Hi Dušan The Ester shell written in Clean compiles via the SKI combinators. It is describe in the paper - 'A Functional Shell that Operates on Typed and Compiled Applications' by Arjen van Weelden and Rinus Plasmeijer which is available here: http://www.st.cs.ru.nl/papers/2004/plar2004-Esther_AFP.pdf Ester is part of the Clean 2.2 distribution, but I've had a quick look at it now and I suspect it has diverged a bit from the version described in the paper. The paper references Antoni Diller's 'Compiling Functional Languages' (Wiley - ISBN 0 471 92027 4) as the source of the algorithms they use. This book is long out of print but it is good and comprehensive. I got my copy second-hand from an affiliate on Amazon UK a few years ago after reading the Ester paper. Amazon UK currently has quite a few copies available - the £8+postage price is pretty cheap, the sellers will post internationally (caveat - I've no experience with any of the affiliates listed). There is a full implementation (in Pascal) in the appendix. Diller references David Turner's paper "A New Implementation Technique for Applicative Languages" (1979 "Software - Practice and Experience", vol 9, pp 31-49). If you have a university affiliation you should be able to source this, I haven't seen it myself. Best wishes Stephen