Thread: for loop of evil

is this loop :

for(;
illegal?

because I used it in one of my programs and it works fine, I think it is called and INFINATE LOOP, anyway, one of my programming books said it was bad practice to use these types of FOR loops..
but gave no reason.

Do you guys know?

Originally Posted by swgh

is this loop :

for(;;)
illegal?

because I used it in one of my programs and it works fine, I think it is called and INFINATE LOOP, anyway, one of my programming books said it was bad practice to use these types of FOR loops..
but gave no reason.

Do you guys know?

Like the others have said, it's perfectly legal.

The "bad practice" is when you use an infinite loop, but it has a non-error terminating condition. Something like:

Code:

  char c;
  using std::cin;

  for (;;) {
    cin.get(c);
    if ( !cin )                  // terminating condition
      break;
    ...
  }

The loop is "advertised" as infinite (no condition test), but there is in fact one. Namely, the end of input. So the "better practice" would be to use a different loop, and put the condition test where it should be:

Code:

  char c;

  while ( std::cin.get(c) ) {
    ...
  }

Of course, this is personal opinion. Some programmers will see no difference here at all, and might be offended if someone suggested that it was somehow "bad". Other programmers will see the difference, and might be offended that you wouldn't take the time to do it the "right way".

My opinion is simply to say what you mean. If the loop should never terminate, then use an infinite loop. If there is a terminating condition, put it where it's supposed to go. Lastly, don't be offended (wink, smile).

HTH,
Will

Originally Posted by whoie

The "bad practice" is when you use an infinite loop, but it has a non-error terminating condition.

I disagree. If the only condition under which the application should exit is when the system hardware dies or is powered down, there is often no need for any terminating condition. In such a case (depending on hardware design) there is not necessarily any means for the software to detect a failure, so it can not choose to exit in response.

I disagree with your disagreement, because that's what I was trying to say. Thank you for the clarification. :-)