Re: [boost] Re: [function types] Formal Review begins today.

From: Jody Hagins (jody-boost-011304_at_[hidden])
Date: 2005-06-07 20:16:11

On Wed, 08 Jun 2005 02:39:25 +0200
Tobias Schwinger <tschwinger_at_[hidden]> wrote:

> OK - if that's what you are trying to do your code look good (in case
> you said  this I must have overlooked it).
> 
> BUT: Careful here! The Tag contained in 'function_type_signature'
> describes the  kind of function type as detailed as possible:
> 
>      is_function_type< function_type_signature< void(*)() >::kind
>                      , void(*)(...) >::value
> 
> evaluates to 'false', because the tag given to 'is_function_type' is:
> 
>      non_variadic_defaultcall_function_pointer
> 
> while the tag computed from void(*)(...) is
> 
>      variadic_defaultcall_function_pointer
> 
> which is not a subset of the above.

Hmmm.  Kinda like getting the most derived type when calling typeid on
an instance of a polymorphic class.  Interesting.  I'm not sure how much
I like that, but I'm not sure about the alternatives either...

> Curious question: what's the intention behind this ?
I dunno.  I just thought it was a possible use of the interface. 
However, one of the thoughts was that I do not necessarily know the tag,
but I have a type.  Maybe something like iterating through a collection
of types, looking for types that are elements of the same type-tag set,
so that I can perform some action (like registering that type with some
multi-signal mechanism).

One of my mottos is: "If you don't want me to do it, don't provide the
interface."  Around here, I am known for "breaking" code the first time
I use it, because I seem to automatically see uses that were not
necessarily intended... it also explains some of the reasons I am so
pedantic about docs.