tasks a-s

Task/Rot-13/Racket/rot-13.rkt

@@ -0,0 +1,17 @@
+#!/bin/env racket
+#lang racket/base
+
+(define (run i o)
+  (for ([ch (in-producer regexp-match #f #rx#"[a-zA-Z]" i 0 #f o)])
+    (define b (bytes-ref (car ch) 0))
+    (define a (if (< b 96) 65 97))
+    (write-byte (+ (modulo (+ 13 (- b a)) 26) a))))
+
+(require racket/cmdline)
+(command-line
+ #:help-labels "(\"-\" specifies standard input)"
+ #:args files
+ (for ([f (if (null? files) '("-") files)])
+   (if (equal? f "-")
+     (run (current-input-port) (current-output-port))
+     (call-with-input-file f ( (i) (run i (current-output-port)))))))