Abstract

The category-theoretic concept of a monad is applied widely as a design pattern for functional programs involving effects. The utility and ubiquity of monads is such that some languages provide syntax to simplify use of this pattern. Comonads, the dual of monads, can be similarly used as a design pattern in functional programming, yet remain relatively under-utilised compared with monads. There are several useful examples of comonads but a lack of syntactic sugar prevents wider adoption and indeed further understanding of comonads as an abstraction mechanism. We propose a lightweight syntax for programming with comonads in Haskell, analogous to the do-notation for monads, accompanied by examples of comonads in the notation.

This is a practise talk for IFL ‘12. Joint work with Alan Mycroft.