I did that with Ruby[1]. I learned things nobody should ever have to learn. But I also came away with a much greater appreciation for the basic model it uses, m

I did that with Ruby[1]. I learned things nobody should ever have to learn. But I also came away with a much greater appreciation for the basic model it uses, most of the biggest warts are at the surface (flip-flops, bizarre rules around how arguments get passed to blocks when the block takes one argument, etc). The way metaclasses work is, imo, one of the most elegant object models I've seen for the amount of power it gives you. It only took a couple hundred lines of code to implement reasonably correctly [2]. And along the way, I wrote another language for expressing some of the higher level VM-stuff (object model, exception propagation, etc). I definitely recommend targeting languages that already have robust test suites. It makes things a lot easier. I was going to do a JS implementation a while ago, and there is a pretty solid suite for that from the ECMA[3], but it's kind of hard to extract. One of the things that made ruby so fun was that the test suite that existed at the time was rubyspec, which is actually written in ruby. Just getting to the point where I could run the specs was a huge moment where the implementation reached a measure of usability. [1] https://github.com/stormbrew/channel9 https://github.com/stormbrew/channel9 -- it's a perennial project for me, it can run an old version of mspec+rubyspec as a ruby 1.8.6 implementation. Note that I skipped the parsing, leaving that to an existing parser written in ruby, because parsing ruby is a bigger project than a ruby-compatible VM. [2] https://github.com/stormbrew/channel9/tree/master/environments/ruby/environment/kernel/alpha https://github.com/stormbrew/channel9/tree/master/environmen... -- see class.c9s and object.c9s for the vm specific script the fundamental implementation of language features is written in. [3] http://test262.ecmascript.org/ http://test262.ecmascript.org/