cl position performances

cl position performances

[Thierry Volpiatto]

Hi,
i wrote a very simple definition of `position' for use in
traverselisp.el,(to avoid warnings) and i noticed that this is faster
than the usual cl `position'.
That can be interesting for very large list.

,----
| (defsubst* traverse-position (item seq &key (test 'eq))
|   "A simple replacement of CL `position'."
|   (loop for i in seq for index from 0
|      when (funcall test i item) return index))
`----

,----
| ELISP> (position (bookmark-get-bookmark "mes_scripts") bookmark-alist)
| 525
| ELISP> (traverse-position (bookmark-get-bookmark "mes_scripts") bookmark-alist)
| 525
`----

,----
| position           2           0.000817      0.0004085
| traverse-position  1           0.000283      0.000283
`----

Also,

would be great all the (great) CL package be more integrated in elisp.

Just an example:

Try to get documentation of this same `position' function with C-h S.

-- 
Thierry Volpiatto

Re: cl position performances

[Stefan Monnier]

> I wrote a very simple definition of `position' for use in
> traverselisp.el,(to avoid warnings) and i noticed that this is faster
> than the usual cl `position'.
> That can be interesting for very large list.

Do you happen to know or have some idea of where the speed difference
comes from?

> Try to get documentation of this same `position' function with C-h S.

Very good point, please post this to bug-gnu-emacs.


        Stefan