Apply.md

MODULE Apply

Apply

type class

interface Apply<F> extends Functor<F> {
  ap: <A, B>(fab: HKT<F, (a: A) => B>, fa: HKT<F, A>) => HKT<F, B>
}

The Apply class provides the ap which is used to apply a function to an argument under a type constructor.

Apply can be used to lift functions of two or more arguments to work on values wrapped with the type constructor f.

Instances must satisfy the following law in addition to the Functor laws:

1. Associative composition: F.ap(F.ap(F.map(fbc, bc => ab => a => bc(ab(a))), fab), fa) = F.ap(fbc, F.ap(fab, fa))

Formally, Apply represents a strong lax semi-monoidal endofunctor.

applyFirst

function

applyFirst<F>(F: Apply<F>): <A, B>(fa: HKT<F, A>, fb: HKT<F, B>) => HKT<F, A>

Combine two effectful actions, keeping only the result of the first

applySecond

function

applySecond<F>(F: Apply<F>): <A, B>(fa: HKT<F, A>, fb: HKT<F, B>) => HKT<F, B>

Combine two effectful actions, keeping only the result of the second

liftA2

function

liftA2<F>(F: Apply<F>): <A, B, C>(f: Curried2<A, B, C>) => Curried2<HKT<F, A>, HKT<F, B>, HKT<F, C>>

Lift a function of two arguments to a function which accepts and returns values wrapped with the type constructor F

liftA3

function

liftA3<F>(
  F: Apply<F>
): <A, B, C, D>(f: Curried3<A, B, C, D>) => Curried3<HKT<F, A>, HKT<F, B>, HKT<F, C>, HKT<F, D>>

Lift a function of three arguments to a function which accepts and returns values wrapped with the type constructor F

liftA4

function

liftA4<F>(
  F: Apply<F>
): <A, B, C, D, E>(f: Curried4<A, B, C, D, E>) => Curried4<HKT<F, A>, HKT<F, B>, HKT<F, C>, HKT<F, D>, HKT<F, E>>

Lift a function of four arguments to a function which accepts and returns values wrapped with the type constructor F