Conditional Critical Regions: State sidebar

I'm going to try and explain this better and justify it in my next post, but here is the State Monad (ala Haskell) in C++11. I have to say, without C++11 this would be even more painful than it already is.

	namespace hask {
	struct Unit { };
	template<typename S>
	struct Stateful {
	template<typename V>
	struct Value
	{
	std::function<std::pair<S,V>(S)> runState;
	};
	};
	template<typename S, typename V>
	typename Stateful<S>::template Value<V> ret(const V& v)
	{
	decltype(ret<S>(v)) rv;
	rv.runState = [=](S s) { return std::make_pair(s, v); };
	return rv;
	}
	template<typename S>
	typename Stateful<S>::template Value<S> get()
	{
	Stateful<S>::Value<S> rv;
	rv.runState = [](S s) { return std::make_pair(s,s); };
	return rv;
	}
	template<typename S>
	typename Stateful<S>::template Value<Unit> put(const S& s)
	{
	Stateful<S>::Value<Unit> rv;
	rv.runState = [=](S ) { return std::make_pair(s, Unit()); };
	return rv;
	}
	template<typename S, typename A, typename R>
	typename Stateful<S>::template Value<R> bind(typename Stateful<S>::template Value<A> a,
	std::function<typename Stateful<S>::template Value<R> (typename A)> f)
	{
	Stateful<S>::Value<R> rv;
	rv.runState = [=](S init) -> std::pair<S,R>
	{
	std::pair<S, A> p = a.runState(init);
	Stateful<S>::Value<R> act2 = f(p.second);
	return act2.runState(p.first);
	};
	return rv;
	}
	template<typename S, typename A, typename R>
	typename Stateful<S>::template Value<R> seq(typename Stateful<S>::template Value<A> a, typename Stateful<S>::template Value<R> r)
	{
	return bind<S,A,R>(a, [=](A) { return r; });
	}
	template<typename S, typename V>
	typename Stateful<S>::template Value<V> lift0(std::function<V()> f)
	{
	Stateful<S>::Value<V> rv;
	rv.runState = [=](S s) { return std::make_pair(s, f()); };
	return rv;
	}
	}
	using namespace hask;
	Stateful<int>::template Value<int> getit = get<int>();
	std::function< decltype(hask::put<int>(0)) (int) > doit = [](int x) { return hask::put(x + 1); };
	Stateful<int>::Value<Unit> incrS = hask::bind<int, int, Unit>(getit, doit);
	std::cout << incrS.runState(7).first << std::endl;

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