Re: Checking conditions unrelated to expression

[Thibaut Verron <thibaut.verron@gmail.com>]

Le dim. 8 déc. 2024 à 13:06, Heime via Users list for the GNU Emacs text
editor <help-gnu-emacs@gnu.org> a écrit :

> It looks like pcase can only be used with some variable condition
>
> This will check condition of featr
>
>   (pcase featr
>      ('this (do-this))
>      ('that (do-that))
>      (_ (message "some message"))
>
> What if I want to check a number of conditions, not all dependent upon
> featr, what should one do?
>
> Suppose I want to test (eq duck 'quack), cannot use a pcase because tests
> are dependent upon featr.
>
>   (pcase featr
>      ('this (do-this))
>      ('that (do-that))
>      (_ (message "some message"))
>

You can use a plain case-switch, rather than a pattern-matching one:

(cond
  ((eq featr 'this) (do-this))
  ((eq featr 'that) (do-that))
  ((eq duck 'quack) (do-duck))
  (t (message "blabla")))

https://www.gnu.org/s/emacs/manual/html_node/elisp/Conditionals.html

You can also replace the first two cases by a pattern-matching case, if
you'd like:

(cond
  (pcase featr
      ('this (do-this) t) ;; important to return non-nil in each branch
      ('that (do-that) t)
      (_ nil))
  ((eq duck 'quack) (do-duck))
   (t (message "blabla")))