Re: [boost] [chrono] Interoperability with ICL and common concepts

Subject: Re: [boost] [chrono] Interoperability with ICL and common concepts
From: Stewart, Robert (Robert.Stewart_at_[hidden])
Date: 2011-03-15 15:38:30

Joachim Faulhaber wrote:
> 2011/3/15 Stewart, Robert <Robert.Stewart_at_[hidden]>:
>
> > Why can't ICL have a customization point for the identity value that
> > defaults to T()?  Then chrono can customize that (assuming there
> > is a suitable value to use).
>
> Hmm ... good simple question. So this implies a solution like this:
>
> //=== in or under boost/chrono/chrono.hpp ==================
>
> namespace boost{namespace icl
> {
>     template<class Type>struct identity_element;
>
>     template<class Rep, class Period>
>     struct identity_element<boost::chrono::duration<Rep,Period> >
>     {
>         typedef boost::chrono::duration<Rep,Period> duration_type;
>         typedef identity_element type;
>
>         static duration_type value()
>         {
>             return duration_type::zero();
>         }
>     };
> }}
>
> //==========================================================
>
> right?

That looks pretty good, except perhaps instead of declaring identity_element in the chrono header, it should include <boost/icl/identity_element.hpp> and just specialize for chrono::duration.  That leaves ICL as the sole owner of the primary specialization.

_____
Rob Stewart                           robert.stewart_at_[hidden]
Software Engineer                     using std::disclaimer;
Dev Tools & Components
Susquehanna International Group, LLP  http://www.sig.com

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