I believe http://www.cs.nott.ac.uk/~gmh/cat.html http://www.cs.nott.ac.uk/~gmh/cat.html was on HN sometime in the last two weeks. It's a very very good introdu

I believe http://www.cs.nott.ac.uk/~gmh/cat.html http://www.cs.nott.ac.uk/~gmh/cat.html was on HN sometime in the last two weeks. It's a very very good introduction to the underlying mathematical structures Haskell uses for its type system.