update

README.md

@@ -145,6 +145,7 @@ for(decl:col) {
 - [字面量、静态断言和成员函数说明符](./modern_C++_30/literalAssert)
 - [是不是应该返回对象？](./modern_C++_30/returnObj)
 - [编译期多态：泛型编程和模板入门](./modern_C++_30/compilerpoly)
+- [译期能做些什么？一个完整的计算世界](./modern_C++_30/compilercompute)
 - [SFINAE：不是错误的替换失败是怎么回事?](./modern_C++_30/SFINAE)
 - [constexpr：一个常态的世界](./modern_C++_30/constexpr)
 

modern_C++_30/compilercompute/IF.cpp

@@ -0,0 +1,54 @@
+//
+// 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;
+}

modern_C++_30/compilercompute/WhileLoop.cpp

@@ -0,0 +1,77 @@
+//
+// Created by light on 20-1-5.
+//
+
+#include <iostream>
+
+using namespace std;
+
+// 使用template实现while循环
+
+template<bool condition,
+        typename Body>
+struct WhileLoop;
+
+template<typename Body>
+struct WhileLoop<true, Body> {
+    typedef typename WhileLoop<
+            Body::cond_value,
+            typename Body::next_type>::type
+            type;
+};
+
+template<typename Body>
+struct WhileLoop<false, Body> {
+    typedef
+    typename Body::res_type type;
+};
+
+template<typename Body>
+struct While {
+    typedef typename WhileLoop<Body::cond_value, Body>::type type;
+};
+template<typename Body>
+using While_t = WhileLoop<Body::cond_value, Body>;
+
+namespace my {
+    template<class T, T v>
+    struct integral_constant {
+        static const T value = v;
+        typedef T value_type;
+        typedef integral_constant<T, v> type;
+    };
+}
+template<int result, int n>
+struct SumLoop {
+
+    // 循环的条件
+    static const bool cond_value =
+            n != 0;
+
+    // 循环后的结果
+    static const int res_value =
+            result;
+
+    // 循环时的状态
+    typedef my::integral_constant<
+            int, res_value>
+            res_type;
+
+    // 循环执行一次时的状态
+    typedef SumLoop<result + n, n - 1>
+            next_type;
+};
+
+template<int n>
+struct Sum {
+    typedef SumLoop<0, n> type;
+};
+
+template<int n>
+using Sum_t = SumLoop<0, n>;
+
+int main() {
+    cout << While<Sum<6>::type>::type::value << endl;
+    cout << While_t<Sum_t<6>>::type::value << endl;
+    return 0;
+}

modern_C++_30/compilercompute/factorial.cpp

@@ -0,0 +1,24 @@
+//
+// Created by light on 19-12-28.
+//
+
+#include <iostream>
+
+using namespace std;
+
+template<int n>
+struct factorial {
+    static_assert(n >= 0, "Arg must be non-negative");
+    static const int value = n * factorial<n - 1>::value;
+};
+
+template<>
+struct factorial<0> {
+    static const int value = 1;
+};
+
+int main() {
+
+    printf("%d\n", factorial<-1>::value);
+    return 0;
+}

modern_C++_30/compilercompute/fmap.cpp

@@ -0,0 +1,39 @@
+//
+// Created by light on 20-1-5.
+//
+
+#include <iostream>
+#include <vector>
+
+using namespace std;
+
+
+template<
+        template<typename, typename>
+        class OutContainer = vector,
+        typename F, class R>
+auto fmap(F &&f, R &&inputs) {
+    typedef decay_t<decltype(f(*inputs.begin()))> result_type;
+
+    OutContainer<result_type, allocator<result_type >> result;
+
+    for (auto &&item:inputs) {
+        result.push_back(f(item));
+    }
+    return result;
+}
+
+// 对每一个数进行加1操作
+int add_1(int x) {
+    return x + 1;
+}
+
+int main() {
+    vector<int> v{1, 2, 3, 4, 5};
+    auto result = fmap(add_1, v);
+
+    for (auto item:result)
+        cout << item << " ";
+    cout<<endl;
+    return 0;
+}