Re: Any interest in a function like this to add to subr.el?

[John Wiegley <jwiegley@gmail.com>]

>>>>> "DG" == Dmitry Gutov <dgutov@yandex.ru> writes:

GD> Then I agree that we want a function like that. We'd want a destructive
GD> version of it as well, though.

Yes, good idea!  How about something like this:

(defun sort-on* (seq predicate accessor)
  "Sort SEQ using PREDICATE applied to values returned by ACCESSOR.
This is a destructive version of `sort-on', which attempts to
reuse storage as much as possible."
  (let ((seq2 seq))
    (while seq2
      (setcar seq2 (cons (funcall accessor (car seq2)) (car seq2)))
      (setq seq2 (cdr seq2))))
  (setq seq (sort* seq #'(lambda (x y) (funcall predicate (car x) (car y)))))
  (let ((seq2 seq))
    (while seq2
      (setcar seq2 (cdar seq2))
      (setq seq2 (cdr seq2)))
    seq))

-- 
John Wiegley                  GPG fingerprint = 4710 CF98 AF9B 327B B80F
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