[boost] Re: [MPL] is_sequence problem

From: Joel (joel_at_[hidden])
Date: 2005-05-06 00:53:30

Joel wrote:
> Brian Braatz wrote:
> 
>> Could it be as simple as missing the namespace on the is_sqeuence<>
>> call?
> 
> 
> Have you tried it? If it was, I wouldn't have bothered the list ;-)
> Try replacing int_<0> with int.

I think the problem is the way mpl::is_sequence is implemented.
It tries to detect the presence of a "tag" typedef and a "begin"
typedef and concludes that a type is an mpl::sequence if it
has both. I've complained a long time ago about this. I think
this behavior is error prone. It's quite easy to come up with
a situation where I have a type T with a "tag" and a "begin"
but is not an MPL sequence. There must be a better way. MPL
should not monopolize on the usage of "tag" and a "begin"
in a type.

Anyway, in any case, is_sequence<int_<0> >::value should never
fail to compile.

Regards,
-- 
Joel de Guzman
http://www.boost-consulting.com
http://spirit.sf.net