Re: [boost] [boost.tr1?] request for a hash<> implementation

From: John Maddock (john_at_[hidden])
Date: 2005-02-05 05:54:52

> There are several Boost-related projects underway around the theme of
> unordered containers (in my case, I'm pretty much on the verge
> of releasing a preview of hashed indices for Boost.MultiIndex.)
> All these projects have the common need of a hash<> implementation
> being available, preferrably promoted to a public namespace rather
> than as an implementation detail.

Agreed.

> Although Boost.TR1's purpose is not to implement new features but
> rather wrap them to achieve std::tr1-compliance, I think it'd be very
> useful if some tr1-hash implementation could be added to Boost.
> For the record, I'm currently using Jeremy Maitin-Shepard and
> Daniel James' implementation in Sanbox files/unordered.tar.gz. I
> think it is a rather solid implementation, taking care of compilers
> witohut PTS such as MSVC++ 6.0/7.0.

Yes, I would also like to see that added - it really just needs some docs - 
there's not that much to review given that the design is fixed by the TR.

> As for the location, my pereference would be boost/functional/hash.hpp.
> Boost.TR1 could embrace this later in boost/tr1/functional.hpp.
>
> Could this be done? Maybe as a separate activity from Boost.TR1?
> Am I entitled to do it myself as part of the upgrade of my library,
> even though this would be adding a new library in disguise? As it
> happens, I think I'll be able to release hashed indices in time for
> Boost 1.33, but this detail can be a showstopper :(

Personally if your just talking about adding boost::hash<> (and not all the 
containers as well), then I would be inclined to suggest that you go ahead, 
although it might be better to place it (temporarily) either in detail, or 
under the pending sub-directories, since it hasn't been reviewed etc. 
Otherwise we might end up with another aligned_storage style clash at some 
point (although a TR-conforming version should always take preference).

Anyone else want to throw in their thoughts?  What's the timescale on the 
unordered container development, how much is there left to do?

John.