[boost] Some SFINAE for vc6

From: David Abrahams (dave_at_[hidden])
Date: 2004-07-19 20:34:52

Tip for those insane persons who are trying to nurse vc6 along:

  Some kinds of SFINAE are possible.

Forming a pointer to a reference, for example, will remove a function
signature from the overload set.  Here's something I did in
Boost.Python just now.  In this case it was only needed for VC6, but
it should work for any SFINAE-ish compiler:

      template <class T>
      explicit object(
          T const& x
# if BOOST_WORKAROUND(BOOST_MSVC, == 1200)
          // use some SFINAE to un-confuse MSVC about its
          // copy-initialization ambiguity claim.
        , typename mpl::if_<is_proxy<T>,int&,int>::type* = 0
# endif 
      )

Ron Garcia reminded me that I had done this for the multi_array
library a while ago, and I realized I had forgotten all about it.  I
thought y'all should know.

-- 
Dave Abrahams
Boost Consulting
http://www.boost-consulting.com