2016 Update

Task/24-game/Elixir/24-game.elixir

@@ -0,0 +1,39 @@
+defmodule Game24 do
+  def main do
+    IO.puts "24 Game"
+    play
+  end
+
+  defp play do
+    IO.puts "Generating 4 digits..."
+    digts = for _ <- 1..4, do: Enum.random(1..9)
+    IO.puts "Your digits\t#{inspect digts, char_lists: :as_lists}"
+    read_eval(digts)
+    play
+  end
+
+  defp read_eval(digits) do
+    exp = IO.gets("Your expression: ") |> String.strip
+    if exp in ["","q"], do: exit(:normal)        # give up
+    case {correct_nums(exp, digits), eval(exp)} do
+      {:ok, x} when x==24 -> IO.puts "You Win!"
+      {:ok, x} -> IO.puts "You Lose with #{inspect x}!"
+      {err, _} -> IO.puts "The following numbers are wrong: #{inspect err, char_lists: :as_lists}"
+    end
+  end
+
+  defp correct_nums(exp, digits) do
+    nums = String.replace(exp, ~r/\D/, " ") |> String.split |> Enum.map(&String.to_integer &1)
+    if length(nums)==4 and (nums--digits)==[], do: :ok, else: nums
+  end
+
+  defp eval(exp) do
+    try do
+      Code.eval_string(exp) |> elem(0)
+    rescue
+      e -> Exception.message(e)
+    end
+  end
+end
+
+Game24.main