Re: [racket-users] Typed Racket: Subtype of a struct typed where one field has a fixed value

[je...@lisp.sh]

I have it on good authority that parametric types are the way to go. Look 
at this:


#lang typed/racket
(struct (α β) point ([x : α] [y : β]))
(define-type Point point)

(define-type FixedY (Point Real 0))


That's it!
On Saturday, January 16, 2021 at 6:26:17 PM UTC+1 sorawe...@gmail.com wrote:

> According to https://docs.racket-lang.org/ts-reference/type-ref.html, 
> `Zero` exists. 
>
> On Sat, Jan 16, 2021 at 8:14 AM je...@lisp.sh  wrote:
>
>> Working in Typed Racket, consider a struct like this:
>>
>> (struct point
>>   ([x : Real]
>>[y : Real]))
>>
>> Is there a way to express the type of those points whose y field is, say, 
>> 0? In other words, I'd like a talk about point structs where x varies 
>> freely, but y is always 0. Obviously, I can make a function that 
>> discriminates this subclass, but I'm not sure how to express it as a type. 
>> I've hunted around in the docs, but I can't quite find what I'm looking for.
>>
>> -- 
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>>  
>> 
>> .
>>
>

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Re: [racket-users] Typed Racket: Subtype of a struct typed where one field has a fixed value

[Sorawee Porncharoenwase]

According to https://docs.racket-lang.org/ts-reference/type-ref.html,
`Zero` exists.

On Sat, Jan 16, 2021 at 8:14 AM je...@lisp.sh  wrote:

> Working in Typed Racket, consider a struct like this:
>
> (struct point
>   ([x : Real]
>[y : Real]))
>
> Is there a way to express the type of those points whose y field is, say,
> 0? In other words, I'd like a talk about point structs where x varies
> freely, but y is always 0. Obviously, I can make a function that
> discriminates this subclass, but I'm not sure how to express it as a type.
> I've hunted around in the docs, but I can't quite find what I'm looking for.
>
> --
> You received this message because you are subscribed to the Google Groups
> "Racket Users" group.
> To unsubscribe from this group and stop receiving emails from it, send an
> email to racket-users+unsubscr...@googlegroups.com.
> To view this discussion on the web visit
> https://groups.google.com/d/msgid/racket-users/ee8bc006-590c-48f6-ac8b-4ef4f88019dfn%40googlegroups.com
> 
> .
>

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