ifndef SymbolAsString

sclass symbol_Tester {

  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 WeakHashMap<Symbol, Bool> symbol_map = newWeakHashMap();

endifndef

static Symbol symbol(S s) {

  ifdef SymbolAsString

  ret s;

  endifdef

  ifndef SymbolAsString

  if (s == null) null;

  synchronized(symbol_map) {

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

    O e = call(symbol_map, 'getEntry, symbol_Tester(s));

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

    if (sym == null)

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

    ret sym;

  }

  endifndef

}

static Symbol symbol(CharSequence s) {

  if (s == null) null;

  ifdef SymbolAsString

  ret str(s);

  endifdef

  ifndef SymbolAsString

  if (s instanceof Symbol) ret (Symbol) s;

  if (s instanceof S) ret symbol((S) s);

  ret symbol(str(s));

  endifndef

}