#lang racket (define plus +) (define pie 3.1415926535) (define (twice n) (+ n n)) (define dbl (lambda (n) (+ n n))) (define fact (lambda (n) (if (< n 2) 1 (* n (fact (- n 1)))))) (define (len lst) (if (null? lst) 0 (+ 1 (len (cdr lst)))))