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From: Artur Malabarba <bruce.connor.am@gmail.com>
To: Stefan Monnier <monnier@iro.umontreal.ca>
Cc: emacs-devel <emacs-devel@gnu.org>,
	Thierry Volpiatto <thierry.volpiatto@gmail.com>
Subject: Re: What to do for faster `remove-duplicates'?
Date: Wed, 6 May 2015 22:18:14 +0100	[thread overview]
Message-ID: <CAAdUY-KnaKM8KUH-47xsjZBKx7kPCgCsj_wM70HCwD9-=1ey2g@mail.gmail.com> (raw)
In-Reply-To: <jwvvbg58m4g.fsf-monnier+emacs@gnu.org>

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On May 6, 2015 9:54 PM, "Stefan Monnier" <monnier@iro.umontreal.ca> wrote:
>
> >>> Looks good, please install.
> >> Not so good as now it is no more destructive for a seq > 100.
>
> Not being destructive doesn't seem like a serious problem to me.

Usually, yes. But here the docstring specifically documents that
"Destructively remove `equal' duplicates from LIST.
Store the result in LIST and return it."

>
> > modified   lisp/subr.el
> > @@ -424,12 +424,12 @@ one is kept."
> >            (unless (gethash elt hash)
> >              (puthash elt elt hash)
> >              (push elt res)))
> > -        (nreverse res))
> > +        (setcdr list (cdr (nreverse res))))
>
> I don't understand what this is intended to do.

It destructively modifies list to be equal to (nreverse res). The car is
already the same, so only the cdr needs to be modified.

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  reply	other threads:[~2015-05-06 21:18 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-05-06  7:33 What to do for faster `remove-duplicates'? Oleh Krehel
2015-05-06 12:59 ` Stefan Monnier
2015-05-06 13:30   ` Oleh Krehel
2015-05-06 13:50     ` Stefan Monnier
2015-05-06 13:51       ` Oleh Krehel
2015-05-06 17:43       ` Thierry Volpiatto
2015-05-06 17:54         ` Oleh Krehel
2015-05-06 18:31         ` Artur Malabarba
2015-05-06 18:33           ` Artur Malabarba
2015-05-06 18:41             ` Oleh Krehel
2015-05-06 19:24               ` Artur Malabarba
2015-05-06 19:32                 ` Oleh Krehel
2015-05-06 21:22                   ` Artur Malabarba
2015-05-06 18:48           ` Thierry Volpiatto
2015-05-06 20:54             ` Stefan Monnier
2015-05-06 20:54           ` Stefan Monnier
2015-05-06 21:18             ` Artur Malabarba [this message]
2015-05-06 14:04     ` Artur Malabarba
2015-05-06 14:13       ` Oleh Krehel
2015-05-06 14:49         ` Artur Malabarba

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