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
