Added in v2.0.0
Signature
export interface Foldable<F> {
readonly URI: F
readonly reduce: <A, B>(fa: HKT<F, A>, b: B, f: (b: B, a: A) => B) => B
readonly foldMap: <M>(M: Monoid<M>) => <A>(fa: HKT<F, A>, f: (a: A) => M) => M
readonly reduceRight: <A, B>(fa: HKT<F, A>, b: B, f: (a: A, b: B) => B) => B
}
Added in v2.0.0
Signature
export interface Foldable1<F extends URIS> {
readonly URI: F
readonly reduce: <A, B>(fa: Kind<F, A>, b: B, f: (b: B, a: A) => B) => B
readonly foldMap: <M>(M: Monoid<M>) => <A>(fa: Kind<F, A>, f: (a: A) => M) => M
readonly reduceRight: <A, B>(fa: Kind<F, A>, b: B, f: (a: A, b: B) => B) => B
}
Added in v2.0.0
Signature
export interface Foldable2<F extends URIS2> {
readonly URI: F
readonly reduce: <E, A, B>(fa: Kind2<F, E, A>, b: B, f: (b: B, a: A) => B) => B
readonly foldMap: <M>(M: Monoid<M>) => <E, A>(fa: Kind2<F, E, A>, f: (a: A) => M) => M
readonly reduceRight: <E, A, B>(fa: Kind2<F, E, A>, b: B, f: (a: A, b: B) => B) => B
}
Added in v2.0.0
Signature
export interface Foldable2C<F extends URIS2, E> {
readonly URI: F
readonly _E: E
readonly reduce: <A, B>(fa: Kind2<F, E, A>, b: B, f: (b: B, a: A) => B) => B
readonly foldMap: <M>(M: Monoid<M>) => <A>(fa: Kind2<F, E, A>, f: (a: A) => M) => M
readonly reduceRight: <A, B>(fa: Kind2<F, E, A>, b: B, f: (a: A, b: B) => B) => B
}
Added in v2.0.0
Signature
export interface Foldable3<F extends URIS3> {
readonly URI: F
readonly reduce: <R, E, A, B>(fa: Kind3<F, R, E, A>, b: B, f: (b: B, a: A) => B) => B
readonly foldMap: <M>(M: Monoid<M>) => <R, E, A>(fa: Kind3<F, R, E, A>, f: (a: A) => M) => M
readonly reduceRight: <R, E, A, B>(fa: Kind3<F, R, E, A>, b: B, f: (a: A, b: B) => B) => B
}
Added in v2.0.0
Signature
export interface Foldable3C<F extends URIS3, E> {
readonly URI: F
readonly _E: E
readonly reduce: <R, A, B>(fa: Kind3<F, R, E, A>, b: B, f: (b: B, a: A) => B) => B
readonly foldMap: <M>(M: Monoid<M>) => <R, A>(fa: Kind3<F, R, E, A>, f: (a: A) => M) => M
readonly reduceRight: <R, A, B>(fa: Kind3<F, R, E, A>, b: B, f: (a: A, b: B) => B) => B
}
Added in v2.2.0
Signature
export interface Foldable4<F extends URIS4> {
readonly URI: F
readonly reduce: <S, R, E, A, B>(fa: Kind4<F, S, R, E, A>, b: B, f: (b: B, a: A) => B) => B
readonly foldMap: <M>(M: Monoid<M>) => <S, R, E, A>(fa: Kind4<F, S, R, E, A>, f: (a: A) => M) => M
readonly reduceRight: <S, R, E, A, B>(fa: Kind4<F, S, R, E, A>, b: B, f: (a: A, b: B) => B) => B
}
Added in v2.0.0
Signature
export interface FoldableComposition<F, G> {
readonly reduce: <A, B>(fga: HKT<F, HKT<G, A>>, b: B, f: (b: B, a: A) => B) => B
readonly foldMap: <M>(M: Monoid<M>) => <A>(fa: HKT<F, HKT<G, A>>, f: (a: A) => M) => M
readonly reduceRight: <A, B>(fa: HKT<F, HKT<G, A>>, b: B, f: (a: A, b: B) => B) => B
}
Added in v2.0.0
Signature
export interface FoldableComposition11<F extends URIS, G extends URIS> {
readonly reduce: <A, B>(fga: Kind<F, Kind<G, A>>, b: B, f: (b: B, a: A) => B) => B
readonly foldMap: <M>(M: Monoid<M>) => <A>(fa: Kind<F, Kind<G, A>>, f: (a: A) => M) => M
readonly reduceRight: <A, B>(fa: Kind<F, Kind<G, A>>, b: B, f: (a: A, b: B) => B) => B
}
Added in v2.0.0
Signature
export interface FoldableComposition12<F extends URIS, G extends URIS2> {
readonly reduce: <E, A, B>(fga: Kind<F, Kind2<G, E, A>>, b: B, f: (b: B, a: A) => B) => B
readonly foldMap: <M>(M: Monoid<M>) => <E, A>(fa: Kind<F, Kind2<G, E, A>>, f: (a: A) => M) => M
readonly reduceRight: <E, A, B>(fa: Kind<F, Kind2<G, E, A>>, b: B, f: (a: A, b: B) => B) => B
}
Added in v2.0.0
Signature
export interface FoldableComposition12C<F extends URIS, G extends URIS2, E> {
readonly reduce: <A, B>(fga: Kind<F, Kind2<G, E, A>>, b: B, f: (b: B, a: A) => B) => B
readonly foldMap: <M>(M: Monoid<M>) => <A>(fa: Kind<F, Kind2<G, E, A>>, f: (a: A) => M) => M
readonly reduceRight: <A, B>(fa: Kind<F, Kind2<G, E, A>>, b: B, f: (a: A, b: B) => B) => B
}
Added in v2.0.0
Signature
export interface FoldableComposition21<F extends URIS2, G extends URIS> {
readonly reduce: <E, A, B>(fga: Kind2<F, E, Kind<G, A>>, b: B, f: (b: B, a: A) => B) => B
readonly foldMap: <M>(M: Monoid<M>) => <E, A>(fa: Kind2<F, E, Kind<G, A>>, f: (a: A) => M) => M
readonly reduceRight: <E, A, B>(fa: Kind2<F, E, Kind<G, A>>, b: B, f: (a: A, b: B) => B) => B
}
Added in v2.0.0
Signature
export interface FoldableComposition22<F extends URIS2, G extends URIS2> {
readonly reduce: <FE, GE, A, B>(fga: Kind2<F, FE, Kind2<G, GE, A>>, b: B, f: (b: B, a: A) => B) => B
readonly foldMap: <M>(M: Monoid<M>) => <FE, GE, A>(fa: Kind2<F, FE, Kind2<G, GE, A>>, f: (a: A) => M) => M
readonly reduceRight: <FE, GE, A, B>(fa: Kind2<F, FE, Kind2<G, GE, A>>, b: B, f: (a: A, b: B) => B) => B
}
Added in v2.0.0
Signature
export interface FoldableComposition22C<F extends URIS2, G extends URIS2, E> {
readonly reduce: <FE, A, B>(fga: Kind2<F, FE, Kind2<G, E, A>>, b: B, f: (b: B, a: A) => B) => B
readonly foldMap: <M>(M: Monoid<M>) => <FE, A>(fa: Kind2<F, FE, Kind2<G, E, A>>, f: (a: A) => M) => M
readonly reduceRight: <FE, A, B>(fa: Kind2<F, FE, Kind2<G, E, A>>, b: B, f: (a: A, b: B) => B) => B
}
Added in v2.0.0
Signature
export interface FoldableComposition2C1<F extends URIS2, G extends URIS, E> {
readonly reduce: <A, B>(fga: Kind2<F, E, Kind<G, A>>, b: B, f: (b: B, a: A) => B) => B
readonly foldMap: <M>(M: Monoid<M>) => <A>(fa: Kind2<F, E, Kind<G, A>>, f: (a: A) => M) => M
readonly reduceRight: <A, B>(fa: Kind2<F, E, Kind<G, A>>, b: B, f: (a: A, b: B) => B) => B
}
Added in v2.0.0
Returns the composition of two foldables
Signature
export declare function getFoldableComposition<F extends URIS2, G extends URIS2, E>(
F: Foldable2<F>,
G: Foldable2C<G, E>
): FoldableComposition22C<F, G, E>
export declare function getFoldableComposition<F extends URIS2, G extends URIS2>(
F: Foldable2<F>,
G: Foldable2<G>
): FoldableComposition22<F, G>
export declare function getFoldableComposition<F extends URIS2, G extends URIS, E>(
F: Foldable2C<F, E>,
G: Foldable1<G>
): FoldableComposition2C1<F, G, E>
export declare function getFoldableComposition<F extends URIS2, G extends URIS>(
F: Foldable2<F>,
G: Foldable1<G>
): FoldableComposition21<F, G>
export declare function getFoldableComposition<F extends URIS, G extends URIS2, E>(
F: Foldable1<F>,
G: Foldable2C<G, E>
): FoldableComposition12C<F, G, E>
export declare function getFoldableComposition<F extends URIS, G extends URIS2>(
F: Foldable1<F>,
G: Foldable2<G>
): FoldableComposition12<F, G>
export declare function getFoldableComposition<F extends URIS, G extends URIS>(
F: Foldable1<F>,
G: Foldable1<G>
): FoldableComposition11<F, G>
export declare function getFoldableComposition<F, G>(F: Foldable<F>, G: Foldable<G>): FoldableComposition<F, G>
Example
import { getFoldableComposition } from 'fp-ts/Foldable'
import { array } from 'fp-ts/Array'
import { option, some, none } from 'fp-ts/Option'
import { monoidString } from 'fp-ts/Monoid'
const F = getFoldableComposition(array, option)
assert.strictEqual(F.reduce([some('a'), some('b'), some('c')], '', monoidString.concat), 'abc')
assert.strictEqual(F.reduce([some('a'), none, some('c')], '', monoidString.concat), 'ac')
Added in v2.0.0
Fold a data structure, accumulating values in some Monoid
, combining adjacent elements using the specified separator
Signature
export declare function intercalate<M, F extends URIS3>(
M: Monoid<M>,
F: Foldable3<F>
): <R, E>(sep: M, fm: Kind3<F, R, E, M>) => M
export declare function intercalate<M, F extends URIS2>(
M: Monoid<M>,
F: Foldable2<F>
): <E>(sep: M, fm: Kind2<F, E, M>) => M
export declare function intercalate<M, F extends URIS2, E>(
M: Monoid<M>,
F: Foldable2C<F, E>
): (sep: M, fm: Kind2<F, E, M>) => M
export declare function intercalate<M, F extends URIS>(M: Monoid<M>, F: Foldable1<F>): (sep: M, fm: Kind<F, M>) => M
export declare function intercalate<M, F>(M: Monoid<M>, F: Foldable<F>): (sep: M, fm: HKT<F, M>) => M
Example
import { intercalate } from 'fp-ts/Foldable'
import { monoidString } from 'fp-ts/Monoid'
import { make, tree } from 'fp-ts/Tree'
const t = make('a', [make('b', []), make('c', []), make('d', [])])
assert.strictEqual(intercalate(monoidString, tree)('|', t), 'a|b|c|d')
Added in v2.0.0
Similar to 'reduce', but the result is encapsulated in a monad.
Note: this function is not generally stack-safe, e.g., for monads which build up thunks a la IO
.
Signature
export declare function reduceM<M extends URIS3, F extends URIS>(
M: Monad3<M>,
F: Foldable1<F>
): <B, A, R, E>(b: B, f: (b: B, a: A) => Kind3<M, R, E, B>) => (fa: Kind<F, A>) => Kind3<M, R, E, B>
export declare function reduceM<M extends URIS3, F extends URIS, E>(
M: Monad3C<M, E>,
F: Foldable1<F>
): <B, A, R>(b: B, f: (b: B, a: A) => Kind3<M, R, E, B>) => (fa: Kind<F, A>) => Kind3<M, R, E, B>
export declare function reduceM<M extends URIS2, F extends URIS>(
M: Monad2<M>,
F: Foldable1<F>
): <B, A, E>(b: B, f: (b: B, a: A) => Kind2<M, E, B>) => (fa: Kind<F, A>) => Kind2<M, E, B>
export declare function reduceM<M extends URIS2, F extends URIS, E>(
M: Monad2C<M, E>,
F: Foldable1<F>
): <B, A>(b: B, f: (b: B, a: A) => Kind2<M, E, B>) => (fa: Kind<F, A>) => Kind2<M, E, B>
export declare function reduceM<M extends URIS, F extends URIS>(
M: Monad1<M>,
F: Foldable1<F>
): <B, A>(b: B, f: (b: B, a: A) => Kind<M, B>) => (fa: Kind<F, A>) => Kind<M, B>
export declare function reduceM<M, F>(
M: Monad<M>,
F: Foldable<F>
): <B, A>(b: B, f: (b: B, a: A) => HKT<M, B>) => (fa: HKT<F, A>) => HKT<M, B>
Example
import { reduceM } from 'fp-ts/Foldable'
import { Monad, some } from 'fp-ts/Option'
import { make, Foldable } from 'fp-ts/Tree'
import { pipe } from 'fp-ts/function'
const t = make(1, [make(2, []), make(3, []), make(4, [])])
assert.deepStrictEqual(
pipe(
t,
reduceM(Monad, Foldable)(0, (b, a) => (a > 2 ? some(b + a) : some(b)))
),
some(7)
)
Added in v2.8.0
Transforms a Foldable
into a read-only array.
Signature
export declare function toArray<F extends URIS4>(
F: Foldable4<F>
): <S, R, E, A>(fa: Kind4<F, S, R, E, A>) => ReadonlyArray<A>
export declare function toArray<F extends URIS3>(F: Foldable3<F>): <R, E, A>(fa: Kind3<F, R, E, A>) => ReadonlyArray<A>
export declare function toArray<F extends URIS3, E>(
F: Foldable3C<F, E>
): <R, A>(fa: Kind3<F, R, E, A>) => ReadonlyArray<A>
export declare function toArray<F extends URIS2>(F: Foldable2<F>): <E, A>(fa: Kind2<F, E, A>) => ReadonlyArray<A>
export declare function toArray<F extends URIS2, E>(F: Foldable2C<F, E>): <A>(fa: Kind2<F, E, A>) => ReadonlyArray<A>
export declare function toArray<F extends URIS>(F: Foldable1<F>): <A>(fa: Kind<F, A>) => ReadonlyArray<A>
export declare function toArray<F>(F: Foldable<F>): <A>(fa: HKT<F, A>) => ReadonlyArray<A>
Example
import { toArray } from 'fp-ts/Foldable'
import { tree, make } from 'fp-ts/Tree'
const t = make(1, [make(2, []), make(3, []), make(4, [])])
assert.deepStrictEqual(toArray(tree)(t), [1, 2, 3, 4])
Added in v2.8.0
Traverse a data structure, performing some effects encoded by an Applicative
functor at each value, ignoring the
final result.
Signature
export declare function traverse_<M extends URIS3, F extends URIS>(
M: Applicative3<M>,
F: Foldable1<F>
): <R, E, A, B>(fa: Kind<F, A>, f: (a: A) => Kind3<M, R, E, B>) => Kind3<M, R, E, void>
export declare function traverse_<M extends URIS2, F extends URIS>(
M: Applicative2<M>,
F: Foldable1<F>
): <E, A, B>(fa: Kind<F, A>, f: (a: A) => Kind2<M, E, B>) => Kind2<M, E, void>
export declare function traverse_<M extends URIS2, F extends URIS, E>(
M: Applicative2C<M, E>,
F: Foldable1<F>
): <A, B>(fa: Kind<F, A>, f: (a: A) => Kind2<M, E, B>) => Kind2<M, E, void>
export declare function traverse_<M extends URIS, F extends URIS>(
M: Applicative1<M>,
F: Foldable1<F>
): <A, B>(fa: Kind<F, A>, f: (a: A) => Kind<M, B>) => Kind<M, void>
export declare function traverse_<M, F>(
M: Applicative<M>,
F: Foldable<F>
): <A, B>(fa: HKT<F, A>, f: (a: A) => HKT<M, B>) => HKT<M, void>
Example
import { array } from 'fp-ts/Array'
import { traverse_ } from 'fp-ts/Foldable'
import { io } from 'fp-ts/IO'
let log = ''
const append = (s: string) => () => (log += s)
traverse_(io, array)(['a', 'b', 'c'], append)()
assert.strictEqual(log, 'abc')
Added in v2.0.0
Use reduceM
instead
Signature
export declare function foldM<M extends URIS3, F extends URIS>(
M: Monad3<M>,
F: Foldable1<F>
): <R, E, A, B>(fa: Kind<F, A>, b: B, f: (b: B, a: A) => Kind3<M, R, E, B>) => Kind3<M, R, E, B>
export declare function foldM<M extends URIS3, F extends URIS, E>(
M: Monad3C<M, E>,
F: Foldable1<F>
): <R, A, B>(fa: Kind<F, A>, b: B, f: (b: B, a: A) => Kind3<M, R, E, B>) => Kind3<M, R, E, B>
export declare function foldM<M extends URIS2, F extends URIS>(
M: Monad2<M>,
F: Foldable1<F>
): <E, A, B>(fa: Kind<F, A>, b: B, f: (b: B, a: A) => Kind2<M, E, B>) => Kind2<M, E, B>
export declare function foldM<M extends URIS2, F extends URIS, E>(
M: Monad2C<M, E>,
F: Foldable1<F>
): <A, B>(fa: Kind<F, A>, b: B, f: (b: B, a: A) => Kind2<M, E, B>) => Kind2<M, E, B>
export declare function foldM<M extends URIS, F extends URIS>(
M: Monad1<M>,
F: Foldable1<F>
): <A, B>(fa: Kind<F, A>, b: B, f: (b: B, a: A) => Kind<M, B>) => Kind<M, B>
export declare function foldM<M, F>(
M: Monad<M>,
F: Foldable<F>
): <A, B>(fa: HKT<F, A>, b: B, f: (b: B, a: A) => HKT<M, B>) => HKT<M, B>
Added in v2.0.0