Reference and const...

[vedanu]

Hi All,

Can someone explain the concept for the below program?

Program:

+++++++

#include <stdio.h>

 

int main()

{

  const int num = 5;

  int &ref = (int &)num;

  ref = ref + 2;

  printf("num addr:%x ref addr:%x,\n",&num,&ref);

  printf("num value=%x ref value=%x\n",num,ref);

}

Output:

++++++



num addr:bfb403b4 ref addr:bfb403b4,

num value=5 ref value=7



Same address but different values?

[shabeebaassia]

Did you compile the program and got output. I compiled the program and got the errors.

[Rubberman]

This is invalid code. You have declared 'num' as a const int (constant integer), yet you have cast it as a reference to a non-constant integer with the line:

int& ref = (int&) num;

Then you try to modify ref, which is just an ALIAS for the num variable, but which since it is a constant, cannot be modified. Bad, bad, bad! If num was NOT const, then this would work, but you could also leave off the casting cruft. IE, try this:

#include <stdio.h>

 

int main(void)
{
  int num = 5;
  int& ref = num;

  ref = ref + 2;

  printf("num addr:%x ref addr:%x,\n", &num, &ref);

  printf("num value=%d ref value=%d\n", num, ref);
}