Wednesday, July 22, 2009

Of Virtual Machines

Hello my dear readers, I have been away too long.

I wanted to give a little visibility to my latest efforts: a Lua Virtual Machine. Yes, you got it right, a Lua Virtual Machine! Bytecode in, execution out! This also means that as soon as the bytecode format changes (and it can happen anytime at discretion of the creators of Lua) everything breaks.

Needless to say its based on the works of Fabio Mascarenhas (Lua2IL) and Kein-Hong Man (A No-Frills introduction to Lua 5.1 VM Instructions).

I really love Lua, I think it's a wonderful language. Not perfect, but it features metamethods and if it's something with "meta-" built-in, it must be cool (once they were called tag methods, as you can glimpse from the source). Jokes aside, metamethods seem to offer this nice extensibility and hooks to language events (indexing, new index creation, various operators, to name a few) that make every change a little microcosm of new features.

Back on topic, this Lua VM is meant to run on non-DLR-ready frameworks, such as the .NET Compact Framework. You might argue that System.Reflection.Emit comes before the DLR, but the latter is the future (had too much of IL emit at once in the past) and I like to look ahead.

I know there have been many wise guys at work on Lua implementations on the CLR, but I took up this challenge mainly for fun and not for fame. If it turns out to be complete enough for regular usage, even better. There's a lot to learn from the learning itself.

You can find the work-in-progress source at the Rainweaver Framework Codeplex page. I make a lot of changes all the time, but the core library should be stable enough to use.

I tried to use Irony to create a Lua AST generator but it looks I'm not smart enough, and I had to fall back to other solutions for the moment. It was cool to find out about monadic parser combinators (LukeH's weblog and Brian's weblog) - read them up because they will make you super smart and taint with functional sexyness your imperative ego. As soon as I manage to play with those concepts a bit, I'll be sure to post more.

Waiting for feedback as usual,
Yours truly,