<A, B>(f: (as: ReadonlyArray<A>) => B): (
self: ReadonlyArray<A>
) => Array<B>
<A, B>(self: ReadonlyArray<A>, f: (as: ReadonlyArray<A>) => B): Array<B>Applies a function to each suffix of the array (starting from each index), collecting the results.
When to use
Use when you need to compute a result from every suffix of an array, such as cumulative aggregations from each position.
Details
For index i, the function receives self.slice(i).
Example (Computing suffix lengths)
import { Array } from "effect"
console.log(Array.extend([1, 2, 3], (as) => as.length)) // [3, 2, 1]export const const extend: {
<A, B>(f: (as: ReadonlyArray<A>) => B): (
self: ReadonlyArray<A>
) => Array<B>
<A, B>(
self: ReadonlyArray<A>,
f: (as: ReadonlyArray<A>) => B
): Array<B>
}
Applies a function to each suffix of the array (starting from each index),
collecting the results.
When to use
Use when you need to compute a result from every suffix of an array, such as
cumulative aggregations from each position.
Details
For index i, the function receives self.slice(i).
Example (Computing suffix lengths)
import { Array } from "effect"
console.log(Array.extend([1, 2, 3], (as) => as.length)) // [3, 2, 1]
extend: {
<function (type parameter) A in <A, B>(f: (as: ReadonlyArray<A>) => B): (self: ReadonlyArray<A>) => Array<B>A, function (type parameter) B in <A, B>(f: (as: ReadonlyArray<A>) => B): (self: ReadonlyArray<A>) => Array<B>B>(f: (as: ReadonlyArray<A>) => Bf: (as: readonly A[]as: interface ReadonlyArray<T>ReadonlyArray<function (type parameter) A in <A, B>(f: (as: ReadonlyArray<A>) => B): (self: ReadonlyArray<A>) => Array<B>A>) => function (type parameter) B in <A, B>(f: (as: ReadonlyArray<A>) => B): (self: ReadonlyArray<A>) => Array<B>B): (self: readonly A[]self: interface ReadonlyArray<T>ReadonlyArray<function (type parameter) A in <A, B>(f: (as: ReadonlyArray<A>) => B): (self: ReadonlyArray<A>) => Array<B>A>) => interface Array<T>Array<function (type parameter) B in <A, B>(f: (as: ReadonlyArray<A>) => B): (self: ReadonlyArray<A>) => Array<B>B>
<function (type parameter) A in <A, B>(self: ReadonlyArray<A>, f: (as: ReadonlyArray<A>) => B): Array<B>A, function (type parameter) B in <A, B>(self: ReadonlyArray<A>, f: (as: ReadonlyArray<A>) => B): Array<B>B>(self: readonly A[]self: interface ReadonlyArray<T>ReadonlyArray<function (type parameter) A in <A, B>(self: ReadonlyArray<A>, f: (as: ReadonlyArray<A>) => B): Array<B>A>, f: (as: ReadonlyArray<A>) => Bf: (as: readonly A[]as: interface ReadonlyArray<T>ReadonlyArray<function (type parameter) A in <A, B>(self: ReadonlyArray<A>, f: (as: ReadonlyArray<A>) => B): Array<B>A>) => function (type parameter) B in <A, B>(self: ReadonlyArray<A>, f: (as: ReadonlyArray<A>) => B): Array<B>B): interface Array<T>Array<function (type parameter) B in <A, B>(self: ReadonlyArray<A>, f: (as: ReadonlyArray<A>) => B): Array<B>B>
} = dual<(...args: Array<any>) => any, <A, B>(self: ReadonlyArray<A>, f: (as: ReadonlyArray<A>) => B) => Array<B>>(arity: 2, body: <A, B>(self: ReadonlyArray<A>, f: (as: ReadonlyArray<A>) => B) => Array<B>): ((...args: Array<any>) => any) & (<A, B>(self: ReadonlyArray<A>, f: (as: ReadonlyArray<A>) => B) => Array<B>) (+1 overload)Creates a function that can be called in data-first style or data-last
(pipe-friendly) style.
When to use
Use to expose one implementation through both direct and pipe-friendly
call styles.
Details
Pass either the arity of the uncurried function or a predicate that decides
whether the current call is data-first. Arity is the common case. Use a
predicate when optional arguments make arity ambiguous.
Example (Selecting data-first or data-last style by arity)
import { Function, pipe } from "effect"
const sum = Function.dual<
(that: number) => (self: number) => number,
(self: number, that: number) => number
>(2, (self, that) => self + that)
console.log(sum(2, 3)) // 5
console.log(pipe(2, sum(3))) // 5
Example (Defining overloads with call signatures)
import { Function, pipe } from "effect"
const sum: {
(that: number): (self: number) => number
(self: number, that: number): number
} = Function.dual(2, (self: number, that: number): number => self + that)
console.log(sum(2, 3)) // 5
console.log(pipe(2, sum(3))) // 5
Example (Selecting data-first or data-last style with a predicate)
import { Function, pipe } from "effect"
const sum = Function.dual<
(that: number) => (self: number) => number,
(self: number, that: number) => number
>(
(args) => args.length === 2,
(self, that) => self + that
)
console.log(sum(2, 3)) // 5
console.log(pipe(2, sum(3))) // 5
dual(
2,
<function (type parameter) A in <A, B>(self: ReadonlyArray<A>, f: (as: ReadonlyArray<A>) => B): Array<B>A, function (type parameter) B in <A, B>(self: ReadonlyArray<A>, f: (as: ReadonlyArray<A>) => B): Array<B>B>(self: readonly A[]self: interface ReadonlyArray<T>ReadonlyArray<function (type parameter) A in <A, B>(self: ReadonlyArray<A>, f: (as: ReadonlyArray<A>) => B): Array<B>A>, f: (as: ReadonlyArray<A>) => Bf: (as: readonly A[]as: interface ReadonlyArray<T>ReadonlyArray<function (type parameter) A in <A, B>(self: ReadonlyArray<A>, f: (as: ReadonlyArray<A>) => B): Array<B>A>) => function (type parameter) B in <A, B>(self: ReadonlyArray<A>, f: (as: ReadonlyArray<A>) => B): Array<B>B): interface Array<T>Array<function (type parameter) B in <A, B>(self: ReadonlyArray<A>, f: (as: ReadonlyArray<A>) => B): Array<B>B> => self: readonly A[]self.globalThis.ReadonlyArray<A>.map<B>(callbackfn: (value: A, index: number, array: readonly A[]) => B, thisArg?: any): B[]Calls a defined callback function on each element of an array, and returns an array that contains the results.
map((_: A_, i: numberi, as: readonly A[]as) => f: (as: ReadonlyArray<A>) => Bf(as: readonly A[]as.globalThis.ReadonlyArray<A>.slice(start?: number, end?: number): A[]Returns a section of an array.
slice(i: numberi)))
)