Abstract not found

It is well known that adding side effects to functional languages changes the operational equivalences of the language. We develop a new language construct, encap, that forces imperative pieces of code to behave purely functionally, i.e., without any visible side effects. The coercion operator encap provides a means of extending the simple reasoning principles for equivalences of code in a functional language to a language with side effects. In earlier work [36], similar coercion operators were developed, but their correctness required the underlying functional language to include parallel operations. The coercion operators developed here are simpler and are proven correct for purely sequential languages. The sequential setting requires the construction of fully abstract models for sequential call-by-value languages and the formulation of a weak form of "monad" suitable for expressing the semantics of call-by-value languages with side effects. 1 Introduction Two pieces of code are...

Functional logic programming and probabilistic programming have demonstrated the broad benefits of combining laziness (non-strict evaluation with sharing of the results) with non-determinism. Yet these benefits are seldom enjoyed in functional programming, because the existing features for non-strictness, sharing, and nondeterminism in functional languages are tricky to combine. We present a practical way to write purely functional lazy non-deterministic programs that are efficient and perspicuous. We achieve this goal by embedding the programs into existing languages (such as Haskell, SML, and OCaml) with high-quality implementations, by making choices lazily and representing data with non-deterministic components, by working with custom monadic data types and search strategies, and by providing equational laws for the programmer to reason about their code.

This note is a historical survey of Christopher Strachey's influence on the development of semantic models of assignment and storage management in procedural languages.

We describe the design of a transaction facility for a language that supports higher-order functions. We factor transactions into four separable features: persistence, undoability, locking, and threads. Then, relying on function composition, we show how we can put them together again. Our "Tinkertoy" approach towards building transactions enables us to construct a model of concurrent, nested, multi-threaded transactions, as well as other non-traditional models where not all features of transactions are present. Key to our approach is the use of higher-order functions to make transactions first-class. Not only do we get clean composability of transactional features, but also we avoid the need to introduce special control and block-structured constructs as done in more traditional transactional systems. We implemented our design in Standard ML of New Jersey. This research is sponsored in part by the Wright Laboratory, Aeronautical Systems Center, Air Force Materiel Command, USAF, and the...

Traditionally, implementations for functional logic languages (FLP) have used depth-first search to implement narrowing, a well-known search strategy. While this approach yields good performance, it is unnecessarily restrictive in the sense that some programs lead to non-termination (the search computes forever in one part of the search space, failing to consider the rest) when clearly they should yield results. As a result, a number of recent FLP research efforts have focused on designing efficient FLP systems based on breadth-first search strategies, which hold an important fairness property: if a solution is known to exist, it will (eventually) be found. The work presented in this paper addresses issues of efficiency in the context of FLC, a FLP compiler that employs fair search and a novel application of first-class stores in its implementation of narrowing. We show that in order to be tractable, FLC needs an efficient data representation