Re: [Boost-users] [mpl] defaults with associative sequence

Subject: Re: [Boost-users] [mpl] defaults with associative sequence
From: Manfred Doudar (manfred.doudar_at_[hidden])
Date: 2010-03-05 20:09:27

On Fri, 05 Mar 2010 14:38:15 -0300
Agustín K-ballo Bergé <kaballo86_at_[hidden]> wrote:

> El 05/03/2010 06:31 a.m., Manfred Doudar escribió:
> > 
> > Hi,
> > 
> > Maybe I am misreading the documentation, but if I have an mpl::map
> > and try and get an element associated with a key all's good, while
> > if I assign a default - I get an error that mpl::at only takes 2 and
> > not 3 template parameters.
> > 
> > Am I doing something blatantly wrong?
> > 
> 
> No. The mpl::at version that takes a default parameter does not exist.
> Documentation and source code are out of synch. When I need it I use
> this implementation:
> 
> typename boost::mpl::eval_if<
>     typename boost::mpl::has_key< Map, Key >::type
>   , boost::mpl::at< Map, Key >
>   , boost::mpl::identity< Default >
> >::type
> 
> Agustín K-ballo Bergé.

Thank you Agustín for your reply, it's appreciated.  --Manfred