module10.lst

来自「Programs for the book Advanced Engineeri」· LST 代码 · 共 1,125 行 · 第 1/2 页

                     " pounds.\n"; 
  cout << "It has a range of " << 
           semi.range() << " miles.\n"; 
  cout << "To go " << dist << " miles semi needs " << 
          dist / semi.get_mpg() << 
          " gallons of fuel.\n\n";   
       
  cout << "Pickup can carry " << pickup.get_cargocap() << 
                     " pounds.\n"; 
  cout << "It has a range of " << 
           pickup.range() << " miles.\n"; 
  cout << "To go " << dist << " miles pickup needs " << 
           dist / pickup.get_mpg() << 
           " gallons of fuel.\n";  
 
  return 0; 
}

listing 12
// Create an off-road vehicle class 
class OffRoad : public Vehicle { 
  int groundClearance; // ground clearance in inches 
public: 
  // ... 
};

listing 13
// A multilevel hierarchy. 
 
#include <iostream> 
#include <cstring> 
using namespace std; 
 
// A class for two-dimensional objects. 
class TwoDShape { 
  // these are private 
  double width; 
  double height; 
public: 
 
  // Default constructor. 
  TwoDShape() { 
    width = height = 0.0; 
  } 
 
  // Constructor for TwoDShape. 
  TwoDShape(double w, double h) { 
    width = w; 
    height = h; 
  } 
 
  // Construct object with equal width and height. 
  TwoDShape(double x) { 
    width = height = x; 
  } 
 
  void showDim() { 
    cout << "Width and height are " << 
             width << " and " << height << "\n"; 
  } 
 
  // accessor functions 
  double getWidth() { return width; } 
  double getHeight() { return height; } 
  void setWidth(double w) { width = w; } 
  void setHeight(double h) { height = h; } 
}; 
 
// Triangle is derived from TwoDShape. 
class Triangle : public TwoDShape { 
  char style[20]; // now private 
public: 
 
  /* A default constructor. This automatically invokes 
     the default constructor of TwoDShape. */ 
  Triangle() { 
    strcpy(style, "unknown"); 
  } 
 
  // Constructor with three parameters. 
  Triangle(char *str, double w, 
           double h) : TwoDShape(w, h) { 
    strcpy(style, str); 
  } 
   
  // Construct an isosceles triangle. 
  Triangle(double x) : TwoDShape(x) { 
    strcpy(style, "isosceles");  
  } 
 
  double area() { 
    return getWidth() * getHeight() / 2; 
  } 
 
  void showStyle() { 
    cout << "Triangle is " << style << "\n"; 
  } 
}; 
 
// Extend Triangle. 
class ColorTriangle : public Triangle { 
  char color[20]; 
public: 
  ColorTriangle(char *clr, char *style, double w, 
                double h) : Triangle(style, w, h) { 
    strcpy(color, clr); 
  } 
 
  // Display the color. 
  void showColor() { 
    cout << "Color is " << color << "\n"; 
  } 
}; 
 
int main() { 
  ColorTriangle t1("Blue", "right", 8.0, 12.0); 
  ColorTriangle t2("Red", "isosceles", 2.0, 2.0); 
 
  cout << "Info for t1:\n"; 
  t1.showStyle(); 
  t1.showDim(); 
  t1.showColor(); 
  cout << "Area is " << t1.area() << "\n"; 
 
  cout << "\n"; 
 
  cout << "Info for t2:\n"; 
  t2.showStyle(); 
  t2.showDim(); 
  t2.showColor(); 
  cout << "Area is " << t2.area() << "\n"; 
 
  return 0; 
}

listing 14
// An example of multiple base classes. 
 
#include <iostream> 
using namespace std; 
 
class B1 { 
protected: 
  int x; 
public: 
  void showx() { cout << x << "\n"; } 
}; 
 
class B2 { 
protected: 
  int y; 
public: 
  void showy() { cout << y << "\n"; } 
}; 
 
// Inherit multiple base classes. 
class D: public B1, public B2 { 
public: 
  /* x and y are accessible because they are 
     protected in B1 and B2, not private. */ 
  void set(int i, int j) { x = i; y = j; } 
}; 
 
int main() 
{ 
  D ob; 
 
  ob.set(10, 20); // provided by D 
  ob.showx();     // from B1 
  ob.showy();     // from B2 
 
  return 0; 
}

listing 15
#include <iostream> 
using namespace std; 
 
class B { 
public: 
  B() { cout << "Constructing base portion\n"; } 
  ~B() { cout << "Destructing base portion\n"; } 
}; 
 
class D: public B { 
public: 
  D() { cout << "Constructing derived portion\n"; } 
  ~D() { cout << "Destructing derived portion\n"; } 
}; 
 
int main() 
{ 
  D ob; 
 
  // do nothing but construct and destruct ob 
 
  return 0; 
}

listing 16
// A short example that uses a virtual function. 
 
#include <iostream> 
using namespace std; 
 
class B { 
public: 
  virtual void who() { // specify a virtual function 
    cout << "Base\n"; 
  } 
}; 
 
class D1 : public B { 
public: 
  void who() { // redefine who() for D1  
    cout << "First derivation\n"; 
  } 
}; 
 
class D2 : public B { 
public: 
  void who() { // redefine who() for D2 
    cout << "Second derivation\n"; 
  } 
}; 
 
int main() 
{ 
  B base_obj; 
  B *p; 
  D1 D1_obj; 
  D2 D2_obj; 
 
  p = &base_obj; 
  p->who();  // access B's who 
 
  p = &D1_obj; 
  p->who(); // access D1's who 
 
  p = &D2_obj; 
  p->who();  // access D2's who 
   
  return 0; 
}

listing 17
// Derive from D1, not B. 
class D2 : public D1 { 
public: 
  void who() { // define who() relative to second_d 
    cout << "Second derivation\n"; 
  } 
};

listing 18
#include <iostream> 
using namespace std; 
 
class B { 
public: 
  virtual void who() { 
    cout << "Base\n"; 
  } 
}; 
 
class D1 : public B { 
public: 
  void who() { 
    cout << "First derivation\n"; 
  } 
}; 
 
class D2 : public B { 
// who() not defined 
}; 
 
int main() 
{ 
  B base_obj; 
  B *p; 
  D1 D1_obj; 
  D2 D2_obj; 
 
  p = &base_obj; 
  p->who();  // access B's who() 
 
  p = &D1_obj; 
  p->who(); // access D1's who() 
 
  p = &D2_obj; 
  p->who(); /* access B's who() because 
               D2 does not redefine it */ 
 
  return 0; 
}

listing 19
// Use virtual functions and polymorphism. 
 
#include <iostream> 
#include <cstring> 
using namespace std; 
 
// A class for two-dimensional objects. 
class TwoDShape { 
  // these are private 
  double width; 
  double height; 
 
  // add a name field 
  char name[20]; 
public: 
 
  // Default constructor. 
  TwoDShape() { 
    width = height = 0.0; 
    strcpy(name, "unknown"); 
  } 
 
  // Constructor for TwoDShape. 
  TwoDShape(double w, double h, char *n) { 
    width = w; 
    height = h; 
    strcpy(name, n); 
  } 
 
  // Construct object with equal width and height. 
  TwoDShape(double x, char *n) { 
    width = height = x; 
    strcpy(name, n); 
  } 
 
  void showDim() { 
    cout << "Width and height are " << 
             width << " and " << height << "\n"; 
  } 
 
  // accessor functions 
  double getWidth() { return width; } 
  double getHeight() { return height; } 
  void setWidth(double w) { width = w; } 
  void setHeight(double h) { height = h; } 
  char *getName() { return name; } 
 
  // Add area() to TwoDShape and make it virtual. 
  virtual double area() {   
    cout << "Error: area() must be overridden.\n";  
    return 0.0;  
  }   
 
}; 
 
// Triangle is derived from TwoDShape. 
class Triangle : public TwoDShape { 
  char style[20]; // now private 
public: 
 
  /* A default constructor. This automatically invokes 
     the default constructor of TwoDShape. */ 
  Triangle() { 
    strcpy(style, "unknown"); 
  } 
 
  // Constructor with three parameters. 
  Triangle(char *str, double w, 
           double h) : TwoDShape(w, h, "triangle") { 
    strcpy(style, str); 
  } 
   
  // Construct an isosceles triangle. 
  Triangle(double x) : TwoDShape(x, "triangle") { 
    strcpy(style, "isosceles");  
  } 
 
  // This now overrides area() declared in TwoDShape. 
  double area() { 
    return getWidth() * getHeight() / 2; 
  } 
 
  void showStyle() { 
    cout << "Triangle is " << style << "\n"; 
  } 
}; 
 
// A derived class of TwoDShape for rectangles. 
class Rectangle : public TwoDShape { 
public: 
 
  // Construct a rectangle.  
  Rectangle(double w, double h) :  
    TwoDShape(w, h, "rectangle") { }  
  
  // Construct a square.  
  Rectangle(double x) :  
    TwoDShape(x, "rectangle") { }  
 
  bool isSquare() { 
    if(getWidth() == getHeight()) return true; 
    return false; 
  } 
 
  // This is another override of area().   
  double area() { 
    return getWidth() * getHeight(); 
  } 
}; 
 
int main() { 
  // declare an array of pointers to TwoDShape objects. 
  TwoDShape *shapes[5]; 
  
  shapes[0] = &Triangle("right", 8.0, 12.0);  
  shapes[1] = &Rectangle(10);  
  shapes[2] = &Rectangle(10, 4);  
  shapes[3] = &Triangle(7.0);  
  shapes[4] = &TwoDShape(10, 20, "generic"); 
  
  for(int i=0; i < 5; i++) {  
    cout << "object is " << 
            shapes[i]->getName() << "\n";  
 
    cout << "Area is " << 
            shapes[i]->area() << "\n";  
  
    cout << "\n";    
  }  
 
  return 0; 
}


listing 20
// Use a pure virtual function. 
 
#include <iostream> 
#include <cstring> 
using namespace std; 
 
// A class for two-dimensional objects. 
class TwoDShape { 
  // these are private 
  double width; 
  double height; 
 
  // add a name field 
  char name[20]; 
public: 
 
  // Default constructor. 
  TwoDShape() { 
    width = height = 0.0; 
    strcpy(name, "unknown"); 
  } 
 
  // Constructor for TwoDShape. 
  TwoDShape(double w, double h, char *n) { 
    width = w; 
    height = h; 
    strcpy(name, n); 
  } 
 
  // Construct object with equal width and height. 
  TwoDShape(double x, char *n) { 
    width = height = x; 
    strcpy(name, n); 
  } 
 
  void showDim() { 
    cout << "Width and height are " << 
             width << " and " << height << "\n"; 
  } 
 
  // accessor functions 
  double getWidth() { return width; } 
  double getHeight() { return height; } 
  void setWidth(double w) { width = w; } 
  void setHeight(double h) { height = h; } 
  char *getName() { return name; } 
 
  // area()is now a pure virtual function 
  virtual double area() = 0; 
 
}; 
 
// Triangle is derived from TwoDShape. 
class Triangle : public TwoDShape { 
  char style[20]; // now private 
public: 
 
  /* A default constructor. This automatically invokes 
     the default constructor of TwoDShape. */ 
  Triangle() { 
    strcpy(style, "unknown"); 
  } 
 
  // Constructor with three parameters. 
  Triangle(char *str, double w, 
           double h) : TwoDShape(w, h, "triangle") { 
    strcpy(style, str); 
  } 
   
  // Construct an isosceles triangle. 
  Triangle(double x) : TwoDShape(x, "triangle") { 
    strcpy(style, "isosceles");  
  } 
 
  // This now overrides area() declared in TwoDShape. 
  double area() { 
    return getWidth() * getHeight() / 2; 
  } 
 
  void showStyle() { 
    cout << "Triangle is " << style << "\n"; 
  } 
}; 
 
// A derived class of TwoDShape for rectangles. 
class Rectangle : public TwoDShape { 
public: 
 
  // Construct a rectangle.  
  Rectangle(double w, double h) :  
    TwoDShape(w, h, "rectangle") { }  
  
  // Construct a square.  
  Rectangle(double x) :  
    TwoDShape(x, "rectangle") { }  
 
  bool isSquare() { 
    if(getWidth() == getHeight()) return true; 
    return false; 
  } 
 
  // This is another override of area().   
  double area() { 
    return getWidth() * getHeight(); 
  } 
}; 
 
int main() { 
  // declare an array of pointers to TwoDShape objects. 
  TwoDShape *shapes[4]; 
  
  shapes[0] = &Triangle("right", 8.0, 12.0);  
  shapes[1] = &Rectangle(10);  
  shapes[2] = &Rectangle(10, 4);  
  shapes[3] = &Triangle(7.0);  
  
  for(int i=0; i < 4; i++) {  
    cout << "object is " << 
            shapes[i]->getName() << "\n";  
 
    cout << "Area is " << 
            shapes[i]->area() << "\n";  
  
    cout << "\n";    
  }  
 
  return 0; 
}