IF.cpp

//
// Created by light on 19-12-28.
//

#include <iostream>

using namespace std;

// 使用template实现IF条件判断

template <bool cond, typename Then, typename Else> struct IF;

template <typename Then, typename Else> struct IF<true, Then, Else> {
  typedef Then result;
};

template <typename Then, typename Else> struct IF<false, Then, Else> {
  typedef Else result;
};

// 判断奇数与偶数
template <int N> struct isEven {
  static const auto RES = IF<N & 1 == 0, true_type, false_type>::result::value;
};

template <int nums1, int nums2> struct Add_ {
  static const int value = nums1 + nums2;
};

template <int nums1, int nums2> struct Sub_ {
  static const int value = nums1 - nums2;
};

// 加减
template <bool cond, int nums1, int nums2> struct addSub {
  static const auto RES =
      IF<cond, Add_<nums1, nums2>, Sub_<nums1, nums2>>::result::value;
};

int main() {
  cout << isEven<10>::RES << endl;
  cout << addSub<true, 10, 2>::RES << endl;
}