Re: [boost] [C++0x] Report from Frankfurt committee meeting

Subject: Re: [boost] [C++0x] Report from Frankfurt committee meeting
From: Vicente Botet Escriba (vicente.botet_at_[hidden])
Date: 2009-08-13 03:35:36

Mathias Gaunard-2 wrote:
> 
> Andrew Sutton wrote:
> 
> I'm also replying to Dave Abrahams here.
> 
> 
>>> a. I doubt we could do as well with error messages
>> 
>> 
>> You can't, but static_assert helps a bit.
> 
> What exactly can't be done?
> Let's consider function templates.
> Using concepts, the overload is masked if the concept is not fulfilled.
> Using SFINAE, the overload is masked if the expressions lead to errors.
> 
> In both cases, the compiler just says there is no match, and eventually 
> gives a list of possible matches.
> 
When you talk about using SFINAE, are you thinking on the Concept Traits
library
(http://neoscientists.org/~tschwinger/boostdev/concept_traits/libs/concept_traits/doc)
that Terje Slettebø and Tobias Schwinger have abandoned because the C++0x
should have Concepts?

> 
> 
>>> c. It wouldn't have the right syntax
> 
> Well, personally, I think defining concepts in terms of expressions is 
> better than doing so in terms of signatures.
> But is the syntax really important?
> 
> 
Not to me. What is important is that this will allows people to experiment
with Concepts in a portable way waiting for the new standard. The transition
should be much more smooth.

> 
>>> d. It wouldn't do the right thing
> 
> 
we can approximate with SFINAE partial ordering, isn't it?

Best,
Vicente
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