diff -r 97df2e4c68fb -r 5c926801f052 src/tree.c
--- a/src/tree.c	Sun Feb 18 13:16:38 2024 +0100
+++ b/src/tree.c	Sun Feb 18 13:38:42 2024 +0100
@@ -109,17 +109,14 @@
     }
 
     // create a working stack
-    size_t work_cap = 32;
-    size_t work_size = 0;
-    void const **work = malloc(sizeof(void*) * work_cap);
-    #define work_add(node) cx_array_add(&work, &work_size, &work_cap, \
-        sizeof(void*), &(node), cx_array_default_reallocator)
+    cx_array_declare(void const*, work);
+    cx_array_initialize(work, 32);
 
     // add the children of root to the working stack
     {
         void *c = tree_children(root);
         while (c != NULL) {
-            work_add(c);
+            cx_array_simple_add(work, c);
             c = tree_next(c);
         }
     }
@@ -146,7 +143,7 @@
             // if children might contain the data, add them to the stack
             void *c = tree_children(node);
             while (c != NULL) {
-                work_add(c);
+                cx_array_simple_add(work, c);
                 c = tree_next(c);
             }
 
@@ -165,7 +162,6 @@
     }
 
     // free the working queue and return
-    #undef workq_add
     free(work);
     return ret;
 }
@@ -180,14 +176,6 @@
     return iter->node;
 }
 
-static void cx_tree_iter_stack_add(
-        struct cx_tree_iterator_s *iter,
-        void *node
-) {
-    cx_array_add(&iter->stack, &iter->depth, &iter->stack_capacity,
-        sizeof(void*), &node, cx_array_default_reallocator);
-}
-
 static void cx_tree_iter_next(void *it) {
     struct cx_tree_iterator_s *iter = it;
     // TODO: support mutating iterator
@@ -195,77 +183,28 @@
     // TODO: implement
 }
 
-
 CxTreeIterator cx_tree_iterator(
         void *root,
-        int passes,
+        bool visit_on_exit,
         ptrdiff_t loc_children,
         ptrdiff_t loc_next
 ) {
     CxTreeIterator iter;
     iter.loc_children = loc_children;
     iter.loc_next = loc_next;
-    iter.requested_passes = passes;
-
-    // invalidate iterator immediately when passes is invalid
-    if ((passes & (CX_TREE_ITERATOR_ENTER |
-                   CX_TREE_ITERATOR_NEXT_CHILD |
-                   CX_TREE_ITERATOR_EXIT)) == 0) {
-        iter.stack = NULL;
-        iter.node = NULL;
-        return iter;
-    }
+    iter.visit_on_exit = visit_on_exit;
 
     // allocate stack
     iter.stack_capacity = 16;
     iter.stack = malloc(sizeof(void *) * 16);
     iter.depth = 0;
 
-    // determine start
-    if ((passes & CX_TREE_ITERATOR_ENTER) == 0) {
-        // we have to skip the first "entering" passes
-        void *s = NULL;
-        void *n = root;
-        iter.counter = 0;
-        do {
-            iter.counter++;
-            iter.source = s;
-            iter.node = n;
-            cx_tree_iter_stack_add(&iter, n);
-            s = n;
-            n = tree_children(n);
-        } while (n != NULL);
-        // found a leaf node s (might be root itself if it has no children)
-
-        // check if there is a sibling
-        n = tree_next(s);
-
-        if (n == NULL) {
-            // no sibling found, exit back to parent node
-            // TODO: implement
-        } else {
-            // there is a sibling
-            if ((passes & CX_TREE_ITERATOR_EXIT) == 0) {
-                // no exit requested, conclude that only next_child is requested
-                iter.source = s;
-                iter.node = n;
-                iter.counter++;
-                iter.current_pass = CX_TREE_ITERATOR_NEXT_CHILD;
-            } else {
-                // exit requested, so we have found our first pass
-                // iter.node and iter.source are still correct
-                iter.current_pass = CX_TREE_ITERATOR_EXIT;
-            }
-        }
-    } else {
-        // enter passes are requested, we can start by entering the root node
-        iter.source = NULL;
-        iter.node = root;
-        iter.current_pass = CX_TREE_ITERATOR_ENTER;
-        iter.counter = 1;
-        iter.depth = 1;
-        iter.stack[0] = root;
-    }
+    // visit the root node
+    iter.node = root;
+    iter.counter = 1;
+    iter.depth = 1;
+    iter.stack[0] = root;
+    iter.exiting = false;
 
     // assign base iterator functions
     iter.base.mutating = false;