-- Copyright 1993-1998, by the Cecil Project
-- Department of Computer Science and Engineering, University of Washington
-- See the LICENSE file for license information.

(--DOC

  `Dominant_union_find_set' is a subclass of `union_find_set' where its
  instances are known to always become the representative member of the 
  equivalence class.
--)

abstract object dominant_union_find_set[T <= union_find_set[T]]
		isa union_find_set[T];


method link_set(x@:`T <= dominant_union_find_set[T],
		y@:`T <= union_find_set[T]):T {
    y.parent := x;
    merge_set(x, y);
    x }

method link_set(x@:`T <= union_find_set[T],
		y@:`T <= dominant_union_find_set[T]):T {
    link_set(y, x) }

method link_set(x@:dominant_union_find_set[`T],
		y@:dominant_union_find_set[`T]):T {
    error("shouldn't have two different dominant ecr's!"); }