list1507.cpp

teach yourself C++ in 21 days 第五版

// Listing 15.7 
//demonstrates use of an array of pointers to functions

#include <iostream>
using namespace std;

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

int main()
{
   int valOne=1, valTwo=2;
   int choice, i;
   const MaxArray = 5;
   void (*pFuncArray[MaxArray])(int&, int&);

   for (i=0; i < MaxArray; i++)
   {
      cout << "(1)Change Values (2)Square (3)Cube (4)Swap: ";
      cin >> choice;
      switch (choice)
      {
        case 1:   pFuncArray[i] = GetVals; break;
        case 2:   pFuncArray[i] = Square; break;
        case 3:   pFuncArray[i] = Cube; break;
        case 4:   pFuncArray[i] = Swap; break;
        default:  pFuncArray[i] = 0;
      }
   }

   for (i=0; i < MaxArray; i++)
   {
      if ( pFuncArray[i] == 0 )
         continue;
      pFuncArray[i](valOne,valTwo);
      PrintVals(valOne,valTwo);
   }
   return 0;
}

void PrintVals(int x, int 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;
}