code for the transpose of a list of lists.

This is the code for a version of transpose, this one is destructive, so
 perhaps should be called transpose!.
?
?This version is about 
seven time faster than the version in maxima list.

?Yours 
sincerely, Pero Garrido
?

?? (defun transpose(m)
? (let (m1)
??? 
(setq m1 (loop for x on (car m) collect x))
??? (transposeaux m)
???
 m1))
??? ??? ?
(defun transposeaux(ll)
? (let (next)
??? 
(loop for l1 in ll
?????? for l2
 in (cdr ll) do
??? ?? (loop for ai = l1 then next 
??? ????? for 
bi on l2 do
??? ??? (setf next (cdr
 ai))
??? ??? (rplacd ai bi))
??? ?finally 
??? ?? (loop for bi
 = l2 then next 
??? ??? while (cdr bi) do
??? ??? (setf next (cdr
 bi)
??? ??? ????? (cdr bi) nil)))??? ???? 
??? ll))

(defmacro
 tra(m)
? `(setq ,m (transpose ,m)))