several changes:

1. moved scan/symbol.go to new package sym and adapted all files that reference Symbol type and its values.
2. new type interval defined by begin, end and step values.
3. replaced operator-range.go with operator-interval.go.
4. replaced range operator begin:end with begin..end..step.
5. new implementation of sub-collection extraction based on new interval literal.

types/array/array-type.go

@@ -18,7 +18,15 @@ func IsArray(v any) (ok bool) {
 	return ok
 }
 
-func NewArrayA(listAny ...any) (list *ArrayType) {
+func NewIntArrayA(listInt ...int) (aRef *ArrayType) {
+	a := make(ArrayType, len(listInt))
+	for i, v := range listInt {
+		a[i] = int64(v)
+	}
+	return &a
+}
+
+func NewArrayA(listAny ...any) (aRef *ArrayType) {
 	if listAny == nil {
 		listAny = []any{}
 	}