일기:2024년 10월 8일

;; remove-first : Sym X Listof(Sym) -> Listof(Sym)
;; usage: (remove-first s los) returns a list with
;;        the same elements arranged in the same
;;        order as los, except that the first
;;        occurrence of the symbol s in removed.
(define remove-first
  (lambda (s los)
    (if (null? los)
      '()
      (if (eqv? (car los) s)
        (cdr los)
        (cons (car los) (remove-first s (cdr los)))))))