persistable sclass ArrayMatrix<A> extends AbstractMatrix<A> {
  A[] data;
  
  *(int *w, int *h) { data = (A[]) new O[w*h]; }
  *(int *w, int *h, A[] *data) {}

  public A get(int x, int y) { ret data[y*w+x]; }
  public void set(int x, int y, A a) { data[y*w+x] = a; }
}