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Subject: Re: [Boost-users] Boost 1.68.0 - boost hashing changed ?
From: Richard Hodges (hodges.r_at_[hidden])
Date: 2018-10-24 11:13:28

On Tue, 23 Oct 2018 at 12:36, degski via Boost-users <
boost-users_at_[hidden]> wrote:

> On Tue, 23 Oct 2018 at 11:25, Miguel Ojeda <
> miguel.ojeda.sandonis_at_[hidden]> wrote:
>> > Well, uhm, because that seems to be quite handy. All NIST
>> implementations do exactly this.
>> No, sorry, that is a completely different use case. Crypto hashes are
>> used, among other things, in network communications, persistent
>> storage, etc. They need to be "fixed" functions, and their standards
>> provide the exact definition. That is not the case at all with
>> std::hash or Boost.Hash.
> For debugging purposes, a fixed function seems quite useful to me.

It's already difficult enough to teach new programmers not to serialise the
result of std/boost hash.

Providing a means to ensure that it's predictable would strengthen the
illusion that it's predictable across compilers and architectures. This
would be a grave error.

I would argue the opposite. std::hash should work hard to ensure that for
any two runs of the same program, the results of a hash will be wildly

This would make it easier to spot incorrect uses of it.


> degski
> --
> *“If something cannot go on forever, it will stop" - Herbert Stein*
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