Re: [boost] is_range metafunction

Subject: Re: [boost] is_range metafunction
From: Daniel Walker (daniel.j.walker_at_[hidden])
Date: 2008-10-08 21:17:29

On Tue, Oct 7, 2008 at 3:06 PM, Joel Falcou <joel.falcou_at_[hidden]> wrote:
> Daniel Walker a écrit :
>>
>> Of course, I think there is a need to package SFINAE techniques as a
>> nice library for compile-time class-based type introspection -
>> something beyond MPL's HAS_XXX. I've done some work on this myself,
>> actually, and I once submitted a patch implementing HAS_XXX for member
>> templates, but I believe it got lost in the SVN migration. This is
>> another topic that doesn't relate to is_range, but yeah, sure, if you
>> have something along these lines, by all means, share it! ;-)
>>
>
> Yeah we kinda miscommunicated on this topic. I'll gather what I have and see
> what is worth sharing.
> basically, what I tried to do was a generic
>
> BOOST_HAS_METHOD_NAMED(foo, (int,int))
>
> that check for presence of a given method with a given prototypes in types
> with variations to catch or not to catch
> const version of a named methods etc. The code is rather simple IIRC as it's
> roaming the internet since ages but
> never put into a proper usable macro I think.

That sounds great. Nice that you handle constness. I would suggest
adding support for volatility, as well, but yeah, sounds good so far.

> I also think we can check what's needed for this and how to put it properly.
> If you think it's worth, maybe we should start
> a new topic and work over this.

Sure! If you have member functions, I have member templates, and
member types are already in MPL, then all we lack are macros for
member data and member function templates. I would suggest naming the
complete set of class-based introspection macros like so:

BOOST_HAS_MEMBER_DATA
BOOST_HAS_MEMBER_TYPE
BOOST_HAS_MEMBER_TEMPLATE
BOOST_HAS_MEMBER_FUNCTION
BOOST_HAS_MEMBER_FUNCTION_TEMPLATE

And of course, if expression SFINAE gets ironed out soon, we could go
ahead and add BOOST_HAS_EXPRESSION and perhaps some metafunctions in
support of concept-based introspection... or maybe a better term for
it would be expression introspection. But one step at a time...

Why don't we both package what we have, upload to vault, and then work
out merging the two and adding the rest in another thread?

Daniel Walker