hyper-reducer

A generalization of reduce() to arbitrary arity.

Introduction

Reduction is a key concept in functional programming which encapsulates the idea of recursively transforming state based on a sequence of input. More concretely, reduce() takes two values (one of which is the previous output), and returns another value. In contrast, reduceN() takes N inputs (it has arbitrary arity). Although reduceN() can ultimately be reduced to regular reduce(), the construction makes certain operations easier to understand and implement.

Insallation

npm i hyper-reducer

Usage

import hyperReducer from 'hyper-reducer'

const reduce2 = hyperReducer(2) // Reduction with arity 2.

const array = [1, 2, 3, 4, 5, 6]

reduce2(array, (a, b0, b1) => a*b0 + b1, initial=[1, 1]) // Returns 10 

The hyperReducer() function takes an arity argument and returns a concrete reducer with that arity. The reducer then takes an array, callback function and (optional) initial set of previous outputs. The initial outputs are set to zero by default.