25 lines
625 B
Plaintext
25 lines
625 B
Plaintext
#lang racket
|
|
|
|
;; draw a graph of cos and deriv^3(cos)
|
|
(require plot)
|
|
(define ((deriv f) x)
|
|
(/ (- (f x) (f (- x 0.001))) 0.001))
|
|
(define (thrice f) (lambda (x) (f (f (f x)))))
|
|
(plot (list (function ((thrice deriv) sin) -5 5)
|
|
(function cos -5 5 #:color 'blue)))
|
|
|
|
;; Print the Greek alphabet
|
|
(for ([i (in-range 25)])
|
|
(displayln
|
|
(integer->char
|
|
(+ i (char->integer #\u3B1)))))
|
|
|
|
;; An echo server
|
|
(define listener (tcp-listen 12345))
|
|
(let echo-server ()
|
|
(define-values (in out) (tcp-accept listener))
|
|
(thread (λ ()
|
|
(copy-port in out)
|
|
(close-output-port out)))
|
|
(echo-server))
|