meta-reduce

reduce.cpp

#include <iostream>
#include <type_traits>


template<template<class, class> class Fun, class Head, class... Tail>
struct reduce: Fun<Head, reduce<Fun, Tail...>> {};

template<template<class, class> class Fun, class Head>
struct reduce<Fun, Head>: Head{};

template<class I1, class I2>
struct plus: std::integral_constant<int, I1::value+I2::value>{};

template<template<class, class> class Fun, int...Args>
struct int_reduce: reduce<Fun, std::integral_constant<int, Args>...>{};

int main() {
	std::cout << int_reduce<plus, 2, 4, -3, 7, 9, 11>::value << '\n';
}