C++のテンプレートメタプログラミングでFIZZBUZZを書いてみた。

fizzbuzz.cpp

#include <iostream>
#include <string>

#define FIZZ "Fizz"
#define BUZZ "Buzz"
#define CRLF "\r\n";

template<int N>
struct num {
  static std::string value() {
    return (N%3==0 || N%5==0) ? "":std::to_string(N).c_str();
  }
};

template<int N>
struct buzz {
  static std::string value() {return "";}
};

template<>
struct buzz<0> {
  static std::string value() {return BUZZ;}
};

template<int N>
struct fizz {
  static std::string value() {return "";}
};

template <>
struct fizz<0> {
  static std::string value() {return FIZZ;}
};

template <int N>
struct check{
  static std::string value() {
    return fizz<N%3>::value() + buzz<N%5>::value() + num<N>::value();
  }
};

template <int N, int M>
struct loop {
  static std::string value() {
    std::string crlf = CRLF;
    std::string val = check<N>::value() + crlf + loop<N+1, M-1>::value();
    return val;
  }
};

template <int N>
struct loop<N, 0> {
  static std::string value() {
    return CRLF;
  }
};

int main()
{

  std::cout << loop<1, 100>::value() << std::endl;
  return 0;
}