/*
File: oop2.cpp

The OOP mechanisms for inheritance and late binding
(i.e., virtual functions) can be used to allow
any "function" derived from the class Int2Int
to be passed to apply().

*/


#include <iostream>
using namespace std ;

//-------------------------------------------

class Int2Int {
public:
   virtual int operator() (int) = 0 ;  // pure virtual
} ;


//-------------------------------------------

class AddX : public Int2Int {

private:
   int m_offset ;

public:
   AddX(int offset = 0) { m_offset = offset ; }

   int operator()(int m) { return m + m_offset ; }
} ;


//-------------------------------------------

class Mult3 : public Int2Int {
public:
   int operator()(int m) { return 3*m ; }
} ;


//-------------------------------------------

void apply(Int2Int& f, int A[], int n) {
   for (int i=0 ; i < n ; i++) {
      A[i] = f( A[i] ) ;
   }
}


int main () {
   int B[10] = { 10, 11, 12, 13, 14, 15, 16, 17, 18, 19} ;

   AddX add3(3) ;
   AddX add5(5) ;


   printf("Before:\n") ;
   for (int i=0 ; i < 10 ; i++) {
      cout << "   B[" << i << "] = " << B[i] << endl ;
   }

   apply (add3, B, 10) ;

   printf("\n\nAfter calling apply(add3, B, 10):\n") ;
   for (int i=0 ; i < 10 ; i++) {
      cout << "   B[" << i << "] = " << B[i] << endl ;
   }

   apply (add5, B, 10) ;

   printf("\n\nAfter calling apply(add5, B, 10):\n") ;
   for (int i=0 ; i < 10 ; i++) {
      cout << "   B[" << i << "] = " << B[i] << endl ;
   }

   Mult3 times3 ;

   apply (times3, B, 10) ;

   printf("\n\nAfter calling apply(times3, B, 10):\n") ;
   for (int i=0 ; i < 10 ; i++) {
      cout << "   B[" << i << "] = " << B[i] << endl ;
   }
}