Re: [boost] Formal Review Request: TypeErasure

Subject: Re: [boost] Formal Review Request: TypeErasure
From: Stewart, Robert (Robert.Stewart_at_[hidden])
Date: 2012-06-08 06:58:04

Nevin Liber wrote:
> On 7 June 2012 16:14, lcaminiti <lorcaminiti_at_[hidden]>
> wrote:
>
> > What if this were possible? Would this be an acceptable way
> > to add custom concepts?
> >
> > BOOST_TYPE_ERASURE_CONCEPT(
> >    concept (sable) ( class S )
> >    (
> >        void member_body(S, f) ( void ) ,
> >        void member_body(S, g) ( void ) ,
> >        void member_body(S, h) ( void )
> >    )
> > )
>
> It would certainly help a lot.  If we want people to replace
> the common idiom of creating AbstractS and storing the
> instantiated object in unique_ptr<AbstractS> (or a different
> smart pointer), the replacement needs to be almost as easy, at
> least for that very common case.

Given the current language constraints, that would be a help.  However, the question was what should be added to the language to make this nicer.  What's more, the use of such macros compounds the problems of templates (long backtraces, no concepts, etc., some of which Steven may well have addressed), by putting everything on one, obscure line (so far as the compiler sees it).

I agree with you, Nevin, that it should be little more difficult, if any, than just declaring an ABC for the interface.  Sebastian's suggestions of compile-time reflection and declaration injection, if feasible, might be just the ticket.  Whatever turns out to be most general, without exposing too much implementation detail which ties implementer's hands, would be nice.

_____
Rob Stewart                           robert.stewart_at_[hidden]
Software Engineer                     using std::disclaimer;
Dev Tools & Components
Susquehanna International Group, LLP  http://www.sig.com

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