id,summary,reporter,owner,description,type,status,milestone,component,version,severity,resolution,keywords,cc
11054,Floating-point comparison of multiprecision values fails if expression template is on,Paul A. Bristow,Raffi Enficiaud,"Floating-point comparison of multiprecision values fails if expression template option is 
on (which is the default for example with 
{{{
boost::multiprecision::cpp_bin_float_50; 

typedef boost::multiprecision::number<boost::multiprecision::cpp_bin_float<50>,
  boost::multiprecision::et_on>
  cpp_bin_float_50_et_on;  // et_on is default so is same as cpp_bin_float_50.)
}}}

The error appears inside Boost.test floating_point_comparision.hpp at an apparently impossible place fpc_detail::fpt_abs.

The actual problem is in class close_at_tolerance operator() line 204

{{{
   FPT diff = fpc_detail::fpt_abs(left - right);
}}}
in order to allow use of expression templates, it is necessary to cast the variable diff to the FPT explicitly, thus:
{{{
   FPT diff = fpc_detail::fpt_abs( static_cast<FPT>(left - right) );
}}}

I can provide an explicit test for this, but it seems such a trivial change.

This change is vital to allow Boost.Test to be used fully with Boost.Multiprecision.




",Bugs,closed,Boost 1.59.0,test,Boost 1.59.0,Problem,fixed,test multiprecision expression template,raffi.enficiaud@…