Re: [Boost-users] [Boost.TypeTraits] Adding specialisations

From: Kirit Sælensminde (kirit.saelensminde_at_[hidden])
Date: 2007-10-02 11:28:29

John Maddock wrote:
> Kirit Sælensminde wrote:
>> I think I have a misunderstanding of what the boost::function_traits
>> is doing. From your explanation it seems that boost::function_traits
>> is there to examine only function signatures where a function type is
>> of the form R( A1, A2, etc. ),
> 
> Correct.

What is the reason for the restriction?

It seems to make a number of common things unnecessarily verbose. For 
example, always having to wrap a some generic callable F with "typename 
boost::remove_pointer< F >::type". We don't need to do that if when we 
use the F. Higher order functions that take things like predicates allow 
us to just use the callable objects, why can't we do the same thing when 
we want to find out which types are involved?

It makes a lot of idioms copied from functional programming much more 
verbose to do than it seems they really need to be. As I say, by adding 
the specialisations myself I can do all sorts of interesting things that 
are too difficult to do otherwise.

For example, by adding specialisations for R(**)(...) I can use 
boost::function_traits with function pointers without needing to 
remember the remove_pointer. And by adding specialisations for 
boost::_bi::bind_t (which I probably have wrong, but stil) I can use 
boost::function_traits with the result of a boost::bind.

What is wrong with that? Or do we need a new library 
Boost.CallableTraits to deal with it?

K

BTW boost::result_of does help with the verbiage if include the 
remove_pointer, but it still doesn't work with the result of a boost::bind.