// cout_friend.cpp  define the cout operator  <<  for a class  
//                  define operator  <  for a class
//                  demonstrate constructor initialization  :var(arg)

// a_class.h      should be in a file by itself

#include <iostream>            // basic console input/output
using namespace std;           // bring standard include files in scope

class A_class
{
  public:
    A_class(int Akey, double Aval): key(Akey), val(Aval) {}
    friend ostream &operator << (ostream &stream, A_class x);
    bool operator < (A_class &y) {return this->key < y.key;}

  private: // bug in VC++ means this has to be public in VC++ only
    int key;
    double val;
};
      


// #include "a_class.h"  // would be needed if lines above were in a_class.h

int main()
{
  A_class a(5,7.5);
  A_class b(6,2.4);

  cout << "a= " << a << "  b= " << b << endl; // using A_class  <<

  if( a < b)  // using  A_class  <
  {
    cout << "OK a < b  because 5 < 6"  << endl;
  }
  else
  {
    cout << "BAD compare on  a < b  fix operator <  definition" << endl;
  }


  return 0;
} // end main

// The lines below should be in a file  a_class.cpp  .cc  .C
// #include "a_class.h"

// The 'friend' statement in A_class makes key and val visible here

ostream &operator<< (ostream &stream, A_class x)
{
  stream << x.key << "  ";
  stream << " $" << x.val << " "; // just demonstrating added output
  return stream;
}

// output of execution is:
// a= 5   $7.5   b= 6   $2.4 
// OK a < b  because 5 < 6