Extract history management in its own module

Author: alco

lib/iex/lib/iex/helpers.ex

@@ -76,19 +76,6 @@ defmodule IEx.Helpers do
     end
   end
 
-  @doc """
-  Prints the history of expressions evaluated during the session along with
-  their results.
-  """
-  def v do
-    history = :queue.to_list(Process.get(:iex_history))
-    Enum.each(history, print_history(&1))
-  end
-
-  defp print_history(config) do
-    IO.puts IEx.color(:info, "#{config.counter}: #{config.cache}#=> #{inspect config.result}\n")
-  end
-
   @doc """
   Prints the documentation for `IEx.Helpers`.
   """
@@ -218,49 +205,26 @@ defmodule IEx.Helpers do
   end
 
   @doc """
-  Retrieves nth expression's value from the history.
-
-  Use negative values to lookup expression values relative to the current one.
-  For instance, v(-1) returns the result of the last evaluated expression.
+  Prints the history of expressions evaluated during the session along with
+  their results.
   """
-  def v(n) when n < 0 do
-    history = Process.get(:iex_history)
-    queue_nth_r(history, abs(n) - 1, :queue.len(history)).result
-  end
-
-  def v(n) when n > 0 do
-    history = Process.get(:iex_history)
-    queue_nth(history, n - 1, :queue.len(history)).result
-  end
-
-  defp queue_nth(_, _, 0) do
-    raise_bounds
-  end
-
-  defp queue_nth(queue, 0, _) do
-    { :value, value } = :queue.peek(queue)
-    value
-  end
-
-  defp queue_nth(queue, n, len) when n > 0 do
-    queue_nth(:queue.drop(queue), n-1, len-1)
-  end
-
-  defp queue_nth_r(_, _, 0) do
-    raise_bounds
+  def v do
+    IEx.History.each(print_history_entry(&1))
   end
 
-  defp queue_nth_r(queue, 0, _) do
-    { :value, value } = :queue.peek_r(queue)
-    value
+  defp print_history_entry(config) do
+    IO.write IEx.color(:info, "#{config.counter}: #{config.cache}#=> ")
+    IO.puts  IEx.color(:eval_result, "#{inspect config.result}\n")
   end
 
-  defp queue_nth_r(queue, n, len) when n > 0 do
-    queue_nth(:queue.drop_r(queue), n-1, len-1)
-  end
+  @doc """
+  Retrieves nth expression's value from the history.
 
-  defp raise_bounds do
-    raise "Out of bounds"
+  Use negative values to lookup expression values relative to the current one.
+  For instance, v(-1) returns the result of the last evaluated expression.
+  """
+  def v(n) do
+    IEx.History.nth(n).result
   end
 
   @doc """

lib/iex/lib/iex/history.ex

@@ -0,0 +1,99 @@
+defmodule IEx.History do
+
+  def init do
+    Process.put :iex_history, :queue.new
+  end
+
+  ### append ###
+
+  def append(entry) do
+    history = Process.get(:iex_history)
+    len = :queue.len(history)
+    limit = IEx.Options.get(:history_size)
+
+    new_history =
+      :queue.in(entry, history)
+      |> limit_history(len + 1, limit)
+    Process.put(:iex_history, new_history)
+  end
+
+  defp limit_history(_, _, 0) do
+    :queue.new
+  end
+
+  defp limit_history(queue, _, limit) when limit < 0 do
+    queue
+  end
+
+  defp limit_history(queue, len, limit) when len > limit do
+    # FIXME: check if the result we're removing had any binaries in it and
+    # garbage collect them
+    limit_history(:queue.drop(queue), len-1, limit)
+  end
+
+  defp limit_history(queue, _, _) do
+    queue
+  end
+
+  ### each ###
+
+  def each(fun) do
+    history = Process.get(:iex_history)
+    each(history, fun)
+  end
+
+  defp each(queue, fun) do
+    case :queue.out(queue) do
+      { { :value, val }, tail } ->
+        fun.(val)
+        each(tail, fun)
+
+      { :empty, _ } -> :ok
+    end
+  end
+
+  ### nth ###
+
+  def nth(n) do
+    history = Process.get(:iex_history)
+    len = :queue.len(history)
+    case n do
+      n when n > 0 ->
+        queue_nth(history, n - 1, len)
+      n when n < 0 ->
+        queue_nth_r(history, -n - 1, len)
+      0 ->
+        raise ArgumentError[]
+    end
+  end
+
+  defp queue_nth(_, _, 0) do
+    raise_bounds
+  end
+
+  defp queue_nth(queue, 0, _) do
+    { :value, value } = :queue.peek(queue)
+    value
+  end
+
+  defp queue_nth(queue, n, len) when n > 0 do
+    queue_nth(:queue.drop(queue), n-1, len-1)
+  end
+
+  defp queue_nth_r(_, _, 0) do
+    raise_bounds
+  end
+
+  defp queue_nth_r(queue, 0, _) do
+    { :value, value } = :queue.peek_r(queue)
+    value
+  end
+
+  defp queue_nth_r(queue, n, len) when n > 0 do
+    queue_nth_r(:queue.drop_r(queue), n-1, len-1)
+  end
+
+  defp raise_bounds do
+    raise "Out of bounds"
+  end
+end

lib/iex/lib/iex/server.ex

@@ -11,7 +11,7 @@ defmodule IEx.Server do
 
   """
   def start(config) do
-    Process.put :iex_history, :queue.new
+    IEx.History.init
 
     { _, _, scope } = :elixir.eval('require IEx.Helpers', [], 0, config.scope)
     config = config.scope(scope)
@@ -136,29 +136,7 @@ defmodule IEx.Server do
   end
 
   defp update_history(config) do
-    limit = IEx.Options.get(:history_size)
-    history = Process.get(:iex_history)
-    len = :queue.len(history)
-    new_history =
-      :queue.in(config, history)
-      |> limit_history(len + 1, limit)
-    Process.put(:iex_history, new_history)
-  end
-
-  defp limit_history(_, _, 0) do
-    :queue.new
-  end
-
-  defp limit_history(queue, _, limit) when limit < 0 do
-    queue
-  end
-
-  defp limit_history(queue, len, limit) when len > limit do
-    limit_history(:queue.drop(queue), len-1, limit)
-  end
-
-  defp limit_history(queue, _, _) do
-    queue
+    IEx.History.append(config)
   end
 
   defp io_get(config) do