[m-rev.] for review: rationalise hash functions across the standard library

[Peter Wang]

On Sun, 16 Feb 2020 13:38:13 +1100 (AEDT), "Zoltan Somogyi" <zoltan.somogyi at runbox.com> wrote:
> 
> 2020-02-16 13:25 GMT+11:00 Peter Wang<novalazy at gmail.com>:
> >> Peter, could you tell me why version_hash_table uses user-defined equality?
> >> The change was done by pbone, but I hope you may have discussed the
> >> issue with him. The discussion on m-rev in May 2013, when the user defined
> >> equality was added, says nothing about *why* it was added, except one
> >> possibly-relevant vague reference to "MC needing it", and I see nothing
> >> relevant in that time frame in m-dev.
> > 
> > I don't know.
> 
> In that case, would you mind if I deleted it? Semantically, yes,
> the equality we want is the one now specified by "where equality is"
> and not the default syntactic equality, but the same is true for
> most of the other collection types, and we don't have user defined
> equality for most of them. So having them for version_hash_tables
> is just a (seemingly) pointless difference from hash_tables themselves.

I don't mind but I don't have or work on any code that would be affected
(AFAIK). You may wish to ask Paul or on mercury-users.

Peter