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What is functional programming in Scala?

Scala is a functional language based on Java. It's a great way to learn functional programming but it also has its disadvantages - for example, the freedom to write non-functional code using pure Java. In this article i will share my experiences on functional programming in Scala.

What is Scala?

Scala is a multi-paradigm programming language providing support for functional programming and object oriented programming. Scala is a strong static type of programming language and built on top of the JVM. It compiles to java byte code. Martin Odersky created Scala in 2004 at Polytechnique Fédérale de Lausanne (EPFL) in Lausanne, Switzerland. The symbol of Scala is the rather well known staircase of EPFL. Scala’s design decisions was aimed to address criticism of Java. It is possible to write Java-like code in Scala but there’s many neat features such as lambda, pattern matching and so on that even without programming in a functional way is useful.

Benefits of Scala

As above mentioned, Scala has a lot of very useful things that Java (at least older versions, although this is changing) are lacking. Writing Java lambda code can be rather difficult and often involves specifying almost everything, while in Scala the support is very good and expressions become simplified. It’s also almost impossible to avoid mentioning functional programming when talking about Scalas benefits. One of the benefits of Scala being functional are immutability and that means avoiding side effects and enables parallel processing. Because of this a very popular use case of Scala is for big data and machine learning. Writing functional code also means it becomes easier to test your code and shorter code that’s easier to reason about.

Disadvantage

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The freedom of Scala is in my opinion the greatest disadvantage of Scala. You are free to technically write Java code inside of Scala. This means that you lose a lot of the benefits from functional programming. When you are working in a project involving multiple developers, this can be a big problem, since one developer may choose to write more Javalike code. For the benefits of Scala to exist, it requires all developers to stick to the Scala standard. Which might be hard to have all developers agree on, hence the freedom is a disadvantage.

Another issue is that Scala uses a lot of Java libraries and sometimes can result in underlying exceptions, that may be hard to handle, especially since Scala is supposed to have eliminated exceptions. There’s also a lack of great Scala libraries and tools in many cases. This is not always a huge problem as you usually can use Java libraries as well, but definitely is a disadvantage.

Functional vs Pure functional

Scala is a great way to get started with functional programming. It also has support to do pure functional programming. There’s many libraries in Scala for doing this, like cats, ScalaZ. But is Scala a “pure functional” language? It’s entirely up to the developer since you’re allowed to write imperative code as part of your program. Purely functional programs can however be written in languages which are not purely functional which complicates things even more. What is certain is that Scala offers a great set of tools to be able to do more “pure functional” programming.

Even though it’s not enforced, the language does encourage functional programming principles and is a great way to get introduced to many core functional programming concepts.

Where to from here?

To learn more about Scala, visit https://www.scala-lang.org/ and https://docs.scala-lang.org/learn.html. From there you can grab some tutorials and get started right away. There’s also a great introduction course at coursera, taught by the language’s author: https://www.coursera.org/learn/progfun1