gistfile1.cpp

/*
bind1 :: (a -> b) -> a -> b
bind1 f t0 = f t0
*/
template<typename R, typename F, typename T0>
struct bind1_impl {
    bind1_impl(F f,T0 t0):f(f),t0(t0){}
    template<typename... T>
    R operator()(T... t) {
        return static_cast<R>(f(t0, t...));
    }
    F f;
    T0 t0;
};
template<typename R, typename F, typename T0>
inline bind1_impl<R, F, T0> bind1(F f, T0 t0) {
    return bind1_impl<R, F, T0>(f, t0);
}


/*
apply_tuple f t = apply_impl f t 0 where
  apply_impl f t n | n == length t = f
  apply_impl f t n                = apply_impl (f (t !! n)) t (n+1)
*/
template<typename R, typename Tuple, int N = 0,
    bool = (std::tuple_size<Tuple>::value==N)>
struct apply_impl;

template<typename R, typename Tuple, int N>
struct apply_impl<R, Tuple, N, true> {
    template<typename F>
    static R apply(F f, Tuple const&) {
        return static_cast<R>(f());
    }
};
template<typename R, typename Tuple, int N, bool>
struct apply_impl {
    template<typename F>
    static R apply(F f, Tuple tuple) {
        return apply_impl<R, Tuple, N+1>
            ::template apply(bind1<R>(f, std::get<N>(tuple)), tuple);
    }
};
template<typename R, typename F, typename Tuple>
inline R apply_tuple(F f, Tuple tuple) {
    return apply_impl<R, Tuple>
        ::template apply(f, tuple);
}