When you need to use map and then flatten, use flatMap. It is not the same as unwrapping a wrapper. It does two actions - mapping and then flattening. That is not the abstraction, flatMap is not about taking a wrapper and flattening. Option(2).flatMap(println) * DOES NOT WORK I had the impression that flatMap takes a wrapper as argument and flattens it. def singleDigitTwice (n : Int) : Option = println('Use flatMap') (0 until 20). Let us look at a flatten example closely first. And this is really useful because the flatMap method is on all Scala. In programming terms, all that I mean is that the None s would get filtered out, and the Some s would get unwrapped on flattening. But then, chocolates is all you care about anyway! You don’t know which eggs were empty and whether all six chocolates in one shell or not. For example, if you had ten easter eggs, and you had four of those empty and one chocolate each in the remaining six eggs, on doing the flatten exercise on the ten shells, you get six chocolates and that is it. The empty shells get obliviated completed.

The shells get destroyed and the chocolates take their place. When you flatten these easter eggs, two things happen. Imagine you are collecting easter eggs and flattening them, some of these easter eggs would have chocolates in them, and some would be empty. If you need to map and then flatten, use flatMap instead.

flatMap kind of works the same, it breaks the shell and gives you the egg, the wrapper is removed and you get the chocolate. We can call it M instead of Monad simply to be more concise.The world has been flattened there. We will model a monad with a generic trait that provides methods unit() and flatMap(). In plain Scala, there’s no such thing out of the box. You will also find the rest of the category theory family (functors, applicatives, monoids and so on). Map operation is one step behind flatMap operation technique and is mostly similar. This gives many results out of it which means that we can get one, two, zero and other many elements from the flatMap operation applications. A new RDD is returned with its application on each element of RDD as a result. If you take a look at some cool functional programming libraries like Scalaz you will find monads there. A flatMap is an operation of transformation. Scala doesn’t come with a built-in monad type like Haskell so we will model the monad ourselves.

bind ( >= in Has kell, flatMap in Scala).

identity ( return in Haskell, unit in Scala).We wrap objects with monads because monads provide us with the following two operations: We wrap gifts with shiny paper because they look pretty. It’s like wrapping a present you take a scarf, a good book or a fancy watch, and wrap it with some shiny paper and a red ribbon. You just take an object and wrap it with a monad. Examples are more as a supplement to the main explanation. Last, but not least, I will provide examples as a primary mean of explaining. But I will also try not to be too simplistic, and by simplistic I mean vague. Stephen Hawking said that he was warned that every equation he put into “A brief history of time” (great book by the way) would halve the sales. I will not get technical, and by technical I mean mathematical. Boring explanations which line up one definition after another without providing the gist of things. I feel the sea is polluted with complex mathematical explanations involving category theory. I am aware that this is a drop in the sea. In my previous post I mentioned how I decided to write about variance despite the fact that there are already several dozen articles about the topic.

Flatmap scala