Practical Foundations for Programming Languages Robert Harper Carnegie Mellon University Spring, 2011 [Version 1.8 of 07.22.2011.] Copyright c 2010 by Robert Harper. All Rights Reserved. The electronic version of this work is licensed under the Cre- ative Commons Attribution-Noncommercial-No Derivative Works 3.0 United States License. To view a copy of this license, visit http://creativecommons.o