Re: [boost] C++11 Metaprogramming

Subject: Re: [boost] C++11 Metaprogramming
From: Dave Abrahams (dave_at_[hidden])
Date: 2012-04-05 10:25:56

on Wed Apr 04 2012, Sebastian Redl <sebastian.redl-AT-getdesigned.at> wrote:

> On 03.04.2012, at 19:20, Dave Abrahams wrote:
>
>> 
>> on Sun Apr 01 2012, Olivier Grant <olivier.grant-AT-gmail.com> wrote:
>> 
>>> Hi Dave,
>>> 
>>> That's going to be an interesting presentation. Here is a small piece of
>>> code that allows to generate a traits structure that determines if a call
>>> can be made on an object with a specific function name and specific
>>> arguments and return value :
>>> 
>>> https://gist.github.com/2276393
>>> (compile with : g++ -std=c++0x -Wall -o has_callable has_callable.cpp)
>>> 
>>> This was not possible in C++03, or at least not completely possible, and
>>> the code is much simpler with C++11 for the cases where it was possible as
>>> well.
>> 
>> Yep, I see.  However, I also have some questions about the utility of
>> such traits.  As I mentioned to Mathias, structural matching is always
>> susceptible to false positives.  What do you use this for?
>
> I have used something like this to define a generic Set concept (bool
> contains(const Set& set, const Value& value)). Since in this concept,
> every normal value represents its own singleton set, I have used
> is_callable to separate out functions and function-like objects that
> return bool.

Hm.  Can you describe this concept more fully, e.g. with a requirements
table or ConceptGCC syntax?

-- 
Dave Abrahams
BoostPro Computing
http://www.boostpro.com