Great project and documentation!

This project is really great, and it’s gonna be a dependency for all of my future projects. I’m only worried that I might end up over using it. I kind of wish there was something like this in the standard library since nested data structures are so pervasive. And I really like the fact that you can throw maps, keyword list, and tuples, nested any which way without worrying about it.
In other words, thank you!

The difference between matching and filtering is that
matching accepts pattern as a predicate. For example

iex> admin_lens = matching(%{role: :admin})
iex> Pathex.view(%User{name: "emoragaf", role: :admin}, admin_lens ~> path(:name))
{:ok, "emoragaf"}
iex> Pathex.view(%User{name: "hissssst", role: nil}, admin_lens ~> path(:name))
:error

will work only with values, which match the pattern %{role: :admin}.

And filtering lens supports any predicate as a function passed into it. For example,

iex> admin_lens = filtering(fn user -> user.role == :admin end)
iex> Pathex.view(%User{name: "emoragaf", role: :admin}, admin_lens ~> path(:name))
{:ok, "emoragaf"}
iex> Pathex.view(%User{name: "hissssst", role: nil}, admin_lens ~> path(:name))
:error

This lens does essentially the same as a matching lens above.

As you can see, every lens created with matching can be expressed with filtering, but matchingis easier to write, read and a is little bit faster than filtering