gistfile1.txt

tag tree_node<@K, @V> {
    empty;
    node(@K, @V, treemap<K, V>, treemap<K, V>);
}

type treemap<@K, @V> = @mutable tree_node<K, V>;

fn init<@K, @V>() -> treemap<K,V> { @mutable empty }

fn insert<@K, @V>(m : &treemap<K, V>, k : &K, v : &V) {
    alt m {
      @empty. {
        *m = node(@k, @v, @mutable empty, @mutable empty);
      }
      @node(@kk, _, _, _) {
        // We have to name left and right individually, because
        // otherwise the alias checker complains.
        if k < kk {
            alt m {
              @node(_, _, left, _) {
                insert(left, k, v);
              }
            }
        }
        else {
            alt m {
              @node(_, _, _, right) {
                insert(right, k, v);
              }
            }
        }
      }
    }
}