Linked-list: added support for operators '<<' and '>>'. Also fixed list insertion: ['x'] >> [1,2] must return [1,2,['x'], not [1,2,'x']; use $([]) to flat a list

iter-factory.go

@@ -11,6 +11,15 @@ import (
 	"git.portale-stac.it/go-pkg/expr/scan"
 )
 
+func NewFormalIterator(value any) (it kern.Iterator) {
+	if value == nil {
+		it = NewArrayIterator([]any{})
+	} else {
+		it = NewArrayIterator([]any{value})
+	}
+	return
+}
+
 func NewIterator(ctx kern.ExprContext, value any, ops []*scan.Term) (it kern.Iterator, err error) {
 	if value == nil {
 		return NewArrayIterator([]any{}), nil