effect/src/Array.ts

The missing standard library for TypeScript, for writing production-grade software.

/**
 * This module provides utility functions for working with arrays in TypeScript.
 *
 * @since 2.0.0
 */

import * as Either from "./Either.js"
import * as Equal from "./Equal.js"
import * as Equivalence from "./Equivalence.js"
import type { LazyArg } from "./Function.js"
import { dual, identity } from "./Function.js"
import type { TypeLambda } from "./HKT.js"
import * as internalArray from "./internal/array.js"
import * as internalDoNotation from "./internal/doNotation.js"
import * as moduleIterable from "./Iterable.js"
import * as Option from "./Option.js"
import * as Order from "./Order.js"
import * as Predicate from "./Predicate.js"
import * as Record from "./Record.js"
import * as Tuple from "./Tuple.js"
import type { NoInfer, TupleOf } from "./Types.js"

/**
 * @category type lambdas
 * @since 2.0.0
 */
export interface ReadonlyArrayTypeLambda extends TypeLambda {
  readonly type: ReadonlyArray<this["Target"]>
}

/**
 * @category models
 * @since 2.0.0
 */
export type NonEmptyReadonlyArray<A> = readonly [A, ...Array<A>]

/**
 * @category models
 * @since 2.0.0
 */
export type NonEmptyArray<A> = [A, ...Array<A>]

/**
 * Builds a `NonEmptyArray` from an non-empty collection of elements.
 *
 * **Example**
 *
 * ```ts
 * import { Array } from "effect"
 *
 * const result = Array.make(1, 2, 3)
 * console.log(result) // [1, 2, 3]
 * ```
 *
 * @category constructors
 * @since 2.0.0
 */
export const make = <Elements extends NonEmptyArray<any>>(
  ...elements: Elements
): NonEmptyArray<Elements[number]> => elements

/**
 * Creates a new `Array` of the specified length.
 *
 * **Example**
 *
 * ```ts
 * import { Array } from "effect"
 *
 * const result = Array.allocate<number>(3)
 * console.log(result) // [ <3 empty items> ]
 * ```
 *
 * @category constructors
 * @since 2.0.0
 */
export const allocate = <A = never>(n: number): Array<A | undefined> => new Array(n)

/**
 * Return a `NonEmptyArray` of length `n` with element `i` initialized with `f(i)`.
 *
 * **Note**. `n` is normalized to an integer >= 1.
 *
 * **Example**
 *
 * ```ts
 * import { makeBy } from "effect/Array"
 *
 * const result = makeBy(5, n => n * 2)
 * console.log(result) // [0, 2, 4, 6, 8]
 * ```
 *
 * @category constructors
 * @since 2.0.0
 */
export const makeBy: {
  /**
   * Return a `NonEmptyArray` of length `n` with element `i` initialized with `f(i)`.
   *
   * **Note**. `n` is normalized to an integer >= 1.
   *
   * **Example**
   *
   * ```ts
   * import { makeBy } from "effect/Array"
   *
   * const result = makeBy(5, n => n * 2)
   * console.log(result) // [0, 2, 4, 6, 8]
   * ```
   *
   * @category constructors
   * @since 2.0.0
   */
  <A>(f: (i: number) => A): (n: number) => NonEmptyArray<A>
  /**
   * Return a `NonEmptyArray` of length `n` with element `i` initialized with `f(i)`.
   *
   * **Note**. `n` is normalized to an integer >= 1.
   *
   * **Example**
   *
   * ```ts
   * import { makeBy } from "effect/Array"
   *
   * const result = makeBy(5, n => n * 2)
   * console.log(result) // [0, 2, 4, 6, 8]
   * ```
   *
   * @category constructors
   * @since 2.0.0
   */
  <A>(n: number, f: (i: number) => A): NonEmptyArray<A>
} = dual(2, <A>(n: number, f: (i: number) => A) => {
  const max = Math.max(1, Math.floor(n))
  const out = new Array(max)
  for (let i = 0; i < max; i++) {
    out[i] = f(i)
  }
  return out as NonEmptyArray<A>
})

/**
 * Return a `NonEmptyArray` containing a range of integers, including both endpoints.
 *
 * **Example**
 *
 * ```ts
 * import { range } from "effect/Array"
 *
 * const result = range(1, 3)
 * console.log(result) // [1, 2, 3]
 * ```
 *
 * @category constructors
 * @since 2.0.0
 */
export const range = (start: number, end: number): NonEmptyArray<number> =>
  start <= end ? makeBy(end - start + 1, (i) => start + i) : [start]

/**
 * Return a `NonEmptyArray` containing a value repeated the specified number of times.
 *
 * **Note**. `n` is normalized to an integer >= 1.
 *
 * **Example**
 *
 * ```ts
 * import { Array } from "effect"
 *
 * const result = Array.replicate("a", 3)
 * console.log(result) // ["a", "a", "a"]
 * ```
 *
 * @category constructors
 * @since 2.0.0
 */
export const replicate: {
  /**
   * Return a `NonEmptyArray` containing a value repeated the specified number of times.
   *
   * **Note**. `n` is normalized to an integer >= 1.
   *
   * **Example**
   *
   * ```ts
   * import { Array } from "effect"
   *
   * const result = Array.replicate("a", 3)
   * console.log(result) // ["a", "a", "a"]
   * ```
   *
   * @category constructors
   * @since 2.0.0
   */
  (n: number): <A>(a: A) => NonEmptyArray<A>
  /**
   * Return a `NonEmptyArray` containing a value repeated the specified number of times.
   *
   * **Note**. `n` is normalized to an integer >= 1.
   *
   * **Example**
   *
   * ```ts
   * import { Array } from "effect"
   *
   * const result = Array.replicate("a", 3)
   * console.log(result) // ["a", "a", "a"]
   * ```
   *
   * @category constructors
   * @since 2.0.0
   */
  <A>(a: A, n: number): NonEmptyArray<A>
} = dual(2, <A>(a: A, n: number): NonEmptyArray<A> => makeBy(n, () => a))

/**
 * Creates a new `Array` from an iterable collection of values.
 * If the input is already an array, it returns the input as-is.
 * Otherwise, it converts the iterable collection to an array.
 *
 * **Example**
 *
 * ```ts
 * import { Array } from "effect"
 *
 * const result = Array.fromIterable(new Set([1, 2, 3]))
 * console.log(result) // [1, 2, 3]
 * ```
 *
 * @category constructors
 * @since 2.0.0
 */
export const fromIterable = <A>(collection: Iterable<A>): Array<A> =>
  Array.isArray(collection) ? collection : Array.from(collection)

/**
 * Creates a new `Array` from a value that might not be an iterable.
 *
 * **Example**
 *
 * ```ts
 * import { Array } from "effect"
 *
 * console.log(Array.ensure("a")) // ["a"]
 * console.log(Array.ensure(["a"])) // ["a"]
 * console.log(Array.ensure(["a", "b", "c"])) // ["a", "b", "c"]
 * ```
 *
 * @category constructors
 * @since 3.3.0
 */
export const ensure = <A>(self: ReadonlyArray<A> | A): Array<A> => Array.isArray(self) ? self : [self as A]

/**
 * Takes a record and returns an array of tuples containing its keys and values.
 *
 * **Example**
 *
 * ```ts
 * import { Array } from "effect"
 *
 * const result = Array.fromRecord({ a: 1, b: 2, c: 3 })
 * console.log(result) // [["a", 1], ["b", 2], ["c", 3]]
 * ```
 *
 * @category conversions
 * @since 2.0.0
 */
export const fromRecord: <K extends string, A>(self: Readonly<Record<K, A>>) => Array<[K, A]> = Record.toEntries

/**
 * Converts an `Option` to an array.
 *
 * **Example**
 *
 * ```ts
 * import { Array, Option } from "effect"
 *
 * console.log(Array.fromOption(Option.some(1))) // [1]
 * console.log(Array.fromOption(Option.none())) // []
 * ```
 *
 * @category conversions
 * @since 2.0.0
 */
export const fromOption: <A>(self: Option.Option<A>) => Array<A> = Option.toArray

/**
 * Matches the elements of an array, applying functions to cases of empty and non-empty arrays.
 *
 * **Example**
 *
 * ```ts
 * import { Array } from "effect"
 *
 * const match = Array.match({
 *   onEmpty: () => "empty",
 *   onNonEmpty: ([head, ...tail]) => `head: ${head}, tail: ${tail.length}`
 * })
 * console.log(match([])) // "empty"
 * console.log(match([1, 2, 3])) // "head: 1, tail: 2"
 * ```
 *
 * @category pattern matching
 * @since 2.0.0
 */
export const match: {
  /**
   * Matches the elements of an array, applying functions to cases of empty and non-empty arrays.
   *
   * **Example**
   *
   * ```ts
   * import { Array } from "effect"
   *
   * const match = Array.match({
   *   onEmpty: () => "empty",
   *   onNonEmpty: ([head, ...tail]) => `head: ${head}, tail: ${tail.length}`
   * })
   * console.log(match([])) // "empty"
   * console.log(match([1, 2, 3])) // "head: 1, tail: 2"
   * ```
   *
   * @category pattern matching
   * @since 2.0.0
   */
  <B, A, C = B>(
    options: {
      readonly onEmpty: LazyArg<B>
      readonly onNonEmpty: (self: NonEmptyReadonlyArray<A>) => C
    }
  ): (self: ReadonlyArray<A>) => B | C
  /**
   * Matches the elements of an array, applying functions to cases of empty and non-empty arrays.
   *
   * **Example**
   *
   * ```ts
   * import { Array } from "effect"
   *
   * const match = Array.match({
   *   onEmpty: () => "empty",
   *   onNonEmpty: ([head, ...tail]) => `head: ${head}, tail: ${tail.length}`
   * })
   * console.log(match([])) // "empty"
   * console.log(match([1, 2, 3])) // "head: 1, tail: 2"
   * ```
   *
   * @category pattern matching
   * @since 2.0.0
   */
  <A, B, C = B>(
    self: ReadonlyArray<A>,
    options: {
      readonly onEmpty: LazyArg<B>
      readonly onNonEmpty: (self: NonEmptyReadonlyArray<A>) => C
    }
  ): B | C
} = dual(2, <A, B, C = B>(
  self: ReadonlyArray<A>,
  { onEmpty, onNonEmpty }: {
    readonly onEmpty: LazyArg<B>
    readonly onNonEmpty: (self: NonEmptyReadonlyArray<A>) => C
  }
): B | C => isNonEmptyReadonlyArray(self) ? onNonEmpty(self) : onEmpty())

/**
 * Matches the elements of an array from the left, applying functions to cases of empty and non-empty arrays.
 *
 * **Example**
 *
 * ```ts
 * import { Array } from "effect"
 *
 * const matchLeft = Array.matchLeft({
 *   onEmpty: () => "empty",
 *   onNonEmpty: (head, tail) => `head: ${head}, tail: ${tail.length}`
 * })
 * console.log(matchLeft([])) // "empty"
 * console.log(matchLeft([1, 2, 3])) // "head: 1, tail: 2"
 * ```
 *
 * @category pattern matching
 * @since 2.0.0
 */
export const matchLeft: {
  /**
   * Matches the elements of an array from the left, applying functions to cases of empty and non-empty arrays.
   *
   * **Example**
   *
   * ```ts
   * import { Array } from "effect"
   *
   * const matchLeft = Array.matchLeft({
   *   onEmpty: () => "empty",
   *   onNonEmpty: (head, tail) => `head: ${head}, tail: ${tail.length}`
   * })
   * console.log(matchLeft([])) // "empty"
   * console.log(matchLeft([1, 2, 3])) // "head: 1, tail: 2"
   * ```
   *
   * @category pattern matching
   * @since 2.0.0
   */
  <B, A, C = B>(
    options: {
      readonly onEmpty: LazyArg<B>
      readonly onNonEmpty: (head: A, tail: Array<A>) => C
    }
  ): (self: ReadonlyArray<A>) => B | C
  /**
   * Matches the elements of an array from the left, applying functions to cases of empty and non-empty arrays.
   *
   * **Example**
   *
   * ```ts
   * import { Array } from "effect"
   *
   * const matchLeft = Array.matchLeft({
   *   onEmpty: () => "empty",
   *   onNonEmpty: (head, tail) => `head: ${head}, tail: ${tail.length}`
   * })
   * console.log(matchLeft([])) // "empty"
   * console.log(matchLeft([1, 2, 3])) // "head: 1, tail: 2"
   * ```
   *
   * @category pattern matching
   * @since 2.0.0
   */
  <A, B, C = B>(
    self: ReadonlyArray<A>,
    options: {
      readonly onEmpty: LazyArg<B>
      readonly onNonEmpty: (head: A, tail: Array<A>) => C
    }
  ): B | C
} = dual(2, <A, B, C = B>(
  self: ReadonlyArray<A>,
  { onEmpty, onNonEmpty }: {
    readonly onEmpty: LazyArg<B>
    readonly onNonEmpty: (head: A, tail: Array<A>) => C
  }
): B | C => isNonEmptyReadonlyArray(self) ? onNonEmpty(headNonEmpty(self), tailNonEmpty(self)) : onEmpty())

/**
 * Matches the elements of an array from the right, applying functions to cases of empty and non-empty arrays.
 *
 * **Example**
 *
 * ```ts
 * import { Array } from "effect"
 *
 * const matchRight = Array.matchRight({
 *   onEmpty: () => "empty",
 *   onNonEmpty: (init, last) => `init: ${init.length}, last: ${last}`
 * })
 * console.log(matchRight([])) // "empty"
 * console.log(matchRight([1, 2, 3])) // "init: 2, last: 3"
 * ```
 *
 * @category pattern matching
 * @since 2.0.0
 */
export const matchRight: {
  /**
   * Matches the elements of an array from the right, applying functions to cases of empty and non-empty arrays.
   *
   * **Example**
   *
   * ```ts
   * import { Array } from "effect"
   *
   * const matchRight = Array.matchRight({
   *   onEmpty: () => "empty",
   *   onNonEmpty: (init, last) => `init: ${init.length}, last: ${last}`
   * })
   * console.log(matchRight([])) // "empty"
   * console.log(matchRight([1, 2, 3])) // "init: 2, last: 3"
   * ```
   *
   * @category pattern matching
   * @since 2.0.0
   */
  <B, A, C = B>(
    options: {
      readonly onEmpty: LazyArg<B>
      readonly onNonEmpty: (init: Array<A>, last: A) => C
    }
  ): (self: ReadonlyArray<A>) => B | C
  /**
   * Matches the elements of an array from the right, applying functions to cases of empty and non-empty arrays.
   *
   * **Example**
   *
   * ```ts
   * import { Array } from "effect"
   *
   * const matchRight = Array.matchRight({
   *   onEmpty: () => "empty",
   *   onNonEmpty: (init, last) => `init: ${init.length}, last: ${last}`
   * })
   * console.log(matchRight([])) // "empty"
   * console.log(matchRight([1, 2, 3])) // "init: 2, last: 3"
   * ```
   *
   * @category pattern matching
   * @since 2.0.0
   */
  <A, B, C = B>(
    self: ReadonlyArray<A>,
    options: {
      readonly onEmpty: LazyArg<B>
      readonly onNonEmpty: (init: Array<A>, last: A) => C
    }
  ): B | C
} = dual(2, <A, B, C = B>(
  self: ReadonlyArray<A>,
  { onEmpty, onNonEmpty }: {
    readonly onEmpty: LazyArg<B>
    readonly onNonEmpty: (init: Array<A>, last: A) => C
  }
): B | C =>
  isNonEmptyReadonlyArray(self) ?
    onNonEmpty(initNonEmpty(self), lastNonEmpty(self)) :
    onEmpty())

/**
 * Prepend an element to the front of an `Iterable`, creating a new `NonEmptyArray`.
 *
 * **Example**
 *
 * ```ts
 * import { Array } from "effect"
 *
 * const result = Array.prepend([2, 3, 4], 1)
 * console.log(result) // [1, 2, 3, 4]
 * ```
 *
 * @category concatenating
 * @since 2.0.0
 */
export const prepend: {
  /**
   * Prepend an element to the front of an `Iterable`, creating a new `NonEmptyArray`.
   *
   * **Example**
   *
   * ```ts
   * import { Array } from "effect"
   *
   * const result = Array.prepend([2, 3, 4], 1)
   * console.log(result) // [1, 2, 3, 4]
   * ```
   *
   * @category concatenating
   * @since 2.0.0
   */
  <B>(head: B): <A>(self: Iterable<A>) => NonEmptyArray<A | B>
  /**
   * Prepend an element to the front of an `Iterable`, creating a new `NonEmptyArray`.
   *
   * **Example**
   *
   * ```ts
   * import { Array } from "effect"
   *
   * const result = Array.prepend([2, 3, 4], 1)
   * console.log(result) // [1, 2, 3, 4]
   * ```
   *
   * @category concatenating
   * @since 2.0.0
   */
  <A, B>(self: Iterable<A>, head: B): NonEmptyArray<A | B>
} = dual(2, <A, B>(self: Iterable<A>, head: B): NonEmptyArray<A | B> => [head, ...self])

/**
 * Prepends the specified prefix array (or iterable) to the beginning of the specified array (or iterable).
 * If either array is non-empty, the result is also a non-empty array.
 *
 * **Example**
 *
 * ```ts
 * import { Array } from "effect"
 *
 * const result = Array.prependAll([2, 3], [0, 1])
 * console.log(result) // [0, 1, 2, 3]
 * ```
 *
 * @category concatenating
 * @since 2.0.0
 */
export const prependAll: {
  /**
   * Prepends the specified prefix array (or iterable) to the beginning of the specified array (or iterable).
   * If either array is non-empty, the result is also a non-empty array.
   *
   * **Example**
   *
   * ```ts
   * import { Array } from "effect"
   *
   * const result = Array.prependAll([2, 3], [0, 1])
   * console.log(result) // [0, 1, 2, 3]
   * ```
   *
   * @category concatenating
   * @since 2.0.0
   */
  <S extends Iterable<any>, T extends Iterable<any>>(that: T): (self: S) => ReadonlyArray.OrNonEmpty<S, T, ReadonlyArray.Infer<S> | ReadonlyArray.Infer<T>>
  /**
   * Prepends the specified prefix array (or iterable) to the beginning of the specified array (or iterable).
   * If either array is non-empty, the result is also a non-empty array.
   *
   * **Example**
   *
   * ```ts
   * import { Array } from "effect"
   *
   * const result = Array.prependAll([2, 3], [0, 1])
   * console.log(result) // [0, 1, 2, 3]
   * ```
   *
   * @category concatenating
   * @since 2.0.0
   */
  <A, B>(self: Iterable<A>, that: NonEmptyReadonlyArray<B>): NonEmptyArray<A | B>
  /**
   * Prepends the specified prefix array (or iterable) to the beginning of the specified array (or iterable).
   * If either array is non-empty, the result is also a non-empty array.
   *
   * **Example**
   *
   * ```ts
   * import { Array } from "effect"
   *
   * const result = Array.prependAll([2, 3], [0, 1])
   * console.log(result) // [0, 1, 2, 3]
   * ```
   *
   * @category concatenating
   * @since 2.0.0
   */
  <A, B>(self: NonEmptyReadonlyArray<A>, that: Iterable<B>): NonEmptyArray<A | B>
  /**
   * Prepends the specified prefix array (or iterable) to the beginning of the specified array (or iterable).
   * If either array is non-empty, the result is also a non-empty array.
   *
   * **Example**
   *
   * ```ts
   * import { Array } from "effect"
   *
   * const result = Array.prependAll([2, 3], [0, 1])
   * console.log(result) // [0, 1, 2, 3]
   * ```
   *
   * @category concatenating
   * @since 2.0.0
   */
  <A, B>(self: Iterable<A>, that: Iterable<B>): Array<A | B>
} = dual(
  2,
  <A>(self: Iterable<A>, that: Iterable<A>): Array<A> => fromIterable(that).concat(fromIterable(self))
)

/**
 * Append an element to the end of an `Iterable`, creating a new `NonEmptyArray`.
 *
 * **Example**
 *
 * ```ts
 * import { Array } from "effect"
 *
 * const result = Array.append([1, 2, 3], 4);
 * console.log(result) // [1, 2, 3, 4]
 * ```
 *
 * @category concatenating
 * @since 2.0.0
 */
export const append: {
  /**
   * Append an element to the end of an `Iterable`, creating a new `NonEmptyArray`.
   *
   * **Example**
   *
   * ```ts
   * import { Array } from "effect"
   *
   * const result = Array.append([1, 2, 3], 4);
   * console.log(result) // [1, 2, 3, 4]
   * ```
   *
   * @category concatenating
   * @since 2.0.0
   */
  <B>(last: B): <A>(self: Iterable<A>) => NonEmptyArray<A | B>
  /**
   * Append an element to the end of an `Iterable`, creating a new `NonEmptyArray`.
   *
   * **Example**
   *
   * ```ts
   * import { Array } from "effect"
   *
   * const result = Array.append([1, 2, 3], 4);
   * console.log(result) // [1, 2, 3, 4]
   * ```
   *
   * @category concatenating
   * @since 2.0.0
   */
  <A, B>(self: Iterable<A>, last: B): NonEmptyArray<A | B>
} = dual(2, <A, B>(self: Iterable<A>, last: B): Array<A | B> => [...self, last])

/**
 * Concatenates two arrays (or iterables), combining their elements.
 * If either array is non-empty, the result is also a non-empty array.
 *
 * @category concatenating
 * @since 2.0.0
 */
export const appendAll: {
  /**
   * Concatenates two arrays (or iterables), combining their elements.
   * If either array is non-empty, the result is also a non-empty array.
   *
   * @category concatenating
   * @since 2.0.0
   */
  <S extends Iterable<any>, T extends Iterable<any>>(that: T): (self: S) => ReadonlyArray.OrNonEmpty<S, T, ReadonlyArray.Infer<S> | ReadonlyArray.Infer<T>>
  /**
   * Concatenates two arrays (or iterables), combining their elements.
   * If either array is non-empty, the result is also a non-empty array.
   *
   * @category concatenating
   * @since 2.0.0
   */
  <A, B>(self: Iterable<A>, that: NonEmptyReadonlyArray<B>): NonEmptyArray<A | B>
  /**
   * Concatenates two arrays (or iterables), combining their elements.
   * If either array is non-empty, the result is also a non-empty array.
   *
   * @category concatenating
   * @since 2.0.0
   */
  <A, B>(self: NonEmptyReadonlyArray<A>, that: Iterable<B>): NonEmptyArray<A | B>
  /**
   * Concatenates two arrays (or iterables), combining their elements.
   * If either array is non-empty, the result is also a non-empty array.
   *
   * @category concatenating
   * @since 2.0.0
   */
  <A, B>(self: Iterable<A>, that: Iterable<B>): Array<A | B>
} = dual(
  2,
  <A>(self: Iterable<A>, that: Iterable<A>): Array<A> => fromIterable(self).concat(fromIterable(that))
)

/**
 * Accumulates values from an `Iterable` starting from the left, storing
 * each intermediate result in an array. Useful for tracking the progression of
 * a value through a series of transformations.
 *
 * **Example**
 *
 * ```ts
 * import { Array } from "effect";
 *
 * const result = Array.scan([1, 2, 3, 4], 0, (acc, value) => acc + value)
 * console.log(result) // [0, 1, 3, 6, 10]
 *
 * // Explanation:
 * // This function starts with the initial value (0 in this case)
 * // and adds each element of the array to this accumulator one by one,
 * // keeping track of the cumulative sum after each addition.
 * // Each of these sums is captured in the resulting array.
 * ```
 *
 * @category folding
 * @since 2.0.0
 */
export const scan: {
  /**
   * Accumulates values from an `Iterable` starting from the left, storing
   * each intermediate result in an array. Useful for tracking the progression of
   * a value through a series of transformations.
   *
   * **Example**
   *
   * ```ts
   * import { Array } from "effect";
   *
   * const result = Array.scan([1, 2, 3, 4], 0, (acc, value) => acc + value)
   * console.log(result) // [0, 1, 3, 6, 10]
   *
   * // Explanation:
   * // This function starts with the initial value (0 in this case)
   * // and adds each element of the array to this accumulator one by one,
   * // keeping track of the cumulative sum after each addition.
   * // Each of these sums is captured in the resulting array.
   * ```
   *
   * @category folding
   * @since 2.0.0
   */
  <B, A>(b: B, f: (b: B, a: A) => B): (self: Iterable<A>) => NonEmptyArray<B>
  /**
   * Accumulates values from an `Iterable` starting from the left, storing
   * each intermediate result in an array. Useful for tracking the progression of
   * a value through a series of transformations.
   *
   * **Example**
   *
   * ```ts
   * import { Array } from "effect";
   *
   * const result = Array.scan([1, 2, 3, 4], 0, (acc, value) => acc + value)
   * console.log(result) // [0, 1, 3, 6, 10]
   *
   * // Explanation:
   * // This function starts with the initial value (0 in this case)
   * // and adds each element of the array to this accumulator one by one,
   * // keeping track of the cumulative sum after each addition.
   * // Each of these sums is captured in the resulting array.
   * ```
   *
   * @category folding
   * @since 2.0.0
   */
  <A, B>(self: Iterable<A>, b: B, f: (b: B, a: A) => B): NonEmptyArray<B>
} = dual(3, <A, B>(self: Iterable<A>, b: B, f: (b: B, a: A) => B): NonEmptyArray<B> => {
  const out: NonEmptyArray<B> = [b]
  let i = 0
  for (const a of self) {
    out[i + 1] = f(out[i], a)
    i++
  }
  return out
})

/**
 * Accumulates values from an `Iterable` starting from the right, storing
 * each intermediate result in an array. Useful for tracking the progression of
 * a value through a series of transformations.
 *
 * **Example**
 *
 * ```ts
 * import { Array } from "effect";
 *
 * const result = Array.scanRight([1, 2, 3, 4], 0, (acc, value) => acc + value)
 * console.log(result) // [10, 9, 7, 4, 0]
 * ```
 *
 * @category folding
 * @since 2.0.0
 */
export const scanRight: {
  /**
   * Accumulates values from an `Iterable` starting from the right, storing
   * each intermediate result in an array. Useful for tracking the progression of
   * a value through a series of transformations.
   *
   * **Example**
   *
   * ```ts
   * import { Array } from "effect";
   *
   * const result = Array.scanRight([1, 2, 3, 4], 0, (acc, value) => acc + value)
   * console.log(result) // [10, 9, 7, 4, 0]
   * ```
   *
   * @category folding
   * @since 2.0.0
   */
  <B, A>(b: B, f: (b: B, a: A) => B): (self: Iterable<A>) => NonEmptyArray<B>
  /**
   * Accumulates values from an `Iterable` starting from the right, storing
   * each intermediate result in an array. Useful for tracking the progression of
   * a value through a series of transformations.
   *
   * **Example**
   *
   * ```ts
   * import { Array } from "effect";
   *
   * const result = Array.scanRight([1, 2, 3, 4], 0, (acc, value) => acc + value)
   * console.log(result) // [10, 9, 7, 4, 0]
   * ```
   *
   * @category folding
   * @since 2.0.0
   */
  <A, B>(self: Iterable<A>, b: B, f: (b: B, a: A) => B): NonEmptyArray<B>
} = dual(3, <A, B>(self: Iterable<A>, b: B, f: (b: B, a: A) => B): NonEmptyArray<B> => {
  const input = fromIterable(self)
  const out: NonEmptyArray<B> = new Array(input.length + 1) as any
  out[input.length] = b
  for (let i = input.length - 1; i >= 0; i--) {
    out[i] = f(out[i + 1], input[i])
  }
  return out
})

/**
 * Determine if `unknown` is an Array.
 *
 * **Example**
 *
 * ```ts
 * import { Array } from "effect"
 *
 * console.log(Array.isArray(null)) // false
 * console.log(Array.isArray([1, 2, 3])) // true
 * ```
 *
 * @category guards
 * @since 2.0.0
 */
export const isArray: {
  /**
   * Determine if `unknown` is an Array.
   *
   * **Example**
   *
   * ```ts
   * import { Array } from "effect"
   *
   * console.log(Array.isArray(null)) // false
   * console.log(Array.isArray([1, 2, 3])) // true
   * ```
   *
   * @category guards
   * @since 2.0.0
   */
  (self: unknown): self is Array<unknown>
  /**
   * Determine if `unknown` is an Array.
   *
   * **Example**
   *
   * ```ts
   * import { Array } from "effect"
   *
   * console.log(Array.isArray(null)) // false
   * console.log(Array.isArray([1, 2, 3])) // true
   * ```
   *
   * @category guards
   * @since 2.0.0
   */
  <T>(self: T): self is Extract<T, ReadonlyArray<any>>
} = Array.isArray

/**
 * Determine if an `Array` is empty narrowing down the type to `[]`.
 *
 * **Example**
 *
 * ```ts
 * import { Array } from "effect"
 *
 * console.log(Array.isEmptyArray([])) // true
 * console.log(Array.isEmptyArray([1, 2, 3])) // false
 * ```
 *
 * @category guards
 * @since 2.0.0
 */
export const isEmptyArray = <A>(self: Array<A>): self is [] => self.length === 0

/**
 * Determine if a `ReadonlyArray` is empty narrowing down the type to `readonly []`.
 *
 * **Example**
 *
 * ```ts
 * import { Array } from "effect"
 *
 * console.log(Array.isEmptyReadonlyArray([])) // true
 * console.log(Array.isEmptyReadonlyArray([1, 2, 3])) // false
 * ```
 *
 * @category guards
 * @since 2.0.0
 */
export const isEmptyReadonlyArray: <A>(self: ReadonlyArray<A>) => self is readonly [] = isEmptyArray as any

/**
 * Determine if an `Array` is non empty narrowing down the type to `NonEmptyArray`.
 *
 * An `Array` is considered to be a `NonEmptyArray` if it contains at least one element.
 *
 * **Example**
 *
 * ```ts
 * import { Array } from "effect"
 *
 * console.log(Array.isNonEmptyArray([])) // false
 * console.log(Array.isNonEmptyArray([1, 2, 3])) // true
 * ```
 *
 * @category guards
 * @since 2.0.0
 */
export const isNonEmptyArray: <A>(self: Array<A>) => self is NonEmptyArray<A> = internalArray.isNonEmptyArray

/**
 * Determine if a `ReadonlyArray` is non empty narrowing down the type to `NonEmptyReadonlyArray`.
 *
 * A `ReadonlyArray` is considered to be a `NonEmptyReadonlyArray` if it contains at least one element.
 *
 * **Example**
 *
 * ```ts
 * import { Array } from "effect"
 *
 * console.log(Array.isNonEmptyReadonlyArray([])) // false
 * console.log(Array.isNonEmptyReadonlyArray([1, 2, 3])) // true
 * ```
 *
 * @category guards
 * @since 2.0.0
 */
export const isNonEmptyReadonlyArray: <A>(self: ReadonlyArray<A>) => self is NonEmptyReadonlyArray<A> =
  internalArray.isNonEmptyArray

/**
 * Return the number of elements in a `ReadonlyArray`.
 *
 * @category getters
 * @since 2.0.0
 */
export const length = <A>(self: ReadonlyArray<A>): number => self.length

const isOutOfBounds = <A>(i: number, as: ReadonlyArray<A>): boolean => i < 0 || i >= as.length

const clamp = <A>(i: number, as: ReadonlyArray<A>): number => Math.floor(Math.min(Math.max(0, i), as.length))

/**
 * This function provides a safe way to read a value at a particular index from a `ReadonlyArray`.
 *
 * @category getters
 * @since 2.0.0
 */
export const get: {
  /**
   * This function provides a safe way to read a value at a particular index from a `ReadonlyArray`.
   *
   * @category getters
   * @since 2.0.0
   */
  (index: number): <A>(self: ReadonlyArray<A>) => Option.Option<A>
  /**
   * This function provides a safe way to read a value at a particular index from a `ReadonlyArray`.
   *
   * @category getters
   * @since 2.0.0
   */
  <A>(self: ReadonlyArray<A>, index: number): Option.Option<A>
} = dual(2, <A>(self: ReadonlyArray<A>, index: number): Option.Option<A> => {
  const i = Math.floor(index)
  return isOutOfBounds(i, self) ? Option.none() : Option.some(self[i])
})

/**
 * Gets an element unsafely, will throw on out of bounds.
 *
 * @since 2.0.0
 * @category unsafe
 */
export const unsafeGet: {
  /**
   * Gets an element unsafely, will throw on out of bounds.
   *
   * @since 2.0.0
   * @category unsafe
   */
  (index: number): <A>(self: ReadonlyArray<A>) => A
  /**
   * Gets an element unsafely, will throw on out of bounds.
   *
   * @since 2.0.0
   * @category unsafe
   */
  <A>(self: ReadonlyArray<A>, index: number): A
} = dual(2, <A>(self: ReadonlyArray<A>, index: number): A => {
  const i = Math.floor(index)
  if (isOutOfBounds(i, self)) {
    throw new Error(`Index ${i} out of bounds`)
  }
  return self[i]
})

/**
 * Return a tuple containing the first element, and a new `Array` of the remaining elements, if any.
 *
 * **Example**
 *
 * ```ts
 * import { Array } from "effect";
 *
 * const result = Array.unprepend([1, 2, 3, 4])
 * console.log(result) // [1, [2, 3, 4]]
 * ```
 *
 * @category splitting
 * @since 2.0.0
 */
export const unprepend = <A>(
  self: NonEmptyReadonlyArray<A>
): [firstElement: A, remainingElements: Array<A>] => [headNonEmpty(self), tailNonEmpty(self)]

/**
 * Return a tuple containing a copy of the `NonEmptyReadonlyArray` without its last element, and that last element.
 *
 * **Example**
 *
 * ```ts
 * import { Array } from "effect";
 *
 * const result = Array.unappend([1, 2, 3, 4])
 * console.log(result) // [[1, 2, 3], 4]
 * ```
 *
 * @category splitting
 * @since 2.0.0
 */
export const unappend = <A>(
  self: NonEmptyReadonlyArray<A>
): [arrayWithoutLastElement: Array<A>, lastElement: A] => [initNonEmpty(self), lastNonEmpty(self)]

/**
 * Get the first element of a `ReadonlyArray`, or `None` if the `ReadonlyArray` is empty.
 *
 * @category getters
 * @since 2.0.0
 */
export const head: <A>(self: ReadonlyArray<A>) => Option.Option<A> = get(0)

/**
 * Get the first element of a non empty array.
 *
 * **Example**
 *
 * ```ts
 * import { Array } from "effect"
 *
 * const result = Array.headNonEmpty([1, 2, 3, 4])
 * console.log(result) // 1
 * ```
 *
 * @category getters
 * @since 2.0.0
 */
export const headNonEmpty: <A>(self: NonEmptyReadonlyArray<A>) => A = unsafeGet(0)

/**
 * Get the last element in a `ReadonlyArray`, or `None` if the `ReadonlyArray` is empty.
 *
 * @category getters
 * @since 2.0.0
 */
export const last = <A>(self: ReadonlyArray<A>): Option.Option<A> =>
  isNonEmptyReadonlyArray(self) ? Option.some(lastNonEmpty(self)) : Option.none()

/**
 * Get the last element of a non empty array.
 *
 * **Example**
 *
 * ```ts
 * import { Array } from "effect"
 *
 * const result = Array.lastNonEmpty([1, 2, 3, 4])
 * console.log(result) // 4
 * ```
 *
 * @category getters
 * @since 2.0.0
 */
export const lastNonEmpty = <A>(self: NonEmptyReadonlyArray<A>): A => self[self.length - 1]

/**
 * Get all but the first element of an `Iterable`, creating a new `Array`, or `None` if the `Iterable` is empty.
 *
 * @category getters
 * @since 2.0.0
 */
export const tail = <A>(self: Iterable<A>): Option.Option<Array<A>> => {
  const input = fromIterable(self)
  return isNonEmptyReadonlyArray(input) ? Option.some(tailNonEmpty(input)) : Option.none()
}

/**
 * Get all but the first element of a `NonEmptyReadonlyArray`.
 *
 * **Example**
 *
 * ```ts
 * import { Array } from "effect"
 *
 * const result = Array.tailNonEmpty([1, 2, 3, 4])
 * console.log(result) // [2, 3, 4]
 * ```
 *
 * @category getters
 * @since 2.0.0
 */
export const tailNonEmpty = <A>(self: NonEmptyReadonlyArray<A>): Array<A> => self.slice(1)

/**
 * Get all but the last element of an `Iterable`, creating a new `Array`, or `None` if the `Iterable` is empty.
 *
 * @category getters
 * @since 2.0.0
 */
export const init = <A>(self: Iterable<A>): Option.Option<Array<A>> => {
  const input = fromIterable(self)
  return isNonEmptyReadonlyArray(input) ? Option.some(initNonEmpty(input)) : Option.none()
}

/**
 * Get all but the last element of a non empty array, creating a new array.
 *
 * **Example**
 *
 * ```ts
 * import { Array } from "effect"
 *
 * const result = Array.initNonEmpty([1, 2, 3, 4])
 * console.log(result) // [1, 2, 3]
 * ```
 *
 * @category getters
 * @since 2.0.0
 */
export const initNonEmpty = <A>(self: NonEmptyReadonlyArray<A>): Array<A> => self.slice(0, -1)

/**
 * Keep only a max number of elements from the start of an `Iterable`, creating a new `Array`.
 *
 * **Note**. `n` is normalized to a non negative integer.
 *
 * **Example**
 *
 * ```ts
 * import { Array } from "effect"
 *
 * const result = Array.take([1, 2, 3, 4, 5], 3)
 * console.log(result) // [1, 2, 3]
 * ```
 *
 * @category getters
 * @since 2.0.0
 */
export const take: {
  /**
   * Keep only a max number of elements from the start of an `Iterable`, creating a new `Array`.
   *
   * **Note**. `n` is normalized to a non negative integer.
   *
   * **Example**
   *
   * ```ts
   * import { Array } from "effect"
   *
   * const result = Array.take([1, 2, 3, 4, 5], 3)
   * console.log(result) // [1, 2, 3]
   * ```
   *
   * @category getters
   * @since 2.0.0
   */
  (n: number): <A>(self: Iterable<A>) => Array<A>
  /**
   * Keep only a max number of elements from the start of an `Iterable`, creating a new `Array`.
   *
   * **Note**. `n` is normalized to a non negative integer.
   *
   * **Example**
   *
   * ```ts
   * import { Array } from "effect"
   *
   * const result = Array.take([1, 2, 3, 4, 5], 3)
   * console.log(result) // [1, 2, 3]
   * ```
   *
   * @category getters
   * @since 2.0.0
   */
  <A>(self: Iterable<A>, n: number): Array<A>
} = dual(2, <A>(self: Iterable<A>, n: number): Array<A> => {
  const input = fromIterable(self)
  return input.slice(0, clamp(n, input))
})

/**
 * Keep only a max number of elements from the end of an `Iterable`, creating a new `Array`.
 *
 * **Note**. `n` is normalized to a non negative integer.
 *
 * **Example**
 *
 * ```ts
 * import { Array } from "effect"
 *
 * const result = Array.takeRight([1, 2, 3, 4, 5], 3)
 * console.log(result) // [3, 4, 5]
 * ```
 *
 * @category getters
 * @since 2.0.0
 */
export const takeRight: {
  /**
   * Keep only a max number of elements from the end of an `Iterable`, creating a new `Array`.
   *
   * **Note**. `n` is normalized to a non negative integer.
   *
   * **Example**
   *
   * ```ts
   * import { Array } from "effect"
   *
   * const result = Array.takeRight([1, 2, 3, 4, 5], 3)
   * console.log(result) // [3, 4, 5]
   * ```
   *
   * @category getters
   * @since 2.0.0
   */
  (n: number): <A>(self: Iterable<A>) => Array<A>
  /**
   * Keep only a max number of elements from the end of an `Iterable`, creating a new `Array`.
   *
   * **Note**. `n` is normalized to a non negative integer.
   *
   * **Example**
   *
   * ```ts
   * import { Array } from "effect"
   *
   * const result = Array.takeRight([1, 2, 3, 4, 5], 3)
   * console.log(result) // [3, 4, 5]
   * ```
   *
   * @category getters
   * @since 2.0.0
   */
  <A>(self: Iterable<A>, n: number): Array<A>
} = dual(2, <A>(self: Iterable<A>, n: number): Array<A> => {
  const input = fromIterable(self)
  const i = clamp(n, input)
  return i === 0 ? [] : input.slice(-i)
})

/**
 * Calculate the longest initial subarray for which all element satisfy the specified predicate, creating a new `Array`.
 *
 * **Example**
 *
 * ```ts
 * import { Array } from "effect"
 *
 * const result = Array.takeWhile([1, 3, 2, 4, 1, 2], x => x < 4)
 * console.log(result) // [1, 3, 2]
 *
 * // Explanation:
 * // - The function starts with the first element (`1`), which is less than `4`, so it adds `1` to the result.
 * // - The next element (`3`) is also less than `4`, so it adds `3`.
 * // - The next element (`2`) is again less than `4`, so it adds `2`.
 * // - The function then encounters `4`, which is not less than `4`. At this point, it stops checking further elements and finalizes the result.
 * ```
 *
 * @category getters
 * @since 2.0.0
 */
export const takeWhile: {
  /**
   * Calculate the longest initial subarray for which all element satisfy the specified predicate, creating a new `Array`.
   *
   * **Example**
   *
   * ```ts
   * import { Array } from "effect"
   *
   * const result = Array.takeWhile([1, 3, 2, 4, 1, 2], x => x < 4)
   * console.log(result) // [1, 3, 2]
   *
   * // Explanation:
   * // - The function starts with the first element (`1`), which is less than `4`, so it adds `1` to the result.
   * // - The next element (`3`) is also less than `4`, so it adds `3`.
   * // - The next element (`2`) is again less than `4`, so it adds `2`.
   * // - The function then encounters `4`, which is not less than `4`. At this point, it stops checking further elements and finalizes the result.
   * ```
   *
   * @category getters
   * @since 2.0.0
   */
  <A, B extends A>(refinement: (a: NoInfer<A>, i: number) => a is B): (self: Iterable<A>) => Array<B>
  /**
   * Calculate the longest initial subarray for which all element satisfy the specified predicate, creating a new `Array`.
   *
   * **Example**
   *
   * ```ts
   * import { Array } from "effect"
   *
   * const result = Array.takeWhile([1, 3, 2, 4, 1, 2], x => x < 4)
   * console.log(result) // [1, 3, 2]
   *
   * // Explanation:
   * // - The function starts with the first element (`1`), which is less than `4`, so it adds `1` to the result.
   * // - The next element (`3`) is also less than `4`, so it adds `3`.
   * // - The next element (`2`) is again less than `4`, so it adds `2`.
   * // - The function then encounters `4`, which is not less than `4`. At this point, it stops checking further elements and finalizes the result.
   * ```
   *
   * @category getters
   * @since 2.0.0
   */
  <A>(predicate: (a: NoInfer<A>, i: number) => boolean): (self: Iterable<A>) => Array<A>
  /**
   * Calculate the longest initial subarray for which all element satisfy the specified predicate, creating a new `Array`.
   *
   * **Example**
   *
   * ```ts
   * import { Array } from "effect"
   *
   * const result = Array.takeWhile([1, 3, 2, 4, 1, 2], x => x < 4)
   * console.log(result) // [1, 3, 2]
   *
   * // Explanation:
   * // - The function starts with the first element (`1`), which is less than `4`, so it adds `1` to the result.
   * // - The next element (`3`) is also less than `4`, so it adds `3`.
   * // - The next element (`2`) is again less than `4`, so it adds `2`.
   * // - The function then encounters `4`, which is not less than `4`. At this point, it stops checking further elements and finalizes the result.
   * ```
   *
   * @category getters
   * @since 2.0.0
   */
  <A, B extends A>(self: Iterable<A>, refinement: (a: A, i: number) => a is B): Array<B>
  /**
   * Calculate the longest initial subarray for which all element satisfy the specified predicate, creating a new `Array`.
   *
   * **Example**
   *
   * ```ts
   * import { Array } from "effect"
   *
   * const result = Array.takeWhile([1, 3, 2, 4, 1, 2], x => x < 4)
   * console.log(result) // [1, 3, 2]
   *
   * // Explanation:
   * // - The function starts with the first element (`1`), which is less than `4`, so it adds `1` to the result.
   * // - The next element (`3`) is also less than `4`, so it adds `3`.
   * // - The next element (`2`) is again less than `4`, so it adds `2`.
   * // - The function then encounters `4`, which is not less than `4`. At this point, it stops checking further elements and finalizes the result.
   * ```
   *
   * @category getters
   * @since 2.0.0
   */
  <A>(self: Iterable<A>, predicate: (a: A, i: number) => boolean): Array<A>
} = dual(2, <A>(self: Iterable<A>, predicate: (a: A, i: number) => boolean): Array<A> => {
  let i = 0
  const out: Array<A> = []
  for (const a of self) {
    if (!predicate(a, i)) {
      break
    }
    out.push(a)
    i++
  }
  return out
})

const spanIndex = <A>(self: Iterable<A>, predicate: (a: A, i: number) => boolean): number => {
  let i = 0
  for (const a of self) {
    if (!predicate(a, i)) {
      break
    }
    i++
  }
  return i
}

/**
 * Split an `Iterable` into two parts:
 *
 * 1. the longest initial subarray for which all elements satisfy the specified predicate
 * 2. the remaining elements
 *
 * @category splitting
 * @since 2.0.0
 */
export const span: {
  /**
   * Split an `Iterable` into two parts:
   *
   * 1. the longest initial subarray for which all elements satisfy the specified predicate
   * 2. the remaining elements
   *
   * @category splitting
   * @since 2.0.0
   */
  <A, B extends A>(refinement: (a: NoInfer<A>, i: number) => a is B): (self: Iterable<A>) => [init: Array<B>, rest: Array<Exclude<A, B>>]
  /**
   * Split an `Iterable` into two parts:
   *
   * 1. the longest initial subarray for which all elements satisfy the specified predicate
   * 2. the remaining elements
   *
   * @category splitting
   * @since 2.0.0
   */
  <A>(predicate: (a: NoInfer<A>, i: number) => boolean): (self: Iterable<A>) => [init: Array<A>, rest: Array<A>]
  /**
   * Split an `Iterable` into two parts:
   *
   * 1. the longest initial subarray for which all elements satisfy the specified predicate
   * 2. the remaining elements
   *
   * @category splitting
   * @since 2.0.0
   */
  <A, B extends A>(self: Iterable<A>, refinement: (a: A, i: number) => a is B): [init: Array<B>, rest: Array<Exclude<A, B>>]
  /**
   * Split an `Iterable` into two parts:
   *
   * 1. the longest initial subarray for which all elements satisfy the specified predicate
   * 2. the remaining elements
   *
   * @category splitting
   * @since 2.0.0
   */
  <A>(self: Iterable<A>, predicate: (a: A, i: number) => boolean): [init: Array<A>, rest: Array<A>]
} = dual(
  2,
  <A>(self: Iterable<A>, predicate: (a: A, i: number) => boolean): [init: Array<A>, rest: Array<A>] =>
    splitAt(self, spanIndex(self, predicate))
)

/**
 * Drop a max number of elements from the start of an `Iterable`, creating a new `Array`.
 *
 * **Note**. `n` is normalized to a non negative integer.
 *
 * **Example**
 *
 * ```ts
 * import { Array } from "effect"
 *
 * const result = Array.drop([1, 2, 3, 4, 5], 2)
 * console.log(result) // [3, 4, 5]
 * ```
 *
 * @category getters
 * @since 2.0.0
 */
export const drop: {
  /**
   * Drop a max number of elements from the start of an `Iterable`, creating a new `Array`.
   *
   * **Note**. `n` is normalized to a non negative integer.
   *
   * **Example**
   *
   * ```ts
   * import { Array } from "effect"
   *
   * const result = Array.drop([1, 2, 3, 4, 5], 2)
   * console.log(result) // [3, 4, 5]
   * ```
   *
   * @category getters
   * @since 2.0.0
   */
  (n: number): <A>(self: Iterable<A>) => Array<A>
  /**
   * Drop a max number of elements from the start of an `Iterable`, creating a new `Array`.
   *
   * **Note**. `n` is normalized to a non negative integer.
   *
   * **Example**
   *
   * ```ts
   * import { Array } from "effect"
   *
   * const result = Array.drop([1, 2, 3, 4, 5], 2)
   * console.log(result) // [3, 4, 5]
   * ```
   *
   * @category getters
   * @since 2.0.0
   */
  <A>(self: Iterable<A>, n: number): Array<A>
} = dual(2, <A>(self: Iterable<A>, n: number): Array<A> => {
  const input = fromIterable(self)
  return input.slice(clamp(n, input), input.length)
})

/**
 * Drop a max number of elements from the end of an `Iterable`, creating a new `Array`.
 *
 * **Note**. `n` is normalized to a non negative integer.
 *
 * **Example**
 *
 * ```ts
 * import { Array } from "effect"
 *
 * const result = Array.dropRight([1, 2, 3, 4, 5], 2)
 * console.log(result) // [1, 2, 3]
 * ```
 *
 * @category getters
 * @since 2.0.0
 */
export const dropRight: {
  /**
   * Drop a max number of elements from the end of an `Iterable`, creating a new `Array`.
   *
   * **Note**. `n` is normalized to a non negative integer.
   *
   * **Example**
   *
   * ```ts
   * import { Array } from "effect"
   *
   * const result = Array.dropRight([1, 2, 3, 4, 5], 2)
   * console.log(result) // [1, 2, 3]
   * ```
   *
   * @category getters
   * @since 2.0.0
   */
  (n: number): <A>(self: Iterable<A>) => Array<A>
  /**
   * Drop a max number of elements from the end of an `Iterable`, creating a new `Array`.
   *
   * **Note**. `n` is normalized to a non negative integer.
   *
   * **Example**
   *
   * ```ts
   * import { Array } from "effect"
   *
   * const result = Array.dropRight([1, 2, 3, 4, 5], 2)
   * console.log(result) // [1, 2, 3]
   * ```
   *
   * @category getters
   * @since 2.0.0
   */
  <A>(self: Iterable<A>, n: number): Array<A>
} = dual(2, <A>(self: Iterable<A>, n: number): Array<A> => {
  const input = fromIterable(self)
  return input.slice(0, input.length - clamp(n, input))
})

/**
 * Remove the longest initial subarray for which all element satisfy the specified predicate, creating a new `Array`.
 *
 * **Example**
 *
 * ```ts
 * import { Array } from "effect"
 *
 * const result = Array.dropWhile([1, 2, 3, 4, 5], x => x < 4)
 * console.log(result) // [4, 5]
 * ```
 *
 * @category getters
 * @since 2.0.0
 */
export const dropWhile: {
  /**
   * Remove the longest initial subarray for which all element satisfy the specified predicate, creating a new `Array`.
   *
   * **Example**
   *
   * ```ts
   * import { Array } from "effect"
   *
   * const result = Array.dropWhile([1, 2, 3, 4, 5], x => x < 4)
   * console.log(result) // [4, 5]
   * ```
   *
   * @category getters
   * @since 2.0.0
   */
  <A>(predicate: (a: NoInfer<A>, i: number) => boolean): (self: Iterable<A>) => Array<A>
  /**
   * Remove the longest initial subarray for which all element satisfy the specified predicate, creating a new `Array`.
   *
   * **Example**
   *
   * ```ts
   * import { Array } from "effect"
   *
   * const result = Array.dropWhile([1, 2, 3, 4, 5], x => x < 4)
   * console.log(result) // [4, 5]
   * ```
   *
   * @category getters
   * @since 2.0.0
   */
  <A>(self: Iterable<A>, predicate: (a: A, i: number) => boolean): Array<A>
} = dual(
  2,
  <A>(self: Iterable<A>, predicate: (a: A, i: number) => boolean): Array<A> =>
    fromIterable(self).slice(spanIndex(self, predicate))
)

/**
 * Return the first index for which a predicate holds.
 *
 * **Example**
 *
 * ```ts
 * import { Array } from "effect"
 *
 * const result = Array.findFirstIndex([5, 3, 8, 9], x => x > 5)
 * console.log(result) // Option.some(2)
 * ```
 *
 * @category elements
 * @since 2.0.0
 */
export const findFirstIndex: {
  /**
   * Return the first index for which a predicate holds.
   *
   * **Example**
   *
   * ```ts
   * import { Array } from "effect"
   *
   * const result = Array.findFirstIndex([5, 3, 8, 9], x => x > 5)
   * console.log(result) // Option.some(2)
   * ```
   *
   * @category elements
   * @since 2.0.0
   */
  <A>(predicate: (a: NoInfer<A>, i: number) => boolean): (self: Iterable<A>) => Option.Option<number>
  /**
   * Return the first index for which a predicate holds.
   *
   * **Example**
   *
   * ```ts
   * import { Array } from "effect"
   *
   * const result = Array.findFirstIndex([5, 3, 8, 9], x => x > 5)
   * console.log(result) // Option.some(2)
   * ```
   *
   * @category elements
   * @since 2.0.0
   */
  <A>(self: Iterable<A>, predicate: (a: A, i: number) => boolean): Option.Option<number>
} = dual(2, <A>(self: Iterable<A>, predicate: (a: A, i: number) => boolean): Option.Option<number> => {
  let i = 0
  for (const a of self) {
    if (predicate(a, i)) {
      return Option.some(i)
    }
    i++
  }
  return Option.none()
})

/**
 * Return the last index for which a predicate holds.
 *
 * **Example**
 *
 * ```ts
 * import { Array } from "effect"
 *
 * const result = Array.findLastIndex([1, 3, 8, 9], x => x < 5)
 * console.log(result) // Option.some(1)
 * ```
 *
 * @category elements
 * @since 2.0.0
 */
export const findLastIndex: {
  /**
   * Return the last index for which a predicate holds.
   *
   * **Example**
   *
   * ```ts
   * import { Array } from "effect"
   *
   * const result = Array.findLastIndex([1, 3, 8, 9], x => x < 5)
   * console.log(result) // Option.some(1)
   * ```
   *
   * @category elements
   * @since 2.0.0
   */
  <A>(predicate: (a: NoInfer<A>, i: number) => boolean): (self: Iterable<A>) => Option.Option<number>
  /**
   * Return the last index for which a predicate holds.
   *
   * **Example**
   *
   * ```ts
   * import { Array } from "effect"
   *
   * const result = Array.findLastIndex([1, 3, 8, 9], x => x < 5)
   * console.log(result) // Option.some(1)
   * ```
   *
   * @category elements
   * @since 2.0.0
   */
  <A>(self: Iterable<A>, predicate: (a: A, i: number) => boolean): Option.Option<number>
} = dual(2, <A>(self: Iterable<A>, predicate: (a: A, i: number) => boolean): Option.Option<number> => {
  const input = fromIterable(self)
  for (let i = input.length - 1; i >= 0; i--) {
    if (predicate(input[i], i)) {
      return Option.some(i)
    }
  }
  return Option.none()
})

/**
 * Returns the first element that satisfies the specified
 * predicate, or `None` if no such element exists.
 *
 * **Example**
 *
 * ```ts
 * import { Array } from "effect"
 *
 * const result = Array.findFirst([1, 2, 3, 4, 5], x => x > 3)
 * console.log(result) // Option.some(4)
 * ```
 *
 * @category elements
 * @since 2.0.0
 */
export const findFirst: {
  /**
   * Returns the first element that satisfies the specified
   * predicate, or `None` if no such element exists.
   *
   * **Example**
   *
   * ```ts
   * import { Array } from "effect"
   *
   * const result = Arr