let's get the obvious contender out of the way: Haskell
This Tweet was deleted by the Tweet author. Learn more
Conversation
This Tweet was deleted by the Tweet author. Learn more
There's an interesting diagrams library for Haskell: archives.haskell.org/projects.haske - as usual the function names are a bit... odd... but it looks neat. haskellbook.com is also rated quite highly for learning too.