I don't know if Simon mentionned it but I found his & al. paper proceedings of the fifth ACM SIGPLAN international conference on on Functional programming, "Composing contracts: an adventure in financial engineering (functional pearl) Pages 280-292" very interesting: http://www.acm.org/pubs/citations/proceedings/fp/351240/p280-jones/ -- Laurent Guerby <guerby@acm.org>