aa.h

// totest.cpp : 콘솔 응용 프로그램에 대한 진입점을 정의합니다.

#include <string>

constexpr unsigned short _make_16(unsigned char a, unsigned char b) {
	return ((unsigned short)((a & 0xff) | ((b & 0xff) << 8)));
}
constexpr unsigned char _lo_8(unsigned short a) {
	return ((unsigned char)(a & 0xff));
}
constexpr unsigned char _hi_8(unsigned short a) {
	return ((unsigned char)(a >> 8) & 0xff);
}

template <size_t I, size_t OFFSET>
struct tokenizer {
	constexpr static int find(int target, const char a[]) {
		return
			a[I] == ',' ?
				target == 0 ?
					_make_16(I + 1, OFFSET - I) :
				tokenizer<I - 1, I - 1>::find(target - 1, a)
				:
				tokenizer<I - 1, OFFSET>::find(target, a);
	}
};
template <size_t OFFSET>
struct tokenizer<0, OFFSET> {
	constexpr static int find(int target, const char a[]) {
		return _make_16(0, OFFSET + 1);
	}
};
template <size_t SIZE>
inline std::string nth_token(int target, const char(&a)[SIZE]) {
	int ret = tokenizer<SIZE - 2, SIZE - 2>::find(target, a);
	return std::string(a + _lo_8(ret), _hi_8(ret));
}

int main()
{
	int a = 5;

	printf("%s\n", nth_token(1, "AB,CD").c_str());

	printf("%d\n", foo(&a));

    return 0;
}