[Klathmon]

Pattern matching will break you.

I get frustrated at least once a week trying to use it in a language that doesn't have it. My brain just thinks in pattern matching!

[macintux]

It's unfortunate when I encounter a language that has a crippled implementation of pattern matching (looking at you, Scala). After using Erlang, it's hard to accept anything less.

[vram22]

How are F#'s and OCaml's implementation of it, in your opinion?

[macintux]

I’ve not tried either, although in my limited exposure to SML it seemed fine.

The other related feature whose lack I regularly lament in most languages is multiple function heads, which apparently is rarely used in the ML family tree, bafflingly.

[sgrove]

I haven't heard the term "multiple function heads" - is it similar to Haskell's way of defining functions? e.g.

    fib 0 = 0
    fib 1 = 1
    fib n = fib (n-1) + fib (n-2)

[yosh]

Yeah, this is Erlang:

    fib(0) -> 0;
    fib(1) -> 1;
    fib(N) -> fib(N-1) + fib(N-2).

[rad_gruchalski]

But these are all compiled into, essentially, a giant case statement. It’s a syntactic sugar. Your last line is missing a dot at the end.

[macintux]

Exactly. I don’t know what the typical industry term for it might be.

[mercer]

Multiple Dispatch / Multimethods (I think?)

[mgradowski]

Pattern matching!

[YorkshireSeason]

What's wrong with Scala's pattern matching?

[macintux]

I shouldn't have said "crippled." It's just much more limited than when used in Erlang.

From digging a bit it appears to be somewhat the JVM's fault[0] and quite a lot of it is simply that it's a different type of language from Erlang.

In Erlang, nearly every line of code involves pattern matching, regardless of whether the developer takes advantage of it or not. Every assignment statement, every function return, every function parameter, is an exercise in pattern matching. It's at the core of the language, not an add-on.

As I mentioned in another comment, a closely-related feature that really shows it to its full advantage is multiple function heads/clauses.

[0]: https://www.scala-lang.org/old/node/11982

[YorkshireSeason]

OK, I also don't like Scala's inability to deconstruct in the parameter list. I come from an ML background where that is possible. But I found it less bothersome in practise than I had originally anticipated.

Erlang has pattern matching on bits [1] which is convenient, that would be nice to have, especially when writing networking software.

[1] P. Gustafsson, K. Sagonas, Efficient manipulation of binary data using pattern matching.

[macintux]

Good point on the binary pattern matching. I’ve rarely used it, but it is quite powerful.

I was pleased to discover Python’s tuple pattern matching in function heads, only to be disappointed that it was removed in Python 3.

[vikingcaffiene]

You are completely right. I work mostly in TypeScript and JavaScript for day to day and I miss pattern matching so much. Object de-structuring is nice and all but once you've seen the possibilities in a language where its a first class citizen... everything else just seems inadequate.

[Klathmon]

It's getting there for us in JS land, slowly but surely! There's still a lot of discussions that need to happen (read as "mostly bikeshedding" IMO), but once they settle on the actual syntax, i'd feel comfortable to start using it with compilers.

https://github.com/tc39/proposal-pattern-matching