Add support for deref and meta

elixir/lib/mal/reader.ex

@@ -16,6 +16,7 @@ defmodule Mal.Reader do
     Regex.scan(regex, input, capture: :all_but_first)
       |> List.flatten
       |> List.delete_at(-1) # Remove the last match, which is an empty string
+      |> Enum.filter(fn token -> not String.starts_with?(token, ";") end)
   end
 
   def read_form([next | rest] = tokens) do
@@ -26,12 +27,22 @@ defmodule Mal.Reader do
       "`" -> create_quote('quasiquote', rest)
       "~" -> create_quote('unquote', rest)
       "~@" -> create_quote('splice-unquote', rest)
+      "@" -> create_quote('deref', rest)
+      "^" -> create_meta(rest)
+      ")" -> throw({:invalid, "unexpected )"})
       _ ->
         token = read_atom(next)
         {token, rest}
     end
   end
 
+  defp create_meta(tokens) do
+    {meta, meta_rest} = read_form(tokens)
+    {token, rest_tokens} = read_form(meta_rest)
+    new_token = [{:symbol, 'with-meta'}, token, meta]
+    {new_token, rest_tokens}
+  end
+
   defp create_quote(quote_type, tokens) do
     {token, rest_tokens} = read_form(tokens)
     new_token = [{:symbol, quote_type}, token]

elixir/step0_repl.ex

@@ -1,34 +0,0 @@
-defmodule Step0Repl do
-  def main do
-    IO.write(:stdio, "user> ")
-    IO.read(:stdio, :line)
-      |> handle_line
-      
-    main
-  end
-
-  defp handle_line(:eof), do: exit(0)
-  defp handle_line(line) do
-    IO.write(:stdio, read_eval_print(line))
-  end
-
-  def read(input) do
-    input
-  end
-
-  def eval(input) do
-    input
-  end
-
-  def print(input) do
-    input
-  end
-
-  def read_eval_print(line) do
-    read(line)
-      |> eval
-      |> print
-  end
-end
-
-Step0Repl.main