Iavor S. Diatchki wrote: > my programs always prove IO(). this must be the best proven theorem in > Haskell. and people just keep on proving it :-) I believe that I have proven more often that undef = undef and my students prove usually that GHC typechecker is a nasty, unforgiving beast. Jerzy Karczmarczuk (of course this posting belongs rather to the list haskell-beer ...)