Add Qex.len(), forwarding to :queue.len(), Retu{=> r}n typo

lib/qex.ex

@@ -42,7 +42,7 @@
   @spec new([term] | Range.t()) :: t
   def new(init_data \\ [])
 
   def new(x..y) do
     %__MODULE__{data: :queue.from_list(Enum.to_list(x..y))}
   end
 
@@ -193,7 +193,7 @@
   end
 
   @doc """
-  Retun the first item in the queue, raise if it's empty
+  Return the first item in the queue, raise if it's empty
 
       iex> q1 = Qex.new 1..3
       iex> Qex.first!(q1)
@@ -224,7 +224,7 @@
   end
 
   @doc """
-  Retun the last item in the queue, raise if it's empty
+  Return the last item in the queue, raise if it's empty
 
       iex> q1 = Qex.new 1..3
       iex> Qex.last!(q1)
@@ -237,4 +237,17 @@
       :empty -> raise "Queue is empty"
     end
   end
+
+  @doc """
+  Return the number of elements in the queue.
+  This operation takes linear time.
+
+      iex> q1 = Qex.new 1..3
+      iex> Qex.len(q1)
+      3
+  """
+  @spec len(t) :: non_neg_integer
+  def len(%__MODULE__{data: q}) do
+    :queue.len(q)
+  end
 end