Re: cond* vs pcase

[Philip Kaludercic <philipk@posteo.net>]

"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?