Zippy is an implementation of the Zippers erlang data structure by Fred Hebert. Its three modules implement three different kind of zippers:

• Zipper lists
• Zipper binary trees
• Zipper forests

It differs from the original library in:

• When returning an {:ok, value} tuple in case of success, functions will also return a {:error, nil} in case of failure.
• All :undefined atoms have been replaced by nil, which I find more idiomatic.
• Idiomatic function names (if_leaf ➜ leaf?) when needed.
• Functions’ first argument is the data structure, which allows chaining operations on it with the |> operator.