37 lines
831 B
Racket
37 lines
831 B
Racket
#lang racket/base
|
|
(require (for-syntax racket/base br/syntax)
|
|
br/define)
|
|
(provide (all-defined-out))
|
|
|
|
(define-macro (until COND EXPR ...)
|
|
#'(let loop ()
|
|
(unless COND
|
|
EXPR ...
|
|
(loop))))
|
|
|
|
(define-macro (while COND EXPR ...)
|
|
#'(let loop ()
|
|
(when COND
|
|
EXPR ...
|
|
(loop))))
|
|
|
|
(define-macro (forever . EXPRS)
|
|
;; todo: would be better with a syntax parameter
|
|
(with-pattern
|
|
([stop (datum->syntax #'EXPRS 'stop)])
|
|
#'(let/ec stop
|
|
(while #t
|
|
. EXPRS))))
|
|
|
|
(module+ test
|
|
(require rackunit)
|
|
(check-equal? (let ([x 5])
|
|
(until (zero? x)
|
|
(set! x (- x 1)))
|
|
x) 0)
|
|
(check-equal? (let ([x 5])
|
|
(while (positive? x)
|
|
(set! x (- x 1)))
|
|
x) 0))
|
|
|