Using map And flatMap In Scala

Shubham Verma explains the map and flatMap functions in Scala:

Consider two sets, A = {-2, -1, 0, 1, 2} and B = {0.5, 1, 1.5, 2.5, 4, 4.5, 5, 5.5} and a function          f: A => B

y = x ^ 2 + 0.5;  x is an element from set A and y corresponds to an element from set B, now we see that function f is applied to every element of set A but the result could be a subset of set B also.

So from the above text, we can draw the analogy that sets A and B can be seen as any collection in programming paradigm. Now what is “f”, so “f” could be seen as a function that takes an element from A and returns an element that exists in B, the point here to note is that, as scala promotes immutability whenever we apply map (or any other transformer) on some collection of type A, it returns a new collection of the same type with elements of type B. It would be helpful to understand it from the snippet below.

val result: List[B] = List[A].map(f: A => B)

So when a map operation is applied on a collection (here a List) of type A, with passing f as its argument it applies that function to every element of List of type A returns a new collection (again a List) of type B.

Read the whole thing.

Related Posts

Writing ssisUnit Tests With C#

Bartosz Ratajczyk shows us how to create ssisUnit tests in MSTest with C#: In the post about using MSTest framework to execute ssisUnit tests, I used parts of the ssisUnit API model. If you want, you can write all your tests using this model, and this post will guide you through the first steps. I will […]

Read More

Sorting Data In Scala

Randhir Singh walks us through several methods of sorting in Scala: sortBy(attribute) Here is signature def sortBy[B](f: A => B)(implicit ord: Ordering[B]): Repr The sortBy function is used to sort one or more attributes. Here is a small example. sort based on a single attribute of the case class. Click through for several examples.

Read More


May 2018
« Apr Jun »