Change inspect string to be runnable

README.md

@@ -15,11 +15,11 @@ CircularBuffer provides a general-purpose circular buffer data structure.
 ```elixir
 # Create a new circular buffer that holds 5 elements
 iex> cb = CircularBuffer.new(5)
-#CircularBuffer<[]>
+CircularBuffer.new([], 5)
 
 # Fill it up
 iex> cb = Enum.into(1..5, cb)
-#CircularBuffer<[1, 2, 3, 4, 5]>
+CircularBuffer.new([1, 2, 3, 4, 5], 5)
 
 # Verify that 1 is the oldest and 5 is the newest element in the buffer
 iex> CircularBuffer.oldest(cb)
@@ -29,7 +29,7 @@ iex> CircularBuffer.newest(cb)
 
 # Add another element. 1 gets pushed out.
 iex> cb = CircularBuffer.insert(cb, 6)
-#CircularBuffer<[2, 3, 4, 5, 6]>
+CircularBuffer.new([2, 3, 4, 5, 6], 5)
 
 # CircularBuffer implements Enumerable so all Enum.* functions work
 iex> Enum.sum(cb)

lib/circular_buffer.ex

@@ -24,7 +24,6 @@ defmodule CircularBuffer do
   like the following works:
 
       iex> cb = Enum.into([1, 2, 3, 4], CircularBuffer.new(3))
-      #CircularBuffer<[2, 3, 4]>
       iex> Enum.map(cb, fn x -> x * 2 end)
       [4, 6, 8]
   """
@@ -48,6 +47,14 @@ defmodule CircularBuffer do
     %CB{a: [], b: [], max_size: size, count: 0}
   end
 
+  @doc """
+  Creates a new circular buffer with a given size and contents
+  """
+  @spec new(Enumerable.t(), non_neg_integer()) :: t()
+  def new(enumerable, size) when is_integer(size) and size >= 0 do
+    Enum.reduce(enumerable, new(size), &insert(&2, &1))
+  end
+
   @doc """
   Inserts a new item into the next location of the circular buffer
   """
@@ -120,6 +127,12 @@ defmodule CircularBuffer do
     cb.count == 0
   end
 
+  @doc """
+  Return the max size of the buffer
+  """
+  @spec max_size(t()) :: non_neg_integer()
+  def max_size(%CB{max_size: max_size}), do: max_size
+
   defimpl Enumerable do
     def count(cb) do
       {:ok, cb.count}
@@ -160,7 +173,13 @@ defmodule CircularBuffer do
     import Inspect.Algebra
 
     def inspect(cb, opts) do
-      concat(["#CircularBuffer<", to_doc(CB.to_list(cb), opts), ">"])
+      concat([
+        "CircularBuffer.new(",
+        to_doc(CB.to_list(cb), opts),
+        ", ",
+        to_doc(CB.max_size(cb), opts),
+        ")"
+      ])
     end
   end
 end

test/circular_buffer_test.exs

@@ -128,9 +128,23 @@ defmodule CircularBufferTest do
     end
   end
 
-  test "can be inspected" do
-    str = inspect(Enum.into([1, 2, 3, 4], CB.new(4)))
-    assert str == "#CircularBuffer<[1, 2, 3, 4]>"
+  property "inspect matches contents" do
+    forall {size, is} <- size_and_list() do
+      buffer = Enum.reduce(is, CB.new(size), fn i, cb -> CB.insert(cb, i) end)
+      {inspected, _} = Code.eval_string(inspect(buffer, limit: :infinity))
+
+      buffer.max_size == inspected.max_size and CB.to_list(inspected) == CB.to_list(buffer)
+    end
+  end
+
+  test "inspecting zero-length buffer" do
+    str = inspect(CB.new(0))
+    assert str == "CircularBuffer.new([], 0)"
+  end
+
+  test "max_size matches created size" do
+    cb = CB.new(15)
+    assert CB.max_size(cb) == 15
   end
 
   test "Enum.slice" do