Re: [Boost-users] [mpl] BOOST_MPL_HAS_XXX_TRAIT_NAMED_DEF

Subject: Re: [Boost-users] [mpl] BOOST_MPL_HAS_XXX_TRAIT_NAMED_DEF
From: Eric Niebler (eric_at_[hidden])
Date: 2009-07-14 20:59:04

Hicham Mouline wrote:
> #include <iostream>
> #include <boost/mpl/has_xxx.hpp>
> #include <boost/mpl/bool.hpp>
> 
> BOOST_MPL_HAS_XXX_TRAIT_NAMED_DEF(has_xxx, xxx, false)
> 
> struct test1 { int xxx; };
> 
> using namespace boost::mpl;
> int main()
> {
>   std::cout<< has_xxx<test1>::value <<std::endl;
>   return 0;
> }
> 
> The output is 0, while it should be 1, shouldn't it?

That macro generates a trait that looks for a nested *type* with the 
specified name. In your case, xxx is a data member, not a type.

HTH,

-- 
Eric Niebler
BoostPro Computing
http://www.boostpro.com