Elixir's intersection types

Elixir is exploring the idea of adding types. During ElixirConf 2023, José Valim talked about the need for an intersection type when specifying types for certain Elixir functions. I checked out the research paper to understand more. Here, I show why we need that type.
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[@1astery1]

Thanks, I was a bit confused, and your video really clarify that!

[@germanvelasco]

So glad to hear that!

[@mythrando]

Thank you, I was confused as well and this cleared it up very nicely!

[@germanvelasco]

Glad to hear it!

[@aarroisi]

I hope that it will be possible to separate the type per each function clause and automatically make all function clause's types are combined with an "and". It will be a lot cleaner.

[@kostasgkoutis8534]

That reminds me a lot function overloading

[@encapsulatio]

Where can I see the video presentations they made on the type system at ElixirConf 2023?

[@germanvelasco]

th-cam.com/video/giYbq4HmfGA/w-d-xo.html

[@defman21]

2:48 I haven’t watched the talks yet, but I’d really appreciate if we could provide a type specification for each of the function’s heads:
$ integer() -> integer()
def negate(x), do: …
$ boolean() -> boolean()
def negate(x), do: …

[@germanvelasco]

Yeah, that would be nice. I don't know if there'll be limitations around that, but I like that we can at least break it into multiple lines. It makes it read very nicely.

[@bo0tzz]

José mentioned that you can format the type either way - all at the top, or above each head.

[@tshakah]

My understanding after watching Jose's video was that you could do this

[@cwhy]

Like your concise videos, and of course Elixir. Gonna be your 667'th subscriber to break the 666 here 😆

[@germanvelasco]

Thanks for looking out for that number! 👀 😂

[@ericg3065]

I still don't see why this is necessary. The guard clause clearly indicates what type of data the function accepts. I just hope Elixir doesn't turn into something similar to TypeScript.

[@germanvelasco]

The guard clause specifies data at runtime. Types would do it at compile time. I too am worried about what types will mean for Elixir, but I know José and team are very careful in their approach. So, I think we'll land with something good -- if they land at all.

[@ericg3065]

@@germanvelasco Oh now I see. I like the simplicity of $ integer() -> integer(). If they go with this approach I hope it replaces typespecs. It's a lot easier on the eyes. Elixir is not perfect and has flaws like any other language but I love it's simplicity and expressiveness. It's the only language I've been able to understand at a high level. I hate to see that go away by introducing more complexity to the language. Thanks so much for all of your contributions to Elixir and keep up the good work :)