[boost] [rational] operator< fails for unsigned value types. Here's a small patch to fix it

From: David Benbennick (dbenbenn_at_[hidden])
Date: 2006-02-19 04:47:26

There's a minor bug in rational.hpp when using unsigned values. 
Consider the following simple program:

#include <boost/rational.hpp>
#include <cassert>

int main(void) {
   boost::rational<unsigned int> x = 0;

   assert(x.operator<(1));
}

The assertion fails.  The reason is that in
rational.hpp::rational<IntType>::operator< (param_type i) are the
lines

    if (num > zero)
        return (num/den) < i;
    else
        return -i < (-num/den);   <-- this is bogus for unsigned types
if num == 0.

Attached are two patches to fix the problem.  The first is a minimal
patch, changing the > to >=.  The second patch changes more: in the
current code, up to 5 comparisons can happen.  In the patched version,
only 3 comparisons are done.

Cheers,
David Benbennick