Uncurried return type in binding?

1

I’m trying to figure out how to create a binding for Jotai where the return type is uncurried.

Essentially I would like the binding type to look like this:

@module("jotai/utils")
external useUpdateAtom: t<'value, 'setValue> => ('value => unit) = "useUpdateAtom"

With the return type being 'value => unit

But as soon as I hit save the compiler curries the type into this:

external useUpdateAtom: (t<'value, 'setValue>, 'value) => unit = "useUpdateAtom"

And this doesn’t work with the library.

The way I’ve fixed it for now is to introduce a special return type:

type returnType<'a> = 'a => unit
external useUpdateAtom: t<'value, 'setValue> => returnType<'value> = "useUpdateAtom"

This works, but I’m wondering if there’s another more idiomatic way to achieve this?

2

Your way is fine, there is also Bind to JS Function | ReScript Language Manual

1 Like
3

Thanks for the link. It works fine with the . uncurrying, but I’m not able to make it work with the @uncurry decorator.

This works:
external useUpdateAtom: (t<'value, 'setValue>, . 'value) => unit = "useUpdateAtom"

But this doesn’t:
external useUpdateAtom: (t<'value, 'setValue>, @uncurry 'value) => unit = "useUpdateAtom"
It throws an error: Cannot infer the arity through the syntax, either [%@uncurry n] or write it in arrow syntax

Well it’s not a big issue, just trying to understand bindings and currying.

Thanks again!

4

The decorator works for input position arguments only. Since you want to return an uncurried function here, it doesn’t work.

1 Like
5

That makes sense, thanks for the explanation :+1:

6

By chance have you seen https://github.com/gaku-sei/re-jotai? Or was that insufficient for a particular use case?

7

Thanks for the link; I did see and star the project. But it turned out to be a little too complex for my understanding of bindings and ReScript when we needed Jotai. So I decided to build our own simpler bindings, mainly to get some exercise writing them. And we also use a couple of Jotai utils which aren’t covered by those bindings yet.

But you bring up a good point. I should consider contributing our util bindings to that project!

1 Like