ptrtofunction.cpp

来自「《24学时精通c++》的光盘内容」· C++ 代码 · 共 90 行

 // Listing 20.5 Using function pointers
 #include <iostream>
 
 void Square (int&,int&);
 void Cube (int&, int&);
 void Swap (int&, int &);
 void GetVals(int&, int&);
 void PrintVals(int, int);
 
 int main()
 {
     void (* pFunc) (int &, int &);
     bool fQuit = false;
 
     int valOne=1, valTwo=2;
     int choice;
     while (fQuit == false)
     {
         std::cout << "(0)Quit (1)Change Values "
             << "(2)Square (3)Cube (4)Swap: ";
         std::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)
             break;
 
         PrintVals(valOne, valTwo);
         pFunc(valOne, valTwo);
         PrintVals(valOne, valTwo);
     }
     return 0;
 }
 
 void PrintVals(int x, int y)
 {
     std::cout << "x: " << x << " y: " << y << std::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)
 {
     std::cout << "New value for ValOne: ";
     std::cin >> rValOne;
     std::cout << "New value for ValTwo: ";
     std::cin >> rValTwo;
 }