Re: We do not use C++ exceptions

David Abrahams wrote:


Yah, that I agree with. In my experience you can weed out one half of
the check. Consider:

template <class T> struct Vector
{
     ...
     T & operator[](int n) { enforce(n >= 0 && n < length_); ... }
}

versus:

template <class T> struct Vector
{
     ...
     T & operator[](size_t n) { enforce(n < length_); ... }
}

If I use unsigned, I get rid of one of the tests. I don't think it's a
huge deal, but it does feel cleaner. Besides, I can use a vector > 2GB
in size on a 32-bit system, at least in theory. The underlying
assumption is that there is no combination of a vector > 2GB and a large
negative integer at the same time, which is reasonable.

However, I get nervous when I got rid of *all* tests when an unsigned
comes around. Then something is bound to run amok somewhere.

double pow(double base, unsigned exponent)
{
     // look, ma! No checks!
     double result = 1;
     while (exponent)
     {
         if (exponent & 1)
         {
             result *= base;
             --exponent;
         }
         else
         {
             result *= result;
             exponent /= 2;
         }
     }
     return result;
}

Well this function is rather prone to returning zero or infinity for
negative small exponents, which are frequent in a program and accepted
no problem. Do I still define it that way? Yes :o). I'm just more
miserable over it than others.

Andrei

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