diff --git a/data-cursor.go b/data-cursor.go
index 97cba92..ea8283a 100644
--- a/data-cursor.go
+++ b/data-cursor.go
@@ -23,24 +23,36 @@ type dataCursor struct {
 	currentFunc Functor
 }
 
+func newDataCursor(ctx ExprContext) (dc *dataCursor) {
+	dc = &dataCursor{
+		index: -1,
+		ctx:   ctx.Clone(),
+	}
+	return
+}
+
 func (dc *dataCursor) String() string {
 	return "$(...)"
 }
 
 func (dc *dataCursor) Current() (item any, err error) { // must return io.EOF at the last item
-	if item, err = dc.currentFunc.Invoke(dc.ctx, currentName, []any{}); err == nil && item == nil {
+	ctx := cloneContext(dc.ctx)
+	if item, err = dc.currentFunc.Invoke(ctx, currentName, []any{}); err == nil && item == nil {
 		err = io.EOF
 	}
+	exportObjects(dc.ctx, ctx)
 	return
 }
 
 func (dc *dataCursor) Next() (item any, err error) { // must return io.EOF after the last item
-	if item, err = dc.nextFunc.Invoke(dc.ctx, nextName, []any{}); err == nil {
+	ctx := cloneContext(dc.ctx)
+	if item, err = dc.nextFunc.Invoke(ctx, nextName, []any{}); err == nil {
 		if item == nil {
 			err = io.EOF
 		} else {
 			dc.index++
 		}
+		exportObjects(dc.ctx, ctx)
 	}
 	return
 }
diff --git a/expr_test.go b/expr_test.go
index ad2f5b6..e1d0885 100644
--- a/expr_test.go
+++ b/expr_test.go
@@ -27,11 +27,22 @@ func TestExpr(t *testing.T) {
 	succeeded := 0
 	failed := 0
 
-	// inputs1 := []inputType{
-	// 	/*   1 */ {`0?{}`, nil, nil},
-	// }
+	inputs1 := []inputType{
+		/*   1 */ {`
+		ds={
+			"init":func(end){@end=end; @current=0 but true},
+			"current":func(){current},
+			"next":func(){
+				((next=current+1) <= end) ? [true] {@current=next but current} :: {nil}
+			}
+		};
+		it=$(ds,3);
+		it++;
+		it++
+`, int64(1), nil},
+	}
 
-	for i, input := range inputs {
+	for i, input := range inputs1 {
 		var expr Expr
 		var gotResult any
 		var gotErr error
diff --git a/operand-iterator.go b/operand-iterator.go
index 0546a35..5f062f6 100644
--- a/operand-iterator.go
+++ b/operand-iterator.go
@@ -77,10 +77,7 @@ func evalIterator(ctx ExprContext, self *term) (v any, err error) {
 		return
 	}
 
-	dc := &dataCursor{
-		index: -1,
-		ctx:   ctx.Clone(),
-	}
+	dc := newDataCursor(ctx)
 
 	if initFunc, exists := ds[initName]; exists && initFunc != nil {
 		var args []any
@@ -91,9 +88,12 @@ func evalIterator(ctx ExprContext, self *term) (v any, err error) {
 		} else {
 			args = []any{}
 		}
-		if dc.resource, err = initFunc.Invoke(dc.ctx, initName, args); err != nil {
+
+		initCtx := dc.ctx.Clone()
+		if dc.resource, err = initFunc.Invoke(initCtx, initName, args); err != nil {
 			return
 		}
+		exportObjects(dc.ctx, initCtx)
 	}
 
 	dc.nextFunc, _ = ds[nextName]