edmz

Unofficial Elixr Un-FAQ

I decided to create a document containing a list of all the small, irrelevant or stupid questions that I have while learning Elixir.

• Why cant I access/set values on Enums with square brackets (eg whatever[x])?

According to Jose Valim, this is by design. The access operation is linear, so you should avoid it if you can.

• How do I activate command line history in IEX?

Suprisingly, there is currently no way to do it. This is a legacy issue with the erlang shell.

• How can I persist the value of a variable? How can I change it if its immutable?

One way is to store it in process. Have a recursive function that stores it and feeds the new value to itself:

def loop(value)
  receive do
    # get or create a new copy the value here, then loop
    loop(new_value)
  end
end

• Is there a way to define an anonymous function with dynamic arity? (ie, arity of N where N is not known at compile time)

You could use a list as arguments. Or you can dynamically create a function with:

:erlang.make_fun(mod, name, arity)

• How do you use the new Logger?

Add :logger to the application list, and then require it in the modules you will use it.

• Is there a process viewer?

Erlang does have one, and it works for elixir too:

:etop.start()