Did you know that you can actually generate a monad automatically given any endofunctor? This is the free monad of that functor. How do we perform this magic trick? Quite simple, everything follows from this data type:

I use OS X, and so for those rare cases where I must deign to run a program designed for Windows I make use of my copy of it hosted in Parallels Desktop. Now, Parallels has been generally good to me, but I recently came across the problem documented in this forum thread where its ability to launch Mac applications from Windows caused some basic file associations in Windows-land to stop working. For example, Excel files were listed as “xls_auto_file” by Explorer and double clicking on them only gave me the “Open With” dialog: not very helpful.

Some time ago, I published a post discussing how we solve the now-notorious FizzBuzz problem with computation in the type system. In the interests of flogging this horse well and truly to death, I’ve since adapted the code to make use of an upcoming GHC feature: type families. These are essentially a form of function at the type level: just what we need to make our FizzBuzz program a little more sane!

I’m very pleased to report that my application for the Google Summer of Code has been accepted! It almost goes without saying to mention that I’ve proposed work on the leading compiler for my language-du-jour: Haskell!

As my final year undergraduate project I’ve implemented Philip Wadler’s and Simon Peyton Jones’ Comprehensive Comprehensions in the Glasgow Haskell Compiler. I’m happy to report that my patch was accepted for inclusion in the compiler, so this is a feature you’ll really be able to use come the release of 6.10!