What is a flat map in Scala?
In Scala, flatMap() method is identical to the map() method, but the only difference is that in flatMap the inner grouping of an item is removed and a sequence is generated. It can be defined as a blend of map method and flatten method.
What is map () in Scala?
Scala map is a collection of key/value pairs. Any value can be retrieved based on its key. Keys are unique in the Map, but values need not be unique. Maps are also called Hash tables. There are two kinds of Maps, the immutable and the mutable.
What is difference between MAP and flatMap in spark?
Spark map function expresses a one-to-one transformation. It transforms each element of a collection into one element of the resulting collection. While Spark flatMap function expresses a one-to-many transformation. It transforms each element to 0 or more elements.
What is a Monad in Scala?
In Scala, Monads is a construction which performs successive calculations. It is an object which covers the other object. It is worth noting that here, the output of an operation at some step is an input to another computations, which is a parent to the recent step of the program stated.
What is headOption in Scala?
The scala collections API provides a function called “headOption”, which returns a Some(value) if there is an item in a list, and a “None” otherwise.
What does ++ mean in Scala?
++= can mean two different things in Scala: 1: Invoke the ++= method. In your example with flatMap , the ++= method of Builder takes another collection and adds its elements into the builder. Many of the other mutable collections in the Scala collections library define a similiar ++= method.
How is map implemented in scala?
Per the Scaladoc, “implements immutable maps using a list-based data structure.” As shown in the examples, elements that are added are prepended to the head of the list. Keys of the map are returned in sorted order. Therefore, all traversal methods (such as foreach) return keys in that order.
What is the difference between map and HashMap in scala?
Scala map is a collection of key/value pairs. Any value can be retrieved based on its key. Keys are unique in the Map, but values need not be unique. HashMap implements immutable map and uses hash table to implement the same.
What is flattening in Spark?
Flatten – Creates a single array from an array of arrays (nested array). If a structure of nested arrays is deeper than two levels then only one level of nesting is removed.
What is lazy evaluation in Scala?
Lazy evaluation or call-by-need is a evaluation strategy where an expression isn’t evaluated until its first use i.e to postpone the evaluation till its demanded. Functional programming languages like Haskell use this strategy extensively.
What is currying in Scala?
Currying in Scala is simply a technique or a process of transforming a function. This function takes multiple arguments into a function that takes single argument. It is applied widely in multiple functional languages. Syntax def function name(argument1, argument2) = operation.
What is a flatMap in Scala?
As I’ve learned over time, in the functional programming world, flatMap is used to work with monads — Scala data types that implement map and flatMap — such as Option, List, Future, etc. Here are a few examples where I demonstrate that:
How to do parallel processing in Scala with flat map?
Parallel processing: We can also achieve parallel processing by using a flat map in Scala. We can easily make our newly created collection parallel by using Parallel collection, then by simply calling the function n newly created parallel collection will process the elements parallel It will also speed up the processing of elements.
How does map () work on option value in Scala?
We know map () is a transformer method, on Option it works just like that the code generated by scala REPL clearly displays that how the transformations are performed by map on an option value.
Is flatMap a combination of map and flatten?
let’s apply map () and flatten () on the stated sequence. let’s apply flatMap () directly on the given sequence. So, we can see here that the output obtained in both the cases is same therefore, we can say that flatMap is a combination of map and flatten method. Now, let’s see some examples of flatMap method.