simple base and derived class example [adding a pure virtual function]

Bjarne Stroustrup “Programming Principles and Practice Using C++”
Chapter 14 Drill 5
Using std_lib_facilities.h by Bjarne Stroustrup.

[code language=”cpp”]
// Philipp Siedler
// Bjarne Stroustrup’s PP
// Chapter 14 Drill 5

#include "std_lib_facilities.h"
using namespace std;

class B1
{
public:
virtual void vf() { cout << "B1::vf" << endl; }
void f() { cout << "B1::f" << endl; }
virtual void pvf() = 0;
};

class D1 : public B1
{
public:
void vf() { cout << "D1::vf" << endl; }
void f() { cout << "D1::f" << endl; }
void pvf() { cout << "D1::pvf" << endl; }
};

void call(B1& b1_ref) {
b1_ref.f();
b1_ref.vf();
b1_ref.pvf();
}

int main()
try
{
cout << "drill 1" << endl;
//B1 b1;
//b1.f();
//b1.vf();
cout << "not allowed, B1::pvf is a pure virtual function" << endl;

cout << "drill 2" << endl;
D1 d2;
d2.f();
d2.vf();
d2.pvf();

cout << "drill 3" << endl;
D1 d3;
call(d3);

keep_window_open();
}
catch (exception& e) {
cout << e.what() << endl;
return 1;
}
catch (…) {
cout << "Exiting" << endl;
return 2;
}
[/code]

Output:
drill 1
not allowed, B1::pvf is a pure virtual function
drill 2
D1::f
D1::vf
D1::pvf
drill 3
B1::f
D1::vf
D1::pvf
Please enter a character to exit

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