Combinatory logic and lambda-calculus, originally devised in the 1920s, have since developed into linguistic tools, especially useful in programming languages. The authors' previous book served as the main reference for introductory courses on lambda-calculus for over 20 years: this long-awaited new version is thoroughly revised and offers a fully up-to-date account of the subject, with the same authoritative exposition. The grammar and basic properties of both combinatory logic and lambda-calculus are discussed, followed by an introduction to type-theory. Typed and untyped versions of the systems, and their differences, are covered. Lambda-calculus models, which lie behind much of the semantics of programming languages, are also explained in depth. The treatment is as non-technical as possible, with the main ideas emphasized and illustrated by examples. Many exercises are included, from routine to advanced, with solutions to most at the end of the book.

• The authors' 1986 version of this book is widely recognised as the best introduction to these topics for the reader with some previous experience of logic; this version builds and updates that framework • Accessible and clear: a non-technical treatment of the subject with the main ideas emphasized and illustrated by examples • Exercises are designed to give practice to beginners and range from elementary to advanced, with solutions to most found at the end of the book