Elixir: How to test multiple values in case condition?

Question

Is there a shorter way to write this:

case testvalue do   200 ->     true   404 ->     true   _ ->     false end 

It returns true for 200 or 404 and false for everything else. It would be nice to write it with an OR condition but this leads to an error:

case testvalue do   200 || 400 ->     true   _ ->     false end 

Answer 1

There's no direct syntax for or in the middle of patterns but you can use a guard:

case testvalue do   n when n in [200, 400] ->     true   _ ->     false end 

You can also use or in guards. This will work too but is more verbose:

case testvalue do   n when n == 200 or n == 400 ->     true   _ ->     false end 

Both will run equally fast as in inside guards is converted into comparisons + or, as mentioned in the docs.

Answer 2

From my experience, it makes more sense in elixir to handle the cases with functions / pattern matching, it's more readable when your code base grows.

I would do something like that:

defp valid_http_response?(200), do: true defp valid_http_response?(400), do: true defp valid_http_response?(_), do: false 

I agree it doesn't really make sense now, but in the future you will be happier :)