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const Right = value => ({
  map: f => Right(f(value)), // Either[E,A].map(fn: A => B): Either[E,B]
  bind(f) { return this.map(f).join() }, // Either[E,A].bind(fn: A => Either[E,B]): Either[E,B]
  join: () => value,
  isRight: () => true,
  isLeft: () => false,
  cata: (l, r) => () => r(value)
})

const Left = value => ({

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const validateLogin = auth => {
  const checkUsername = auth => auth.username
    ? Right(auth)
    : Left('No Username')
  const checkPassword = auth => auth.password
    ? Right(auth)
    : Left('Password Empty')
  const checkMatch = auth => (auth.username === 'jihad' && auth.password === 'jihad123')
    ? Right(auth.username)
    : Left('Username && password mismatch')

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// form/utils.js
const createEitherFromConstraints = (obj, cons) => cons.reduce((acc, con) => acc.bind(con), Either.of(obj))


// module/auth/constraints.js
const checkUsername = auth => auth.username
  ? Right(auth)
  : Left('No Username')
const checkPassword = auth => auth.password
  ? Right(auth)

dewey92

const incr = x => x + 1
const add  = curry((x, y) => x + y)
const sum3 = curry((x, y, z) => x + y + z)

liftA(incr, Functor1) === pure(incr).ap(Functor1)
liftA2(add, Functor1, Functor2) === pure(add).ap(Functor1).ap(Functor2)
liftA3(sum3, Functor1, Functor2, Functor3) === pure(sum3).ap(Functor1).ap(Functor2).ap(Functor3)

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/* Cara 1: dengan Higher Order Function */
const add = x => y => x + y
const add1 = add(1) // y => 1 + y
console.log(add1(3))
// => 4


/* Cara 2: pakai library biar gampang (Lodash, Ramda, etc) */
import { curry } from 'ramda'

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const getChild = person => Maybe(person.child)
const getName = person => person.name
const textPenghulu = curry((co, ce) => `Saya nikahkan ${co} dan ${ce}, sah!`)

const jihad = getName(getChild(mnunirFam))
const pita = getName(getChild(wawanFam))

console.log(textPenghulu(jihad, pita)
// Result:   "Saya nikahkan undefined dan undefined, sah!"
// Expected: "Saya nikahkan Jihad dan Puspita, sah!"

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const incr = x => x + 1
const add = curry((x, y)) => x + y
const sum3 = curry((x, y, z)) => x + y + z

const maybe1 = Maybe(1)
const maybe2 = Maybe(2)
const maybe3 = Maybe(3)

/* Pada dasarnya, liftA merupakan kombinasi dari map dan ap */

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const jihad = liftA(getName, getChild(munirFam)) // Maybe('Jihad')
const pita = liftA(getName, getChild(wawanFam))  // Maybe('Puspita')

console.log(liftA2(textPenghulu, jihad, pita))
// => Maybe('Saya nikahkan Jihad dan Puspita, sah!')

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// add :: Number → Number → Number
const add = (x, y) => x + y

// mathMsg :: (Number → Number → Number) → Number → Number → String
const mathMsg = (mathOp, x, y) => {
  const result = mathOp(x, y)

  return `The result of ${x} and ${y} is ${result}`
}

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// map :: (a → b) → [a] → [b]
const map = fn => arr => arr.map(fn)


// :: (Int → String) → [Int] → [String]
map(x => x.toString())([1, 2, 3])
# ['1', '2', '3']

// :: (Int → Int) → [Int] → [Int]
map(x => x + 1)([1, 2, 3])