Hello, I've come to the conclusion that JIT compilation is essential to avoid abstract penalties even for typed languages. The one sentence summary is that the C++ inline keyword is exactly the opposite of what you want: in a JIT language you can have a "flatten" function that recursively inlines everything that a function calls (including closures). Thus, I'm curious about whether pypy could be practically applied to a typed front end language, say with the following basic set of features: 1. Packed storage such as C structs and arrays. 2. A Hindley Milner polymorphic type system with type classes. In particular, what restrictions does pypy impose on storage layout? For example, would it be able to handle dynamically-typed homogeneous lists, represented as a single pointer to a type object and an array of structs required to be of that type? Also, if pypy can target LLVM, how do you imagine the two JIT systems cooperating (if at all)? Thanks! Geoffrey