(define (comb m lst)
  (cond ((= m 0) '(()))
        ((null? lst) '())
        (else (append (map (lambda (y) (cons (car lst) y))
                           (comb (- m 1) (cdr lst)))
                      (comb m (cdr lst))))))

(comb 3 '(0 1 2 3 4))