[boost] Re: is_convertible love

From: David Abrahams (dave_at_[hidden])
Date: 2003-02-19 15:31:38

David Abrahams <dave_at_[hidden]> writes:

> I'm in love with the new is_convertible; I can now detect "move-copy"
> types like auto_ptr!  Could the old is_convertible do this?
>
>
>     #include <boost/type_traits/is_convertible.hpp>
>     #include <boost/static_assert.hpp>
>     #include <memory>
>
>     int main()
>     {
>         BOOST_STATIC_ASSERT(
>             (boost::is_convertible<
>                  std::auto_ptr<int>, std::auto_ptr<int>
>              >::value));
>
>         BOOST_STATIC_ASSERT(
>             (boost::is_convertible<
>                  std::auto_ptr<int>&, std::auto_ptr<int>
>              >::value));
>
>         BOOST_STATIC_ASSERT(
>             (!boost::is_convertible<
>                  std::auto_ptr<int> const&, std::auto_ptr<int>
>              >::value));
>
>         BOOST_STATIC_ASSERT(
>             (!boost::is_convertible<
>                  std::auto_ptr<int> const, std::auto_ptr<int>
>              >::value));
>     }

OK, I give up.  This doesn't work for GCC.  Does anybody have a clever
route to detecting types whose copy ctor have a non-const RHS?  It's
fine to assume that an accessible copy ctor exists.

TIA,
Dave

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com