#lang racket/base #| Why on earth are these here? Because first, etc. don't work on cyclic lists: (define web-colors (shared ([W (cons "white" G)] [G (cons "grey" W)]) W)) (first web-colors) fails with expected argument of type <list>. But car/cdr still do the trick per email from mflatt, 10/20/2011. So we suppress the built-in functions from lang/htdp-advanced and provide these instead. |# (define first car) (define rest cdr) (define second cadr) (define third caddr) (define fourth cadddr) (define (fifth l) (list-ref l 4)) (define (sixth l) (list-ref l 5)) (define (seventh l) (list-ref l 6)) (define (eighth l) (list-ref l 7)) (provide first rest second third fourth fifth sixth seventh eighth)