Re: [boost] [multiindex] internal scope_guard has changed access from public to protected

Subject: Re: [boost] [multiindex] internal scope_guard has changed access from public to protected
From: Thorsten Ottosen (thorsten.ottosen_at_[hidden])
Date: 2010-05-29 17:31:20

Jeffrey Lee Hellrung, Jr. skrev:

> However, it appears Thorsten's implementation creates a null_guard if 
> the condition *is* true (the boolean is named "is_null", after all). I'd 
> consider Joaquin's semantics to be less confusing.

Oh, I overlooked that. I simple did what felt most natural
from a usage perspective, to avoid negating the constant. AFAICT, this 
the most common usage scenario. Thus when I see

   make_guard_if<boost::has_nothrow_copy<T>::value>( ... )

I don't read the _if alone (as part of what is being returned), but I 
read the whole make_guard_if<> as a tool that generates guards as needed
depending on has_nothrow_copy<>.

Joaquin, what is your take on this?

> Also, since I'm here, perhaps you should have a make_obj_guard_if_c 
> taking the boolean template parameter, while make_obj_guard_if takes a 
> Boost.MPL boolean constant class.  This is the convention used by 
> Boost.EnableIf and Boost.MPL (among other Boost libraries), right?

The if_c<> code is usually pure meta code which is not the case here.

-Thorsten