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From: "B. Pym" <Nobody447095@here-nor-there.org>
Newsgroups: comp.lang.lisp,comp.lang.scheme
Subject: Merging strings
Date: Fri, 4 Jul 2025 14:22:14 -0000 (UTC)
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You have a list contain both strings and numbers.
Generate a new list in which the adjacent strings
have been concatenated.

Scheme

(define (merge-strings List)
  (reverse
    (fold
      (lambda (e accum)
        (if (and (string? e) (pair? accum) (string? (car accum)))
          (cons (string-append (car accum) e) (cdr accum))
          (cons e accum)))
      '()
      List)))

(merge-strings '("1" "2" 3 4 "5" "6" 7 8 "9"))
  ===>
("12" 3 4 "56" 7 8 "9")