Re: [Boost-users] [mpl] insert not inserting?

----- Mensaje original ----- De: Scott Meyers Fecha: Miércoles, Marzo 28, 2007 11:49 pm Asunto: Re: [Boost-users] [mpl] insert not inserting? Para: boost-users@lists.boost.org

Ovanes Markarian wrote:

...

mpl::insert is an own type but you need the new sequence type with is accessed via: mpl::insert<...>::type

Thanks very much. When I change the corresponding to code to:

typedef mpl::insert::type BaseClasses;

then Base is inserted, but the resulting sequence has only A and Base in it, not A and B and Base, i.e., the type B is somehow being lost. Any idea why?

I think you want to write mpl::end<Constraints>::type

Also, I'll be honest: I don't know when to use ::type and when not to. Is there a good description somewhere (either online or in the MPL book) that will clarify the situation for me?

Well, excuse me if the following is obvious to you, but ::type is to a metafunction what actual invocation is to a run-time function. So, mpl::end<Constraints> refers to the name of the entity, but does not actually compute its "return value" unless you add the ::type suffix. Sort of like the difference between &foo and foo() in the run-time world. Joaquín M López Muñoz Telefónica, Investigación y Desarrollo