Re: Checking conditions unrelated to expression

[Heime via Users list for the GNU Emacs text editor <help-gnu-emacs@gnu.org>]

Sent with Proton Mail secure email.

On Monday, December 9th, 2024 at 12:31 AM, Thibaut Verron <thibaut.verron@gmail.com> wrote:

> 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")))


But I cannot do the other way round, right?  Cannot have a pcase using featr
as EXP, but checking something else.