id,summary,reporter,owner,description,type,status,milestone,component,version,severity,resolution,keywords,cc
567,rational.hpp::gcd returns a negative value sometimes,dbenbenn,Jonathan Turkanis,"{{{
boost/rational.hpp provides a gcd function, which is
supposed to be non-negative.  It sometimes returns a
negative value, which can cause problems in other parts
of rational.hpp.  For example, assuming long is a
4-byte type,

boost::gcd<long>(6, -2147483648)

returns -2.  As a result,

boost::rational<long>(-1073741821, 6) + 
boost::rational<long>(-1073741827, 6)

produces an invalid rational number, 1073741824/-3,
instead of the correct answer -1073741824/3.

Here is a small patch to fix the problem.  Note that
this is how boost/math/common_factor_rt.hpp calculates
the greatest common divisor.
}}}",Patches,closed,,None,None,,Fixed,,