Re: [boost] [MPL] wrapper for if_ selecting integral_c

Subject: Re: [boost] [MPL] wrapper for if_ selecting integral_c
From: David Abrahams (dave_at_[hidden])
Date: 2008-10-21 15:01:32

on Tue Oct 21 2008, "Jordans, R." <r.jordans-AT-student.tue.nl> wrote:

> I've written the template myself, but I need to be able to compile it on different
> systems (Linux, OS-X and Windows) and I'm not sure if every compiler will like it
>
> My code for the template is as follows:
>
> namespace boost {
>     namespace mpl {
>         template <typename C, typename T, T value1, T value2>
>            struct if_integral_c
>         {
>             static const T value =
>               if_<C, integral_c<T, value1>, integral_c<T, value2> >::type::value;
>         };
>     }
> }

        template <typename C, typename T, T value1, T value2>
        struct if_integral_c
          : integral_c<T,(C::type::value?value1:value2)>
        {};

would be more correct and more interoperable.

> But from what I've understood not all compilers like it when you use a
> template typename parameter as type for other template parameters

Sorry, I don't understand what you mean.

-- 
Dave Abrahams
BoostPro Computing
http://www.boostpro.com