[Boost-users] Re: Mpl problem

From: David Abrahams (dave_at_[hidden])
Date: 2004-07-19 21:54:57

"Arkadiy Vertleyb" <vertleyb_at_[hidden]> writes:

> "Delfin Rojas" <drojas_at_[hidden]> wrote
>
>> I am having a problem with the mpl library and I wonder if someone could
>> help me with it. Basically I am trying to get a joint_view of two
>> mpl::vector types and I get an error message on mpl/clear.hpp saying
>>
>> clear_traits< Tag >
>>         ::template algorithm< Sequence >
>>
>> base class undefined.
>>
>> I tried including several of the mpl hpp files, the ones that seemed could
>> have something to do with this problem but that didn't help. I also get a
>> similar problem trying to use mpl::push_back. In this case I get
>>
>> push_back_traits< Tag >
>>         ::template algorithm< Sequence,T >
>>
>> Base class undefined.
>>
>> On the other hand mpl::push_front and mpl::insert compile beautifully.
>
> The error messages you are getting basically say:
>
> "This algorithm is undefined for this type of sequence."

Exactly.  Like all other views, joint_view is not extensible.  How
could you push_back onto a view, anyway?  push_back is supposed to
return the same "kind" of sequence as its input, but you can't add an
element to a joint_view.

-- 
Dave Abrahams
Boost Consulting
http://www.boost-consulting.com