[plt-scheme] A new version of Typed Scheme

From: Sam Tobin-Hochstadt (samth at ccs.neu.edu)
Date: Wed Feb 24 14:08:55 EST 2010

On Wed, Feb 24, 2010 at 1:55 PM, Jay McCarthy <jay.mccarthy at gmail.com> wrote:
> I think it would be nice to go through common problems doing
> conversion.

This is a good suggestion, but ...

> A simple thing I can think of that hits me every time is
> that I think a function will work like:
> (: f (All (A) (A -> (Listof A))))
> (define (f a)
>  ...)
> but f calls some polymorphic function and ts can't infer that the
> parameter is A, so I have to re-write it to:
> (define: (A) (f [a : A]) : (Listof A)
>  ...)
> to get the A in scope.

`A' is in scope in both of these definitions:

#lang typed/scheme

(: f (All (A) (A -> (Listof A))))
(define (f a)
 (list ((inst values A) a)))

works fine for me.

sam th
samth at ccs.neu.edu

Posted on the users mailing list.