The thing that confused me the most in the beginning was the syntactic sugar for Keyword lists. I kept seeing these odd things in the options list for functions and I had no idea what they really were.
IO.inspect Process.list, width: 40
I cargo culted a lot of code until I actually made the connection that line is really.
IO.inspect(Process.list, [{:width , 40}])
I have to say that sometimes some of the syntactic sugar can make things a little more difficult to mentally parse for me. Maybe that’s just me though.
Yeah, the keyword lists sugar for function arguments gets me often. Just have to get used to it I guess.
Agreed on this one. Elixir used to have a ListDict module that was a sort of “superclass” of the current Keyword module that helped to make that explicit. However, once Erlang got large map support, it because superfluous. Now the leap from list to Keyword list has no intermediate step.
The implicit handling of it as the final param in a function call (reminiscent of Ruby) further adds to its mystical quality.
… And on top of that, the order of keywords does matter.
def foo(name: name, type: type) will not be matched when calling foo(type: "elephant", name: "Dumbo").
Wow, that doesn’t stop to look confusing no matter how much I look at it 
I was actually wondering if something like that is possible, but now that I see it I’m not sure I’d like to know
Btw, where did you stumble upon that?
Most likely in this situation: Pipe operator and functions (not function calls)
i.e. for an ad hoc parameter reorder to continue the current chain (not recommended).
Y was using to restructure the return value from previous function, but better to write a separate function so things look clean.
If you haven’t seen pattern matching before, that might be difficult to get used to.
This isn’t really a gotcha - it’s one of Elixir’s strengths of course , but someone new to Elixir would find it difficult to understand a lot of code if they’re unfamiliar with pattern matching.
3 things I have noticed when giving courses[*] that people coming from a non-functional background can have problems with are immutable data, pattern matching, and recursion. But once you grasp them you never want to go back.
Robert
[*] It has mainly been erlang courses, and now elixir courses, but at this level they are the same.