adding a string to every element in a list

adding a string to every element in a list

[Matt Price]

hi,

it's not obvious to me how i would do something as simple as iterating
through the elements of a list, modifying each element in hte same way.
so in python i would have a list:

mylist = ["a" "silly" "list"]
for element in mylist:
	element += ADD
and the new list would be ["aADD" "sillyADD" "listADD"]

i'm making a list of vcards from a string containing many vcards:
(let 
((matches (split-string (shell-command-to-string 
                 (concat "/home/matt/mutt-eds-query "  namestring)) "^END:VCARD" t)))))
but unfortunately i need to retain the seperator string, so i want to
iterate over each element of the list, changing each element.  i have no
doubt this is trivial in lisp, but my documentation searches always take
me back to cons, car, and cdr, which don't seem like the easiest tools
for this task, though maybe it's just that i don't really understan
recursion... 

thanks again,
matt


-- 
Matt Price
matt.price@utoronto.ca

Re: adding a string to every element in a list

[Matthew Flaschen]

Matt Price wrote:
> i have no doubt this is trivial in lisp, but my documentation searches always take
> me back to cons, car, and cdr, which don't seem like the easiest tools
> for this task, though maybe it's just that i don't really understan
> recursion... 

Just use mapcar, and it will handle the recursion:

(setq list (list "dog" "cat" "fish"));
(mapcar (lambda (arg) (concat arg "food")) list)

Matt Flaschen

RE: adding a string to every element in a list

[Drew Adams]

> it's not obvious to me how i would do something as simple as iterating
> through the elements of a list, modifying each element in hte 
> same way. mylist = ["a" "silly" "list"]
> and the new list would be ["aADD" "sillyADD" "listADD"]

C-h f mapcar

Re: adding a string to every element in a list

[Matt Price]

thanks matt,

i don't know why this didn't occur to me -- i was hung up on modifying
the original list, i guess, not thinking i could just create a new one.

anyway thanks to you and to drew, who also replied.

matt


On Mon, 2008-11-17 at 01:06 -0500, Matthew Flaschen wrote:
> Matt Price wrote:
> > i have no doubt this is trivial in lisp, but my documentation searches always take
> > me back to cons, car, and cdr, which don't seem like the easiest tools
> > for this task, though maybe it's just that i don't really understan
> > recursion... 
> 
> Just use mapcar, and it will handle the recursion:
> 
> (setq list (list "dog" "cat" "fish"));
> (mapcar (lambda (arg) (concat arg "food")) list)
> 
> Matt Flaschen
-- 
Matt Price
matt.price@utoronto.ca

RE: adding a string to every element in a list

[Drew Adams]

> i don't know why this didn't occur to me -- i was hung up on modifying
> the original list, i guess, not thinking i could just create 
> a new one.

All of the mapping functions are good to know, as is `dolist'.

In general, don't even think about modifying list structure.
When you really need to do that, you will know it. ;-)

See the discussion here about list modification, in thread "Adding
Lists/Sequences" (2008-09):
http://lists.gnu.org/archive/html/help-gnu-emacs/2008-09/msg00809.html