[racket] [Typed Racket] define-predicate for union with functions

From: Eric Dobson (eric.n.dobson at gmail.com)
Date: Mon May 20 11:07:13 EDT 2013

No, you cannot define predicates for function types. If you explain
the problem you have, we might be able to explain another solution
that will work.

On Mon, May 20, 2013 at 1:32 AM, Paul Leger <pleger at gmail.com> wrote:
> Hi all,
>       Maybe, this question is very easy. In the following code, I try
> defining a predicate for T2, but I cannot because T1 it is a function.
> (define-type T1 (Symbol -> Any) )
> (define-type T2 (U Symbol Number T1))
> ;(define-predicate T1? Procedure) ;this line is useless
> (define-predicate T2? T2)
>> Type Checker: Type T2 could not be converted to a contract. in: T2
> My unsuccessful answer is:
>   (define-type T2 (U Symbol Number Procedure))
> I do not like it because I lose the relationship between T1 and T2. Are
> there some possibility
> Thank in advance,
> Paul
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