Hi Karel, I'm a (the? ;-) very keen user of CAL (ex user at the moment, as work and family doesn't leave me enough time for side projects). Pro: - Very solid and high quality, practically bug-free in my experience. - Performs some useful optimisations (self tail recursion as iteration, unboxing of primitives, strictness annotations/analysis) which can give you Java-level performance in some cases. - Good (IMHO) though verbose Java interop -- you can often turn Java types into CAL types rather than needing to wrap them in another layer. Con: - Haskell 98 type system (actually I found that a bit of a pro for learning fp) - Less syntactic sugar (do notation, equational definitions, pattern matching outside case statements) - Few users. There are occasional commits to forks of CAL at https://github.com/levans/Open-Quark and Luke Evans says that work on CAL continues at Indicee, but there's little visible activity. None of these points are in comparison to Frege, which I haven't used at all. Tom