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Happy Programmers’ Day [1], everyone!
A feast isn’t a feast, though, until it has a proper way of celebrating it. The Pi Day [2], for instance, has one: you eat a pie (preferably exactly at 1:59:26.535am), but I haven’t heard of any way of celebrating the Programmers’ Day, so I had to invent one. An obvious way would be to write a program, preferably a non-trivial one, but that requires time and dedication, which not everyone is able to readily spare.
So here’s my idea: on Programmers’ Day, dust off a program that you wrote some time ago — something that is just lying around in some far corner of your hard disk, that you haven’t looked at in years, but that you had fun writing — and put it on GitHub [3] for all the world to see, to share the joy of programming.
Let me initialize the new tradition by doing this myself. Here’s HAZE [4], the Haskellish Abominable Z-machine Emulator. It was my final assignment for a course in Advanced Functional Programming, in my fourth year at the Uni, way back in 2004. It is an emulator for an ancient kind of virtual machine, the Z-machine [5], written from scratch in Haskell. It allows you to play text adventure games, such as Zork [6], much in the vein of Frotz [7]. It’s not very complete, and supports versions of the Z-machine up to 3 only, so newer games won’t run on it as it stands, but Zork is playable.
It probably won’t even compile in modern Haskell systems: it was originally written for GHC version 6.2.1, and extensively uses the FiniteMap data type, which was obsoleted shortly after and is no longer found in modern systems. I should have Linux and Windows binaries lying around (yes, I had compiled it under Windows, using MinGW/PDCurses); I’ll put them on GitHub once I find them.
My mind now wanders ten years back in time, to the days when I was writing it. It took me about three summer weeks to write HAZE from scratch, most of that time on a slow laptop where it took quite a lot of seconds to get GHC to compile even a simple thing. I would do some of it differently if I were doing it now — for one, the state of a “ZMachine” is a central datatype to HAZE, and you’ll find a lot of functions that take and return ZMachines, so a state monad is an obvious choice; I didn’t understand monads well enough back then. But I still remember how I had the framework in place already and I was adding implementations of Z-code opcodes, one by one, to “ZMachine/ZCode/Impl.hs”, recompiling, rerunning, getting messages about unimplemented opcodes, when all of a sudden I got the familiar message about a white house and a small mailbox. Freude!
I hope you enjoy looking at it at least half as much as I had enjoyed writing it.