Calculate Average (C++ Template Metaprogramming)

average_cpp_tmp.cpp

#include <type_traits>
#include <cstdio>

template<int... Items>
struct intlist;

template<typename intlist, int I>
struct push_back;

template<int I, int Head, int... Remainder>
struct push_back<intlist<Head, Remainder...>, I> {
	typedef intlist<Head, Remainder..., I> value;
};

template<int I>
struct push_back<intlist<>, I> {
	typedef intlist<I> value;
};

typedef push_back<intlist<>, 1>::value push_back_1;
static_assert(std::is_same<push_back_1, intlist<1>>::value == 1, "");
typedef push_back<push_back_1, 2>::value push_back_2;
static_assert(std::is_same<push_back_2, intlist<1, 2>>::value == 1, "");


template<typename intlist>
struct length;

template<int Head, int... Remainder>
struct length< intlist<Head, Remainder...>> {
	enum {
		value = 1 + length<intlist<Remainder...>>::value
	};
};

template<>
struct length < intlist<> > {
	enum {
		value = 0
	};
};

static_assert(length<intlist<>>::value == 0, "");
static_assert(length<intlist<1>>::value == 1, "");
static_assert(length<intlist<1, 2>>::value == 2, "");

template<typename intlist>
struct sum;

template<int Head, int... Remainder>
struct sum < intlist<Head, Remainder...> > {
	enum {
		value = Head + sum<intlist<Remainder...>>::value
	};
};
template<>
struct sum < intlist<> > {
	enum {
		value = 0
	};
};

static_assert(sum<intlist<>>::value == 0, "");
static_assert(sum<intlist<1>>::value == 1, "");
static_assert(sum<intlist<1, 2>>::value == 3, "");

template<int Number, int Size>
struct divide {
	enum {
		value = Number / Size,
		remainder = Number % Size
	};

	static float get_value() {
		float val = value + (float)(remainder) / Size;
		return val;
	}
};

static_assert(divide<9, 4>::value == 2, "");
static_assert(divide<9, 4>::remainder == 1, "");

namespace AverageFunction {
	// 정수 리스트에 값을 집어넣은 다음 평균을 구하는 코드(?)
	typedef intlist<> empty;
	typedef push_back<empty, 1>::value list_1;
	typedef push_back<list_1, 2>::value list_2;
	typedef push_back<list_2, 4>::value list_3;
	typedef push_back<list_3, 8>::value list_4;
	typedef push_back<list_4, 16>::value target_list;

	const int list_size = length<target_list>::value;
	const int list_sum = sum<target_list>::value;

	const float retval = divide<list_sum, list_size>::get_value();
}

int main() {
	printf("Average = %f\n", AverageFunction::retval);
	return 0;
}