From: Stefan Monnier <monnier@iro.umontreal.ca>
To: emacs-devel@gnu.org
Cc: Nicolas Petton <nicolas@petton.fr>
Subject: Re: [Emacs-diffs] master 387e1e1: New version of `seq-let' based on a pcase pattern
Date: Mon, 11 May 2015 00:15:05 -0400 [thread overview]
Message-ID: <jwvzj5bzsky.fsf-monnier+emacsdiffs@gnu.org> (raw)
In-Reply-To: <E1YrVuR-00064X-CK@vcs.savannah.gnu.org> (Nicolas Petton's message of "Sun, 10 May 2015 18:25:03 +0000")
> + (pcase-defmacro seq (bindings)
> + `(and ,@(seq--make-pcase-bindings bindings)))
If you put a docstring in there, it will appear in "C-h f pcase RET", so
you can use it to document the particular format you support.
Also I see the following problems:
- You only accept the form (seq <binding>) rather than (seq <binding1>
<binding2> ...), so typical cases will have to use (seq (a b)) instead
(seq a b).
- The above pcase pattern doesn't check that it's indeed a `seq'.
You should add a (pred seq-p). It will automatically be optimized
away in `pcase-let', but is indispensable for the `pcase' situation to
do the right thing.
> +(defun seq--make-pcase-bindings (args &optional bindings nested-indexes)
[...]
> + (seq-doseq (name args)
> + (unless rest-marker
> + (pcase name
> + ((pred seq-p)
IIUC, this means that (pcase-let (((seq a (seq b c)) <obj>)) <body>)
will bind the `seq' variable to the first element of the nested sequence
(and `a' to the second and `b' to the third), whereas I think it should
bind `b' to the first element of the nested sequence (which is what
would happen if you simply removed this branch of this `pcase').
I think removing this case will also remove the need for seq--nested-elt.
> + (push `(app (seq--reverse-args #'seq--nested-elt
> + (reverse (cons ,index ',nested-indexes)))
> + ,name)
This reverse plus seq--reverse-args business seems
hideously inefficient. Why do you need that?
Stefan
next parent reply other threads:[~2015-05-11 4:15 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20150510182502.23307.63648@vcs.savannah.gnu.org>
[not found] ` <E1YrVuR-00064X-CK@vcs.savannah.gnu.org>
2015-05-11 4:15 ` Stefan Monnier [this message]
2015-05-11 13:42 ` [Emacs-diffs] master 387e1e1: New version of `seq-let' based on a pcase pattern Nicolas Petton
2015-05-11 15:06 ` Stefan Monnier
2015-05-11 21:13 ` Nicolas Petton
2015-05-11 21:35 ` Nicolas Petton
2015-05-12 1:03 ` Stefan Monnier
2015-05-12 6:51 ` Nicolas Petton
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