crocks/core/mconcatMap.js

A collection of well known Algebraic Datatypes for your utter enjoyment.

/** @license ISC License (c) copyright 2016 original and current authors */
/** @author Ian Hofmann-Hicks (evil) */

var compose = require('./compose')

var foldWith =
  function (m) { return function (x, y) { return x.concat(m(y)); }; }

// mconcatMap :: Monoid M => M -> (b -> a) -> ([ b ] | List b) -> M a
function mconcatMap(M, f, xs) {
  return xs.reduce(foldWith(compose(M, f)), M.empty())
}

module.exports = mconcatMap