effect-io-ai

Package: effect
Module: Array

Array.span

Splits an iterable into two arrays: the longest prefix where the predicate holds, and the remaining elements.

When to use

Use when you need both the longest predicate-matching prefix and the remaining elements.

Details

Equivalent to [takeWhile(pred), dropWhile(pred)], but more efficient because it runs in a single pass. Supports refinements for type narrowing of the prefix.

Example (Splitting at predicate boundary)

import { Array } from "effect"

console.log(Array.span([1, 3, 2, 4, 5], (x) => x % 2 === 1)) // [[1, 3], [2, 4, 5]]

See

• takeWhile for keeping only the matching prefix
• dropWhile for keeping only the elements after the matching prefix
• splitWhere for splitting at the first element that satisfies a predicate

Signature

declare const span: { <A, B extends A>(refinement: (a: NoInfer<A>, i: number) => a is B): (self: Iterable<A>) => [init: Array<B>, rest: Array<Exclude<A, B>>]; <A>(predicate: (a: NoInfer<A>, i: number) => boolean): (self: Iterable<A>) => [init: Array<A>, rest: Array<A>]; <A, B extends A>(self: Iterable<A>, refinement: (a: A, i: number) => a is B): [init: Array<B>, rest: Array<Exclude<A, B>>]; <A>(self: Iterable<A>, predicate: (a: A, i: number) => boolean): [init: Array<A>, rest: Array<A>]; }

Source

Since v2.0.0