diff -r 6ce8cfa10a96 -r 2856c74e18ba src/cx/iterator.h
--- a/src/cx/iterator.h	Sat Jan 22 17:15:14 2022 +0100
+++ b/src/cx/iterator.h	Sat Jan 22 18:49:06 2022 +0100
@@ -57,16 +57,6 @@
  */
 struct cx_iterator_s {
     /**
-     * If the iterator is position-aware, contains the index of the element in the underlying collection.
-     * Otherwise, this field is usually uninitialized.
-     */
-    size_t index;
-    /**
-     * Internal data.
-     */
-    void *data;
-
-    /**
      * True iff the iterator points to valid data.
      */
     bool (*valid)(CxIterator const *) __attribute__ ((__nonnull__));
@@ -80,6 +70,29 @@
      * Advances the iterator.
      */
     void (*next)(CxIterator *) __attribute__ ((__nonnull__));
+
+    /**
+     * Handle for the current element, if required.
+     */
+    void *elem_handle;
+
+    /**
+     * Handle for the source collection, if any.
+     */
+    void *src_handle;
+
+    /**
+     * If the iterator is position-aware, contains the index of the element in the underlying collection.
+     * Otherwise, this field is usually uninitialized.
+     */
+    size_t index;
+
+    /**
+     * Users may set this to true, if the current element shall be removed from the underlying collection
+     * when the iterator advances.
+     * Has no effect on iterators that are not based on a collection.
+     */
+    bool remove;
 };
 
 /**