(define member? (lambda (a l)
    (cond ((null? l) #f)
          ((equal? a (car l)) #t)
          (else (member? a (cdr l))))))


(define (flatten l)
     (cond ((null? l) l)
           ((not (list? l)) (cons l '()))
           (else (append (flatten (car l)) (flatten (cdr l))))))

(define (map f l)
     (cond ((null? l) l)
           (else (cons (apply f (car l)) (map f (cdr l))))))


(define (remove a l)
  (cond ((null? l) l)
	((equal? a (car l)) (remove a (cdr l)))
	(else (cons (car l) (remove a (cdr l))))))

(define (nodups l)
  (cond ((null? l) l)
	(else (let ((a (car l)))
		(cons a (nodups (remove a (cdr l))))))))