[racket] [typed] optional parameter

On Fri, Nov 11, 2011 at 12:07 PM, Paul Leger <pleger at gmail.com> wrote:
> On 11/11/2011 11:02 AM, Sam Tobin-Hochstadt wrote:
>>
>> Unfortunately, Typed Racket needs a little more help from the
>> programmer here.  This will work:
>>
>> #lang typed/racket
>> (: g (case->  (->  Number)
>>              (Number ->  Number)))
>> (define (g [#{x : Number} 10]) x)
>>
>> I hope to make what you wrote work eventually, but it doesn't yet.
>
> I think this solution does not work if you are using modules. For example:
>
> (module my-module typed/racket
>
>  (: g (case-> (-> Number)
>               (Number -> Number)))
>
>  (define (g  [#{x : Number} 10]) a)
>  )
>
> The type-checker says:
> "define: not an identifier, identifier with default, or keyword for
> procedure argument in: (#(x : Number) 10)"
>
> Do I need a extra piece of code If I want to use a function with optional
> parameters inside of a module?


The "#{...}" thing needs the cooperation of the #lang line, rather
than the (module ...) form that you're using for writing your module.

Try writing your module with #lang typed/racket, like this:

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
#lang typed/racket
(: g (case-> (-> Number)
             (Number -> Number)))
(define (g  [#{x : Number} 10]) x)
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;