On Sep 29, 2015, at 3:25 PM, Sam Tobin-Hochstadt <[email protected]> wrote:
> I think something problematic is happening with type inference here,
> and better types could be picked. Right now, Typed Racket is doing
> this:
>
> (compose (λ (x) x) (inst (λ #:forall (a) ({x : a}) x) Nothing))
>
> when it should probably do
>
> (compose (λ (x) x) (inst (λ #:forall (a) ({x : a}) x) Any))
>
> However, using polymorphic arguments (such as your second function)
> to polymorphic functions (such as `compose`) in general won't produce
> the results you want, and I recommend writing the instantiation you
> want explicitly.
Well yes, that's where I started with inst. The Nothing told me I was on the
wrong track with inst.
What you might be saying is 'use inst for compose'.
-- Matthias
>
> Sam
>
> On Tue, Sep 29, 2015 at 2:33 PM, Matthias Felleisen
> <[email protected]> wrote:
>>
>> Why does this
>>
>>> (compose (λ (x) x) (λ #:forall (a) ({x : a}) x))
>>
>> have this type:
>>
>>> - : (-> Nothing Any)
>>
>> Thanks -- Matthias
>>
>>
>>
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