fma in boost/units/cmath.hpp?

[Nick]

I've recently had a compile fail with fma on boost::units types. However, it appears this has been implemented in boost/units/cmath.hpp, but it has been explicitly disabled using an #if 0.

 git show e634a7c6 
commit e634a7c6bef7180ec34387fd7bb7c0236c17a990
Author: Steven Watanabe <[e-mail]>
Date:   Sat Jun 7 17:15:24 2008 +0000

    Remove compiler specific code from cmath.  Disable functions which cannot be implemented easily using Boost.Math

    [SVN r46217]

Is there any reason why we can't re-enable these code paths today?

Edit: I enabled those code paths, and it appears to be working. However, I had to add a couple other overloads:

template<class Unit, class Y>
inline 
BOOST_CONSTEXPR
quantity<Unit,Y>
fma BOOST_PREVENT_MACRO_SUBSTITUTION (const Y& q1,
                                      const quantity<Unit,Y>& q2,
                                      const quantity<Unit,Y>& q3)
{
    using std::fma;
    return quantity<Unit,Y>::from_value(fma(q1,q2.value(),q3.value()));
}

template<class Unit, class Y>
inline 
BOOST_CONSTEXPR
quantity<Unit,Y>
fma BOOST_PREVENT_MACRO_SUBSTITUTION (const quantity<Unit, Y>& q1,
                                      const Y& q2,
                                      const quantity<Unit,Y>& q3)
{
    using std::fma;
    return quantity<Unit,Y>::from_value(fma(q1.value(),q2,q3.value()));
}

I imagine the case where a and x have "inverse units" and a*x+b is dimensionless could also be supported.

Patchfile: units_patch.txt