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Re: Replace trivial pcase occurrences in the Emacs sources

From: Garreau\, Alexandre
Subject: Re: Replace trivial pcase occurrences in the Emacs sources
Date: Thu, 01 Nov 2018 02:34:30 +0100
User-agent: Gnus (5.13), GNU Emacs 25.1.1 (i686-pc-linux-gnu, GTK+ Version 3.22.11) of 2017-09-15, modified by Debian

On 2018-10-31 at 13:48, Clément Pit-Claudel wrote:
> On 31/10/2018 12.13, Eli Zaretskii wrote:
>>> Cc: address@hidden
>>> From: Dmitry Gutov <address@hidden>
>>> Date: Wed, 31 Oct 2018 18:05:44 +0200
>>>> Can someone enlighten me regarding those "holes"?  What does that
>>>> allude to?
>>> I stole the term from Clement here: 
>>> http://lists.gnu.org/archive/html/emacs-devel/2018-10/msg00590.html
>> Ah, the elements that are assigned by destructuring?  I indeed hoped
>> we could identify in some way the patterns which satisfy that
>> condition.  I didn't give up yet.
> Regarding the word "holes": I think these ","-prefixed symbols are
> typically called "pattern-matching variables", or "placeholders".
> "holes" is the more colloquial term, the idea being that if you "fill"
> the "holes" in the pattern with the appropriate values, you get the
> original data back (formally, you perform a "substitution" of the
> "placeholders").
> Regarding the term "destructuring pattern": I think it's perfect.  The
> only other decent alternative I can think of would be
> "variable-binding pattern".

So may we not define “destructuring pattern” as a “structure pattern
that use placeholders”, a “structure pattern” as a “pattern only
matching a structure, whose subpatterns match its subelements”, and a
“placeholder” as a “match-everything symbol that binds what it match to
its name”?

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