Re: cl.el sort* efficiency

[Juanma Barranquero]

On 12/22/06, Kevin Ryde <address@hidden> wrote:

> I noticed that cl sort* function calls the given :key function within
> every comparison, which is not good if key extraction is a big slow
> calculation.

[...]

> The code below is an idea to build key results in an alist and sort
> that.

You're implementing a Schwartzian Transform
(http://en.wikipedia.org/wiki/Schwartzian_transform) inside sort*,
which is kinda odd.

IMHO is the responsibility of the user of sort* to know whether
comparisons are going to be expensive and preprocess the data to help
in the comparison. You're doing an optimization at the wrong level:
perhaps I'm using it with so light a comparison function that your
method makes it more expensive...

Perhaps you could encapsulate your ST in a function and use it as a
wrapper for sort*.

                   /L/e/k/t/u