static WeakHashMap2 internPerProgram_map = new WeakHashMap2;

static S internPerProgram(S s) {
  if (s == null) null;
   synchronized(internPerProgram_map) {
    WeakHashMap2.Entry<S, Bool> e = internPerProgram_map.getEntry(s);
    S sym = e == null ? null : (S) e.get();
    if (sym == null)
      internPerProgram_map.put(sym = s, Bool.TRUE);
    ret sym;
  }
}