| What is the status of Rob Ennals' optimistic evaluation work? I'm told | that it has been removed from GHC. This is extremely depressing to me. More precisely, it never got into GHC. It was always on a heavily-modified branch. Rob's thesis was fantastic work. But although it sounded simple to start with, when he'd worked out all the details it was very, very complicated. Read his thesis! Simon and I decided that it was too big a complication to drag into our main compiler, and then maintain in perpetuity. It would not be so bad if it was a somewhat orthogonal feature, but it wasn't -- it percolated into many bits of the compiler and runtime system. It was cool stuff. Maybe bright person can figure out an easier way to do it. But I'm afraid we have no plans to incorporate it at the moment. Having said that, it wasn't a silver bullet! I very much doubt that it makes the difference between Haskell being usable for your work in machine learning, and not being usable. You may well need control over space, which is undoubtedly Haskell's weak spot. But remember, lazy evaluation can *reduce* space usage as well as increase it --- and the profiling tools plus seq and (perhaps!) bang patterns may give you the control you need. Simon