(Nils' Scheme Snippets)

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(list->set list) => list

Purpose

Convert list to set. A set is a list containing only unique members.

Arguments

a	list

Example

(list->set '(a b c b c)) => (a b c)

(define (list->set a)
  (letrec
    ((l->s
       (lambda (a r)
         (cond ((null? a)
                 (reverse r))
               ((member (car a) r)
                 (l->s (cdr a) r))
               (else (l->s (cdr a)
                           (cons (car a) r)))))))
    (l->s a '())))