add Chapter08

Chapter08/tmpt_enable_if.cpp

@@ -0,0 +1,34 @@
+#include <cstdio>
+#include <type_traits>
+
+struct point { 
+    int x; 
+    int y; 
+
+    point operator+(const point& other) const { 
+        return point{x + other.x, y + other.y}; 
+    } 
+
+    void print() { 
+        printf("x = %d, y = %d\r\n", x, y); 
+    } 
+}; 
+
+template<typename T> 
+std::enable_if<std::is_arithmetic<T>::value, T>::type 
+add(T a, T b) { 
+   return a + b;  
+} 
+
+int main() { 
+
+    auto a = add(1, 2); // OK 
+    auto b = add(1.1, 2.1); // OK 
+
+    point p_a{1, 2};  
+    point p_b{2, 1};   
+    auto c = add(p_a, p_b); // compile-error 
+
+    return 0; 
+
+}