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Comment by unregistereddev | Hacker News Reader

Pattern matching is a neat tool to keep in the toolbox. When it's the right tool for the job, it is really cool and is a lot cleaner than a bunch of conditional checks. However, I rarely reach for it. Maybe my use cases are unusual? I am genuinely curious how often other developers find pattern matching to be the best tool for the job.

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Pattern matching is what makes sum types ergonomic enough to be used. Many a Java design doesn't use said interface-based sum types because it's so cumbersome to use them. But whena language has pattern matching, then suddenly designing with sum types in mind is done a lot, and therefore you see examples of good pattern matching everywhere.

When I teach Scala, a very high percentage of the teaching time is ultimately down to re-introducing how to design business domains, because seasoned devs just reach for large classes with a million optional fields, which not only can represent valid systems states, but thousands of invalid ones.

In languages that have strong support for pattern matching, whether it be on values or types, I find myself reaching for it instead of conditionals. It's all about the explicitness for me. You have to list out all the cases you care about, so there's no room for ambiguity. Plus, the compiler will usually warn you if you've missed a case, which is like a built-in bug catcher. It's also great for working with immutable data, less state to worry about. And let's talk about readability; the code basically documents itself because you can see the shape of the data right in front of you. You can even destructure data on the fly, pulling out exactly what you need. If you're using a statically-typed language, pattern matching adds an extra layer of type safety. And, not to forget, it nudges you toward a more functional style of coding, which I find leads to cleaner, more modular code. So yeah, I reach for pattern matching quite a bit; it often feels like the right tool for the job.

When available, I pretty much always use pattern matching. It tends to shorten code while not reducing clarity (often increasing it) which means fewer opportunities for errors to creep in. Statically typed languages that can detect incomplete case handling also reduces the chances for some errors (as long as you don't make a catch-all case) but also helps when you change something so that a new case is needed. It also tends to shift the code to the left, reducing the indentation. So shorter, clearer, less unnecessary indentation. Generally a positive.

It probably depends on the language you're using. Pattern matching is awesome in Erlang and Elixir. In most other languages it ranges from "nice" to "bleh".

Pattern matching is awesome in Rust. It carries the stellar legacy of Haskell.

Patterns are somewhat nice to have, but for me they’re difficult to read, and not because my brain isn’t used to them. The simple identifier instanceof is about all I’ll use _most_ of the time. Otherwise, yes they are more concise, but lose too much information in the process.

I’d rather see a boatload load of other features before patterns. I’ve been experimenting with project manifold[1]. _That_ is the path Java sb on. Just my take.

1. https://github.com/manifold-systems/manifold

One example for you: anytime you needed to use the "Visitor pattern" to do a transformation from one representation to another - you don't need it now. Sealed classes and pattern matching will be more succinct and easier to reason about.

I think that you can replace almost any If else with pattern matching. Pattern matching makes type checks easier, which if you are really heavily using types through your program, makes pattern matching even better.

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