[boost] rational.hpp requires working unary minus

From: Yuriy Koblents-Mishke (yurakm_at_[hidden])
Date: 2006-04-28 00:19:41

Test Code:

    std::numeric_limits<long> lm;
    boost::rational<long> mn( lm.min() );

    std::cout <<  mn << '=' << mn / 1 << std::endl;

Output:

-2147483648/1=1/0

Reason:

lm.min() == -2147483648

lm.max() == 2147483647

and unary minus is not well defined for lm.min();
on my system

-lm.min() == -2147483648

The problem is expected with any computer representing negative integers
using binary two's compliment.