/*
   I've got a binary tree full of data, and some other data
   structure that is supposed to contain the same data in
   the same order. I want to make sure of that.

   Easy. I can do an in-order enumeration of the tree, and
   at each node get the next data item from the other data
   structure and compare.
*/

manifest { t_data = 0, t_left = 1, t_right = 2, sizeof_t = 3 }

let internal_compare(ptr, other) be
     // ptr is the pointer to the root node of the tree,
     // other is some kind of enumerator for the other structure
{ let ok;
  if ptr = nil then
    resultis true;
  ok := internal_compare(ptr ! t_left, other);
  if not ok then
    resultis false;
  if not equal(ptr ! t_data, getnext(other)) then
    resultis false;
  ok := internal_compare(ptr ! t_right, other);
  resultis ok }

let compare(tree, otherthing) be
{ let enum = enumerator(otherthing);
  let ok = internal_compare(tree, enum);
  if not ok then
    resultis false;
  if not empty(enum) then
    resultis false;
  resultis true }