The Accessor library makes it nicer to work with nested functional data
structures.
An accessor is a value that understands how to reach data within a larger data structure, independently from what you intend to do with it. Accessors allow you to read and write data and perform possibly-monadic traversals. By composing accessors, you can work with increasingly complex data structures.
In case you have ever heard of “lenses”, this is an OCaml implementation of that idea.
See the tutorial for more information.