soegaard

#lang racket
(define ns (make-base-namespace))
(define port (open-input-string "(define x 41) (+ x 1)"))
(for ([expr (in-port read port)])
  (displayln (eval expr ns)))

soegaard

#lang racket
(define-syntax c
  (make-set!-transformer
   (lambda (stx)
     (syntax-case stx (set!)
       [(set! id v) #'(error 'set! "c is immutable")]
       [id (identifier? #'id)  #'42]))))

c
(set! c 43)

soegaard

#lang racket
(module+ constants (provide c) (define c 42))

(require (submod "." constants))  ; incorrect!

c
(set! c (+ c 1))

soegaard

#lang racket
(module constants racket
  (provide e pi)
  (define e 2.1718281828)
  (define pi (* 355/113 1.0)))

(require 'constants)

pi
; (set! pi (+ pi 1))

soegaard

#lang racket
(struct foo: (x y)
  #:reflection-name 'foo
  #:transparent)

(define (make-foo x y)
  (match* (x y)
    [((? number?) (? number?)) (foo: x y)]
    [(_ _) (error 'foo/test "elements must be numbers")]))

soegaard

#lang racket
(require racket/draw (for-syntax syntax/parse) pict unstable/gui/pict)

(define-syntax defv (make-rename-transformer #'define-values))
(define-syntax defm (make-rename-transformer #'match-define))
(define-syntax def  (make-rename-transformer #'define))

(define-match-expander color:
  (λ (stx) 
    (syntax-parse stx 

soegaard

#lang racket
(require racket/draw)

(define bm (make-object bitmap% 400 400))
(define dc (new bitmap-dc% [bitmap bm]))
(define p (new dc-path%))

(send p move-to 300 200)
(send p arc 100 100 200 200 0 (* 2 pi))
(send p line-to 400 200)

soegaard

(define-syntax (myapply stx)
  (define (is-underscore? x) (equal? '_ (syntax->datum x)))
  (syntax-case stx ()
    [(_ fun . args)
     (let* ([missing-ids (dar (filter is-underscore? (syntax->list #'args)))]
            [new-ids     (dar (take (length missing-ids) (generate-temporaries #'args)))]
            [new-args    (dar (replace-if is-underscore?  (syntax->list #'args) new-ids))])
       (with-syntax ([(new-arg ...) new-args]
                     [(new-id ...) new-ids])
         #'(lambda (new-id ...) (fun new-arg ...))))]))

soegaard

raco setup: --- installing collections ---
raco setup: --- post-installing collections ---
raco setup: post-installing: <pkgs>/gui-lib/mred
raco setup: post-installing: <pkgs>/gui-lib/racket/gui
raco setup: post-installing: <pkgs>/mzcom
raco setup: post-installing: <pkgs>/mzscheme-lib/mzscheme
raco setup: post-installing: <pkgs>/racket-doc/help
raco setup: --- checking package dependencies ---
raco setup: package declares no dependencies: "abnf"
raco setup: package declares no dependencies: "set"

soegaard

#lang racket
(require syntax/parse)

(define-syntax-class term
  (pattern ((~literal t) t)))

(define-syntax-class operator
  (pattern ((~literal o) op)))
 
(define-splicing-syntax-class term-op