A type system is a syntactic method for enforcing levels of abstraction in programs. The study of type systems--and of programming languages from a type-theoretic perspective--has important applications in software engineering, language design, high-performance compilers, and security.This text provides a comprehensive introduction both to type systems in computer science and to the basic theory of programming languages. The approach is pragmatic and operational; each new concept is motivated by programming examples and the more theoretical sections are driven by the needs of implementations. Dependencies between chapters are explicitly identified, allowing readers to choose a variety of paths through the material. The core topics include the untyped lambda-calculus, simple type systems, type reconstruction, universal and existential polymorphism, subtyping, bounded quantification, recursive types, kinds, and type operators.
I enjoy writing and in addition to my published books I offer free Open Content material on this web page. I both enjoy and appreciate feedback on ideas for material and reporting any errors. I offer free web books on Java and artificial intelligence programming, Common Lisp programming, and a new but still incomplete book The Software Design and Development Book. I am also working on a Ruby AI book and a short paper on AI design patterns. I also have a link to an old paper on AI, Go and Consciousness (updated 1/25/2004) available here. I have a short paper Jumpstarting the Semantic Web available here (new version 1/14/2005). I am also starting to include my fiction (short stories) here in addition to computer science web books.
The Little Book of Semaphores is a free (in both senses of the word) textbook that introduces the principles of synchronization for concurrent programming. In most computer science curricula, synchronization is a module in an Operating Systems class. OS textbooks present a standard set of problems with a standard set of solutions, but most students don't get a good understanding of the material or the ability to solve similar problems. The approach of this book is to identify patterns that are useful for a variety of synchronization problems and then show how they can be assembled into solutions. After each problem, the book offers a hint before showing a solution, giving students a better chance of discovering solutions on their own. The book covers the classical problems, including "Readers-writers," "Producer-consumer", and "Dining Philosophers." In addition, it collects a number of not-so-classical problems