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From: Andy Moreton <andrewjmoreton@gmail.com>
To: emacs-devel@gnu.org
Subject: Re: Any interest in a function like this to add to subr.el?
Date: Wed, 19 Oct 2016 14:46:02 +0100	[thread overview]
Message-ID: <vz1mvi0laed.fsf@gmail.com> (raw)
In-Reply-To: m2mvi17ddl.fsf@newartisans.com

On Tue 18 Oct 2016, John Wiegley wrote:

> (defun sort-on (seq predicate accessor)
>   "Sort SEQ use PREDICATE applied to values returned by ACCESSOR.
> This implements the so-called Schwartzian transform, which has
> the performance advantage of applying ACCESSOR at most once per
> element in the list, as opposed to using `sort' with a PREDICATE
> that applies the ACCESSOR.
> Note: this function is only a win over `sort' if ACCESSOR is
> compute-intensive; otherwise, it uses more intermediate cons
> cells than regular `sort', and so represents a memory for CPU
> tradeoff."
>   (mapcar #'cdr (sort (mapcar #'(lambda (x) (cons (funcall accessor x) x)) seq)
>                       #'(lambda (x y) (funcall predicate (car x) (car y))))))

Doesn't a specialised routine like this belong in subr-x.el ? At least
initially, until it is demonstrated that there is widespread need for it
in emacs core.

    AndyM




  parent reply	other threads:[~2016-10-19 13:46 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-10-18 17:53 Any interest in a function like this to add to subr.el? John Wiegley
2016-10-18 20:13 ` Dmitry Gutov
2016-10-18 20:34   ` John Wiegley
2016-10-18 21:09     ` Dmitry Gutov
2016-10-18 21:25       ` John Wiegley
2016-10-19  5:01         ` Ken Raeburn
2016-10-19  6:02           ` John Wiegley
2016-10-19 14:51         ` Stefan Monnier
2016-10-19 14:48       ` Stefan Monnier
2016-10-19 23:12         ` Dmitry Gutov
2016-10-20  1:48           ` Stefan Monnier
2016-10-19 13:46 ` Andy Moreton [this message]
2016-10-19 14:52   ` Stefan Monnier

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