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(require 'common-list-functions)
(define (permute lst)
(define (aux set head)
(cond ((null? set) head)
(else
(map (lambda (x)
(aux (set-difference set (list x))
(cons x head)))
set))))
(aux lst '()))
(define (permute-2 lst)
(let ((result '()))
(define (aux set head)
(if (null? set)
(set! result (cons head result))
(for-each (lambda (x)
(aux (set-difference set (list x))
(cons x head)))
set)))
(aux lst '())
result))
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