Re: [boost] [lambda] [result_of] Lambda enhancements

Subject: Re: [boost] [lambda] [result_of] Lambda enhancements
From: Daniel Walker (daniel.j.walker_at_[hidden])
Date: 2010-04-01 16:38:03

On Thu, Apr 1, 2010 at 2:11 PM, Steven Watanabe <watanabesj_at_[hidden]> wrote:
> AMDG
>
> Adam Butcher wrote:
>>
>> Perhaps this would have been better as two separate mails but since it
>> is all lambda related I have included it as one (despite one patch
>> actually being to the result_of library).
>>
>> <snip>
>> Is there an MPL/type_traits predicate generator for portable nested
>> template detection?  I am aware of BOOST_MPL_HAS_XXX_TRAIT_(NAMED_)DEF
>> but I couldn't see any generator around that area that would do nested
>> template detection.  We have such a facility in our code base but it
>> will have only been tried on GCC 4 and VC9 (maybe also VC7.1).
>>
>
> See http://svn.boost.org/trac/boost/ticket/861

As I recall, much of the code here was meant as infrastructure to
support general template introspection; i.e. detecting member class
templates and function templates in addition to the member types and
variables detected by has_xxx. At the time there didn't seem to be
much demand, so I set the project aside. If you're only concerned with
detecting member class templates, I'm sure there's more straight
forward implementations around that don't rely as heavily on
preprocessor metaprogramming.

> and http://svn.boost.org/trac/boost/ticket/864

This patch seemed to be missing, so I re-uploaded it. The patch was
the result of (no pun intended) some discussion. I found an e-mail
with an overview here http://tinyurl.com/2jgtld. To my knowledge, the
patch was never applied. It's been a few years, but my recollection is
that a rewrite of lambda was anticipated, which would address these
issues, and there was little demand for result_of/lambda compatibility
in the meantime. Also, there was no active maintainer for the lambda
library.

~Daniel