improved usability of the list iterator

operator-builtin.go

@@ -4,6 +4,8 @@
 // operator-builtin.go
 package expr
 
+import "io"
+
 //-------- builtin term
 
 func newBuiltinTerm(tk *Token) (inst *term) {
@@ -18,17 +20,19 @@ func newBuiltinTerm(tk *Token) (inst *term) {
 
 func evalBuiltin(ctx ExprContext, self *term) (v any, err error) {
 	var childValue any
-	var it Iterator
 
 	if childValue, err = self.evalPrefix(ctx); err != nil {
 		return
 	}
 
 	count := 0
-	if isList(childValue) {
-		list, _ := childValue.(*ListType)
-		it := NewFlatArrayIterator(*list)
-		for moduleSpec, err1 := it.Next(); err1 == nil; moduleSpec, err1 = it.Next() {
+	if isString(childValue) {
+		module, _ := childValue.(string)
+		count, err = ImportInContextByGlobPattern(ctx, module)
+	} else {
+		var moduleSpec any
+		it := NewAnyIterator(childValue)
+		for moduleSpec, err = it.Next(); err == nil; moduleSpec, err = it.Next() {
 			if module, ok := moduleSpec.(string); ok {
 				if ImportInContext(ctx, module) {
 					count++
@@ -41,11 +45,9 @@ func evalBuiltin(ctx ExprContext, self *term) (v any, err error) {
 				break
 			}
 		}
-	} else if isString(childValue) {
-		module, _ := childValue.(string)
-		count, err = ImportInContextByGlobPattern(ctx, module)
-	} else {
-		err = self.errIncompatibleType(childValue)
+		if err == io.EOF {
+			err = nil
+		}
 	}
 	if err == nil {
 		v = count