It's true that you can create custom guards, but they are still very limited, and they can only be made of a small list of allowed expressions [0]. [0]: https:

It's true that you can create custom guards, but they are still very limited, and they can only be made of a small list of allowed expressions [0]. [0]: https://hexdocs.pm/elixir/1.6.6/guards.html#list-of-allowed-expressions https://hexdocs.pm/elixir/1.6.6/guards.html#list-of-allowed-...