How does flatMap work 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.

How do futures work Scala?

Future represents a result of an asynchronous computation that may or may not be available yet. When we create a new Future, Scala spawns a new thread and executes its code. Once the execution is finished, the result of the computation (value or exception) will be assigned to the Future.

What is Future sequence in Scala?

This Future. sequence() function converts a list of Futures into a single Future that means collections of Futures into a single Future. In simple words, List[Future[T]] ======> Future[List[T]] . It is also known as composing Futures.

Does Scala have onComplete blocking?

onComplete() we are no longer blocking for the result from the Future but instead we will receive a callback for either a Success or a Failure.

What is difference between MAP and flatMap in Scala?

flatMap(): The flatMap() method is similar 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. The flatMap method acts as a shorthand to map a collection and then immediately flatten it.

How does reduce work in Scala?

Scala | reduce() Function

1. The reduce() method is a higher-order function that takes all the elements in a collection (Array, List, etc) and combines them using a binary operation to produce a single value.
2. The order in which numbers are selected for operation by the reduce method is random.
3. Output :

What are options in Scala?

Scala Option[ T ] is a container for zero or one element of a given type. An Option[T] can be either Some[T] or None object, which represents a missing value.

What is promise in Scala?

In other words, the Promise is a write handle to a value that will be available at some point in the future. It allows us to put the value of a completed asynchronous operation into the Future, and change the state of the Future from not completed to completed by invoking the success method.

How do you find the future value?

There is a formula to calculate present value of future benefits, which is: PV = (FV)(1+i)ᵑ, where PV is present value, FV is future value, i is the interest rate, and ᵑ is the number of compounding periods per year.

What is fold in Scala?

The fold function is applicable to both Scala’s Mutable and Immutable collection data structures. The fold method takes an associative binary operator function as parameter and will use it to collapse elements from the collection. The fold method allows you to also specify an initial value.

Are futures monads?

Futures can be considered monads if you never construct them with effectful blocks (pure, in-memory computation), or if any effects generated are not considered as part of semantic equivalence (like logging messages).

Is it worth to learn Scala?

There is admittedly some truth to the statement that “Scala is hard”, but the learning curve is well worth the investment. Scala is a type-safe JVM language that incorporates both object oriented and functional programming into an extremely concise, logical, and extraordinarily powerful language.

What is the use of flatMap in Scala?

In Scala flatmap method is used on the collection and data structures of scale, as the name suggests it is the combination of two things methods i.e. map and Flatten method. If we use a flat map on any collection then it will apply both this method map and flatten method on the given collection.

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.

How do I know if flatMap will return an option?

As a quick Scala tip, if you haven’t worked with the flatMap on an Option much, it can help to know that flatMap ’s function should return an Option, which you can see in this REPL example: You can tell this by looking at the function signature in the scaladoc for the flatMap method on the Option class:

What is the difference between map and flatMap in Python?

Both map and flatMap return an Option in the end, but these examples show the difference between the custom functions you should pass into flatMap and map: flatMap should return an Option, and map should return a simple type that’s not wrapped in an Option.