frengl.cpp

来自「本课程主要介绍面向对象程序设计的方法和c++语言的基本概念。以c++语言中的面向」· C++ 代码 · 共 50 行

// frengl.cpp
// friend overloaded + operator
#include <iostream>
using namespace std;
////////////////////////////////////////////////////////////////
class Distance                    //English Distance class
   {
   private:
      int feet;
      float inches;
   public:
      Distance()                  //constructor (no args)
         { feet = 0; inches = 0.0; }
      Distance( float fltfeet )   //constructor (one arg)
         {                        //convert float to Distance
         feet = int(fltfeet);           //feet is integer part
         inches = 12*(fltfeet-feet);    //inches is what's left
         }
      Distance(int ft, float in)  //constructor (two args)
         { feet = ft; inches = in; }
      void showdist()             //display distance
         { cout << feet << "\'-" << inches << '\"'; }
      friend Distance operator + (Distance, Distance); //friend
   };
//--------------------------------------------------------------				  
Distance operator + (Distance d1, Distance d2) //add D1 to d2
   {
   int f = d1.feet + d2.feet;        //add the feet
   float i = d1.inches + d2.inches;  //add the inches
   if(i >= 12.0)                  //if inches exceeds 12.0,
      { i -= 12.0; f++;  }        //less 12 inches, plus 1 foot
   return Distance(f,i);          //return new Distance with sum
   }
//--------------------------------------------------------------
int main()
   {
   Distance d1 = 2.5;                //constructor converts
   Distance d2 = 1.25;               //float-feet to Distance
   Distance d3;
   cout << "\nd1 = "; d1.showdist(); 
   cout << "\nd2 = "; d2.showdist();

   d3 = d1 + 10.0;                   //distance + float: OK
   cout << "\nd3 = "; d3.showdist();
   d3 = 10.0 + d1;                   //float + Distance: OK
   cout << "\nd3 = "; d3.showdist();
   cout << endl;
   return 0;
   }