An API for construction of free-form strategies of access and manipulation of
elements of arbitrary data structures. It allows to implement efficient
composite patterns, e.g., a simultaneous update and lookup of an element, and
even more complex things.
Strategies are meant to be interpreted by the host data structure libraries.
Thus they allow to implement all access and modification patterns of a data
structure with just a single function, which interprets strategies.
This library provides pure and monadic interfaces, so it supports both
immutable and mutable data structures.