Recursion is used extensively in functional programming. It is indeed iteration through nested data structures. Therefore patterns are identified to generalise the nested structure iteration. Using these patterns can factor out the recursion mechanism from application specific logic for code simplicity. That's the purpose of recursion scheme.

This talk points out different recursion problems are having similar patterns. The recursion scheme is introduced to support these patterns. It will discuss how the common iteration mechanics is separated from the application specific logic by using the patterns, aka morphisms, provided by the recursion scheme. The fundamental pattern, catamorphism, and a few other commonly-used morphisms will be illustrated with some recursion examples.

The aim of the talk is to give audience an idea of how recursion can be implemented in simple and elegant ways by applying the various morphisms provided by the recursion schemes.

My team works on Atlassian Marketplace, a project which started 10 years ago and uses Scala, Haskell and Nix. The Marketplace code uses concepts such as applicative functors, monad transformers and lenses. People joining the team mostly learned concepts as they needed to, through experimentation and asking questions.

Last year we started hosting functional programming classes for more fundamental and broad understanding. We've been using the Data61 (formerly NICTA) Functional Programming Course with a lot of success. This talk will describe how we teach FP, what we've learned about teaching FP and the challenges we face.