Jonfk

What I learned from Functional Programming Principles

23 Feb 2015

Functional Programming Principles is a course taught at Ecole polytechnique fédérale de lausanne and on coursera by Prof. Martin Odersky.

I originally took the class to get familiar with scala before tackling the more interesting class by Martin ‘Principles of Reactive Programming’ which is about asynchronous computation and distributed computation. I had already had an intro to functional programming through SML in the COMP302 class taught at McGill by the brilliant Prof. Brigitte Pientka.

The class starts with a model of evaluation for functional programming that is a useful mental model of how to think about functional programs. It is interesting to note that SICP does a similar introduction to programming which I think is better than the usual hello world program many intro cs classes start with.

The rest of the class is about functional programming in scala and the various data structures available in the extensive scala standard library, such as lists, sets, maps and streams. The type hierarchy of the collections library is as follows:

+--Iterable
   +--Seq
      +--IndexedSeq
         +--Vector
         +--(Array)  Imported from java does not subclass IndexSeq but
         +--(String) Use wrappers to behave like IndexedSeq
      +--LinearSeq
         +--List
   +--Set
   +--Map

Martin also when through some inductive proofs on properties of lists and trees. He also showed how for-expressions can be mapped to map and flatMap and can be more readable in many situations. The course ended with how to operate on lazy collections such as streams.

I liked the course overall as it was a good refresher on functional programming as well and a way to gain familiarity to Scala which is probably a factor for why Scala is gaining popularity in some circles. Scala is an interesting language which mixes object oriented programming with functional programming in a way that feels very natural.

You can see my notes on the course at : Link