[c++] monad - fix

template<int n> struct Const {};
...
// compile Arg2 = getArg 1
template<>
struct Compile<Arg2> : GetArg<1> {};
...
template<class L, class R>
struct Compile<Times<L, R> > {
  int operator()(Args args)
  {
    return Bind<Compile<L>, Bind<Compile<R>, Return> > (
      Compile<L>(),
      [](int left) -> Bind<Compile<R>, Return> {
        return Bind<Compile<R>, Return>(
          Compile<R>(),
          [left](int right) -> Return {
            return Return(left * right);
          }
        );
      }
    )(args);
  }
};