sodapopcan
Why does `elem/2` exist?
I’ve been in the Elixir world for five years—not super long but also not super short. In this time I have seen lots of code that uses elem/2 but not once have I ever seen a situation where it made code clearer and in fact has always made code less clear. It seems its main use it to “not break pipelines.” To put it lightly: this is a non-goal. I have never run into a situation where pattern matching isn’t way way way waaaaaaaay clearer than elem/2, even if it means breaking the pipe.
IMO if we ever see an Elixir 2.0 this function should be removed from the language. But please tell me why elem/2 is indispensable to your Elixir work! I realize I’m using very dismissive language but I’m genuinely curious if there is a good use-case for it I’ve never thought of.
Marked As Solved
zachallaun
An example from a project I contribute to: Lexical.Document.Lines
The key insight is that a tuple provides O(1) access to any of its elements, whereas a list is O(n). So if you need a data structure that provides fast access to any arbitrary line of a document, you reach for a tuple. (And then you use elem/2 for access, since you don’t know what its length will be.)
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dorgan
- You have tuples, a fixed size array of elements.
- You can access them by a random index.
- There is no syntax to access a random index of a tuple
- Pattern matching requires you to know the length of the tuple up-front
I think it makes sense to have such a function be part of the standard library. The reasoning is quite simple: if you provide a builtin data structure, it makes sense to provide an API to read and write to it.
Wether or not it’s idiomatic to access a random element of a tuple is a whole different topic.
dimitarvp
sodapopcan
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slouchpie
That is weird. I have the same behavior. I can not let this go. Why does :pub not “tab out” to :public? There must be a reason.
Update: I think I got it
Any module that is Application “kernel” or “stdlib” or “erts” will tab out.
Otherwise it will not.
:public_key is in its own “public_key” application.
Similarly, :pretty_pr, :os_sup and :release_handler will not tab out.
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