> On Nov 13, 2017, at 3:25 PM, Stuart Hungerford <stuart.hungerf...@gmail.com>
> wrote:
>
> Hi,
>
> I'm trying to create a Typed Racket function that compares to 2-vectors of
> integers with an optional error term that defaults to 1:
>
> #lang typed/racket
>
>
> (define-type Reading (Vector Integer Integer))
>
>
> (: close? (->* (Reading Reading) (Integer) Boolean))
> (define/match (close? r1 r2 [err 1])
> [((vector a b) (vector c d) e)
> (and (= a (+ c e)) (= b (+ d e)))])
>
>
> In untyped Racket the function compiles and runs as I expected. In Typed
> Racket the pattern-matched values all seem to have type "Any".
>
> I think there's some interaction between Typed Racket's typing rules and the
> define/match macro that I haven't understood properly? As a complete Racket
> newb I may also be going about this the wrong way. Any advice much
> appreciated.
This seems to be a problem with define/match specifically, since define +
match* works fine for this function:
(: close? (->* (Reading Reading) (Integer) Boolean))
(define (close? r1 r2 [err 1])
(match* (r1 r2 err)
[((vector a b) (vector c d) e)
(and (= a (+ c e)) (= b (+ d e)))]))
Others: Does define/match do anything that would make Typed Racket see it
differently from define + match*? It seems like define/match expands to define
+ match*/derived anyway. The only thing that's different is which define it's
expanding to. So is expanding to Racket's define instead of TR's causing the
problem?
Alex Knauth
>
> Thanks,
>
> Stu
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