Re: [Boost-users] [mpl] Is it possible to mpl_assert dependingonthe derivation of a class

From: Martin Apel (martin.apel_at_[hidden])
Date: 2007-08-21 09:59:39

Hughes, James wrote:
>
>     Just a quick addendum to this. I tried out a combination of the
>     two - using a BOOST_STATIC_ASSERT((boost::is_base_of<Base, T>
>     >::value)) inside the do_it function described above, and found
>     what I thought was odd behaviour with is_base_of.
>
>     The following excerpt shows the behaviour
>
>     class A {};
>
>     class B : public A {};
>
>     typedef A C;
>
>      BOOST_STATIC_ASSERT((boost::is_base_of<A,B> >::value))    // this
>     passes
>
>      BOOST_STATIC_ASSERT((boost::is_base_of<A,C> >::value))    // this
>     fails
>
>     I would expect both to pass, as is_base_of should return true when
>     both parameters are the same, and I thought that typedef did make
>     classes the same/equivalent
>
>     http://www.boost.org/doc/html/boost_typetraits/reference.html#boost_typetraits.is_base_of
>
>     Is there something I am missing about typedef? Or is
>     boost::is_base_of unable to handles the aliasing?
>
>     James
>
>      
>
Hi James,

I tried this with GCC 4.2 and 3.4.6 under Linux. It passes for both
cases. So it might be your compiler, which is doing something wrong.

Martin