Re: [boost] [type_traits] Rewrite and dependency free version

Subject: Re: [boost] [type_traits] Rewrite and dependency free version
From: John Maddock (jz.maddock_at_[hidden])
Date: 2015-02-01 05:45:55

>> 2) What do we do about common_type?
>
> This is still not addressed, right?
>
> Can you say what the current state of the rewrite is, the intention of how
> it will be used (ie, replace existing vs maintained in parallel), and
> blockers to reaching that point?

I've been suffering from sudden laptop failure, which is why I've been 
silent on this - I'll post more when I'm up and running again - but the 
current version of the branch should have a common_factor which only has 
dependencies outside of Boost.Config for broken/obsolete compilers 
(please note: I haven't fully tested/checked this, and won't until my 
new laptop arrives sometime next week).  In such a case I think it would 
be acceptable to manually mark up that header with some "don't track 
dependencies" directive and require users to manually add Boost.Typeof 
to their list of required modules if they're using an old compiler.

Note that we need some kind of markup facility to deal with optional 
dependencies anyway - to avoid the "everything depends on Serialization" 
issue.  So maybe something like:

/*

BPM nodepend
BPM start_message
Note: If you're using boost::common_type with a compiler that supports 
neither the decltype nor typeof keywords, then you will need to manually
add the "typeof" library to your download list.
BPM end_message

*/

Other than that, I've nearly finished testing the new version and IMO it 
looks good enough to simply replace the old version - but again more later.

John.