Re: [Boost-users] MPL and conditional compilation

From: Joaquin M Lopez Munoz (joaquin_at_[hidden])
Date: 2005-08-26 05:04:18

Alan M. Carroll <amc <at> network-geographics.com> writes:
> 
> Is this as simple as it gets?
> Ah, finally, I have an MPL variant that works:
>  struct get_key_type { template < typename T > struct apply { typedef 
typename T::key_type type; }; };
>         typedef typename boost::mpl::eval_if_c<IS_OUTER,
>                  typename boost::mpl::apply<get_key_type, PAYLOAD>,
>                  typename boost::mpl::identity<PAYLOAD>
>        >::type testing;

You can make it simpler:

template<typename T>
struct get_key_type
{
  typedef typename T::key_type type;
};

typedef typename boost::mpl::eval_if_c<
  IS_OUTER,
  get_key_type<PAYLOAD>,
  boost::mpl::identity<PAYLOAD>
>::type testing;

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo