Monads are functional design patterns that wrap objects and provide two operations: identity (unit) and bind (flatMap). They follow three laws: left-identity, right-identity, and associativity. Common monads in Scala include List, Option, Future, and Try. Monads allow calculations to be chained together by passing the output of one as the input to the next.

1. MONAD
FUNCTIONAL DESIGN PATTERN

2. What is Monad ?
 A Monad is not a class or a trait; it is a concept.
 A Monad is an object that wraps another object in Scala, like wrapping a present.
 In Monads, the output of a calculation at any step is the input to other calculations, which run as a
parent to the current step.
 We wrap gifts with shiny paper because they look pretty. We wrap objects with monads because
monads provide us with the following two operations:
 identity (unit in Scala)
 bind (flatMap in Scala)

3. Identity - Unit ()
 “Give me anything and I will hand it over to you wrapped in a bag. That’s my job.”—Unit
 In case of our monad trait, if we give it a value of type A, it will return a value of type M[A].
 In Scala, Unit is usually the apply method, a special method that doesn’t need to be named. A.apply()
is the same as A() which is the same as A{}.

4. Bind – flatMap()
 “Tell me to do anything on what is inside the bag
and I will do it, first by unpacking the bag and then
repacking it with new thing in it.”—map
 “Give me stuff doubly wrapped into bag and I will
return you the same stuff but with a single
wrapping”—flatten
 The bag with unit, map and flatten makes
a Monad.
 Monad!. It’s like a Functor who knows how
to flatten.

5. Monad Laws
 Left-identity law unit(x).flatMap(f) == f(x)
 Right-identity law Monad[X].flatMap(unit) == Monad[X]
 Associativity law m.flatMap(f).flatMap(g) == m.flatMap(x ⇒ f(x).flatMap(g))

6. Monads
 List
 Option
 Future
 Try
class mPackaging{
def flatMapOp(firstList : List[String], secondList : List[String] ):
List[String]= {
firstList.flatMap { x => secondList
.map { y => x + y }
}
}
}
object mPackaging{
def main(args: Array[String]): Unit = {
val monad = List("unit","bind")
val gift = List("packaging","opaeration")
println(apply.flatMapOp(monad, gift))
}
def apply: mPackaging = new mPackaging()
}

7. References
 https://medium.com/beingprofessional/understanding-functor-and-
monad-with-a-bag-of-peanuts-8fa702b3f69e
 https://medium.freecodecamp.org/demystifying-the-monad-in-scala-
cc716bb6f534