A common attraction to functional programming is the ease with which proofs can be given of program properties. A common disappointment with functional programming is the difficulty of expressing input/output (I/O) while at the same time being able to verify programs. Here, the author shows how a theory of functional programming can be smoothly extended to admit both an operational semantics for functional I/O and verification of programs engaged in I/O. He obtains, for the first time, operational semantics for the three most widely implemented I/O mechanisms for lazy languages, and proves that the three are equivalent in expressive power. He also develops semantics for a form of monadic I/O and verifies a simple programming example. These theories of functional I/O are based on an entirely operational theory of functional programming, developed using Abramsky's "applicative bisimulation." Graduate students and researchers will gain much from reading this book.

Most object-oriented or functional languages are higher order languages, i.e. ones in which the means of manipulation (e.g. object or function) can itself be manipulated. This 1998 book contains a collection of original articles about recent developments in operational semantics for higher order programming languages by some of the leading researchers in the field. Operational techniques are important because they are closer to implementations and language definitions than more abstract mathematical techniques such as denotational semantics. One of the exciting developments reflected by the book is that mathematical structures and techniques used in denotational semantics (such as fixpoint induction) may be recovered from a purely operational starting point. The book surveys and introduces techniques such as contextual equivalence, applicative bisimulation, logical relations, improvement relations, explicit models of memory management, and labelling techniques for confluence properties. It treats a variety of higher order languages, based on functions, processes and objects, with and without side effects, typed and untyped.

This book constitutes the refereed proceedings of the 6th International Conference on Foundations of Software Science and Computation Structures, FOSSACS 2003, held in Warsaw, Poland in April 2003. The 26 revised full papers presented together with an invited paper were carefully reviewed and selected  from 96 submissions. Among the topics covered are algebraic models; automata and language theory; behavioral equivalences; categorical models; computation processes over discrete and continuous data; computation structures; logics of programs; models of concurrent, reactive, distributed, and mobile systems; process algebras and calculi; semantics of programming languages; software specification and refinement; transition systems; and type systems and type theory.