Transduction

Clojure's transducers in Scala.

Inspired by Clojure's implementation (obviously) and this Haskell implementation and theory.

Documentation can be found here.

What are they?

Transducers are applicable objects that transform reducers. If you've ever worked with folding or reduction in a functional language, a reducer is simply a representation of the reduction function used in those functions.

A reducer has three effective signatures:

• Identity: The identity of the reducer. Given when no initial value is used for the reduction. E.g. for integer reducers, 0 is the default identity for addition reductions, and 1 is the default identity for multiplication reductions. (identity: R)
• Completion: The "finaliser" of a reducer. Called upon the result of the reduction as a final transformation. (completion: R => R)
• Step: The actual reduction part of a reducer. Called with the current accumulated reduction and the current item to be reduced. (stepL: R => A => R, stepR: A => R => R)

A transducer adds a layer of transformation onto these reducers, and can be both stateful or stateless. They are also composeable using simple function composition.

This library aims to provide interfaces for creating immutable and mutable state transducers and the ability to use them.