Sunday, April 25, 2021

How programming languages contribute to clean code

I had a conversation with some friends about the programming languages different companies use. Many companies only choose the most popular language such as Java and C#. They believe "Developers can write clean code in any languages" so just pick one which has the biggest resource pool to make hiring easier.

However, clean code is the key for a technology company to succeed. It provides the company to maintain a fast pace for its delivery. Companies who limit the languages don't realize that they might be losing the speed of delivery, which can be measured by four key metrics.

What decides the level of clean code?

The good code is working code (pass all the tests) with very good readability (reveal intentions) as well as least elements (no duplication). The good code also allows the reader to exit early so they can understand the code quickly by reading the minimal amount of information.

We have been trying to achieve that for decades. Many frameworks, libraries, language features (I’ll call it “styles” in the rest of the article) have been introduced for this purpose to allow developers to write less and clear code for more things, to separates the concerns of different levels of abstractions.

However, we have a problem that all of the styles are contextual. If we use a low-level style (close to computer interaction such as copying an array from memory A to memory B) to solve the high-level problems (close to the real world such as generating an invoice), the code is very hard to be clean. But if we use a high-level style to solve the high-level problems, we can write much cleaner code easily. So it’s all about putting the right styles in the right places. The more styles a programming language provides, the higher chance to have clean code. But there is also a higher chance to have messy code as well if we fail to choose the right styles.

So many people think the level of clean code totally depends on the developers.

Is that true? Do languages have no contribution to clean code?

Styles supported by different languages

I choose 4 languages as examples, but keep in mind that there isn’t a language that supports all the styles (no language rules all):

  • Java - it is a pure OO language. It supports basic lambda expression since Java 8. But the capability of the language is very limited. Most time we have to write code in low-level styles to solve problems.
  • C# - very similar to Java. But because of LINQ syntax which is more powerful than stream in Java, it allows developers to write cleaner code in high-level styles. However, the patterns are still very limited.
  • Kotlin - it has massive improvements on the basic syntax from Java. It also creates immutable collections which provide a much better experience than stream. However, due to the lack of ways to combine types and methods, it is still hard to keep complicated logic clean.
  • Scala -  it is a multi-paradigm language. It supports many styles from low-level styles to high-level styles. It supports 7 levels of mastery in functional programming which Kotlin/Java/C# can only support 2 levels because we can’t implement type classes easily. Also because of the for-expression and implicity features, it allows developers to easily separate the different levels of abstractions.

From these examples, we can see different languages do support different numbers of styles. Some support much more styles than others, which means they provide more options to allow good developers to write cleaner code. On the other hand, it will be very hard for developers to write clean code if the right styles are not supported by a certain language.

Relationship among clean code, developers, and languages

So the relationship among clean code, developers, and languages look like this:

Notice: the diagram does not say a language is better than another, it says some languages provide more options than others. As long as developers make the right choice, they can write better code in a language than others. And the more options a language provide, the better code it can be.


Changing a language does not guarantee an increase in your team performance. However, stopping good developers to write better code guarantees a decrease in your team performance. Companies that want long-term success should allow good developers to choose a more powerful language when they reach the bottleneck. It helps the company to attract more good developers as well as to continuously improve the team performance.


How languages evolve?

By the way, good developers also try to extend the language to support the styles they want until it’s too hard, then they create a new programming language. Many new languages die because they couldn’t fit the purpose. Only a few survive with a strong community and its ecosystem. They can normally be safely chosen for commercial use.

Be careful about choosing a language for learning purpose

Trying new languages in a long-term system is dangerous. Writing clean code in a language requires a certain level of proficiency in that language. It takes time to learn. We should practice the new language in coding dojos first, then experiment with it in some short-term products or very simple products which you can rewrite within a week by your mastered language.

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