[plt-scheme] Predicates from Types

On Wed, Apr 1, 2009 at 11:43 PM, Sam TH <samth at ccs.neu.edu> wrote:
> On Wed, Apr 1, 2009 at 7:01 PM, Paulo J. Matos <pocmatos at gmail.com> wrote:
>> Is there then a way to extract a predicate from a type? Given I assume
>> the answer is no, what's the best solution for this?
>> Right now I had to define :
>> (: Predicate? (Any -> Boolean))
>> (define (Predicate? u)
>>     (or (Quantifier? u) (Logic-Predicate? u) ...))
>
> This is the right solution, but you probably want the type:
>
> (: Predicate? (Any -> Boolean : Predicate))
>

Now you lost me here... Why do I need the ": Predicate" part? and what
does it do?

Cheers,

Paulo Matos

> --
> sam th
> samth at ccs.neu.edu
>



-- 
Paulo Jorge Matos - pocmatos at gmail.com
Webpage: http://www.personal.soton.ac.uk/pocm