Declaratively solving Google Code Jam problems with Picat

In this paper we present several examples of solving algorithmic problems from the Google Code Jam programming contest with Picat programming language using declarative techniques: constraint logic programming and tabled logic programming. In some cases the use of Picat simplifies the implementation compared to conventional imperative programming languages, while in others it allows to directly convert the problem statement into an efficiently solvable declarative problem specification without inventing an imperative algorithm

Linear-Logic Based Analysis of Constraint Handling Rules with Disjunction

Constraint Handling Rules (CHR) is a declarative committed-choice programming language with a strong relationship to linear logic. Its generalization CHR with Disjunction (CHRv) is a multi-paradigm declarative programming language that allows the embedding of horn programs. We analyse the assets and the limitations of the classical declarative semantics of CHR before we motivate and develop a linear-logic declarative semantics for CHR and CHRv. We show how to apply the linear-logic semantics to decide program properties and to prove operational equivalence of CHRv programs across the boundaries of language paradigms

The CIAO Multi-Dialect Compiler and System: An Experimentation Workbench for Future (C)LP Systems

CIAO is an advanced programming environment supporting Logic and Constraint programming. It offers a simple concurrent kernel on top of which declarative and non-declarative extensions are added via librarles. Librarles are available for supporting the ISOProlog standard, several constraint domains, functional and higher order programming, concurrent and distributed programming, internet programming, and others. The source language allows declaring properties of predicates via assertions, including types and modes. Such properties are checked at compile-time or at run-time. The compiler and system architecture are designed to natively support modular global analysis, with the two objectives of proving properties in assertions and performing program optimizations, including transparently exploiting parallelism in programs. The purpose of this paper is to report on recent progress made in the context of the CIAO system, with special emphasis on the capabilities of the compiler, the techniques used for supporting such capabilities, and the results in the áreas of program analysis and transformation already obtained with the system

Explanations and Proof Trees

This paper proposes a model for explanations in a set theoretical framework using the notions of closure or fixpoint. In this approach, sets of rules associated with monotonic operators allow to define proof trees. The proof trees may be considered as a declarative view of the trace of a computation. We claim they are explanations of the results of a computation. This notion of explanation is applied to constraint logic programming, and it is used for declarative error diagnosis. It is also applied to constraint programming, and used for constraint retraction

A calculus for higher-order concurrent constraint programming with deep guards

We present a calculus providing an abstract operational semantics forhigher-order concurrent constraint programming. The calculus isparameterized with a first-order constraint system and provides first-class abstraction, guarded disjunction, committed-choice, deepguards, dynamic creation of unique names, and constraint communication.The calculus comes with a declarative sublanguage for which computation amounts to equivalence transformation of formulas. The declarative sublanguage can express negation. Abstractions are referred to by names, which are first-class values. This way we obtain a smooth and straight forward combination of first-order constraints with higher-order programming. Constraint communication is asynchronous and exploits the presence of logic variables. It provides a notion of state that is fully compatible with constraints and concurrency. The calculus serves as the semantic basis of Oz, a programming language and system under development at DFKI

Kiel Declarative Programming Days 2013

This report contains the papers presented at the Kiel Declarative Programming Days 2013, held in Kiel (Germany) during September 11-13, 2013. The Kiel Declarative Programming Days 2013 unified the following events: * 20th International Conference on Applications of Declarative Programming and Knowledge Management (INAP 2013) * 22nd International Workshop on Functional and (Constraint) Logic Programming (WFLP 2013) * 27th Workshop on Logic Programming (WLP 2013) All these events are centered around declarative programming, an advanced paradigm for the modeling and solving of complex problems. These specification and implementation methods attracted increasing attention over the last decades, e.g., in the domains of databases and natural language processing, for modeling and processing combinatorial problems, and for high-level programming of complex, in particular, knowledge-based systems

A Concurrent Operational Semantics for Constraint Functional Logic Programming

In this paper we describe a sound and complete concurrent operational semantics for constraint functional logic programming languages which allows to model declarative applications in which the interaction between demand-driven narrowing and constraint solving helps to prune the search space, leading to shorter goal derivations. We encode concurrency into the generic CFLP(D) scheme, a uniform foundation for the operational semantics of constraint functional logic programming systems parameterized by a constraint solver over the given domain D. In this concurrent version of the CFLP(D) scheme, goal solving processes can be executed concurrently and cooperate together to perform their specific tasks via demand-driven narrowing and declarative residuation guided by constrained definitional trees, constraint solving, and communication by synchronization on logical variables