Fix bug in prefix's enumerable implementation.

lib/enumerable/ip/prefix.ex

@@ -43,7 +43,7 @@ defimpl Enumerable, for: IP.Prefix do
       iex> ~i(192.0.2.128/29)
       ...> |> Stream.filter(fn a -> rem(IP.Address.to_integer(a), 2) == 0 end)
       ...> |> Enum.map(fn a -> IP.Address.to_string(a) end)
-      ["192.0.2.130", "192.0.2.132", "192.0.2.134"]
+      ["192.0.2.128", "192.0.2.130", "192.0.2.132", "192.0.2.134"]
   """
   @spec reduce(Prefix.t(), Enumerable.acc(), Enumerable.reducer()) :: Enumerable.result()
   def reduce(_, {:halt, acc}, _fun), do: {:halted, acc}
@@ -75,9 +75,10 @@ defimpl Enumerable, for: IP.Prefix do
         {:done, acc}
 
       pos ->
-        pos = pos + 1
         next = Address.from_integer!(pos, version)
-        reduce({prefix, pos, last}, fun.(next, acc), fun)
+        reduce({prefix, pos + 1, last}, fun.(next, acc), fun)
     end
   end
+
+  def slice(_), do: {:error, __MODULE__}
 end

test/enumerable/ip/prefix_test.exs

@@ -2,4 +2,9 @@ defmodule EnumerableIPPrefixTest do
   use ExUnit.Case
   import IP.Sigil
   doctest Enumerable.IP.Prefix
+
+  # Regression: https://gitlab.com/jimsy/ip/issues/1
+  test "correctly returns the first address in the range" do
+    assert Enum.take(~i(10.10.10.0/24), 1) == [~i(10.10.10.0)]
+  end
 end