Thank-you Matthias
That's neat!
And yes, I can write a basic macro. By introducing #:freevar I was able to
improve the blame situation, but the abstraction is a bit leaky ...
(define-syntax-rule (define/tight (fn args ...)
ctc
body ...)
(begin
(define (fn args ...) (fn/impl args ...))
(define/contract (fn/impl args ...)
ctc
#:freevar fn ctc ; Directs blame to "fn/impl" rather than the
enclosing module
body ...)))
Dan
On Sat, May 6, 2017 at 11:15 AM, Matthias Felleisen <matth...@ccs.neu.edu>
wrote:
>
> Sure:
>
> #lang racket
>
> (define/contract [unsafe-factorial n]
> (-> (and/c integer? (>=/c 0)) (and/c integer? (>=/c 0)))
> (if (zero? n)
> 1
> (* n (factorial (- n 10)))))
> (define (factorial n) (unsafe-factorial n)) ;; cross the boundary and go
> right back in
> (unsafe-factorial 5) ; Does not terminate
>
>
> I suspect you can implement this with a macro now.
>
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