Freezing, thawing, and copy elision.
This library provides a class for types which present the same underlying data in both an immutable (frozen) as well as a mutable (thawed) form, and various functions to manipulate them. Some of the functions allow for copy elision.
Instances are provided for the array types from the primitive, array, and vector packages, but this is mainly for completeness: there is nothing these instances do which vector doesn't already do better. The main purpose, rather, is to assist new types, for instance types whose implementation relies on destructive-update foreign imports, and cases when writing a full stream fusion framework isn't practical.
There are three modules:
- Data.PhaseChange
This module exports the class without its methods, together with functions which guarantee referential transparency (provided that instances are well-behaved). This is the module you should normally import to work with PhaseChangeable data.
- Data.PhaseChange.Unsafe
This module exports functions which can break referential transparency if they are used improperly. Be careful.
- Data.PhaseChange.Impl
This module exports the class along with its methods. Import it if you want to define a new instance.