[plt-scheme] match for Promise

With your example, I tried this and it throws an error on promise?. untyped identifier imported blah blah.
Still trying get it working. Thanks anyways Dave. 

#lang typed-scheme

(require scheme/match
         scheme/promise
         web-server/dispatch/extend)

(define-coercion-match-expander promise promise? force)

(define foo (delay 42))

(: bar : ((Promise Integer) -> Integer))
(define (bar prom)
  (match prom
    [(promise x) x]
    [else (error "Unknown" 'bar)]))

(bar foo) 

Hari


----- Original Message -----
From: "David Herman" <dherman at ccs.neu.edu>
To: krhari at ccs.neu.edu
Cc: "plt-scheme List" <plt-scheme at list.cs.brown.edu>
Sent: Sunday, February 28, 2010 5:18:30 PM GMT -05:00 US/Canada Eastern
Subject: Re: [plt-scheme] match for Promise

Oh-- I've no idea how to make it work with Typed Scheme, though. Sorry,

Dave

On Feb 28, 2010, at 2:08 PM, David Herman wrote:

> A quick implementation:
> 
> ;; --
> #lang scheme/base
> 
> (require scheme/match
>         scheme/promise
>         web-server/dispatch/extend)
> 
> (define-coercion-match-expander promise promise? force)
> ;; --
> 
> Example:
> 
>> (define foo
>    (delay (begin (printf "forced!\n") 42)))
>> foo
> #<promise:foo>
>> (match foo
>    [(promise x) x])
> forced!
> 42
> 
> [It seems to me define-coercion-match-expander is useful enough to belong in scheme/match.]
> 
> Dave
> 
> On Feb 27, 2010, at 1:02 AM, krhari at ccs.neu.edu wrote:
> 
>> Hi,
>> In Typed Scheme, I have a structure which has a field of type 
>> 
>> (Promise (Pair A B)).
>> 
>> Is it possible to use match for this(for Promise)? 
>> 
>> Thanks
>> Hari
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>