Re: [Boost-users] [parameter] Parameter-Enabled Class Templates:combining keyword and deduction for the same parameter

From: JOAQUIN LOPEZ MU?Z (joaquin_at_[hidden])
Date: 2007-07-19 15:18:58

----- Mensaje original -----
De: David Abrahams <dave_at_[hidden]>
Fecha: Jueves, Julio 19, 2007 9:06 pm
Asunto: Re: [Boost-users] [parameter] Parameter-Enabled Class 
Templates:combining keyword and deduction for the same parameter
Para: boost-users_at_[hidden]

> 
> on Thu Jul 19 2007, Joaquín Mª López Muñoz <joaquin-AT-tid.es> wrote:
> 
> > The docs explain that a parameter can be named:
> >
> >   typedef parameter::parameters<
> >     required<tag::threading_policy>
> >     ...
> >   > class_signature;
> >   ...
> >   class_<threading_policy<single_threaded>,...>;
> >
> > or else be deduced:
> >
> >   typedef parameter::parameters<
> >     required<
> >       deduced<tag::threading_policy>,
> >       is_base_and_derived<threading_policy_marker,_>
> >     >
> >     ...
> >   > class_signature;
> >   ...
> >   class multithreaded: threading_policy_marker{...};
> >   class_<multithreaded,...>;
> >
> > Now, is it possible to combine these two options into one, so 
> > that the two syntaxes
> >
> >   class_<threading_policy<single_threaded>,...>;
> >   class_<multithreaded,...>;
> >
> > are accepted? If so, how?
> 
> Just used deduced<tag::threading_policy>; deduced parameters can be
> deduced from argument types or from the names attached to named
> arguments.

Just to be sure: so, given the parameter specification

  required<deduced<tag::T>,F>,

Boost.Parameter matches it to T<X> even if X does *not* satisfy
F, correct?

Thank you,

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo