Apologies for the site being down at the moment. I'd reset the server but I'm in Chicago. I know that PLT Scheme recently had a system for optional types implem

Apologies for the site being down at the moment. I'd reset the server but I'm in Chicago. I know that PLT Scheme recently had a system for optional types implemented and there was a paper posted on Lambda-the-ultimate.org. I think it's in SVN. http://lambda-the-ultimate.org/node/2622 http://lambda-the-ultimate.org/node/2622 Apparently, Bigloo has supported this for a while: http://www-sop.inria.fr/mimosa/fp/Bigloo/doc/bigloo-22.html http://www-sop.inria.fr/mimosa/fp/Bigloo/doc/bigloo-22.html One should also consider that there are implementations like Gambit-C and Chicken that compile to type-annotated languages, not that it's necessarily what you had in mind. Just food for thought.