Path

This page describes what a Pathex.t() is and how to create and use one

Note:

This is documentation about inner Pathex API and subject to change

You shouldn't read this unless you are interested in Pathex internals or want to hack into Pathex

Basic

• Create: As described in README and Pathex simple paths can be created with Pathex.path/2 and Pathex.sigil_P/2 macros

• Use: This paths then can be called using macro-helpers from Pathex like Pathex.view/2 or Pathex.force_set/3

• Prebuilt: some non-trivial prebuilt lenses are avaliable in Pathex.Lenses module

Internal representation

Every path-closure is a closure of two arguments:

• Operation name (atom)
• Operation arguments, tuple which size depends on an operation

Currently every path-closure has 3 operations:

path_closure =
  fn
    # Operation which gets value from structure and retuns `function.(value)`
    :view,         {structure, function} -> ...

    # Operation which returns new structure with updated value
    :update,       {structure, function} -> ...

    # Operation which returns new structure with updated value, or default set
    :force_update, {structure, function, default} -> ...
  end

Path-closure requirements

• Path-closure must return {:ok, any()} | :error for every valid operation call and raise if non-exsisting operation is called

• Path-closures created by Pathex.path/2 or Pathex.sigil_P/2 are totally pure functions with no side effects

• Function passed as second element in tuple must return {:ok, term()} | :error or throw :path_not_found