Fresh from my practice with Haskell, I built a lexer and layout manager for Epigram 2 today. You can
darcs get http://www.e-pig.org/darcs/Pig09/
for not much action. But I start as I hope to continue, with all the source living in an lhs2TeX document — the ‘Epitome’:
make dvi
and you’re away.
I promise not to implement λ-calculus again until I’ve written a parser to feed it.
The plan, by the way, is to implement an electrical stooge, a kind of annoying co-author who reads what you’ve done and comments out the bits which don’t typecheck. In time, you may be able to persuade this unlikely conspirator also to do some work.