Re: [boost] [date-time][threads] Integrating C++0x clocks, time points, and durations into Boost?

From: Beman Dawes (bdawes_at_[hidden])
Date: 2008-06-18 09:06:47

Beman Dawes wrote:
> A slightly updated version of
> http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2615.html was 
> accepted at the C++ committee meeting last week. It provides clocks, 
> time points, and time durations for the C++0x standard library, and 
> slightly modifies the threads interface already voted into C++0x to use 
> these features. The only change in the version of the proposal actually 
> voted in, IIRC, was to leave identity alone. The final document will 
> appear in the post-meeting mailing in about two weeks.
> 
> Although these clock and time features evolved from Boost Date-Time, the 
> actual realization is quite different. So we've got a transition that 
> has to be managed. I'd personally like to see that transition occur 
> quickly, both because Boost.Threads depends on these features, and 
> because I can now bring forward an improved Boost.Timer based on these 
> features.
> 
> One suggestion is for Boost to provide an implementation of the headers 
> to be added to C++0x, and then to use those headers in the various Boost 
> libraries that need them. But I haven't thought it out in any detail.
> 
> How should we proceed? Comments? Ideas? Suggestions?

I've emailed Howard to see if his prototype implementation can be made 
available with the Boost license. The answer was yes, but he points out 
that an independent implementation would be better in terms of flushing 
out issues with the proposed text for the standard.

The proposal has several components:

* common_type: "common_type is a trait that takes 1 or more types, and 
returns a type which all of the types will convert to." Presumably it 
should be added to Boost.TypeTraits. It is closely related to promote<>.

* ratio: "ratio is a general purpose utility inspired by Walter Brown 
allowing one to easily and safely compute rational values at compile 
time." The proposal puts this in the Utilities chapter of the standard 
library. It has a lot of similarity to type traits.

* duration/clock/time_point: This stuff is closely related to 
Boost.DateTime, yet because it is part of C++0x it needs special 
treatment WRT header names, namespaces, documentation, etc.

* threads: Interface changes to use the new duration/clock/time_point 
features. This clearly lands in the lap of Anthony and the other 
Boost.Threads maintainers.

--Beman