Practical Foundations for Programming Languages

"Harper's book provides a comprehensive treatment of the foundations of computation. He touches on a surprising range of concepts that arise in language design: from simple types to polymorphism to dependent types to modules; from strict to lazy to parallel computation; and from proof techniques for reasoning about extensional behavior to practical, compositional cost models in the presence of garbage collection. More importantly, throughout the book he uses types and the principles of type theory to organize the material and help us discover the orthogonal, composable abstractions that arise naturally not only in the design of programming languages but also in logics and mathematics. This approach helps uncover the fundamental structure lurking inside programming languages of today, and provides a principled approach to the designs for tomorrow."
Greg Morrisett, School of Engineering and Applied Sciences, Harvard University

"Starting with a mathematically simple framework and organizing principles that give type systems a central role, Bob Harper's magnum opus reveals the theory of programming languages as a coherent scientific subject with both breadth and elegance. His enormous experience, pithy views, and great good taste are evident throughout a book that deserves to become a classic."
Andrew Pitts, Computer Laboratory, University of Cambridge

"This book offers an excellent introduction to a wide range of programming language concepts. They are all uniformly and carefully explained, using techniques that are very useful in practice for both analysis and implementation of programming languages. The book is authored by one of the most prominent researchers in type theory for programming languages. The presentation is very effective and based on the author's years of experience teaching the material."
Lars Birkedal, Professor, IT University of Copenhagen