bug#69709: `sort` interface improvement and universal ordering predicate

[Eshel Yaron]

Hi,

Mattias Engdegård <mattias.engdegard@gmail.com> writes:

> Now the origin/scratch/sort-key branch contains a draft proposal. Summary:
>
> * Our timsort has now the key function handling from the original code 
> (ported to Emacs).
> * New keyword-based calling convention for `sort`. The old one is still there 
> and works as before.
> * New `value-less-p` universal ordering predicate.
> * No manual updates yet.
> * NEWS entries are there.
> * `sort-on` is now completely superfluous (slower, less convenient) and 
> should be removed.

In case it hasn't already been mentioned, AFAICT this also applies to
`minibuffer--sort-by-key` (which is very similar to `sort-on`).

> * Performance seems fine from initial tests. More comprehensive benchmarking 
> will be done.
>
> Some things that I haven't made up my mind about:
>
> * Better name for `value-less-p`:
>     value<
>     {generic,universal,standard,lisp}{-less-p,<}
>
> * Maybe the :destructive keyword be called :inplace or :in-place instead? 
> Shorter, less violent.
>
> * Should the :reverse keyword be called :reversed or even :descending ?
>
> * Internally, `value-less-p` computes a 3-way result; it would be easy
> to expose that to Lisp as `value-compare`, could be useful.
>
> * The design space for `value-less-p` is vast: the current code is an
> attempt at intuitive semantics without too much complexity.

Perhaps the "standard order" of Prolog terms programs could be an
interesting reference:
https://www.swi-prolog.org/pldoc/man?section=standardorder


Best,

Eshel