Functor overview

A Functor is a type constructor which supports a mapping operation map.

map can be used to turn functions a -> b into functions f a -> f b whose argument and return types use the type constructor f to represent some computational context.

Instances must satisfy the following laws:

  1. Identity: F.map(fa, a => a) <-> fa
  2. Composition: F.map(fa, a => bc(ab(a))) <-> F.map(F.map(fa, ab), bc)

Added in v2.0.0

Table of contents

mapping

flap

Signature

export declare function flap<F extends URIS4>(
  F: Functor4<F>
): <A>(a: A) => <S, R, E, B>(fab: Kind4<F, S, R, E, (a: A) => B>) => Kind4<F, S, R, E, B>
export declare function flap<F extends URIS3>(
  F: Functor3<F>
): <A>(a: A) => <R, E, B>(fab: Kind3<F, R, E, (a: A) => B>) => Kind3<F, R, E, B>
export declare function flap<F extends URIS2>(
  F: Functor2<F>
): <A>(a: A) => <E, B>(fab: Kind2<F, E, (a: A) => B>) => Kind2<F, E, B>
export declare function flap<F extends URIS>(F: Functor1<F>): <A>(a: A) => <B>(fab: Kind<F, (a: A) => B>) => Kind<F, B>
export declare function flap<F>(F: Functor<F>): <A>(a: A) => <B>(fab: HKT<F, (a: A) => B>) => HKT<F, B>

Added in v2.10.0

model

Functor (interface)

Signature

export interface Functor<F> {
  readonly URI: F
  readonly map: <A, B>(fa: HKT<F, A>, f: (a: A) => B) => HKT<F, B>
}

Added in v2.0.0

Functor1 (interface)

Signature

export interface Functor1<F extends URIS> {
  readonly URI: F
  readonly map: <A, B>(fa: Kind<F, A>, f: (a: A) => B) => Kind<F, B>
}

Added in v2.0.0

Functor2 (interface)

Signature

export interface Functor2<F extends URIS2> {
  readonly URI: F
  readonly map: <E, A, B>(fa: Kind2<F, E, A>, f: (a: A) => B) => Kind2<F, E, B>
}

Added in v2.0.0

Functor2C (interface)

Signature

export interface Functor2C<F extends URIS2, E> {
  readonly URI: F
  readonly _E: E
  readonly map: <A, B>(fa: Kind2<F, E, A>, f: (a: A) => B) => Kind2<F, E, B>
}

Added in v2.0.0

Functor3 (interface)

Signature

export interface Functor3<F extends URIS3> {
  readonly URI: F
  readonly map: <R, E, A, B>(fa: Kind3<F, R, E, A>, f: (a: A) => B) => Kind3<F, R, E, B>
}

Added in v2.0.0

Functor3C (interface)

Signature

export interface Functor3C<F extends URIS3, E> {
  readonly URI: F
  readonly _E: E
  readonly map: <R, A, B>(fa: Kind3<F, R, E, A>, f: (a: A) => B) => Kind3<F, R, E, B>
}

Added in v2.2.0

Functor4 (interface)

Signature

export interface Functor4<F extends URIS4> {
  readonly URI: F
  readonly map: <S, R, E, A, B>(fa: Kind4<F, S, R, E, A>, f: (a: A) => B) => Kind4<F, S, R, E, B>
}

Added in v2.0.0

utils

bindTo

Signature

export declare function bindTo<F extends URIS4>(
  F: Functor4<F>
): <N extends string>(name: N) => <S, R, E, A>(fa: Kind4<F, S, R, E, A>) => Kind4<F, S, R, E, { readonly [K in N]: A }>
export declare function bindTo<F extends URIS3>(
  F: Functor3<F>
): <N extends string>(name: N) => <R, E, A>(fa: Kind3<F, R, E, A>) => Kind3<F, R, E, { readonly [K in N]: A }>
export declare function bindTo<F extends URIS3, E>(
  F: Functor3C<F, E>
): <N extends string>(name: N) => <R, A>(fa: Kind3<F, R, E, A>) => Kind3<F, R, E, { readonly [K in N]: A }>
export declare function bindTo<F extends URIS2>(
  F: Functor2<F>
): <N extends string>(name: N) => <E, A>(fa: Kind2<F, E, A>) => Kind2<F, E, { readonly [K in N]: A }>
export declare function bindTo<F extends URIS2, E>(
  F: Functor2C<F, E>
): <N extends string>(name: N) => <A>(fa: Kind2<F, E, A>) => Kind2<F, E, { readonly [K in N]: A }>
export declare function bindTo<F extends URIS>(
  F: Functor1<F>
): <N extends string>(name: N) => <A>(fa: Kind<F, A>) => Kind<F, { readonly [K in N]: A }>
export declare function bindTo<F>(
  F: Functor<F>
): <N extends string>(name: N) => <A>(fa: HKT<F, A>) => HKT<F, { readonly [K in N]: A }>

Added in v2.10.0

let

Signature

export declare const let: typeof let_

Added in v2.13.0

let_

Signature

function let_<F extends URIS4>(
  F: Functor4<F>
): <N extends string, A, B>(
  name: Exclude<N, keyof A>,
  f: (a: A) => B
) => <S, R, E>(
  fa: Kind4<F, S, R, E, A>
) => Kind4<F, S, R, E, { readonly [K in keyof A | N]: K extends keyof A ? A[K] : B }>
function let_<F extends URIS3>(
  F: Functor3<F>
): <N extends string, A, B>(
  name: Exclude<N, keyof A>,
  f: (a: A) => B
) => <R, E>(fa: Kind3<F, R, E, A>) => Kind3<F, R, E, { readonly [K in keyof A | N]: K extends keyof A ? A[K] : B }>
function let_<F extends URIS3, E>(
  F: Functor3C<F, E>
): <N extends string, A, B>(
  name: Exclude<N, keyof A>,
  f: (a: A) => B
) => <R>(fa: Kind3<F, R, E, A>) => Kind3<F, R, E, { readonly [K in keyof A | N]: K extends keyof A ? A[K] : B }>
function let_<F extends URIS2>(
  F: Functor2<F>
): <N extends string, A, B>(
  name: Exclude<N, keyof A>,
  f: (a: A) => B
) => <E>(fa: Kind2<F, E, A>) => Kind2<F, E, { readonly [K in keyof A | N]: K extends keyof A ? A[K] : B }>
function let_<F extends URIS2, E>(
  F: Functor2C<F, E>
): <N extends string, A, B>(
  name: Exclude<N, keyof A>,
  f: (a: A) => B
) => (fa: Kind2<F, E, A>) => Kind2<F, E, { readonly [K in keyof A | N]: K extends keyof A ? A[K] : B }>
function let_<F extends URIS>(
  F: Functor1<F>
): <N extends string, A, B>(
  name: Exclude<N, keyof A>,
  f: (a: A) => B
) => (fa: Kind<F, A>) => Kind<F, { readonly [K in keyof A | N]: K extends keyof A ? A[K] : B }>
function let_<F>(
  F: Functor<F>
): <N extends string, A, B>(
  name: Exclude<N, keyof A>,
  f: (a: A) => B
) => (fa: HKT<F, A>) => HKT<F, { readonly [K in keyof A | N]: K extends keyof A ? A[K] : B }>

Added in v2.13.0

map

map composition.

Signature

export declare function map<F extends URIS3, G extends URIS>(
  F: Functor3<F>,
  G: Functor1<G>
): <A, B>(f: (a: A) => B) => <R, E>(fa: Kind3<F, R, E, Kind<G, A>>) => Kind3<F, R, E, Kind<G, B>>
export declare function map<F extends URIS2, G extends URIS2>(
  F: Functor2<F>,
  G: Functor2<G>
): <A, B>(f: (a: A) => B) => <EF, EG>(fa: Kind2<F, EF, Kind2<G, EG, A>>) => Kind2<F, EF, Kind2<G, EG, B>>
export declare function map<F extends URIS2, G extends URIS>(
  F: Functor2<F>,
  G: Functor1<G>
): <A, B>(f: (a: A) => B) => <E>(fa: Kind2<F, E, Kind<G, A>>) => Kind2<F, E, Kind<G, B>>
export declare function map<F extends URIS, G extends URIS3>(
  F: Functor1<F>,
  G: Functor3<G>
): <A, B>(f: (a: A) => B) => <R, E>(fa: Kind<F, Kind3<G, R, E, A>>) => Kind<F, Kind3<G, R, E, B>>
export declare function map<F extends URIS, G extends URIS2>(
  F: Functor1<F>,
  G: Functor2<G>
): <A, B>(f: (a: A) => B) => <E>(fa: Kind<F, Kind2<G, E, A>>) => Kind<F, Kind2<G, E, B>>
export declare function map<F extends URIS, G extends URIS>(
  F: Functor1<F>,
  G: Functor1<G>
): <A, B>(f: (a: A) => B) => (fa: Kind<F, Kind<G, A>>) => Kind<F, Kind<G, B>>
export declare function map<F, G extends URIS2>(
  F: Functor<F>,
  G: Functor2<G>
): <A, B>(f: (a: A) => B) => <E>(fa: HKT<F, Kind2<G, E, A>>) => HKT<F, Kind2<G, E, B>>
export declare function map<F, G extends URIS>(
  F: Functor<F>,
  G: Functor1<G>
): <A, B>(f: (a: A) => B) => (fa: HKT<F, Kind<G, A>>) => HKT<F, Kind<G, B>>
export declare function map<F, G>(
  F: Functor<F>,
  G: Functor<G>
): <A, B>(f: (a: A) => B) => (fa: HKT<F, HKT<G, A>>) => HKT<F, HKT<G, B>>

Added in v2.10.0

zone of death

FunctorComposition11 (interface)

Signature

export interface FunctorComposition11<F extends URIS, G extends URIS> {
  readonly map: <A, B>(fa: Kind<F, Kind<G, A>>, f: (a: A) => B) => Kind<F, Kind<G, B>>
}

Added in v2.0.0

FunctorComposition12C (interface)

Signature

export interface FunctorComposition12C<F extends URIS, G extends URIS2, E> {
  readonly map: <A, B>(fa: Kind<F, Kind2<G, E, A>>, f: (a: A) => B) => Kind<F, Kind2<G, E, B>>
}

Added in v2.0.0

FunctorComposition12 (interface)

Signature

export interface FunctorComposition12<F extends URIS, G extends URIS2> {
  readonly map: <E, A, B>(fa: Kind<F, Kind2<G, E, A>>, f: (a: A) => B) => Kind<F, Kind2<G, E, B>>
}

Added in v2.0.0

FunctorComposition21 (interface)

Signature

export interface FunctorComposition21<F extends URIS2, G extends URIS> {
  readonly map: <E, A, B>(fa: Kind2<F, E, Kind<G, A>>, f: (a: A) => B) => Kind2<F, E, Kind<G, B>>
}

Added in v2.0.0

FunctorComposition22C (interface)

Signature

export interface FunctorComposition22C<F extends URIS2, G extends URIS2, E> {
  readonly map: <FE, A, B>(fa: Kind2<F, FE, Kind2<G, E, A>>, f: (a: A) => B) => Kind2<F, FE, Kind2<G, E, B>>
}

Added in v2.0.0

FunctorComposition22 (interface)

Signature

export interface FunctorComposition22<F extends URIS2, G extends URIS2> {
  readonly map: <FE, GE, A, B>(fa: Kind2<F, FE, Kind2<G, GE, A>>, f: (a: A) => B) => Kind2<F, FE, Kind2<G, GE, B>>
}

Added in v2.0.0

FunctorComposition23C (interface)

Signature

export interface FunctorComposition23C<F extends URIS2, G extends URIS3, E> {
  readonly map: <FE, R, A, B>(fa: Kind2<F, FE, Kind3<G, R, E, A>>, f: (a: A) => B) => Kind2<F, FE, Kind3<G, R, E, B>>
}

Added in v2.2.0

FunctorComposition23 (interface)

Signature

export interface FunctorComposition23<F extends URIS2, G extends URIS3> {
  readonly map: <FE, R, E, A, B>(fa: Kind2<F, FE, Kind3<G, R, E, A>>, f: (a: A) => B) => Kind2<F, FE, Kind3<G, R, E, B>>
}

Added in v2.2.0

FunctorComposition2C1 (interface)

Signature

export interface FunctorComposition2C1<F extends URIS2, G extends URIS, E> {
  readonly map: <A, B>(fa: Kind2<F, E, Kind<G, A>>, f: (a: A) => B) => Kind2<F, E, Kind<G, B>>
}

Added in v2.0.0

FunctorCompositionHKT1 (interface)

Signature

export interface FunctorCompositionHKT1<F, G extends URIS> {
  readonly map: <A, B>(fa: HKT<F, Kind<G, A>>, f: (a: A) => B) => HKT<F, Kind<G, B>>
}

Added in v2.0.0

FunctorCompositionHKT2C (interface)

Signature

export interface FunctorCompositionHKT2C<F, G extends URIS2, E> {
  readonly map: <A, B>(fa: HKT<F, Kind2<G, E, A>>, f: (a: A) => B) => HKT<F, Kind2<G, E, B>>
}

Added in v2.0.0

FunctorCompositionHKT2 (interface)

Signature

export interface FunctorCompositionHKT2<F, G extends URIS2> {
  readonly map: <E, A, B>(fa: HKT<F, Kind2<G, E, A>>, f: (a: A) => B) => HKT<F, Kind2<G, E, B>>
}

Added in v2.0.0

FunctorComposition (interface)

Signature

export interface FunctorComposition<F, G> {
  readonly map: <A, B>(fa: HKT<F, HKT<G, A>>, f: (a: A) => B) => HKT<F, HKT<G, B>>
}

Added in v2.0.0

getFunctorComposition

Use map instead.

Signature

export declare function getFunctorComposition<F extends URIS2, G extends URIS3, E>(
  F: Functor2<F>,
  G: Functor3C<G, E>
): FunctorComposition23C<F, G, E>
export declare function getFunctorComposition<F extends URIS2, G extends URIS2, E>(
  F: Functor2<F>,
  G: Functor2C<G, E>
): FunctorComposition22C<F, G, E>
export declare function getFunctorComposition<F extends URIS2, G extends URIS2>(
  F: Functor2<F>,
  G: Functor2<G>
): FunctorComposition22<F, G>
export declare function getFunctorComposition<F extends URIS2, G extends URIS, E>(
  F: Functor2C<F, E>,
  G: Functor1<G>
): FunctorComposition2C1<F, G, E>
export declare function getFunctorComposition<F extends URIS2, G extends URIS>(
  F: Functor2<F>,
  G: Functor1<G>
): FunctorComposition21<F, G>
export declare function getFunctorComposition<F extends URIS, G extends URIS2, E>(
  F: Functor1<F>,
  G: Functor2C<G, E>
): FunctorComposition12C<F, G, E>
export declare function getFunctorComposition<F extends URIS, G extends URIS2>(
  F: Functor1<F>,
  G: Functor2<G>
): FunctorComposition12<F, G>
export declare function getFunctorComposition<F extends URIS, G extends URIS>(
  F: Functor1<F>,
  G: Functor1<G>
): FunctorComposition11<F, G>
export declare function getFunctorComposition<F, G>(F: Functor<F>, G: Functor<G>): FunctorComposition<F, G>

Added in v2.0.0