Ecky Putrady - Practical Web Development with Haskell: Master the Essential Skills to Build Fast and Scalable Web Applications

I was instantly hooked into Haskell when I stumbled upon this piece of code:

It is indeed not the most efficient implementation of a quicksort algorithm, but it is so terse while fully capturing the main idea of quicksort. I find it to be elegant.

Haskell is infamously known as a difficult programming language to learn. It is true, but only if you are accustomed to OOP or an imperative way of thinking. If you are already familiar with Java, you can spend a weekend learning C# and be productive with it. Its because they are quite similar enough. The same thing cannot be said for Haskell. Haskell is significantly different from those programming languages. You need to think differently. And this way of thinking takes time to learn. In my experience, learning Haskell is like learning Java or C# for the first time when you have no prior knowledge of programming.

So why would one want to invest time to build applications in Haskell? What makes it worth the initial learning curve?

Haskell is a statically typed programming language. Statically typed languages are languages in which the types are checked at compile time. It prevents you from doing stupid things, like passing in a string to a function that expects an integer. It is always better to catch these problems up front rather than three days later in production when a specific input is sent to the system. You might have lost the context already and you are supposed to enjoy your weekend!

Most statically-typed programming languages are correlated with verbosity. It is a sound statement. Since you are required to annotate the types, you are indeed writing more code. For example, in Java, you would write something like this:

See the String there? Its a type that you need to tell the compiler so that it can check your code for correctness.

Fortunately, Haskell has type inference. Type inference allows you to omit the types almost entirely. The compiler will still be able to tell you if your code is not correct. The same example can be rewritten in Haskell as:

In this example, the compiler knows that name must be a string because the operations being applied to it are string operations.

The preceding example also shows how Haskell code could be so terse. Besides the syntax, there are many other features in Haskell that help you write concise code, such as higher order function and partial function applications. These features, for example, allow you to replace loops with a one-liner. Its powerful for processing and transforming data.

Learning Haskell did change the way I think about programming. In OOP, I used to think in terms of long-lived organisms called objects interacting with each other. I used to think about how to structure my objects into the correct hierarchy. Thats how OOP is taught. Remember the Cat extends Animal in OOP 101?

After learning Haskell, I think in terms of data transformation. What I usually do in my work so far can be boiled down to just transforming one kind of data into another kind of data. Its straightforward. I notice that I now write less code to achieve the same amount of functionalities with fewer defects.

Nowadays, you might have noticed that mainstream programming languages include more and more functional programming constructs. Java 8, for example, introduces Optional (from Haskells Maybe), and most importantly, lambda function. Recently created programming languages like Swift, Kotlin, or Scala also favor immutability, a concept from functional programming. Its more apparent now where the industry is heading.

So, again, why would one want to invest time to build applications in Haskell? The short answer is, Haskell lets you write applications faster and more correctly.

As I have said earlier, Haskell is infamously difficult to learn. Part of it is because there are not many resources on the subject yet, especially if you want to apply Haskell to your day-to-day job. If you investigate mainstream programming languages, there are a lot of resources that teach you how to use them.