support bazel complie this project and format code.

learn_class/modern_cpp_30/compilercompute/IF.cpp

@@ -0,0 +1,43 @@
+//
+// 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;
+}