Hi > Dmitry Antonyuk (lomeo) came up with a piece of code that hung GHC 6.6: It's a documented bug in GHC: http://www.haskell.org/ghc/docs/latest/html/users_guide/bugs.html#bugs-ghc "GHC's inliner can be persuaded into non-termination using the standard way to encode recursion via a data type" Thanks Neil