!7

sclass Symbol {

  S text;

  *() {}

  *(S *text, bool dummy) {} // weird signature to prevent accidental calling

  public int hashCode() { ret main.hashCode(text); }

  toString { ret text; }

  public bool equals(O o) {

    ret this == o;

  }

}

sclass SymbolTester {

  S text;

  *() {}

  *(S *text) {}

  public int hashCode() { ret main.hashCode(text); }

  public bool equals(O o) {

    ret o instanceof Symbol && eq(text, o/Symbol.text);

  }

}

static new WeakHashMap<Symbol, Bool> symbolMap;

static Symbol symbol(S s) {

  if (s == null) null;

  synchronized(symbolMap) {

    // This is a trick that works because of how WeakHashMap compares keys.

    SymbolTester test = new(s);

    //WeakHashMap2.Entry<Symbol, Bool> e = symbolMap.getEntry(test);

    //Symbol sym = e == null ? null : e.get();

    O e = call(symbolMap, 'getEntry, test);

    Symbol sym = e == null ? null : ((WeakReference<Symbol>) e).get();

    if (sym == null)

      symbolMap.put(sym = Symbol(s, false), Bool.TRUE);

    ret sym;

  }

}

p {

  S s1 = "a", s2 = lower("A");

  assertNotIdentical(s1, s2); // Now more clearly showing the improvement

  Symbol a = symbol(s1);

  Symbol a2 = symbol(s2);

  assertEquals("a", str(a));

  assertEquals("a", str(a2));

  assertIdentical(a, a2);

  Symbol b = symbol("b");

  assertEquals("b", str(b));

  print("OK");

}