Re: MPL::lambda issue: what am I doing wrong?

From: Brian Simpson (yg-boost-users_at_[hidden])
Date: 2003-07-11 11:16:40

"Aleksey Gurtovoy" <alexy_at_[hidden]> wrote:
> Brian Simpson wrote:
> > I want to express a "type-mapping" scheme.  My implementation idea is
> this:
> > have the user define an MPL sequence comprised exclusively of std::pair
> > derivations.  He can then instantiate my template class with his
sequence
> as
> > the argument.  My template then derives two MPL sequences, one
containing
> > the "first" types, the other containing the "second" types.
> >
[...]
> > I'm using gcc3.2.2 on Solaris 9.
>
> Brian, I don't have access to gcc 3.2.2 at the moment, but it looks like
> they are still not able to handle the class template arity issues
> correctly (your example also fails with an internal compiler error on
3.2).
[...]
> The good news is that if you re-write your metaprogram as follows, it
> will work:
[...]
>
> If you want to know more details, just ask :).
>
> HTH,
> Aleksey
>
 That does help.
It gets me to the next (apparent) obstacle, which is that I need to define a
variant using the types in the derived sequence (the second_types, to be
specific).
I'm putting together another post for that one.

BTW,  would it be possible, using mpl::fold, to get Borland5 to do this?  I
know that it won't support mpl::lambda, and I'd like my code to compile on
Borland5 in addition to gcc3.2.2 .  I'll be looking into it, but if you can
alert me that it's not possible, that would save me time :).

I'm sure I'll be asking for more details later, but for now the
documentation is coming through for me.

Thanks!
Brian