list1509.cpp

teach yourself C++ in 21 days 第五版

// Listing 15.9. 
// Using typedef to make pointers to functions more readable

#include <iostream>
using namespace std;

void Square(int&,int&);
void Cube(int&, int&);
void Swap(int&, int &);
void GetVals(int&, int&);
typedef  void (*VPF) (int&, int&) ;
void PrintVals(VPF,int&, int&);

int main()
{
   int valOne=1, valTwo=2;
   int choice;
   bool fQuit = false;

   VPF pFunc;

   while (fQuit == false)
   {
      cout << "(0)Quit (1)Change Values (2)Square (3)Cube (4)Swap: ";
      cin >> choice;
      switch (choice)
      {
        case 1:   pFunc = GetVals; break;
        case 2:   pFunc = Square; break;
        case 3:   pFunc = Cube; break;
        case 4:   pFunc = Swap; break;
        default:  fQuit = true; break;
      }
      
      if (fQuit == false)
         PrintVals ( pFunc, valOne, valTwo);
   }
   return 0;
}

void PrintVals( VPF pFunc,int& x, int& y)
{
   cout << "x: " << x << " y: " << y << endl;
   pFunc(x,y);
   cout << "x: " << x << " y: " << y << endl;
}

void Square (int & rX, int & rY)
{
   rX *= rX;
   rY *= rY;
}

void Cube (int & rX, int & rY)
{
   int tmp;

   tmp = rX;
   rX *= rX;
   rX = rX * tmp;

   tmp = rY;
   rY *= rY;
   rY = rY * tmp;
}

void Swap(int & rX, int & rY)
{
   int temp;
   temp = rX;
   rX = rY;
   rY = temp;
}

void GetVals (int & rValOne, int & rValTwo)
{
   cout << "New value for ValOne: ";
   cin >> rValOne;
   cout << "New value for ValTwo: ";
   cin >> rValTwo;
}