fp-ts

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Overview

The Chain type class extends the Apply type class with a chain operation which composes computations in sequence, using the return value of one computation to determine the next computation.

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

  1. Associativity: F.chain(F.chain(fa, afb), bfc) <-> F.chain(fa, a => F.chain(afb(a), bfc))

Note. Apply’s ap can be derived: (fab, fa) => F.chain(fab, f => F.map(f, fa))

Table of contents

Chain (interface)

Signature

export interface Chain<F> extends Apply<F> {
  readonly chain: <A, B>(fa: HKT<F, A>, f: (a: A) => HKT<F, B>) => HKT<F, B>
}

Added in v1.0.0

Chain1 (interface)

Signature

export interface Chain1<F extends URIS> extends Apply1<F> {
  readonly chain: <A, B>(fa: Type<F, A>, f: (a: A) => Type<F, B>) => Type<F, B>
}

Chain2 (interface)

Signature

export interface Chain2<F extends URIS2> extends Apply2<F> {
  readonly chain: <L, A, B>(fa: Type2<F, L, A>, f: (a: A) => Type2<F, L, B>) => Type2<F, L, B>
}

Chain2C (interface)

Signature

export interface Chain2C<F extends URIS2, L> extends Apply2C<F, L> {
  readonly chain: <A, B>(fa: Type2<F, L, A>, f: (a: A) => Type2<F, L, B>) => Type2<F, L, B>
}

Chain3 (interface)

Signature

export interface Chain3<F extends URIS3> extends Apply3<F> {
  readonly chain: <U, L, A, B>(fa: Type3<F, U, L, A>, f: (a: A) => Type3<F, U, L, B>) => Type3<F, U, L, B>
}

Chain3C (interface)

Signature

export interface Chain3C<F extends URIS3, U, L> extends Apply3C<F, U, L> {
  readonly chain: <A, B>(fa: Type3<F, U, L, A>, f: (a: A) => Type3<F, U, L, B>) => Type3<F, U, L, B>
}

flatten (function)

Signature

export function flatten<F extends URIS3>(
  chain: Chain3<F>
): <U, L, A>(mma: Type3<F, U, L, Type3<F, U, L, A>>) => Type3<F, U, L, A>
export function flatten<F extends URIS3, U, L>(
  chain: Chain3C<F, U, L>
): <A>(mma: Type3<F, U, L, Type3<F, U, L, A>>) => Type3<F, U, L, A>
export function flatten<F extends URIS2>(chain: Chain2<F>): <L, A>(mma: Type2<F, L, Type2<F, L, A>>) => Type2<F, L, A>
export function flatten<F extends URIS2, L>(
  chain: Chain2C<F, L>
): <A>(mma: Type2<F, L, Type2<F, L, A>>) => Type2<F, L, A>
export function flatten<F extends URIS>(chain: Chain1<F>): <A>(mma: Type<F, Type<F, A>>) => Type<F, A>
export function flatten<F>(chain: Chain<F>): <A>(mma: HKT<F, HKT<F, A>>) => HKT<F, A> { ... }

Added in v1.0.0