Yes, I view lambda lifting as an optimization and my implementations provide both, closures and combinators. I guess that a global program transformation could

Yes, I view lambda lifting as an optimization and my implementations provide both, closures and combinators. I guess that a global program transformation could eliminate all closures from a purely functional program, but I'm not attempting to do this -- mostly because lambda lifting cannot be applied to many closures that mutate free variables. For instance, the lambda functions created in the expansion of Scheme's LETREC cannot be lambda-lifted.