Functional Programming

Numbers are values. Strings are values. Booleans are values. In Functional Programming, functions simply are simply values as well. This view on programming leads to an elegant and expressive programming paradigm which we will investigate in this course. During the course, we will use the programming language Haskell. The majority of the concepts we will consider applies in other (functional) languages as well.

Participants are not expected to be fluent in Haskell from the beginning. We will spend the first three weeks of the semester on a Haskell Ramp-Up. Things will progress rather fast, though. The majority of the semester will be used for the good stuff: intermediate and advanced topics, of which there are plenty.

Syllabus

This course will provide an introduction to Haskell (first half) and then touch on intermediate-level topics. We will discuss (topics in parentheses will be addressed if we'll find the time):

Values and types
Function definitions (guards, pattern matching)
List processing
Algebraic data types
Type classes
Domain-specific languages (DSLs; shallow and deep embedding)
Laziness
Functors. Applicative Functors, Monads
(Monadic parsing)
(Applications: breadth-first search, path finding)

Forum

Discussion around this course and Haskell in general are encouraged in the forum. ⚠️ If you want to participate in the exercises, you absolutely need to register in the forum, as we use it to create/administer student accounts in this course. Thus, please stop by regularly, have a look, and say "hi".

Tutorial and Exercises

We will provide weekly exercise sheets (hand-out: Friday, hand-in by Thursday night).
You are admitted to the final exam if you score at least ⅔ of the overall exercise points.
Scoring well in the exercises leads to bonus points in the final exam.

Haskell (GHC, Haskell Platform)

The course will use the de-facto standard Haskell compiler GHC and its interactive variant (also known as read-eval-print loop or REPL) GHCi. We strongly suggest you download and install the so-called Haskell Platform which includes both GHC and GHCi (and more). Available for virtually all operating systems, including Windows, Linux, macOS. Make sure to install the recent version.

Literature

The following introductory books and courses on Haskell are recommend reading — some of these are available online:

Bird: Thinking Functionally with Haskell, Cambridge University Press 2014
Keller, Chakravarthy: "Learning Haskell", online course in development.
FP Complete: The School of Haskell, extensive and growing set of interactive online tutorials, from basic to advanced.
Lipovača: "Learn You a Haskell for Great Good", No Starch Press 2011. Available online at learnyouahaskell.com/chapters
Allen, Moronuki: "Haskell Programming — from first principles". Work on this book is still in progress at haskellbook.com, early access available.
O'Sullivan, Stewart, Goerzen: “Real World Haskell”, O’Reilly 2010. Available online at book.realworldhaskell.org
A growing and tagged collection of papers, blogs, and tutorial articles on Haskell: dohaskell

We will refer to additional material for the individual topics during the semester.

Additional material (code, data)

Nr File Download

Nr	File	Download
1	chewie.hs The Hello, World! of Haskell. Compile with Haskell compiler ghc via `ghc --make chewie.hs`, execute on the command line with `./chewie`. Load into REPL ghci via `ghci chewie.hs`, then evaluate function `main`.
2	isPrime.hs Prime number test. Efficient thanks to lazy evaluation of `factors` (a comparison with the empty list `[]` can be decided once the first element of `factors` has been found).

chewie.hs

The Hello, World! of Haskell.

Compile with Haskell compiler ghc via ghc --make chewie.hs, execute on the command line with ./chewie.
Load into REPL ghci via ghci chewie.hs, then evaluate function main.

isPrime.hs

Prime number test. Efficient thanks to lazy evaluation of factors (a comparison with the empty list [] can be decided once the first element of factors has been found).