Musings about FP and CS

A log of my journey through FP and CS

Intro to functional programming

by Clément Delafargue on October 25, 2012

Tagged as: fp, teaching.

I’ve been faced with an interesting challenge: teach Functional Programming to last year students at Centrale Nantes.

Some context

The students did not have any background in FP, even though they have a strong level in math after two years of preparatory classes.

Most of them have only seen C and Java.

I got a two hour window to make them discover FP.


I’ve found it a bit difficult to design this course. Should I show them just a functional language and let them infer functional programming from it ? Should I talk about more abstract notions and stay closer to the essence of FP ? I chose to stand in middle ground, and split the presentation in two parts: the first part would be about fundamental notions about FP, the other part would be the presentation of a functional language and a quick problem-solving session with it.


I began by describing different programming paradigms and insisted on the declarative nature of FP. I then proceeded on explaining a few key characteristics of FP (immutability, recursion, limited side effects).

I also chose to mention quickly the Curry-Howard isomorphism to show the deep relation between proofs and programs. I did not have the time to elaborate on type systems, though.

After having explained the fundamental parts, I went on with Haskell. Chosing Haskell over other functional languages was easy, it’s the purest yet practical language I know of. I could also have used SML, but I have a poor knowledge of it.

I began by running quickly over Haskell’s syntax. I could have insisted a bit more on pattern matching.

During the rest of the session, I solved small problems on the whiteboard to show students the functional problem-solving mindset. A few of them were quite active and got it quite fast.

I had a few minutes left, so I decided to quickly show them some category theory constructs and how it enabled them to take great advantage from simple abstractions. Thanks to their math background, a Monoid was a familiar concept for many of them and I’ve been able to show how this abstract, mathematical construct was helpful with more concrete problems.

The feedback I got from the students and a teacher who attended the class was generally positive. It was a bit fast and technical, but interesting.

Apart from the talk, I gave a list of must read books and papers (SICP, Why FP matters, Learn You A Haskell…) but I’m not sure how many of them have been looking at it yet.

Slides (in French), PDF

Slides (in French), markdown

I should do it again next year and I’m looking forward feedback from functional programmers. If you have suggestions, please let me know, the current structure is far from being perfect and I’m willing to improve it.

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