update

Signed-off-by: YdrMaster <ydrml@hotmail.com>

Author: YdrMaster

exercises/15_class_derive/main.cpp

@@ -2,43 +2,45 @@
 
 // READ: 派生类 <https://zh.cppreference.com/w/cpp/language/derived_class>
 
+static int i = 0;
+
 struct X {
     int x;
 
     X(int x_) : x(x_) {
-        std::cout << "X(" << x << ')' << std::endl;
+        std::cout << ++i << ". " << "X(" << x << ')' << std::endl;
     }
     X(X const &other) : x(other.x) {
-        std::cout << "X(X const &) : x(" << x << ')' << std::endl;
+        std::cout << ++i << ". " << "X(X const &) : x(" << x << ')' << std::endl;
     }
     ~X() {
-        std::cout << "~X(" << x << ')' << std::endl;
+        std::cout << ++i << ". " << "~X(" << x << ')' << std::endl;
     }
 };
 struct A {
     int a;
 
     A(int a_) : a(a_) {
-        std::cout << "A(" << a << ')' << std::endl;
+        std::cout << ++i << ". " << "A(" << a << ')' << std::endl;
     }
-    A(A const &other) : A(other.a) {
-        std::cout << "A(A const &) : a(" << a << ')' << std::endl;
+    A(A const &other) : a(other.a) {
+        std::cout << ++i << ". " << "A(A const &) : a(" << a << ')' << std::endl;
     }
     ~A() {
-        std::cout << "~A(" << a << ')' << std::endl;
+        std::cout << ++i << ". " << "~A(" << a << ')' << std::endl;
     }
 };
 struct B : public A {
     X x;
 
     B(int b) : A(1), x(b) {
-        std::cout << "B(" << a << ", X(" << x.x << "))" << std::endl;
+        std::cout << ++i << ". " << "B(" << a << ", X(" << x.x << "))" << std::endl;
     }
     B(B const &other) : A(other.a), x(other.x) {
-        std::cout << "B(B const &) : A(" << a << "), x(X(" << x.x << "))" << std::endl;
+        std::cout << ++i << ". " << "B(B const &) : A(" << a << "), x(X(" << x.x << "))" << std::endl;
     }
     ~B() {
-        std::cout << "~B(" << a << ", X(" << x.x << "))" << std::endl;
+        std::cout << ++i << ". " << "~B(" << a << ", X(" << x.x << "))" << std::endl;
     }
 };
 
@@ -52,6 +54,7 @@ int main(int argc, char **argv) {
     static_assert(sizeof(A) == ?, "There is an int in A");
     static_assert(sizeof(B) == ?, "B is an A with an X");
 
+    i = 0;
     std::cout << std::endl
               << "-------------------------" << std::endl
               << std::endl;
@@ -65,5 +68,10 @@ int main(int argc, char **argv) {
     // THINK: 这样的代码是“安全”的吗？
     // NOTICE: 真实场景中不太可能出现这样的代码
 
+    i = 0;
+    std::cout << std::endl
+              << "-------------------------" << std::endl
+              << std::endl;
+
     return 0;
 }