Re: Partition for Emacs Lisp

[Marc Tfardy]

Pascal J. Bourguignon schrieb:
> Marc Tfardy <bum@cyk.cyk> writes:
>
>> Hi!
>>
>> I looking for a ELISP function that do the job like Partition in
>> Mathematica. The simplest case:
>>
>> (partition '(a b c d e f) 2)
>> should return:
>> ((a b) (c d) (e f))
>
> (defun partition-list (list length)
>   (loop
>      while list
>      collect (subseq list 0 length)
>      do (setf list (nthcdr length list))))
>
> (defun partition-vector (vector length)
>   (loop
>      for i = 0 then (+ i length)
>      while (< i (length vector))
>      collect (subseq vector i (+ i length))))
>
> (defun partition (sequence length)
>    (etypecase sequence
>       (list   (partition-list sequence length))
>       (string (partition-vector sequence length)) ; emacs lisp strings are 
not vectors!
>       (vector (partition-vector sequence length))))
>
> (partition '[a b c d e f] 2)  -> ([a b] [c d] [e f])
> (partition '(a b c d e f) 2)  -> ((a b) (c d) (e f))
> (partition '"abcdef" 2)       -> ("ab" "cd" "ef")

Thanks a lot!!


>> Is there something ready out from the box?
>
> Perhaps.  But if you didn't search in the manual,

I did search in the manual and in internet but without success.


> it must be because it would take more time than to write partition
> yourself

Sure, but my lisp skills are not so brilliant, so after ca. one hour
searching I've capitulate and posted my question. I had already
suspected the loop as a possible solution but the loop syntax was so
harrowing that I've given up.


> so I didn't search in the manual either, and wrote it to steal you the
> fun of writing it yourself.

Oh my friend - it is no problem! :-) Thanks again!

regards
Marc