These proceedings from the September 2003 Fourth International Symposium on Trends in Functional Programming, held in Edinburgh, UK, address the research problems at the forefront of the practical application of functional programming languages. Papers examine topics including resource-aware functional programing for the JVM, testing reactive systems with GAST, implementation of mobile Haskell, and testing scheme programming assignments automatically. Each paper ends with conclusions and overviews of related work. There is no subject index. The book is distributed in the US by ISBS. Annotation ©2004 Book News, Inc., Portland, OR