module12.lst

来自「Programs for the book Advanced Engineeri」· LST 代码 · 共 1,141 行 · 第 1/2 页

  dQb.put(30.03); 
 
  cout << "Contents of double queue dQa: "; 
  for(int i=0; i < 3; i++) 
    cout << dQa.get() << " "; 
  cout << endl; 
 
  cout << "Contents of double queue dQb: "; 
  for(int i=0; i < 3; i++) 
    cout << dQb.get() << " "; 
  cout << endl; 
 
  return 0; 
}

listing 18
// Demonstrate new and delete. 
 
#include <iostream> 
#include <new> 
using namespace std; 
 
int main() 
{ 
  int *p; 
 
  try { 
    p = new int; // allocate space for an int 
  } catch (bad_alloc xa) { 
    cout << "Allocation Failure\n"; 
    return 1; 
  } 
 
  *p = 100; 
 
  cout << "At " << p << " "; 
  cout << "is the value " << *p << "\n"; 
 
  delete p; 
 
  return 0; 
}

listing 19
// Initialize memory. 
 
#include <iostream> 
#include <new> 
using namespace std; 
 
int main() 
{ 
  int *p; 
 
  try { 
    p = new int (87); // initialize to 87 
  } catch (bad_alloc xa) { 
    cout << "Allocation Failure\n"; 
    return 1; 
  } 
 
  cout << "At " << p << " "; 
  cout << "is the value " << *p << "\n"; 
 
  delete p; 
 
  return 0; 
}

listing 20
// Allocate an array. 
 
#include <iostream> 
#include <new> 
using namespace std; 
 
int main() 
{ 
  int *p, i; 
 
  try { 
    p = new int [10]; // allocate 10 integer array 
  } catch (bad_alloc xa) { 
    cout << "Allocation Failure\n"; 
    return 1; 
  } 
 
  for(i=0; i<10; i++ ) 
    p[i] = i; 
 
  for(i=0; i<10; i++) 
    cout << p[i] << " "; 
 
  delete [] p; // release the array 
 
  return 0; 
}

listing 21
// Allocate an object. 
 
#include <iostream> 
#include <new> 
using namespace std; 
 
class Rectangle { 
  int width; 
  int height; 
public: 
  Rectangle(int w, int h) { 
    width = w; 
    height = h; 
    cout << "Constructing " << width << 
          " by " << height << " rectangle.\n"; 
  } 
 
  ~Rectangle() {  
     cout << "Destructing " << width << 
          " by " << height << " rectangle.\n"; 
  }  
 
  int area() { 
    return width * height; 
  } 
}; 
 
int main() 
{ 
  Rectangle *p; 
 
  try { 
    p = new Rectangle(10, 8); 
  } catch (bad_alloc xa) { 
    cout << "Allocation Failure\n"; 
    return 1; 
  } 
 
  cout << "Area is " << p->area(); 
 
  cout << "\n"; 
 
  delete p; 
 
  return 0; 
}

listing 22
// Allocate an array of objects. 
 
#include <iostream> 
#include <new> 
using namespace std; 
 
class Rectangle { 
  int width; 
  int height; 
public: 
  Rectangle() {  
    width = height = 0; 
    cout << "Constructing " << width << 
          " by " << height << " rectangle.\n"; 
  } 
 
  Rectangle(int w, int h) { 
    width = w; 
    height = h; 
    cout << "Constructing " << width << 
          " by " << height << " rectangle.\n"; 
  } 
 
  ~Rectangle() {  
     cout << "Destructing " << width << 
          " by " << height << " rectangle.\n"; 
  }  
 
  void set(int w, int h) { 
    width = w; 
    height = h; 
  } 
 
  int area() { 
    return width * height; 
  } 
}; 
 
int main() 
{ 
  Rectangle *p; 
 
  try { 
    p = new Rectangle [3]; 
  } catch (bad_alloc xa) { 
    cout << "Allocation Failure\n"; 
    return 1; 
  } 
 
  cout << "\n"; 
 
  p[0].set(3, 4); 
  p[1].set(10, 8); 
  p[2].set(5, 6); 
 
  for(int i=0; i < 3; i++) 
    cout << "Area is " << p[i].area() << endl; 
 
  cout << "\n"; 
 
  delete [] p; 
 
  return 0; 
}

listing 23
// Demonstrate a namespace. 
 
namespace CounterNameSpace { 
  int upperbound; 
  int lowerbound; 
 
  class counter { 
     int count; 
   public: 
     counter(int n) {  
       if(n <= upperbound) count = n; 
       else count = upperbound; 
     } 
 
     void reset(int n) { 
       if(n <= upperbound) count = n; 
     } 
 
     int run() { 
       if(count > lowerbound) return count--; 
       else return lowerbound; 
     } 
  }; 
}

listing 24
// Demonstrate a namespace. 
 
#include <iostream> 
using namespace std; 
 
namespace CounterNameSpace { 
  int upperbound; 
  int lowerbound; 
 
  class counter { 
     int count; 
   public: 
     counter(int n) {  
       if(n <= upperbound) count = n; 
       else count = upperbound; 
     } 
 
     void reset(int n) { 
       if(n <= upperbound) count = n; 
     } 
 
     int run() { 
       if(count > lowerbound) return count--; 
       else return lowerbound; 
     } 
  }; 
} 
 
int main() 
{ 
  CounterNameSpace::upperbound = 100; 
  CounterNameSpace::lowerbound = 0; 
 
  CounterNameSpace::counter ob1(10); 
  int i; 
 
  do { 
    i = ob1.run(); 
    cout << i << " "; 
  } while(i > CounterNameSpace::lowerbound); 
  cout << endl; 
 
  CounterNameSpace::counter ob2(20); 
 
  do { 
    i = ob2.run(); 
    cout << i << " "; 
  } while(i > CounterNameSpace::lowerbound); 
  cout << endl; 
 
  ob2.reset(100); 
  CounterNameSpace::lowerbound = 90; 
  do { 
    i = ob2.run(); 
    cout << i << " "; 
  } while(i > CounterNameSpace::lowerbound); 
 
  return 0; 
}

listing 25
namespace NS { 
  int i; 
} 
 
// ... 
 
namespace NS { 
  int j; 
}

listing 26
// Demonstrate using. 
 
#include <iostream> 
using namespace std; 
 
namespace CounterNameSpace { 
  int upperbound; 
  int lowerbound; 
 
  class counter { 
     int count; 
   public: 
     counter(int n) {  
       if(n <= upperbound) count = n; 
       else count = upperbound; 
     } 
 
     void reset(int n) { 
       if(n <= upperbound) count = n; 
     } 
 
     int run() { 
       if(count > lowerbound) return count--; 
       else return lowerbound; 
     } 
  }; 
} 
 
int main() 
{ 
  // use only upperbound from CounterNameSpace 
  using CounterNameSpace::upperbound;  
 
  // now, no qualification needed to set upperbound  
  upperbound = 100; 
 
  // qualification still needed for lowerbound, etc. 
  CounterNameSpace::lowerbound = 0; 
 
  CounterNameSpace::counter ob1(10); 
  int i; 
 
  do { 
    i = ob1.run(); 
    cout << i << " "; 
  } while(i > CounterNameSpace::lowerbound); 
  cout << endl; 
 
  // Now, use entire CounterNameSpace 
  using namespace CounterNameSpace; 
 
  counter ob2(20); 
 
  do { 
    i = ob2.run(); 
    cout << i << " "; 
  } while(i > lowerbound); 
  cout << endl; 
 
  ob2.reset(100); 
  lowerbound = 90; 
  do { 
    i = ob2.run(); 
    cout << i << " "; 
  } while(i > lowerbound); 
 
  return 0; 
}

listing 27
// Use a static instance variable. 
 
#include <iostream> 
using namespace std; 
 
class ShareVar { 
  static int num; 
public: 
  void setnum(int i) { num = i; }; 
  void shownum() { cout << num << " "; } 
}; 
 
int ShareVar::num; // define num 
 
int main() 
{ 
  ShareVar a, b; 
 
  a.shownum(); // prints 0 
  b.shownum(); // prints 0 
 
  a.setnum(10); // set static num to 10 
 
  a.shownum(); // prints 10 
  b.shownum(); // also prints 10 
 
  return 0; 
}

listing 28
// Refer to static variable through its class name. 
 
#include <iostream> 
using namespace std; 
 
class Test { 
public: 
  static int num; 
  void shownum() { cout << num << endl; } 
}; 
 
int Test::num; // define num 
 
int main() 
{ 
  Test a, b; 
 
  // Set num through its class name. 
  Test::num = 100; 
 
  a.shownum(); // prints 100 
  b.shownum(); // prints 100 
 
  // Set num through an object. 
  a.num = 200; 
 
  a.shownum(); // prints 200 
  b.shownum(); // prints 200 
 
  return 0; 
} 


listing 29
// Demonstrate a static member functions. 
 
#include <iostream> 
using namespace std; 
 
class Test { 
  static int count; 
public: 
 
  Test() { 
    count++; 
    cout << "Constructing object " << 
             count << endl; 
  } 
 
  ~Test() { 
     cout << "Destroying object " <<  
             count << endl; 
     count--; 
  } 
  
  static int numObjects() { return count; } 
}; 
 
int Test::count; 
 
int main() { 
  Test a, b, c; 
 
  cout << "There are now " << 
          Test::numObjects() << 
          " in existence.\n\n"; 
 
  Test *p = new Test(); 
 
  cout << "After allocating a Test object, " << 
          "there are now " << 
          Test::numObjects() << 
          " in existence.\n\n"; 
 
  delete p; 
 
  cout << "After deleting an object, " << 
          " there are now " << 
          a.numObjects() << 
          " in existence.\n\n"; 
 
  return 0; 
}

listing 30
// A simple example that uses typeid. 
 
#include <iostream> 
#include <typeinfo> 
using namespace std; 
 
class MyClass { 
  // ... 
}; 
 
int main() 
{ 
  int i, j; 
  float f; 
  MyClass ob; 
 
  cout << "The type of i is: " << typeid(i).name(); 
  cout << endl; 
  cout << "The type of f is: " << typeid(f).name(); 
  cout << endl; 
  cout << "The type of ob is: " << typeid(ob).name(); 
  cout << "\n\n"; 
 
  if(typeid(i) == typeid(j)) 
    cout << "The types of i and j are the same\n"; 
 
  if(typeid(i) != typeid(f)) 
    cout << "The types of i and f are not the same\n"; 
 
  return 0; 
}

listing 31
// An example that uses typeid on a polymorphic class heirarchy. 
 
#include <iostream> 
#include <typeinfo> 
using namespace std; 
 
class Base { 
  virtual void f() {}; // make Base polymorphic 
  // ... 
}; 
 
class Derived1: public Base { 
  // ... 
}; 
 
class Derived2: public Base { 
  // ... 
}; 
 
int main() 
{ 
  Base *p, baseob; 
  Derived1 ob1; 
  Derived2 ob2; 
 
  p = &baseob; 
  cout << "p is pointing to an object of type "; 
  cout << typeid(*p).name() << endl; 
 
  p = &ob1; 
  cout << "p is pointing to an object of type "; 
  cout << typeid(*p).name() << endl; 
 
  p = &ob2; 
  cout << "p is pointing to an object of type "; 
  cout << typeid(*p).name() << endl; 
 
  return 0; 
}