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

[Andy Moreton]

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