#include <iostream>
using namespace std;

class CPolygon {
  protected:
    int width, height;
  public:
    void set_values (int a, int b)
      { width=a; height=b;}
  };

class CRectangle: public CPolygon {
  public:
    CRectangle() : width(3) {}
    int area ()
      { return (width * height); }
  };


Compile error:
$ g++ poly.cpp 
poly.cpp: In constructor ‘CRectangle::CRectangle()’:
poly.cpp:15: error: class ‘CRectangle’ does not have any field named ‘width’