re: need help with data structure problem

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Sujet : re: need help with data structure problem
De : Nobody447095 (at) *nospam* here-nor-there.org (B. Pym)
Groupes : comp.lang.lisp
Date : 21. Jun 2025, 00:39:55
Autres entêtes
Organisation : A noiseless patient Spider
Message-ID : <1034rga$akhr$1@dont-email.me>
User-Agent : XanaNews/1.18.1.6
hi, I need to write a function  (join_similar expr) where expr is
adata structure with the following format ( (x1 y1) (x2 y2) (x3 y3)...
(xn yn)),
 
join_similar  will return an expression like ( (x1 y1 y2) (x3 y3) ...)
when x1=x2
 
for instance:
*(join_similar '((3 4) (7 5) (3 6) (7 8) (3 9) (0 1))
 
would return:
((3 4 6 9) (7 5 8) (0 1))


Kenny Tilton wrote:

Lieven Marchand wrote:
CL-USER 9 > (defun join-similar (list)
              (loop with ht = (make-hash-table)
                    for (first second) in list
                    do
                    (pushnew second (gethash first ht nil))
                    finally (return (loop for first being each hash-key in ht using (hash-value rest) collect (cons first rest)))))
JOIN-SIMILAR
 
Isn't LOOP beautiful? <g,d&r>
 
<g> No...
 
(defun join-similar (pairs &aux result)
  (dolist (pair pairs (nreverse result))
    (nconc (or (assoc (first pair) result)
               (first (push (list (first pair)) result)))
           (list (second pair)))))

Gauche Scheme

(use gauche.collection)   ;; group-collection

(define (meld groups)
  (map (lambda(xs) (cons (caar xs) (map cadr xs))) groups))

(define (join-similar pairs)
  (meld (group-collection pairs :key car :test equal?)))

(join-similar '((foo 4)(bar 7)(foo 5)(bar 8)(fun 9)))

  ===>
((foo 4 5) (bar 7 8) (fun 9))

Date Sujet#  Auteur
21 Jun 25 * Re: need help with data structure problem6B. Pym
21 Jun 25 +* Re: need help with data structure problem2B. Pym
21 Jun 25 i`- Re: need help with data structure problem1B. Pym
21 Jun 25 +- Re: need help with data structure problem1B. Pym
30 Jun 25 `* Re: need help with data structure problem2B. Pym
30 Jun 25  `- Re: need help with data structure problem1B. Pym

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