Re: [boost] [interprocess] boost::hash - different values for the same input?

Subject: Re: [boost] [interprocess] boost::hash - different values for the same input?
From: Daniel James (dnljms_at_[hidden])
Date: 2016-01-13 18:09:57

On 13 January 2016 at 22:18, Andrey Semashev <andrey.semashev_at_[hidden]> wrote:
>
> Do you think we could add a few well-known hash functions to Boost.Hash so
> that they could be used for consistent results?

I think that would be best handled in a new library. I don't really
want to enhance the existing one beyond its current scope, especially
as the current standard proposal is a bit different to it, and
supports alternative hash functions. Adding extra functions would
probably also mean that it wouldn't be a header only library, which
would be a problem.

If you haven't seen the new proposal, it's at:

http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/p0029r0.html

There's an implementation at:

https://github.com/google/hashing-demo/tree/N0029R0

I assume that something based on that proposal is likely to be
accepted. You could just use it (maybe I should add a macro to change
the default hash function in unordered....), or perhaps a boost
implementation could be based on it. One advantage of a new library is
that it can have much stricter compiler requirements which should
simplify the implementation.