Writing a Compiler in Haskell

In the useless memories department, xkcd’s cartoon today took me back:

In my junior year of college, I took the standard programming languages course that goes over fun stuff like how programming languages are put together. The main project for the class, of course, is to build a compiler for a small language. The twist was, that the professor for this class happened to be one of the designers of the Haskell language, so you can guess what programming language the compilers had to be written in.

The thing is, this class took place probably in the fall of 1990 or the spring of 1991. According to Wikipedia, Haskell debuted in 1990, so first and foremost the tools we were working with were… uh, primitive at best. I think the Haskell interpreter was written in Common LISP, and basically you took your program, invoked the interpreter on it, went and got yourself a nice cup of tea (so to speak), and then came back to an answer (if you were lucky), an undecipherable error message (if you were only kind of unlucky), or just nothing (most of the time). Definitely honed the skill of “psychic debugging.”

Anyway, with a brand-new language (that, of course, had no manuals or books written about it yet) and an alpha-level (at best) compiler, as I remember it at least half the class never even managed to get something working. I somehow managed to grok enough of Haskell to be able to write a functioning compiler that took our toy language in and produced correct output. I was one of the lucky ones. But here’s the thing…

It was, without a doubt, one of the most beautiful programs that I’ve ever written. Just a real work of art, with the data flowing through the code in one of the most natural ways I’ve ever seen. Just awesome. It’s the one piece of code that I look back on and wish that I still had a copy of.

So I’ve always had a soft spot in my heart for Haskell. Even if nobody else could actually understand what it was doing or why.

You should also follow me on Twitter here.

Leave a Reply