[boost] [mpl] bug: has_xxx, default bool parameter

From: Daniel Wallin (dalwan01_at_[hidden])
Date: 2004-09-03 03:37:28

The traits generated with BOOST_MPL_HAS_XXX_TRAIT_DEF() doesn't work
with lambda on VC7.1+. I think the problem is the default bool
parameter:

   template< typename T, bool fallback_ = default_ > struct trait \
                         ^^^^^^^^^^^^^^^^^^^^^^^^^

This template will never match:

   template<template<typename ..> class F, class U1 .. UN>
   struct lambda<F<U1 .. UN> >;

So lambda breaks. I guess the solution is to stop using a default bool
parameter and use a class type instead.

-- 
Daniel Wallin