Practical Cats: Functor and Applicative

In this post, I ’m going to introduce you some useful aspects of Cats library, mostly code snippets and I ’m not going to delve into any theory or mathematics. Hopefully you will use them in your daily codes, resulting in much more simpler and readable code. map using Functor You are already familiar with the prominent map method in Scala. Informally, a functor is any context with a map method.

Case Study - Solve Crosswords Puzzle

As a software engineer, I always enjoy solving problems and that’s why I sometimes go to the coding challenge websites like hackerrank and pick one problem to solve. This time I searched in functional programming category and crosswords-101 caught my eye and I decided to solve it in Scala in a very clean and understandable way and not in a contest style way of programming! This article is going to reveal how I solved this puzzle.

Slick Actions Composition

Problem You want to insert a new row to a table which has auto increment primary key; Also some additional information must be persist in other tables. At the end you also want to return the inserted generated ID. Imaging you are developing a new web application, and you are working on user registration code. Each time a new user signs up, you want to store his credential in users table and all of his roles in userRoles table.

More Readable Code in Scala

As a Java developer, I ’ve always had argument with my colleagues to use Scala instead Java. They complained that Scala is a complex language and Java is a more readable and simple one so I never had the opportunity to use Scala well. Fortunately, recently I ’ve just joined to the startup company called, and we use Scala for all the backend services. A few days ago, I was working on a peace of code in Scala to register a new user into the database.

Writing Internal DSL in Scala

Definition of DSL A DSL is a computer language, specialized for a specific domain. A DSL is essentially the opposite of a general programming languages(GPL), I mean every language that can be used to develop something. For example, Java, C#, and Scala are all GPL languages. With a DSL, we want only to solve a specific domain problem, so we design the language specifically for the domain. A DSL can’t be used outside of the domain, because it is not designed for flexibility.