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Curry is a multi-paradigm declarative language aiming to amalgamate functional, logic, and concurrent programming paradigms. Curry combines in a seamless way features from functional programming and (concurrent) logic programming. Curry’s operational semantics is based on the combination of lazy reduction of expressions together with a possibly non-deterministic binding of free variables occurring in expressions. Moreover, (equational) constraints can be executed concurrently which provides for passive constraints and concurrent computation threads that are synchronized on logical variables. machine for executing Curry programs. The machine is designed to provide a link for compiling Curry programs into Java but it can also be a basis for implementations of Curry in other (object-oriented) languages. The main emphasis of the Java-based implementation is the exploitation of Java threads to implement the concurrent and nondeterministic features of Curry.

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In this paper we propose a new concept to deal with dynamic predicates in functional logic programs. The definition of a dynamic predicate can change over time, i.e., one can add or remove facts that define this predicate. Our approach is easy to use and has a clear semantics that does not depend on the particular (demand-driven) evaluation strategy of the underlying implementation. In particular, the concept is not based on (unsafe) side effects so that the order of evaluation does not influence the computed results—an essential requirement in non-strict languages. Dynamic predicates can also be persistent so that their definitions are saved across invocations of programs. Thus, dynamic predicates are a lightweight alternative to the explicit use of external database systems. Moreover, they extend one of the classical application areas of logic programming to functional logic programs. We present the concept, its use and an implementation in a Prolog-based compiler. 1 Motivation and Related Work Functional logic languages [11] aim to integrate the best features of functional and logic languages in order to provide a variety of programming concepts to the programmer. For instance, the concepts of demand-driven evaluation, higherorder functions, and polymorphic typing from functional programming can be combined with logic programming features like computing with partial information (logical variables), constraint solving, and non-deterministic search for solutions. This combination leads to optimal evaluation strategies [2] and new design patterns [4] that can be applied to provide better programming abstractions, e.g., for implementing graphical user interfaces [13] or programming dynamic web pages [14]. However, one of the traditional application areas of logic programming is not yet sufficiently covered in existing functional logic languages: the combination

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This paper presents a new program analysis framework to approximate call patterns and their results in functional logic computations. We consider programs containing non-strict, nondeterministic operations in order to make the analysis applicable to modern functional logic languages like Curry or TOY. For this purpose, we present a new fixpoint characterization of functional logic computations w.r.t. a set of initial calls. We show how programs can be analyzed by approximating this fixpoint. The results of such an approximation have various applications, e.g., program optimization as well as verifying safety properties of programs. 1

Monads have been recognized by Moggi as an elegant device for dealing with stateful computation in functional programming languages. It is thus natural

ACL2 is a first-order applicative programming language based on Common Lisp. It is also a mathematical logic for which a mechanical theoremprover has been implemented in the style of the Boyer-Moore theorem prover. The ACL2 system is used primarily in the modeling and verification of computer hardware and software, where the executability of the language allows models to be used as prototype designs or "simulators." To support efficient execution of certain kinds of models, especially models of microprocessors, ACL2 provides "single-threaded objects," structures with the usual "copy on write" applicative semantics but for which writes are implemented destructively. Syntactic restrictions insure consistency between the formal semantics and the implementation. The design of single-threaded objects has been influenced both by the need to make execution efficient and the need to make proofs about them simple. We discuss the issues. 1 Background "ACL2" stands for "A Computational Logic for...

This paper presents an environment to support high-level database programming in the multi-paradigm declarative programming language Curry. We define an application programming interface (API) that abstracts from the concrete database access methods. The API supports transactions and exploits Curry’s type system to ensure a strict separation between queries and updates. In order to ensure database updates that are safe w.r.t. an intended data model (e.g., containing specific relations between entities), we assume a description of the data dependencies in the entity-relationship (ER) model from which all access and update operations related to the database are generated. We propose a representation of ER diagrams in the declarative language Curry so that they can be constructed by various tools and then translated into this representation. Furthermore, we have implemented a compiler from this representation into a Curry program that provides safe access and update operations based on the API for database programming.