C++ Preprocessing Directives in Debugging

#include <iostream>
#include <cstdlib>                       // For random number generator
#include <ctime>                         // For time function

using std::cout;//from  ww w  . ja v a 2s  . co m
using std::endl;

#define TESTINDEX

// Function to generate a random integer 0 to count-1
int random(int count)
{
  return static_cast<int>( count*static_cast<unsigned long>(std::rand())/(RAND_MAX+1UL));
}

int main()
{
  int a {10}, b {5};
  int result {};

  int (*pfun[])(int, int) {fun::sum, fun::product, fun::difference};

  int fcount {sizeof pfun/sizeof pfun[0]};
  int select {};
  srand(static_cast<unsigned>(time(0)));

  for(int i {} ; i < 10 ; ++i) {
      select = random(fcount); // Generate random index 0 to fcount-1

      #ifdef TESTINDEX
      std::cout << "Random number = " << select << std::endl;
      if((select >= fcount) || (select < 0))
      {
        std::cout << "Invalid array index = " << select << std::endl;
        return 1;
      }
      #endif

      result = pfun[select](a, b); // Call random function
      cout << "result = " << result << endl;
  }
  result = pfun[1](pfun[0](a, b), pfun[2](a, b));
  std::cout <<"The product of the sum and the difference = " << result << std::endl;
}