Tuple overview

Extension to the Effect Tuple module providing safe single-element construction, element replication, and prefix prepending.

Mental model

• Tuples are fixed-length arrays whose element types are tracked individually by TypeScript.
• This module focuses on a small set of constructors and editing helpers; combine them with Effect’s Tuple for the rest.

Common tasks

• Construct: {@link of}, {@link replicate}
• Edit: {@link prependElement}

Quickstart

Example (Build a [1] tuple from Array.map)

import { Array, pipe } from "effect"
import * as MTuple from "@parischap/effect-lib/MTuple"

console.log(pipe([1, 2, 3], Array.map(MTuple.of))) // [[1], [2], [3]]

Table of contents

• Constructors
  • of
  • replicate
• Utils
  • prependElement

Constructors

of

Builds a single-element tuple [a].

• Prefer this over Tuple.make inside callbacks of variadic-aware iterators (Array.map, Array.filter, …): those iterators pass extra arguments (the index, the source) and Tuple.make, being variadic, would silently include them. For example, pipe([1, 2, 3], Array.map(Tuple.make)) yields [[1, 0], [2, 1], [3, 2]] rather than the probably-intended [[1], [2], [3]].

Example (Single-element tuple)

import { Array, pipe } from "effect"
import * as MTuple from "@parischap/effect-lib/MTuple"

console.log(pipe([1, 2, 3], Array.map(MTuple.of))) // [[1], [2], [3]]

Signature

export declare const of: <A>(a: A) => [A]

replicate

Builds a tuple of length n whose every element is a.

• n is captured at the type level, so the result is typed Tuple<A, N>.

Example (Replicate a value)

import { pipe } from "effect"
import * as MTuple from "@parischap/effect-lib/MTuple"

console.log(pipe("x", MTuple.replicate(3))) // ['x', 'x', 'x']

Signature

export declare const replicate: <N extends number>(n: N) => <A>(a: A) => MTypes.Tuple<A, N>

Utils

prependElement

Returns [that, ...self], prepending that to the head of self while preserving the tuple type.

Example (Prepend an element)

import { pipe } from "effect"
import * as MTuple from "@parischap/effect-lib/MTuple"

console.log(pipe([2, 3] as const, MTuple.prependElement(1))) // [1, 2, 3]

Signature

export declare const prependElement: <B>(that: B) => <A extends ReadonlyArray<unknown>>(self: A) => [B, ...A]