diff --git a/_build/test/lib/list_ops/.compile.elixir b/_build/test/lib/list_ops/.compile.elixir
index 25c25af..3eb5246 100644
--- a/_build/test/lib/list_ops/.compile.elixir
+++ b/_build/test/lib/list_ops/.compile.elixir
@@ -2,4 +2,5 @@ v2.
 {<<"_build/test/lib/list_ops/ebin/Elixir.ListOps.beam">>,'Elixir.ListOps',
  module,<<"lib/list_ops.ex">>,
  ['Elixir.Kernel'],
- [],[],nil}.
+ [erlang],
+ [],nil}.
diff --git a/_build/test/lib/list_ops/ebin/Elixir.ListOps.beam b/_build/test/lib/list_ops/ebin/Elixir.ListOps.beam
index 7f8520c..06c4055 100644
Binary files a/_build/test/lib/list_ops/ebin/Elixir.ListOps.beam and b/_build/test/lib/list_ops/ebin/Elixir.ListOps.beam differ
diff --git a/lib/list_ops.ex b/lib/list_ops.ex
index 3010084..de5e0b1 100644
--- a/lib/list_ops.ex
+++ b/lib/list_ops.ex
@@ -1,2 +1,54 @@
 defmodule ListOps do
+
+  def count(list), do: do_count(list, 0)
+
+  def do_count([head|tail], count), do: do_count(tail, count + 1)
+  def do_count([], count), do: count
+
+
+  def reverse(list), do: do_reverse(list, [])
+
+  def do_reverse([head|tail], result), do: do_reverse(tail, [head|result])
+  def do_reverse([], result), do: result
+
+
+  def map(list, function), do: do_map(list, function, [])
+
+  def do_map([head|tail], function, result), do: do_map(tail, function, [function.(head)|result])
+  def do_map([], _, result), do: reverse(result)
+
+
+  def filter(list, function), do: do_filter(list, function, [])
+
+  def do_filter([head|tail], function, result) do
+    if function.(head) do
+      do_filter(tail, function, [head|result])
+    else
+      do_filter(tail, function, result)
+    end
+  end
+  def do_filter([], _function, result), do: reverse(result)
+
+
+  def reduce(list, initial, function), do: do_reduce(list, initial, function)
+
+  def do_reduce([head|tail], memo, function), do: do_reduce(tail, function.(head,memo), function)
+  def do_reduce([], memo, _function), do: memo
+
+
+  def append(list1, list2), do: do_append(list1, list2, [])
+
+  def do_append([head|tail], list2, result), do: do_append(tail, list2, [head|result])
+  def do_append([], [head|tail], result), do: do_append([], tail, [head|result])
+  def do_append([], [], result), do: reverse(result)
+
+
+  def concat(lists), do: do_concat(lists, [])
+
+  def do_concat([[head|tail]|tail2], result), do: do_concat([tail|tail2], [head|result])
+  def do_concat([[],[head|tail]|tail2], result), do: do_concat([tail|tail2], [head|result])
+  def do_concat([[]|tail2], result), do: do_concat(tail2, result)
+  def do_concat([], result), do: reverse(result)
+
+
 end
diff --git a/test/list_ops_test.exs b/test/list_ops_test.exs
index 99f06ff..db343fa 100644
--- a/test/list_ops_test.exs
+++ b/test/list_ops_test.exs
@@ -27,85 +27,85 @@ defmodule ListOpsTest do
     assert ListOps.reverse(Enum.to_list(1..1_000_000)) == Enum.to_list(1_000_000..1)
   end
 
-  # test "map of empty list" do
-  #   assert ListOps.map([], &(&1+1)) == []
-  # end
-  #
-  # test "map of normal list" do
-  #   assert ListOps.map([1,3,5,7], &(&1+1)) == [2,4,6,8]
-  # end
-  #
-  # test "map of huge list" do
-  #   assert ListOps.map(Enum.to_list(1..1_000_000), &(&1+1)) ==
-  #     Enum.to_list(2..1_000_001)
-  # end
-  #
-  # test "filter of empty list" do
-  #   assert ListOps.filter([], &odd?/1) == []
-  # end
-  #
-  # test "filter of normal list" do
-  #   assert ListOps.filter([1,2,3,4], &odd?/1) == [1,3]
-  # end
-  #
-  # test "filter of huge list" do
-  #   assert ListOps.filter(Enum.to_list(1..1_000_000), &odd?/1) ==
-  #     Enum.map(1..500_000, &(&1*2-1))
-  # end
-  #
-  # test "reduce of empty list" do
-  #   assert ListOps.reduce([], 0, &(&1+&2)) == 0
-  # end
-  #
-  # test "reduce of normal list" do
-  #   assert ListOps.reduce([1,2,3,4], -3, &(&1+&2)) == 7
-  # end
-  #
-  # test "reduce of huge list" do
-  #   assert ListOps.reduce(Enum.to_list(1..1_000_000), 0, &(&1+&2)) ==
-  #     Enum.reduce(1..1_000_000, 0, &(&1+&2))
-  # end
-  #
-  # test "reduce with non-commutative function" do
-  #   assert ListOps.reduce([1,2,3,4], 10, fn x, acc -> acc - x end) == 0
-  # end
-  #
-  # test "append of empty lists" do
-  #   assert ListOps.append([], []) == []
-  # end
-  #
-  # test "append of empty and non-empty list" do
-  #   assert ListOps.append([], [1,2,3,4]) == [1,2,3,4]
-  # end
-  #
-  # test "append of non-empty and empty list" do
-  #   assert ListOps.append([1,2,3,4], []) == [1,2,3,4]
-  # end
-  #
-  # test "append of non-empty lists" do
-  #   assert ListOps.append([1,2,3], [4,5]) == [1,2,3,4,5]
-  # end
-  #
-  # test "append of huge lists" do
-  #   assert ListOps.append(Enum.to_list(1..1_000_000), Enum.to_list(1_000_001..2_000_000)) ==
-  #     Enum.to_list(1..2_000_000)
-  # end
-  #
-  # test "concat of empty list of lists" do
-  #   assert ListOps.concat([]) == []
-  # end
-  #
-  # test "concat of normal list of lists" do
-  #   assert ListOps.concat([[1,2],[3],[],[4,5,6]]) == [1,2,3,4,5,6]
-  # end
-  #
-  # test "concat of huge list of small lists" do
-  #   assert ListOps.concat(Enum.map(1..1_000_000, &[&1])) ==
-  #     Enum.to_list(1..1_000_000)
-  # end
-  #
-  # test "concat of small list of huge lists" do
-  #   assert ListOps.concat(Enum.map(0..9, &Enum.to_list((&1*100_000+1)..((&1+1)*100_000)))) ==
-  #     Enum.to_list(1..1_000_000)
-  # end
+   test "map of empty list" do
+     assert ListOps.map([], &(&1+1)) == []
+   end
+
+   test "map of normal list" do
+     assert ListOps.map([1,3,5,7], &(&1+1)) == [2,4,6,8]
+   end
+
+   test "map of huge list" do
+     assert ListOps.map(Enum.to_list(1..1_000_000), &(&1+1)) ==
+       Enum.to_list(2..1_000_001)
+   end
+
+   test "filter of empty list" do
+     assert ListOps.filter([], &odd?/1) == []
+   end
+
+   test "filter of normal list" do
+     assert ListOps.filter([1,2,3,4], &odd?/1) == [1,3]
+   end
+
+   test "filter of huge list" do
+     assert ListOps.filter(Enum.to_list(1..1_000_000), &odd?/1) ==
+       Enum.map(1..500_000, &(&1*2-1))
+   end
+
+   test "reduce of empty list" do
+     assert ListOps.reduce([], 0, &(&1+&2)) == 0
+   end
+
+   test "reduce of normal list" do
+     assert ListOps.reduce([1,2,3,4], -3, &(&1+&2)) == 7
+   end
+
+   test "reduce of huge list" do
+     assert ListOps.reduce(Enum.to_list(1..1_000_000), 0, &(&1+&2)) ==
+       Enum.reduce(1..1_000_000, 0, &(&1+&2))
+   end
+
+   test "reduce with non-commutative function" do
+     assert ListOps.reduce([1,2,3,4], 10, fn x, acc -> acc - x end) == 0
+   end
+
+   test "append of empty lists" do
+     assert ListOps.append([], []) == []
+   end
+
+   test "append of empty and non-empty list" do
+     assert ListOps.append([], [1,2,3,4]) == [1,2,3,4]
+   end
+
+   test "append of non-empty and empty list" do
+     assert ListOps.append([1,2,3,4], []) == [1,2,3,4]
+   end
+
+   test "append of non-empty lists" do
+     assert ListOps.append([1,2,3], [4,5]) == [1,2,3,4,5]
+   end
+
+   test "append of huge lists" do
+     assert ListOps.append(Enum.to_list(1..1_000_000), Enum.to_list(1_000_001..2_000_000)) ==
+       Enum.to_list(1..2_000_000)
+   end
+
+   test "concat of empty list of lists" do
+     assert ListOps.concat([]) == []
+   end
+
+   test "concat of normal list of lists" do
+     assert ListOps.concat([[1,2],[3],[],[4,5,6]]) == [1,2,3,4,5,6]
+   end
+
+   test "concat of huge list of small lists" do
+     assert ListOps.concat(Enum.map(1..1_000_000, &[&1])) ==
+       Enum.to_list(1..1_000_000)
+   end
+
+   test "concat of small list of huge lists" do
+     assert ListOps.concat(Enum.map(0..9, &Enum.to_list((&1*100_000+1)..((&1+1)*100_000)))) ==
+       Enum.to_list(1..1_000_000)
+   end
 end