guards.ex

# Not recommended: macros
defmodule Account.Guards do
  defmacro is_private(first_name, email) do
    quote do
      not(is_nil(unquote(first_name))) and
      not(unquote(email) == unquote(first_name))
    end
  end
end

# Recommended: defguard
defmodule Account.Guards do
  defguard is_private(first_name, email) when not(is_nil(first_name)) and not(email == first_name)
end