Implement Collectable protocol

Author: keathley

lib/circular_buffer.ex

@@ -90,4 +90,16 @@ defmodule CircularBuffer do
       {:ok, cb.count, &Enumerable.List.slice(CB.to_list(cb), &1, &2)}
     end
   end
+
+  defimpl Collectable do
+    def into(original) do
+      collector_fn = fn
+        cb, {:cont, elem} -> CB.insert(cb, elem)
+        cb, :done -> cb
+        _cb, :halt -> :ok
+      end
+
+      {original, collector_fn}
+    end
+  end
 end

test/circular_buffer_test.exs

@@ -49,6 +49,14 @@ defmodule CircularBufferTest do
     end
   end
 
+  property "can be collected" do
+    forall {size, is} <- size_and_list() do
+      buffer = Enum.reduce(is, CB.new(size), fn i, cb -> CB.insert(cb, i) end)
+
+      Enum.into(is, CB.new(size)) == buffer
+    end
+  end
+
   property "the number of elements never exceeds the size of the buffer" do
     forall {size, is} <- size_and_list() do
       buffer = Enum.reduce(is, CB.new(size), fn i, cb -> CB.insert(cb, i) end)