On Monday 11 November 2002 04:56 am, Aleksey Gurtovoy wrote:
[snip my limited example]
>  Hmm, interesting, so if this actually worked, we would be happy:
> 
[snip nifty-looking is_callable implementation]
> 
>  ?

Well, you need to do some trickery to make it work when R=void, but otherwise 
I think we would be _very_ happy if this worked. Is there a tweak to the core 
language that would guarantee such a thing?

>  > The reason I mention is_instantiable instead of __is_well_formed
>  > is that is_instantiable can keep a class template interface, whereas
>  > __is_well_formed would require a new grammar production.
> 
>  From http://aspn.activestate.com/ASPN/Mail/Message/1412095 I've got an
>  impression that implementors are not too concerned about it.
> 
>  After all, '__is_well_formed' might be as easy to implement as this:
> 
>      void process_is_well_formed( args )
>      {
>          try
>          {
>              process_sizeof( args );
>              args.expression_result = true;
>          }
>          catch (compiler_error const& )
>          {
>              args.expression_result = false;
>          }
>      }
> 
>  :)

At one time in GCC, checking for compilability was as easy as:

  cp_silent++;
  // instantiate the thing you want to check
  cp_silent--;
  
	Doug
_______________________________________________
Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost