Should `position' be implemented in Emacs core and preloaded?

[Tino Calancha]

Hello Emacs,

sometimes i wonder why functions as useful as `position'
are an alias for `cl-position' instead of part of the core. I mean,
they could be implemented out of cl-lib and be preloaded.
Maybe for other more specialized functions is reasonable to load
`cl-lib', but IMO not to just use a fundamental function
as `position' is.

The functions i have in mind are: `position', `position-if',
`position-if-not' and `subsetp'.

*) `position': very fundamental operation on a sequence.  It
    deserves to be preloaded.
*) `position-if': i like this function very much, it's powerful.
*) `position-if-not': similar as previous one.
*) `subsetp': Another fundamental operation; it allow to check if
    several elements belong to one sequence in a compact way.
    For instance, compare:

(let ((options '(?a ?b ?v ?c)))
  (when (and (member ?a options)
             (member ?b options)
             (member ?c options))
    (message "All are included")))
=> "All are included"

;; with:

(let ((options '(?a ?b ?v ?c)))
  (when (subsetp '(?a ?b ?c) options)
    (message "All are included")))
=> "All are included"

I) We might implement them in, for instance, subr.el.
   This could break backward compatibility in code using
   the alias in cl.el, though; not in the current Emacs
   source code AFAICT.

II) Alternatively, they could be implemented in a lighter
    lib; i guess the natural candidate is seq.el.
    Note that this lib already has `seq-position'.

III) We might keep everything as it is.

IV) Other options that i couldn't imagine.

I would be glad to read your opinions about this idea.
Thank you very much.
Tino