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Re: cond* vs pcase
From: |
Philip Kaludercic |
Subject: |
Re: cond* vs pcase |
Date: |
Tue, 06 Feb 2024 16:50:02 +0000 |
"Alfred M. Szmidt" <ams@gnu.org> writes:
> "Alfred M. Szmidt" <ams@gnu.org> writes:
>
> > I use pcase often; but I use it just as a better cond. For example I
> find this
> > handy:
> >
> > (defvar foo nil) <-- foo is some symbol
> >
> > (pcase foo
> > ('bar (do-some-bar-stuff))
> > ('baz (do-some-baz-fluff)))
> >
> > cl-case seems more appropriate here (wish cl-case was just case ...)
>
> Why more appropriate?
>
> Because your not doing pattern matching, you're comparing against a
> set of strings/symbols/numbers/....
Simply because pattern matching is a more powerful generalisation,
capable of expressing case-distinction; in the end it compiles down to
almost the same code anyway.
> I always think of pcase as Elisp's case. In
> addition, pcase avoids the danger of naively writing
>
> (cl-case foo
> ('bar (do-some-bar-stuff))
> ('baz (do-some-baz-fluff)))
>
> and then getting surprised when foo evaluates to `quote'.
>
> Suprises will happy, you will get suprises with pcase and cond* too --
> I find it suprising that to match over symbols requires pattern
> matching. One might also question why you (well, no you specifically)
> are comparing against (quote bar) etc? That is a suprise in it self...
I don't understand your point here. If one expects the cases to be
evaluated, then quoting makes sense if you want to match a symbol. It
is not true, but common enough that the byte compiler emits a warning.
> > or this:
> >
> > (setq foo "some-string")
> >
> > (pcase foo
> > ("foo" (do-foo-case))
> > ("bar" (do-bar-case)))
> >
> > Same here, with (intern foo) ...
>
> Being able to do equal instead of eql is also something that speaks in
> favour of pcase...
>
> It speaks more in favor of having CASE where you can change the
> comparison operator or a CASE-STRING or similar, not something much
> more generic pcase (or even cond*!) -- i.e. why use pcase/cond* when
> you're not using any of the features that are the main point of those
> two macros.
I am sorry, but I don't follow your point here either. Is the general
claim, that one should only use whatever exactly and at most satisfies
the needs at hand?
- cond* vs pcase, Arthur Miller, 2024/02/05
- Re: cond* vs pcase, Eli Zaretskii, 2024/02/05
- Re: cond* vs pcase, Alfred M. Szmidt, 2024/02/05
- Re: cond* vs pcase, Philip Kaludercic, 2024/02/05
- Re: cond* vs pcase, Arthur Miller, 2024/02/06
- Re: cond* vs pcase, Alfred M. Szmidt, 2024/02/06
- RE: [External] : Re: cond* vs pcase, Drew Adams, 2024/02/06
- Re: cond* vs pcase,
Philip Kaludercic <=
- Re: cond* vs pcase, Alfred M. Szmidt, 2024/02/06
- Re: cond* vs pcase, Philip Kaludercic, 2024/02/06
- Re: cond* vs pcase, Alfred M. Szmidt, 2024/02/06
- Re: cond* vs pcase, Philip Kaludercic, 2024/02/06
- RE: [External] : Re: cond* vs pcase, Drew Adams, 2024/02/06
- RE: [External] : Re: cond* vs pcase, Drew Adams, 2024/02/06
- RE: [External] : Re: cond* vs pcase, Adam Porter, 2024/02/06
- RE: [External] : Re: cond* vs pcase, Drew Adams, 2024/02/06
- Re: [External] : Re: cond* vs pcase, Arthur Miller, 2024/02/07
- Re: [External] : Re: cond* vs pcase, Po Lu, 2024/02/07