I'm sat at the Haskell Hackathon, and dons is doing a demonstration of a tool called vacuum which can observe the state of ghc's heap while a program is running, in various states of evaluation. I'm getting pretty excited that this could be used to generate a hat trace using ghc-api, rather than hat-trans. I wanted to check if anyone had looked at the API this is using or not, and if anyone knows of any immediate trip-wires that I might encounter thinking about this. Bob