Proof-of-concept of an Elixir construct like `case` but that matches strings against regexps. #elixirlang

regex_case.exs

defmodule RegexCase do
  defmacro regex_case(string, do: lines) do
    new_lines = Enum.map lines, fn ({:->, context, [[regex], result]}) ->
      condition = quote do: String.match?(unquote(string), unquote(regex))
      {:->, context, [[condition], result]}
    end

    # Base case if nothing matches; "cond" complains otherwise.
    base_case = quote do: (true -> nil)
    new_lines = new_lines ++ base_case

    quote do
      cond do
        unquote(new_lines)
      end
    end
  end
end

defmodule Run do
  import RegexCase

  def run do
    regex_case "hello" do
      ~r/x/ -> IO.puts("matches x")
      ~r/e/ -> IO.puts("matches e")
      ~r/y/ -> IO.puts("matches y")
    end
  end
end

Run.run

A third idea is to just keep the current code and use an empty regex as the base case, since it will match any string:

regex_case "hello" do
  ~r/x/ -> IO.puts("matches x")
  ~r// -> IO.puts("no match")
end

This one won't work if you're expecting non-string input.

Awesome the second example with provide the true is a nicer syntax! thank you Henrik