[PRL] don't

[Sam TH]

I think we should be more precise here.  (don 't 3) shouldn't be
valid, and (don (quote t) (launch-the-nukes)) is right out.

(define-syntax (don stx)
  (syntax-case stx ()
    [(don (q t) . _)
     (and (eq? (syntax->datum #'q) 'quote)
          (eq? (syntax->datum #'t) 't)
          (let* ([don-start (syntax-position #'don)]
                 [don-end (+ don-start (syntax-span #'don) -1)]
                 [q-start (syntax-position #'q)]
                 [t-start (syntax-position #'t)])
            (= t-start (+ 1 q-start) (+ 2 don-end))))
     #'(void)]
    [_ #'"Hi, I'm Don."]))

On Wed, Nov 11, 2009 at 8:42 AM, Dave Herman <dherman at ccs.neu.edu> wrote:
> They think they're pretty special:
>
>     http://www.reddit.com/r/programming/comments/a26fe/dont/
>
> We can (kind of) do this, too:
>
>     (define-syntax (don stx)
>       (syntax-case stx ()
>         [(don (q t) . _)
>          (and (eq? (syntax->datum #'q) 'quote)
>               (eq? (syntax->datum #'t) 't))
>          #'(void)]
>         [_ #'"Hi, I'm Don."]))
>
>     > (don't (display "hello, world"))
>     > (don't (delete-file "/etc/passwd"))
>     > (don't (exit))
>
> And *my* version even comes with a bonus Don:
>
>     > don
>     "Hi, I'm Don."
>
> Dave
>
>
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-- 
sam th
samth at ccs.neu.edu