Extending haskell with effectful property abstraction

Functional programming paradigm can be used to build high-level software, especially when combined with a strong type system, like in Haskell. Functions are first-order values in functional languages. Haskell's Lens type generalizes properties (i.e. accessors/mutators) found in other programming languages. However the structure of Lens type prevents using lenses for data that can be accessed with side-effects. Examples of such data are synchronized properties, file content or remote data. This paper presents an alternative data type for property abstraction, called Reference that can be used in these cases.