CODEWITHSUNDEEP
typescriptgenericsinheritancefunctional-programmingapply
Benjamin Vincent
Benjamin Vincent

Reputation: 496

TypeScript Generic Types problem: Workaround required

I am stuck and I don't know what is the current ⸘workaround‽...

This probleme is describe in this issue: Microsoft/TypeScript/#1213...

I am trying to implement the Chain specification:

(I need to pass a type to the ApType so that on line 12 (in the snippet below) the Apply is not hard coded but generic to also take types extended from any IApply)

m['fantasy-land/chain'](f)

A value that implements the Chain specification must also implement the Apply specification.

a['fantasy-land/ap'](b)

I did a FunctorSimplex which is then extended by a FunctorComplex then extended by the Apply but now that I want to extend Apply as a Chain it is breaking...

So I need that (image below and link to code):

Screenshot

Permalink to the code snippet lines 11 to 22 in 7ff8b9c

export type ApType<A = unknown> = <B = unknown>(
  ap: Apply<(val: A) => B>,
) => IApply<B>;

/* [...] */

export interface IApply<A = unknown> extends FunctorComplex<A> {
  /** `Fantasy-land/ap :: Apply f => f a ~> f (a -> b) -> f b` */
  ap: ApType<A>;
}

Upvotes: 0

Views: 126

Answers (1)

Praveenkumar
Praveenkumar

Reputation: 2182

I think what you are looking for is higher kinded type (HKT). In Typescript, HKT can be achieved using something called as module augmentation. Check this article. You can refer fp-ts implementations too.

Upvotes: 1

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