From: Dmitry Gutov <dgutov@yandex.ru>
To: Alan Mackenzie <acm@muc.de>, emacs-devel@gnu.org
Subject: Re: A protest against pcase, pcase-let, pcase-let*
Date: Tue, 31 Mar 2015 22:25:30 +0300 [thread overview]
Message-ID: <551AF4AA.3040300@yandex.ru> (raw)
In-Reply-To: <20150331180029.GF2871@acm.fritz.box>
On 03/31/2015 09:00 PM, Alan Mackenzie wrote:
> OK, maybe pcase itself has a page in the elisp manual, but this page is
> very difficult to understand, certainly for me. I have attempted quite
> a lot of times to make sense of it, and failed.
I think it's pretty nice. It provides pattern matching, as well as
destructuring (something that previously required the use of cl-lib), in
a concise and performant way.
The docs can look a bit dense at first, but after reading them carefully
and experimenting a bit, I'm sure most people can get a hang of it.
> There are two possibilities here: (i) the page is difficult because
> pcase is itself difficult.
It's not trivial. Pattern matching is, usually, a feature of more
advanced programming languages. But that doesn't mean we shouldn't use it.
> pcase-let and pcase-let* are totally absent from the elisp manual.
> Their doc strings say nothing more than "Like `let' but where you can
> use `pcase' patterns for bindings.", without giving any clue as to what
> "`pcase' patterns" are, or what the syntax and semantics of their
> "use" of them for bindings look like.
`pcase' patterns are described in the `pcase' docstring, and in the
manual entry for it.
The semantics of use of them for bindings should be pretty apparent
after you understand how to use `pcase' itself.
> As an aside, I suspect that edebug will not be useful in (possibly
> large) uses of these forms, given that they are implemented as macros
> rather than special forms.
It worked well when I tried it.
next prev parent reply other threads:[~2015-03-31 19:25 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-03-31 18:00 A protest against pcase, pcase-let, pcase-let* Alan Mackenzie
2015-03-31 18:29 ` John Wiegley
2015-04-18 1:47 ` Ted Zlatanov
2015-03-31 19:25 ` Dmitry Gutov [this message]
2015-04-01 7:46 ` Daniel Colascione
2015-04-01 9:59 ` Phillip Lord
2015-04-01 12:04 ` Nic Ferrier
2015-04-01 12:16 ` Dmitry Gutov
2015-04-01 13:53 ` Stefan Monnier
2015-04-02 7:19 ` Richard Stallman
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