I'm pretty sure Moon (who is a famous old-school lisp hacker) will have at least some prototyping quality implementation somewhere, the design is to detailed for a mere thought experiment and there are longer code snippets around:
I read about PLOT years ago and thought the approach to syntax (and macros) was quite clever; I don't remember the exact details but it was the first time I had seen something that was both hygenic and not horribly complex to implement.
BTW, his markdown alternative (MMD -- Moon's Mark Down) also looks pretty nice (expressive and lightweight, but unlike org mode or other monstrosities trivial to parse and unambigious). http://users.rcn.com/david-moon/MMD/HTML/index.html
http://users.rcn.com/david-moon/PLOT/page-35.html
I read about PLOT years ago and thought the approach to syntax (and macros) was quite clever; I don't remember the exact details but it was the first time I had seen something that was both hygenic and not horribly complex to implement.
BTW, his markdown alternative (MMD -- Moon's Mark Down) also looks pretty nice (expressive and lightweight, but unlike org mode or other monstrosities trivial to parse and unambigious). http://users.rcn.com/david-moon/MMD/HTML/index.html
He also has a ~700 LOC standalone python implementation which includes the sequence diagram drawing code: http://users.rcn.com/david-moon/MMD/MMD.py.