Past Meetup

Laws for Folds and Theorems for Free + The Aeson JSON Parser

This Meetup is past

33 people went


Please be sure to make it before 18:00 else you'll be locked in the foyer. Call Ben on 0488145427 if you get stuck. :)

The Aeson JSON Parser by Fraser Tweedale

JSON is everywhere. Developers often need to work with JSON serialisations of nonstandard data types, and aeson makes it fast and easy to do this in Haskell.

Fraser will introduce aeson and demonstrate basic use before recounting his experiences using aeson in a web crypto library. The talk will wrap with an overview of aeson's advanced features and a comparison with some other JSON libraries.

A basic understanding of types and typeclasses in Haskell or similar languages is assumed.

Fraser drank the FP Flavor Aid. His day job is Ruby and Javascript but functional code keeps creeping in and he considers this a Good Thing.

Laws for Folds and Theorems for Free by David Laing

The laws associated with typeclasses are often expressing information that the type system cannot. There are also many laws that come directly from the types of various functions.

We'll look at the fold fusion law, which we'll derive, and the laws that arise from it. This talk will cover those laws and an example of using them to transform a small program to improve the performance of a program while preserving the semantics.

We'll also look at natural transformations, which describe relationships between functors, and "free theorems", which can be derived solely from the types of polymorphic functions.