compose

compose :: (Function f, Function g, ...) => Function f ∘ g ∘ ...

description

Returns a function which composes its given parameter functions right to left. Function composition is at the heart of functional programming, and that's why it is one of conductor's most important functions.

But that's not all! compose also has magic powers: it composes synchronous functions, asynchronous functions or even a mix of both! It accepts as many arguments as the rightmost function does, and has the same arity.

examples

basic example

import { compose } from 'conductor'

const times2 = x => 2 * x
const minus3 = x => x - 3

compose(minus3, times2)(5) // 7 === (2 * 5) - 3 : functions are composed right to left

arity preservation

import {compose} from '@waldojeffers/conductor'

const multiply = (x, y) => x * y
const minus3 = x => x - 3

compose(minus3, multiply)(2, 5) // 7 === (2 * 5) - 3
compose(minus3, multiply)(2)(5) // 7
compose(minus3, multiply).length // 2

Even if multiply and minus3 do not accept the same number of arguments, compose will help you make their composition a breeze! It will simply accept as many arguments as multiply does : 2. You can verify that by accessing the length property on the composition's result. Even better, compose's result will be curried, even if its rightmost argument is not.

synchronous and asynchronous function composition

import {compose} from '@waldojeffers/conductor'

const times2 = x => 2 * x
const minus3 = x => x - 3
const times2Async = async x => times2(x) // async keyword makes it return a Promise
const minus3Async = async x => minus3(x) // async keyword makes it return a Promise

compose(minus3, times2)(5) // 7
await compose(minus3Async, times2Async)(2, 5) // 7 : we need to await because it is an async function
await compose(minus3, times2Async) // 7
await compose(minus3Async, times2) // 7

Even if multiply and minus3 do not accept the same number of arguments, compose will help you make their composition a breeze! It will simply accept as many arguments as multiply does : 2. You can verify this by accessing the length property on the composition's result. Even better, compose's result will be curried, even if its rightmost argument is not.