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
(^(a b)
(apply string-append (map x->string (list a sep b))))
""
(map fun lst)))

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

(mapconcat square '(2 3 4) '---)
===>
"4---9---16"

B. Pym wrote:

> 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
> (^(a b)
> (apply string-append (map x->string (list a sep b))))
> ""
> (map fun lst)))
>
> (mapconcat values '(one "two" three) '-)
> ===>
> "one-two-three"
>
> (mapconcat square '(2 3 4) '---)
> ===>
> "4---9---16"

Shorter:

(define (mapconcat fun lst sep)
(string-join (map (compose x->string fun) lst) (x->string sep)))

On 2024-08-30, B. Pym <Nobody447095@here-nor-there.org> wrote:
> Shorter:
>
> (define (mapconcat fun lst sep)
> (string-join (map (compose x->string fun) lst) (x->string sep)))

"Concatenate" is a pleonasm for "catenate", which is based on a
Latin root for "chain". Chaining is implicitly together ("con").
Even the Unix dolts understood this, so we have /bin/cat
and strcat, and not /bin/concat and strconcat.

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