#lang scheme/base
(provide (all-defined-out))

(define (assoc-remove k l)
  (cond
    ((null? l) '())
    ((eq? (car (car l)) k)
     (assoc-remove k (cdr l)))
    (else
     (cons (car l) (assoc-remove k (cdr l))))))

(define (choose l)
  (list-ref l (random (length l))))

(define (list-contains k l)
  (cond 
    ((null? l) #f)
    ((eq? (car l) k) #t)
    (else (list-contains k (cdr l)))))