectorCase) String() string {
-	var sb strings.Builder
-	if sc.filterList != nil {
-		sc.filterList.ToString(&sb)
-		sb.WriteByte(' ')
-	}
-	sb.WriteByte('{')
-	sb.WriteString(sc.caseExpr.String())
-	sb.WriteByte('}')
-	return sb.String()
-}
+// func (sc *selectorCase) String() string {
+// 	var sb strings.Builder
+// 	if sc.filterList != nil {
+// 		sc.filterList.ToString(&sb)
+// 		sb.WriteByte(' ')
+// 	}
+// 	sb.WriteByte('{')
+// 	sb.WriteString(sc.caseExpr.String())
+// 	sb.WriteByte('}')
+// 	return sb.String()
+// }
 
 func newSelectorCaseTerm(row, col int, filterList *scan.Term, caseExpr kern.Expr) *scan.Term {
 	tk := scan.NewValueToken(row, col, sym.SymSelectorCase, "", &selectorCase{filterList: filterList, caseExpr: caseExpr})
@@ -46,9 +43,14 @@ func newSelectorCaseTerm(row, col int, filterList *scan.Term, caseExpr kern.Expr
 
 // -------- eval selector case
 func evalSelectorCase(ctx kern.ExprContext, opTerm *scan.Term) (v any, err error) {
-	var ok bool
-	if v, ok = opTerm.Value().(*selectorCase); !ok {
-		err = fmt.Errorf("selector-case expected, got %T", opTerm.Value())
-	}
+	v, _ = opTerm.Value().(*selectorCase)
 	return
 }
+
+// func evalSelectorCase(ctx kern.ExprContext, opTerm *scan.Term) (v any, err error) {
+// 	var ok bool
+// 	if v, ok = opTerm.Value().(*selectorCase); !ok {
+// 		err = fmt.Errorf("selector-case expected, got %T", opTerm.Value())
+// 	}
+// 	return
+// }
diff --git a/operator-interval.go b/operator-interval.go
index 670d4de..41520fe 100644
--- a/operator-interval.go
+++ b/operator-interval.go
@@ -88,9 +88,9 @@ func checkIntervalComponent(t kern.Term, value any) (component int64, err error)
 	return
 }
 
-func errIntervalInvalidSpecification(t kern.Term) error {
-	return t.Errorf("invalid %s specification", interval.TypeName)
-}
+// func errIntervalInvalidSpecification(t kern.Term) error {
+// 	return t.Errorf("invalid %s specification", interval.TypeName)
+// }
 
 func errIntervalUnexpectedExpression(t *scan.Term) error {
 	return t.Errorf("unexpected %s expression", interval.TypeName)
diff --git a/parser.go b/parser.go
index 1625026..0fc721a 100644
--- a/parser.go
+++ b/parser.go
@@ -173,33 +173,28 @@ func (parser *parser) parseList(scanner *scan.Scanner, ctx parserContext, termSy
 	itemExpected := false
 	itemCtx := remFlags(ctx, allowIndex)
 	for lastSym != termSym && lastSym != sym.SymEos {
-		// zeroRequired := scanner.Current().Sym == sym.SymDoubleDot
 		var itemTree *scan.Ast
 		if itemTree, err = parser.parseItem(scanner, itemCtx, sym.SymComma, termSym); err == nil {
 			root := itemTree.Root()
 			if root != nil {
-				if hasFlag(ctx, allowIndex) && root.Symbol() == sym.SymDoubleDot {
-					changeColonToInterval(root)
+				if root.Symbol() == sym.SymDoubleDot {
+					if hasFlag(ctx, allowIndex) {
+						changeColonToInterval(root)
+					} else {
+						// err = root.Errorf("unexpected range expression")
+						err = errIntervalUnexpectedExpression(root)
+						break
+					}
 				}
-				if !hasFlag(ctx, allowIndex) && root.Symbol() == sym.SymInterval {
-					// err = root.Errorf("unexpected range expression")
-					err = errIntervalUnexpectedExpression(root)
-					break
-				}
-				args = append(args, root)
-				// if hasFlag(ctx, allowIndex) && root.Symbol() == sym.SymInterval && 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")
-				// 		err = errIntervalInvalidSpecification(root)
-				// 		break
-				// 	}
-				// 	zeroTk := scan.NewValueToken(root.Tk.Row(), root.Tk.Col(), sym.SymInteger, "0", int64(0))
-				// 	zeroTerm := scan.NewTerm(zeroTk)
-				// 	zeroTerm.SetParent(root)
-				// 	root.Children[0] = zeroTerm
+				// if hasFlag(ctx, allowIndex) && root.Symbol() == sym.SymDoubleDot {
+				// 	changeColonToInterval(root)
 				// }
+				// if !hasFlag(ctx, allowIndex) && root.Symbol() == sym.SymInterval {
+				// 	// err = root.Errorf("unexpected range expression")
+				// 	err = errIntervalUnexpectedExpression(root)
+				// 	break
+				// }
+				args = append(args, root)
 			} else if itemExpected {
 				prev := scanner.Previous()
 				err = prev.ErrorExpectedGot("list-item")
diff --git a/t_builtin-iterator_test.go b/t_builtin-iterator_test.go
index 37d738a..27d9c93 100644
--- a/t_builtin-iterator_test.go
+++ b/t_builtin-iterator_test.go
@@ -14,7 +14,7 @@ func TestFuncRun(t *testing.T) {
 	inputs := []inputType{
 		/*   1 */ {`builtin "iterator"; it=$(1,2,3); run(it)`, nil, nil},
 		/*   2 */ {`builtin "iterator"; run($(1,2,3), func(index,item){item+10})`, nil, nil},
-		/*   3 */ {`builtin "iterator"; run($(4), func(index,item){status=status+item; true}, {"status":0})`, int64(6), nil},
+		/*   3 */ {`builtin "iterator"; run($(..4), func(index,item){status=status+item; true}, {"status":0})`, int64(6), nil},
 		/*   4 */ {`builtin ["iterator", "fmt"]; run($(1,2,3), func(index,item){println(item+10)})`, nil, nil},
 		/*   5 */ {`builtin "iterator"; run(nil)`, nil, `paramter "iterator" must be an iterator, passed <nil> [nil]`},
 		/*   6 */ {`builtin "iterator"; run($(1,2,3), nil)`, nil, nil},
@@ -26,6 +26,6 @@ func TestFuncRun(t *testing.T) {
 
 	//t.Setenv("EXPR_PATH", ".")
 
-	// runTestSuiteSpec(t, section, inputs, 3)
+	// RunTestSuiteSpec(t, section, inputs, 3)
 	RunTestSuite(t, section, inputs)
 }
diff --git a/t_common_test.go b/t_common_test.go
index d763b1d..499750f 100644
--- a/t_common_test.go
+++ b/t_common_test.go
@@ -131,7 +131,7 @@ func doTest(t *testing.T, ctx kern.ExprContext, section string, input *inputType
 				good = false
 			}
 		} else {
-			t.Errorf(">>>%s/%d: `%s` -> got-err = <nil>, expected-err = %v [%s]", section, count, input.source, input.wantResult, kern.TypeName(input.wantResult))
+			t.Errorf(">>>%s/%d: `%s` -> result = %v [%s], got-err = <nil>, expected-err = %v", section, count, input.source, gotResult, kern.TypeName(gotResult), wantErr)
 			good = false
 		}
 	}
diff --git a/t_context_test.go b/t_context_test.go
index 08a0422..727ea77 100644
--- a/t_context_test.go
+++ b/t_context_test.go
@@ -83,7 +83,7 @@ func TestList(t *testing.T) {
 
 	inputs := []inputType{
 		/*  1 */ {`$$(5)`, list.NewLinkedListA(5), nil},
-		/*  2 */ {`$$($(2))`, list.NewLinkedListA(0, 1), nil},
+		/*  2 */ {`$$($(..2))`, list.NewLinkedListA(0, 1), nil},
 		/*  3 */ {`string(($$global).funcs.bool)`, `bool(value):boolean{}`, nil},
 	}
 
diff --git a/t_expr_test.go b/t_expr_test.go
index efe5f0e..2250914 100644
--- a/t_expr_test.go
+++ b/t_expr_test.go
@@ -31,8 +31,12 @@ func TestExpr(t *testing.T) {
 		/*  15 */ {`a=3; a*=2)+1; a`, nil, `[1:11] unexpected token ")"`},
 		/*  16 */ {`v=[2]; a=1; v[a-=1]=5; v[0]`, int64(5), nil},
 		/*  17 */ {`true ? {"a"} :: {"b"}`, "a", nil},
-		/*  18 */ {`$$`, dict.NewDict(map[any]any{"vars": dict.NewDict(nil), "funcs": dict.NewDict(nil)}), nil},
-		/*  19 */ {`
+		/*  18 */ {`2 ? {"a"}`, nil, `[1:2] no case catches the value (2) of the selection expression`},
+		/*  19 */ {`2 ? 5`, nil, "[1:6] expected `{`, got `5`"},
+		/*  20 */ {`a=2; ${a}`, int64(2), nil},
+		/*  21 */ {`$_=2; $_`, int64(2), nil},
+		/*  22 */ {`$$`, dict.NewDict(map[any]any{"vars": dict.NewDict(nil), "funcs": dict.NewDict(nil)}), nil},
+		/*  23 */ {`
 		ds={
 			"init":func(@end){@current=0 but true},
 			//"current":func(){current},
@@ -44,11 +48,9 @@ func TestExpr(t *testing.T) {
 		it++;
 		it++
 `, int64(1), nil},
-		/*  20 */ {`a=2; ${a}`, int64(2), nil},
-		/*  21 */ {`$_=2; $_`, int64(2), nil},
 	}
 	// t.Setenv("EXPR_PATH", ".")
 
-	// runTestSuiteSpec(t, section, inputs, 21)
+	// RunTestSuiteSpec(t, section, inputs, 19)
 	RunTestSuite(t, section, inputs)
 }
diff --git a/t_index_test.go b/t_index_test.go
index e45b3fe..c8b2ffb 100644
--- a/t_index_test.go
+++ b/t_index_test.go
@@ -41,10 +41,14 @@ func TestCollections(t *testing.T) {
 		/*  25 */ {`[<0,1,2,3,4>][0..]`, list.NewLinkedListA(0, 1, 2, 3, 4), nil},
 		/*  26 */ {`[<0,1,2,3,4>][0..-1..2]`, list.NewLinkedListA(0, 2), nil},
 		/*  27 */ {`[<0,1,2,3,4>][-1..0..2]`, list.NewLinkedListA(4, 2), nil},
+		/*  28 */ {`[-1..0..2]`, nil, `[1:8] unexpected interval expression`},
+		/*  29 */ {`"abcdef"['x'..]`, nil, `[1:14] interval expression expected integer, got string (x)`},
+		/*  30 */ {`"abcdef"[1+..]`, nil, `[1:12] infix operator "+" requires two non-nil operands, got 1`},
+		/*  31 */ {`"abcdef"[1..4+]`, nil, `[1:15] infix operator "+" requires two non-nil operands, got 1`},
 	}
 
 	t.Setenv("EXPR_PATH", ".")
 
-	// RunTestSuiteSpec(t, section, inputs, 27)
+	// RunTestSuiteSpec(t, section, inputs, 30)
 	RunTestSuite(t, section, inputs)
 }
diff --git a/t_iter-iter_test.go b/t_iter-iter_test.go
index 2d90709..dc0c9fa 100644
--- a/t_iter-iter_test.go
+++ b/t_iter-iter_test.go
@@ -13,10 +13,10 @@ import (
 func TestIterIterator(t *testing.T) {
 	section := "Iter-Iter"
 	inputs := []inputType{
-		/*   1 */ {`it=$(4); $$($(it) filter ${_}==100)`, list.NewLinkedListA(), nil},
-		/*   2 */ {`it=$(4); $$($(it, $_) filter ${_}==100)`, list.NewLinkedListA(), nil},
-		/*   3 */ {`it=$(4); $(it, 10+$_, last-1) digest ${_}`, int64(12), nil},
-		/*   4 */ {`f=func(n){last-n}; it=$(4); $(it, 10+$_, f(-1)) digest ${_}`, int64(14), nil},
+		/*   1 */ {`it=$(..4); $$($(it) filter ${_}==100)`, list.NewLinkedListA(), nil},
+		/*   2 */ {`it=$(..4); $$($(it, $_) filter ${_}==100)`, list.NewLinkedListA(), nil},
+		/*   3 */ {`it=$(..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)
diff --git a/t_iterator_test.go b/t_iterator_test.go
index eb90a1a..da4ac92 100644
--- a/t_iterator_test.go
+++ b/t_iterator_test.go
@@ -39,12 +39,15 @@ 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++`, array.NewArray([]any{int64(1), "one"}), nil},
-		/*  23 */ {`$$($(1,4,0))`, nil, `step cannot be zero`},
-		/*  24 */ {`$$($(1,4,-1))`, nil, `step cannot be negative when start < stop`},
-		/*  25 */ {`$$($(4,1,1))`, nil, `step cannot be positive when start > stop`},
+		/*  23 */ {`$$($(1..4..0))`, nil, `[1:11] invalid interval specification: step must be positive`},
+		/*  24 */ {`$$($(1..4..-1))`, nil, `[1:11] invalid interval specification: step must be positive`},
+		/*  25 */ {`$$($(4..1..1))`, list.NewLinkedListA(4, 3, 2), nil},
+		/*  26 */ {`it=$(1..5..2); it++`, int64(1), nil},
+		/*  27 */ {`it=$(1.5..5..2); it++`, nil, `[1:13] interval expression expected integer, got float (1.5)`},
+		/*  28 */ {`it=$(.."z"); it++`, nil, `[1:7] interval expression expected integer, got string (z)`},
 	}
 
-	// runTestSuiteSpec(t, section, inputs, 25)
+	// RunTestSuiteSpec(t, section, inputs, 27)
 	RunTestSuite(t, section, inputs)
 }
 
@@ -138,9 +141,9 @@ func TestFilterIterator(t *testing.T) {
 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 ${_}`, int64(2), nil},
+		/*   1 */ {`$(..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)
@@ -166,8 +169,8 @@ func TestMapIterator(t *testing.T) {
 	section := "Iterator-Map"
 	inputs := []inputType{
 		/*   1 */ {`$$([3,4,5] map ${_#})`, list.NewLinkedListA(1, 2, 3), nil},
-		/*   2 */ {`#$$($(10) map ${_})`, int64(10), nil},
-		/*   3 */ {`#$$($(10,0) map ${_})`, int64(10), nil},
+		/*   2 */ {`#$$($(..10) map ${_})`, int64(10), nil},
+		/*   3 */ {`#$$($(10..0) map ${_})`, int64(10), nil},
 		/*   4 */ {`builtin "os.file"; $$(fileLineIterator("test-file.txt") map ${__})`, list.NewLinkedListA(0, 1), nil},
 		/*   5 */ {`$$(["1", "2", "3"] map int())`, nil, `int(): too few params -- expected 1, got 0`},
 	}