The RLISP '88 programming system introduces an evolutionary approach to software development that enables small groups of programmers to advance the state of the art over a period of many years. Each new system is built on top of the old; yet, like an Irishman's hammer, little remains of the original program code. This book presents a style of durable programming for domain specialists and computer scientists alike. Exercises at the end of each chapter encourage its use as a textbook.