if1live/intlist_car_cdr.cpp

## intlist_car_cdr.cpp
/*
type list를 참조해서 만든 int list와 car, cdr
reference : http://coliru.stacked-crooked.com/a/0af9789bed2adaf7
*/
#include <type_traits>
#include <climits>

template<int... Items>
struct intlist;

template<typename intlist>
struct car;

template<int Head, int... Remainder>
struct car < intlist<Head, Remainder...> > {
	enum {
		value = Head
	};
};

template<>
struct car < intlist<> > {
	enum {
		value = INT_MAX
	};
};

static_assert(car<intlist<1, 2, 3>>::value == 1, "");
static_assert(car<intlist<>>::value == INT_MAX, "");

template<typename intlist>
struct cdr;

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


template<int Head>
struct cdr < intlist<Head> > {
	typedef intlist<> value;
};

static_assert(car<cdr<intlist<1, 2, 3>>::value>::value == 2, "");

static_assert(car<intlist<1>>::value == 1, "");
static_assert(std::is_same<cdr<intlist<1>>::value, intlist<>>::value == 1, "");


static_assert(car<intlist<1, 2, 3>>::value == 1, "");
static_assert(car<cdr<intlist<1, 2, 3>>::value>::value == 2, "");
static_assert(car<cdr<cdr<intlist<1, 2, 3>>::value>::value>::value == 3, "");
static_assert(car<cdr<cdr<cdr<intlist<1, 2, 3>>::value>::value>::value>::value == INT_MAX, "");
int main() {}
	/*
	type list를 참조해서 만든 int list와 car, cdr
	reference : http://coliru.stacked-crooked.com/a/0af9789bed2adaf7
	*/
	#include <type_traits>
	#include <climits>

	template<int... Items>
	struct intlist;

	template<typename intlist>
	struct car;

	template<int Head, int... Remainder>
	struct car < intlist<Head, Remainder...> > {
	enum {
	value = Head
	};
	};

	template<>
	struct car < intlist<> > {
	enum {
	value = INT_MAX
	};
	};

	static_assert(car<intlist<1, 2, 3>>::value == 1, "");
	static_assert(car<intlist<>>::value == INT_MAX, "");

	template<typename intlist>
	struct cdr;

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


	template<int Head>
	struct cdr < intlist<Head> > {
	typedef intlist<> value;
	};

	static_assert(car<cdr<intlist<1, 2, 3>>::value>::value == 2, "");

	static_assert(car<intlist<1>>::value == 1, "");
	static_assert(std::is_same<cdr<intlist<1>>::value, intlist<>>::value == 1, "");


	static_assert(car<intlist<1, 2, 3>>::value == 1, "");
	static_assert(car<cdr<intlist<1, 2, 3>>::value>::value == 2, "");
	static_assert(car<cdr<cdr<intlist<1, 2, 3>>::value>::value>::value == 3, "");
	static_assert(car<cdr<cdr<cdr<intlist<1, 2, 3>>::value>::value>::value>::value == INT_MAX, "");
	int main() {}