I would like the thank Don Syme, the creator of F#, for pioneering research into programming languages and for thrusting the incredibly powerful ML family of languages into the limelight of mainstream software development.

Xavier Leroy, everyone at projet Cristal and the Debian package maintainers for making OCaml so practically useful.

Stephen Elliott and Sergei Taraskin and their group at the University of Cambridge for teaching me how to be a research scientist and letting me pursue crazy ideas when I should have been working.

Ioannis Baltopoulos and Enrique Nell for proofreading this book and giving essential feedback.

J. D. H.