crocks/pointfree/alt.js

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

/** @license ISC License (c) copyright 2017 original and current authors */
/** @author Ian Hofmann-Hicks (evil) */

var curry = require('../core/curry')
var fl = require('../core/flNames')
var isAlt = require('../core/isAlt')
var isSameType = require('../core/isSameType')

// alt : Alt m => m a -> m a -> m a
function alt(m, x) {
  if(!(isAlt(m) && isSameType(m, x))) {
    throw new TypeError(
      'alt: Both arguments must be Alts of the same type'
    )
  }

  return (x[fl.alt] || x.alt).call(x, m)
}

module.exports = curry(alt)