Pascal Bourguignon wrote:

> Teemu Likonen <tlikonen@iki.fi> writes:
>
> > It's a Common Lisp newbie here; I'm more experienced in Emacs Lisp. I
> > wonder if there is similar function in CL like Emacs Lisp's "mapconcat":
> >
> > (mapconcat 'identity '("one" "two" "three") "-")
> > => "one-two-three"
> >
> > I can do the same in CL with this:
> >
> > (let ((list '("one" "two" "three")))
> > (format nil "~{~a-~}~a" (butlast list) (car (last list))))
> >
> > But I have a feeling that there could be a more elegant way. Is there?
>
> Yes, write: (mapconcat 'identity '("one" "two" "three") "-") ; elegant!
>
>
> Of course, with:
>
>
> (defun mapconcat (fun list sep)
> (when list
> (let ((~sep (with-output-to-string (*standard-output*)
> (map nil (lambda (ch) (princ (if (char= #\~ ch) "~~" ch)))
> sep))))
> (format nil (format nil "~~A~~{~A~~A~~}" ~sep)
> (funcall fun (first list))
> (mapcar fun (rest list))))))
>
>
>
> (mapconcat 'identity '("one" "two" "three") "-")
> --> "one-two-three"
>
> (mapconcat (lambda (x) (concatenate 'string "[" x "]")) '("one" "two" "three") "
> ~")
> --> "[one]~[two]~[three]"

Gauche Scheme:

(define (mapconcat fun lst sep)
(reduce-right
(cut string-append <> sep <>)
""
(map fun lst)))

(mapconcat values '("one" "two" "three") "-")
===>
"one-two-three"

(mapconcat x->string '("one" 2 three) "-")
===>
"one-2-three"