Merge pull request Mooophy#496 from eipi10ydz/master

add ex18.25.cpp

ch18/README.md

@@ -145,25 +145,7 @@ delete pb;//Ok, part of interface
 >define a virtual member named print and a virtual destructor.  From these base
 >classes we derive the following classes, each of which redefines the print function.
 
-```cpp
-class D1 : public Base1 {/* ... */};
-class D2 : public Base2 {/* ... */};
-class MI : public D1, public D2 {/* ... */};
-
-//Using the following pointers, determine which funciton is used in each call:
-
-Base1 *pb1 = new MI;
-Base2 *pb2 = new MI;
-D1 *pd1 =new MI;
-D2 *pd2 = new MI;
-```
-
-(a), (b), and (c) will all call the MI version of print.
-All of the pointer class types contain virtual versions of print so, they will look for derived definitions of print.
-
-(d) The MI destructor is called then the base1 destructor is called.
-(e) The MI destructor, then the D1 destructor, then the base 1 destructor is called.
-(f) The MI destructor, then the D2 destructor, then the Base2 destructor is called.
+[cpp](./ex18.25.cpp "Exercise 18.25")
 
 ## Exercise 18.26
 
@@ -319,4 +301,4 @@ protected:
     char cval;//need to qualify ambiguous with other cval.
 };
 class VMI : public Derived1, public Derived2 { };
-```
+```

ch18/ex18.25.cpp

@@ -0,0 +1,105 @@
+/***************************************************************************
+ *  @file       ex18.25.cpp
+ *  @author     eipi10
+ *  @date       15  Aug 2016
+ *  @remark     This code is for the exercises from C++ Primer 5th Edition
+ *  @note
+ ***************************************************************************/
+//
+// Exercise 18.25
+// Assume we have two base classes, Base1 and Base 2, each of which define a 
+// virtual member named print and a virtual destructor. From these base classes 
+// we derive the following classes, each of which redefines the print function.
+// Answer:
+// (a)MI
+// (b)MI
+// (c)MI
+// (d)MI, D2, Base2, D1, Base1
+// (e)MI, D2, Base2, D1, Base1
+// (f)MI, D2, Base2, D1, Base1
+// (d), (e), (f) will call all the destructor, for "Destructors are always 
+// invoked in the reverse order from which the constructors are run." in
+// Page 805
+
+// gcc 6.1.0 x86_64-pc-linux-gnu
+// results:
+// pb1 print...........
+// Print from MI
+// pd1 print...........
+// Print from MI
+// pd2 print...........
+// Print from MI
+// delete pb2...........
+// MI
+// D2
+// Base2
+// D1
+// Base1
+// delete pd1...........
+// MI
+// D2
+// Base2
+// D1
+// Base1
+// delete pd2...........
+// MI
+// D2
+// Base2
+// D1
+// Base1
+
+#include <iostream>
+
+struct Base1
+{
+	/* ... */
+	virtual void print(){std::cout << "Print from Base1" << std::endl;}
+	virtual ~Base1(){std::cout << "Base1" << std::endl;}
+};
+struct Base2
+{
+	/* ... */
+	virtual void print(){std::cout << "Print from Base2" << std::endl;}
+	virtual ~Base2(){std::cout << "Base2" << std::endl;}
+};
+
+struct D1 : public Base1 
+{
+	/* ... */
+	void print() override {std::cout << "Print from D1" << std::endl;}
+	~D1() override {std::cout << "D1" << std::endl;}
+};
+struct D2 : public Base2 
+{
+	/* ... */
+	void print() override {std::cout << "Print from D2" << std::endl;}
+	~D2() override {std::cout << "D2" <<std::endl;}
+};
+struct MI : public D1, public D2 
+{
+	/* ... */
+	void print() override {std::cout << "Print from MI" << std::endl;}
+	~MI() override {std::cout << "MI" << std::endl;}
+};
+
+//Using the following pointers, determine which funciton is used in each call:
+
+int main()
+{
+	Base1 *pb1 = new MI;
+	Base2 *pb2 = new MI;
+	D1 *pd1 =new MI;
+	D2 *pd2 = new MI;
+	std::cout << "pb1 print..........." << std::endl;
+	pb1 -> print();
+	std::cout << "pd1 print..........." << std::endl;
+	pd1 -> print();
+	std::cout << "pd2 print..........." << std::endl;
+	pd2 -> print();
+	std::cout << "delete pb2..........." << std::endl;
+	delete pb2;
+	std::cout << "delete pd1..........." << std::endl;
+	delete pd1;
+	std::cout << "delete pd2..........." << std::endl;
+	delete pd2;
+}