Func Monoid

func-monoid.js

const func = createMonoid({
  indentity: x => x,

  // The code below can't run but conceptually valid
  // In Haskell or Purescript, it's easier to write Monoid instance
  semigroup: (f, g) => x => f(x).append(f(g)),
});

// toStr :: Int -> String
const toStr = x => parseInt(x)
// replicateJihad :: Int -> String
const replicateJihad = xs => 'Jihad'.repeat(xs)

log(func.id) // x => x
log(func.append(toStr, replicateJihad)(2)) // '2JihadJihad'
log(func.append(replicateJihad, toStr)(2)) // 'JihadJihad2'
log(func.append(replicateJihad, func.id)(2)) // 'JihadJihad'
log(func.append(func.id, toStr)(2)) // '2'