ackerman_lodash_reduce.js

// After
// Hutton, Graham. "A tutorial on the universality and expressiveness of fold." Journal of Functional Programming 9.04 (1999): 355-372.
// Lodash has no currying making it necessary to call a few partials. Fold is reduce in lodash and the order of 
// the arguments is different. _.reduce(data, fn, initial) = fold(fn, inital, data)

var _ = require('lodash')

var ack = _.partial(
  _.reduce,
  _,
  (g, x) =>
    _.partial(_.reduce, _, (xs, y) => g(xs), g([1])),
  _.partial(_.concat, [1], _)
  )


var arr = (n) => {
  return Array.apply(null, Array(n)).map((n) => 1)
}

var ackn = (n,m) => {
  return ack(arr(n))(arr(m)).length
}

console.log("ack(0,1):", ackn(0,1))
console.log("ack(1,0):", ackn(1,0))
console.log("ack(1,1):", ackn(1,1))
console.log("ack(2,1):", ackn(2,1))
console.log("ack(1,2):", ackn(1,2))
console.log("ack(3,4):", ackn(3,4))