Question

Is it better to cast the iterator condition right operand from size_t to int, or iterate potentially past the maximum value of int? Is the answer implementation specific?

int a;
for (size_t i = 0; i < vect.size(); i++)
{
    if (some_func((int)i))
    {
        a = (int)i;
    }
}

int a;
for (int i = 0; i < (int)vect.size(); i++)
{
    if (some_func(i))
    {
        a = i;
    }
}

Answer 1

I almost always use the first variation, because I find that about 80% of the time, I discover that some_func should probably also take a size_t.

If in fact some_func takes a signed int, you need to be aware of what happens when vect gets bigger than INT_MAX. If the solution isn’t obvious in your situation (it usually isn’t), you can at least replace some_func((int)i) with some_func(numeric_cast<int>(i)) (see Boost.org for one implementation of numeric_cast). This has the virtue of throwing an exception when vect grows bigger than you’ve planned on, rather than silently wrapping around to negative values.