[racket] Determining type from a syntax object

This is exactly what predicates are for, in general.  However, you
can't have predicates that check things about functions -- there's no
information there at runtime to look at. Typed Racket functions are
just plain Racket functions. We could add some extra metadata to every
value that held its type, and then implement this operation, but that
would require fundamental changes to Racket.

Even if we wanted to do that, what if `f` came in from untyped Racket?

Sam

On Mon, Jun 16, 2014 at 2:49 PM, Alexander D. Knauth
<alexander at knauth.org> wrote:
> Would there be a way to test the type for making decisions at run-time (not
> just with predicates)?
>
> For example:
> (cond [(:has-type? f (Number -> Any))
>        (f 1)]
>       [(:has-type? f (String -> Any))
>        (f "1")])
>
> On Jun 16, 2014, at 6:54 AM, Matthias Felleisen <matthias at ccs.neu.edu>
> wrote:
>
>
> That's what I thought you wanted it for so my answer stands -- Matthias
>
>
>
> On Jun 15, 2014, at 12:55 AM, Spencer Florence wrote:
>
> This is about making decisions at compile time. Specifically I have a
> sequence of expressions I want to partition into expressions of some type T
> and expressions of other types.
>
>
> On Sat, Jun 14, 2014 at 7:34 PM, Robby Findler <robby at eecs.northwestern.edu>
> wrote:
>>
>> Would it be enough to expand into an 'ann' expression? Or do you need
>> to make decisions at compile time based on whether or not the types
>> worked?
>>
>> Robby
>>
>> On Sat, Jun 14, 2014 at 2:04 PM, Matthias Felleisen
>> <matthias at ccs.neu.edu> wrote:
>> >
>> > No, TR expands first, then checks. -- Matthias
>> >
>> >
>> >
>> >
>> > On Jun 14, 2014, at 2:59 PM, Spencer Florence wrote:
>> >
>> >> Hey All,
>> >>
>> >> I'm trying to take advantage of typed/racket in a few macros. Is there
>> >> any way to check the type of an expression from its syntax object? something
>> >> like:
>> >>
>> >> (:has-type? (-> Void) #'expression)
>> >>
>> >>
>> >> --Spencer
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>
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