Re: [boost] [guidelines] why template errors suck

Subject: Re: [boost] [guidelines] why template errors suck
From: John Bytheway (jbytheway+boost_at_[hidden])
Date: 2010-10-04 04:48:12

On 04/10/10 00:39, Mathias Gaunard wrote:
> On 28/09/2010 19:14, David Abrahams wrote:
>> Unfortunately, without real concepts we may not be able to do better,
>> because the pseudo-signature approach inserts type conversions that
>> we'd have to write by hand.  Now here's an interesting thought: write
>> a library using TMP that generates "concept wrappers" that will force
>> the necessary conversions.  Would require heavy use of rvalue
>> references to avoid needless copies.  Hmm...
> 
> A crazy idea if you want to be TMP-heavy: maybe you could represent the
> valid expressions with Proto and infer an archetype from these.
> 
> This could provide better syntax than the "operator_increment" thing you
> suggested in some other part of the thread.

Indeed, I already had that idea, and I implemented a proof-of-concept.
I guess my posts went unnoticed in this huge sprawling thread.  See:

http://article.gmane.org/gmane.comp.lib.boost.devel/208946
http://article.gmane.org/gmane.comp.lib.boost.devel/208996

As you suggest, I think it should be possible to use a single definition
to check models against concepts, make archetypes, and do concept-based
overloading.  What I'm not sure is whether (a) it's worthwhile to do it,
and (b) whether it would be worth attempting the more ambitious "concept
wrappers" idea Dave suggests above.

John Bytheway