Re: [External] : Re: Shrinking the C core

[João Távora]

On Mon, Sep 11, 2023 at 9:37 PM Tomas Hlavaty <tom@logand.com> wrote:

> not really, it seems that CL:SORT is a bad example

The example was for comparing to Emacs's lisp 'sort', where
IMO it's much easier to do

  (cl-sort things-having-foo #'< :key #'foo)

than

  (sort things-having-foo (lambda (a b) (< (foo a) (foo b))))

As to the advantage of @key key vs &optional key it is -- in my
eyes,  at least -- that you already know its meaning from many other
functions.

> (btw why two functions and not extra stablep keyword argument?)

Why not? Maybe that makes passing sort and stable-sort to higher
order functions more practical?

> it could have been defined as:
>
>    sort sequence predicate &optional key => sorted-sequence
>    stable-sort sequence predicate &optional key => sorted-sequence
>
> and the same could be done in elisp which would be backwards compatible

Sure, but if according to your conjecture Elisp's grew a &optional
arg, why couldn't it grow a &key arg and be backwards compatible?

> > Let's look at a traditional Elisp macro define-minor-mode.
>
> the usual CL argument list does not seem to be able to express arguments
> of such shape
>
> it looks like whoever extended the original argument list did it
> "weirdly" using custom ad-hoc single-use argument list parser.

Quite likely the cl machinery wasn't available at the time...  But yes,
Greenspun's 10th.

> > are maintenance hazards, the macro now accepts keyword arguments
>
> in CL, the arguments would normally be in a list before body, something
> like
>
>    (define-minor-mode MODE ([KEYWORD VAL ... ]) [DOC] &rest BODY)

OK, but this is irrelevant.  This is a macro, not a function.
For all practical purposes it was extended with keyword arguments.
In fact you could have used cl-lib's cl-destructuring-bind.

João