Which is the preferred condition in loop?

Question

int n = 5;
for(int i = 0;i!=n;i++)//condition !=
{
//executing 5times
}

int n = 5;
for(int i = 0;i<n;i++)//condition <
{
//executing 5times

}

Which one is preferred?

This was example from "Accelerated C++ : practical programming by example / Andrew Koenig, Barbara E. Moo." Just wanted to know why the Author prefers the first one

Answer 1

The second. For two reasons

1. The less than (or sometimes <=) is the usual way that most coder write these, and it's better to stick to convention if possible - the != will probably make most coders look twice to check if there's something odd in the loop whereas the < will be instantly understood.

2. The != depends on an exact condition. If the interior of the loop is modified during maintenance and i accidentally incremented inside the loop then you would end up with an infinite loop. Generally it's always better to make your termination condition as wide as possible - it's simply more robust.

2 is of course the reason why 1.

Answer 2

I would say < as it captures a wider set of conditions. Suppose that n wasn't constant but returned from a function which on rare occasions returned -1. In that event, you'd have a much longer loop (until the int wraps around to a -ve value!) with the != version of the loop.