dyoo

#lang racket/base

;; Playing with input-port-append and transplant-input-port,
;; with the idea of adding the #lang line for arbitrary text
;; without screwing up the original input port's locations.
(provide prepend-lang-line)


(require racket/port)

dyoo

#lang racket

(provide dir)

(define ns (make-base-namespace))

;; Provides a "dir"-like function on a module.
(define (dir module-path)
  (parameterize ([current-namespace ns])
    (dynamic-require module-path (void))  ;; make sure _not_ to cause the module to evaluate.

dyoo

#lang racket

(define ns (make-base-namespace))

(define (play module-path)
  (parameterize ([current-namespace ns])
    (dynamic-require module-path #f)
    (define-values (module-variable-exports module-syntax-exports)
      (module->exports module-path))
    

dyoo

#lang racket
 
(require data/heap
         data/bit-vector)
 
;; A node is either an interior, or a leaf.
;; In either case, they record an item with an associated frequency.
(struct node (freq) #:transparent)
(struct interior node (left right) #:transparent)
(struct leaf node (val) #:transparent)

dyoo

#lang racket

(syntax-case #'(this is a vector: #(3 4 5)) ()
  [(a b c d #(x y z))
   (list #'x #'y #'z)])

dyoo

#lang racket/base
(require racket/port)
(require racket/tcp)


(define (start-irc #:irc-hostname [irc-hostname "chat.freenode.net"]
                   #:irc-portno [irc-portno 6667]
                   #:irc-nick [irc-nick "nyuracket"] 
                   #:irc-user [irc-user "racket"]
                   #:irc-realname [irc-realname "nyuracket"])

dyoo

#lang racket

(define ns (make-base-namespace))
(parameterize ([current-namespace ns])
  (read-eval-print-loop))

dyoo

#lang racket
(require racket/provide
         (prefix-in racket: racket))
(define count 'count)
(provide (except-out 
          (filtered-out (lambda (name)
                          (and (regexp-match? #rx"^racket:" name)
                               (regexp-replace #rx"^racket:" name "")))
                        (all-from-out racket))
          racket:count)

dyoo

#lang racket

(define (my-expand-path-with-env a-path-string)
  (define (lookup var)
    (getenv (substring var 1)))
  
  (regexp-replace* #px"\\$\\w+" a-path-string  lookup))

(my-expand-path-with-env "$HOME/foo/bar")

dyoo

#lang racket

(define (parse-date-string str)
  (match str
    [(pregexp #px"^(\\d{4})-(\\d{2})-(\\d{2})$" (list _ year month day))
     (list (string->number year)
           (string->number month)
           (string->number day))]))

(parse-date-string "2013-03-10")