Re: [boost] [variant] make_variant_over requirement

From: Joel de Guzman (joel_at_[hidden])
Date: 2007-02-17 19:25:08

Tobias Schwinger wrote:
> Joel de Guzman wrote:
>> Hi,
>>
>> In the variant docs, in the make_variant_over section
>> (Using a type sequence to specify bounded types), it is
>> not clear what MPL sequence concept it is referring to.
>>
>> I was hoping it is a Forward Sequence, but I realized that
>> when I try to use make_variant_over with a Forward Sequence,
>> it fails trying to use mpl::clear, which hints that
>> make_variant_over requires an MPL Extensible Sequence.
>> This is rather undesirable. Is there a reason why this is so?
>> Can't we lessen the requirement? The situation makes it not
>> possible to use mpl views or fusion views for example.
> 
> Well, one could slowly but surely create an extensible sequence with 
> mpl::copy.

Yeah, that's more or less what I do, for now.

> I had a quick take at this one to make things work without wasting 
> compile time, see attached patch (tested with GCC4).

Thanks! Now, I'll just wait for the variant author(s) to pick this
up.

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