elem/2 can be used in guards, pattern matching cannot
elem/2 is O(1) access to a vector (the only other O(1) example is binaries).
Pattern matching with large tuples is verbose and it’s easy to get the wrong element (why count wildcard matches when you can write the correct index into a function argument).
In the future, it seems we will get O(1) update of tuples in contexts where the compiler knows there are no shared references. So maybe time to incorporate :erlang.setelement/3 into Elixir somehow.
