Monthly Downloads: 235
Programming language: Elixir
License: BSD 2-clause "Simplified" License
Tags: Macros    
Latest version: v0.2.1

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Fast. Really fast.

What is Pathex?

Pathex is a library for performing fast actions with nested data structures in Elixir. With pathex you can trivially set, get and update values in structures. It provides all necessary logic to manipulate data structures in different ways

Why another library?

Existing methods of accesssing data in nested structures are either slow (Focus for example) or do not provide much functionality (put_in or get_in for example). For example setting the value in structure with Pathex is 5-10x faster than Focus or 2x faster than put_in

You can checkout benchmarks at https://github.com/hissssst/pathex_bench

Complete documentation

You can find complete documentation with examples, howto's, guides as https://hexdocs.pm/pathex


def deps do
    {:pathex, "~> 1.0.0"}


  1. You need to import and require Pathex since it's manly operates macros require Pathex import Pathex, only: [path: 1, path: 2, "~>": 2]

Note: There is no __using__/2 macro since it's better to explicitly define what macros will be exported

  1. You need to create the path which defines the path to the item in elixir structure you want to get:

    path_to_strees = path :user / :private / :addresses / 0 / :street
    path_in_json = ~P"users/1/street"json

    This creates closure with fn which can get, set and update values in this path

  2. Use the path!

    {:ok, "6th avenue" = street} =
      user: %{
        id: 1,
        name: "hissssst",
        private: %{
          phone: "123-456-789",
          addresses: [
             [city: "City", street: "6th avenue", mail_index: 123456]
    |> Pathex.view(path_to_streets)
    "users" => %{
    "1" => %{"street" => "6th avenue"}
    } = Pathex.force_set!(%{}, path_in_json, street)


  1. Paths are really a set of pattern-matching cases. This is done to extract maximum efficency from BEAM's pattern-matching compiler elixir # code for viewing variables for path iex> path 1 / "y" # almost equals to case do %{1 => x} -> case x do %{"y" => res} -> {:ok, res} _ -> :error end [_, x | _] -> case x do %{"y" => res} -> {:ok, res} _ -> :error end t when is_tuple(t) and tuple_size(t) > 1 -> case x do %{"y" => res} -> {:ok, res} _ -> :error end end
  2. Paths for special specifications can be created with sigils elixir iex> mypath = ~P[user/name/firstname]json iex> Pathex.over(%{"user" => %{"name" => %{"firstname" => "hissssst"}}}, mypath, &String.capitalize/1) {:ok, %{"user" => %{"name" => %{"firstname" => "Hissssst"}}}} elixir iex> mypath = ~P[:hey/"hey"]naive iex> Pathex.set([hey: %{"hey" => 1}], mypath, 2) {:ok, [hey: %{"hey" => 2}]}
  3. You can use variables inside paths elixir iex> index = 1 iex> mypath = path :name / index iex> Pathex.view %{name: {"Linus", "Torvalds"}}, mypath {:ok, "Torvalds"} iex> index = 0 # Note that captured variables can not be overriden iex> Pathex.view %{name: {"Linus", "Torvalds"}}, mypath {:ok, "Torvalds"}
  4. You can create composition of lenses elixir iex> path1 = path :user iex> path2 = path :phones / 1 iex> composed_path = path1 ~> path2 iex> Pathex.view %{user: %{phones: ["123-456-789", "987-654-321", "000-111-222"]}}, composed_path {:ok, "987-654-321"}
  5. Paths can be applied to different types of structures elixir iex> user_path = path :user iex> Pathex.view %{user: "hissssst"}, user_path {:ok, "hissssst"} iex> Pathex.view [user: "hissssst"], user_path {:ok, "hissssst"}

No Magic

Pathex paths are just closures created with fn. Any path or ~P is a macro for creating a closure. Pathex.view/2, Pathex.set/3, Pathex.over/3 and etc are just macros for calling these closures. Pathex.~>/2 is a simple macro which creates composition of two closures



  • If you have any suggestions or wan't to change something in this library don't hesitate to open an issue
  • If you have any whitepapers about functional lenses, you can add them in a PR to the bottom of this readme