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ACM SIGPLAN Workshop on Partial Evaluation and Program Manipulation

作者： Riesco, Adrian Rodriguez-Hortala, Juan Univ Complutense Madrid Dept Sistemas Informat & Computac E-28040 Madrid Spain

ISBN: (纸本)9781605587271

non-strict non-deterministic functions are one of the most distinctive features of functional-logic languages. Traditionally, two semantic alternatives have been considered for this kind of functions: call-time choice and run-time choice. While the former is the standard choice of modern implementations of FLP, the latter lacks some basic properties mainly compositionality that have prevented its use in practical FLP implementations. Recently, a new compositional plural semantics for FLP has been proposed. Although this semantics allows an elegant encoding of some problems in particular those with an implicit manipulation of sets of values, call-time choice still remains the best option for many common programming patterns. In this paper we explore the expressive possibilities of the combination of singular and plural non-determinism. After formalizing the intended semantics by means of a logic calculus, several significant examples exploiting the capabilities of the semantics are presented. These examples have been tested and developed in a Maude-based prototype whose implementation is outlined.

关键词： non-deterministic functions Semantics Program transformation Term rewriting Maude

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An approach to declarative programming based on a rewriting logic

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JOURNAL OF LOGIC PROGRAMMING 1999年第1期40卷 47-87页

作者： González-Moreno, JC Hortalá-González, MT López-Fraguas, FJ Rodríguez-Artalejo, M Univ Complutense Madrid Fac Matemat Dept Sistemas Informat & prog E-28040 Madrid Spain

We propose an approach to declarative programming which integrates the functional and relational paradigms by taking possibly non-deterministic lazy functions as the fundamental notion. Classical equational logic does not supply a suitable semantics in a natural way. Therefore, we suggest to view programs as theories in a constructor-based conditional rewriting logic. We present proof calculi and a model theory for this logic, and we prove the existence of free term models which provide an adequate intended semantics for programs. We develop a sound and strongly complete lazy narrowing calculus, which is able to support sharing without the technical overhead of graph rewriting and to identify safe cases for eager variable elimination. Moreover, we give some illustrative programming examples, and we discuss the implementability of our approach. (C) 1999 Elsevier Science Inc. All rights reserved.

关键词： declarative programming non-deterministic functions constructor-based rewriting logic lazy narrowing

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Singular and plural functions for functional logic programming

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THEORY AND PRACTICE OF LOGIC PROGRAMMING 2014年第1期14卷 65-116页

作者： Riesco, Adrian Rodriguez-Hortala, Juan Univ Complutense Madrid Fac Informat Dept Sistemas Informat & Computac Madrid 28040 Spain

Modern functional logic programming (FLP) languages use non-terminating and non-confluent constructor systems (CSs) as programs in order to define non-strict and non-deterministic functions. Two semantic alternatives have been usually considered for parameter passing with this kind of functions: call-time choice and run-time choice. While the former is the standard choice of modern FLP languages, the latter lacks some basic properties - mainly compositionality - that have prevented its use in practical FLP systems. Traditionally it has been considered that call-time choice induces a singular denotational semantics, while run-time choice induces a plural semantics. We have discovered that this latter identification is wrong when pattern matching is involved, and thus in this paper we propose two novel compositional plural semantics for CSs that are different from run-time choice. We investigate the basic properties of our plural semantics - compositionality, polarity, and monotonicity for substitutions, and a restricted form of the bubbling property for CSs - and the relation between them and to previous proposals, concluding that these semantics form a hierarchy in the sense of set inclusion of the set of values computed by them. Besides, we have identified a class of programs characterized by a simple syntactic criterion for which the proposed plural semantics behave the same, and a program transformation that can be used to simulate one of the proposed plural semantics by term rewriting. At the practical level, we study how to use the new expressive capabilities of these semantics for improving the declarative flavor of programs. As call-time choice is the standard semantics for FLP, it still remains the best option for many common programming patterns. Therefore, we propose a language that combines call-time choice and our plural semantics, which we have implemented in the Maude system. The resulting interpreter is then employed to develop and test several signif

关键词： non-deterministic functions semantics program transformation term rewriting Maude

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Integrating XPath with the Functional-Logic Language Toy

Integrating XPath with the Functional-Logic Language Toy

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13th International Symposium on Practical Aspects of Declarative Languages

作者： Caballero, Rafael Garcia-Ruiz, Yolanda Saenz-Perez, Fernando Univ Complutense Madrid Dept Sistemas Informat & Computac E-28040 Madrid Spain Univ Complutense Madrid Depart Inge Soft & Inteli E-28040 Madrid Spain

ISBN: (纸本)9783642183775

This paper presents a programming framework for incorporating XPath queries into the functional-logic language Toy. The proposal exploits the language characteristics, including non-determinism, logic variables, and higher-order functions and patterns. Our setting covers a wide range of standard XPath axes and tests. In particular reverse axes are implemented thanks to the double nature of XPath queries, which are both higher-order functions and data terms in our setting. The combination of these two different worlds, the functional-logic paradigm and the XML query language XPath, is very enriching for both of them. From the point of view of functional-logic programming, the language is now able to deal with XML documents in a very simple way. From the point of view of XPath, our approach presents several nice properties as the generation of XML test-cases for XPath queries, which can be useful for finding bugs in erroneous queries.

关键词： Functional-Logic Programming non-deterministic functions XPath Queries Higher-Order Patterns

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XQuery in the Functional-Logic Language Toy 20th

XQuery in the Functional-Logic Language Toy

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20th International Workshop on Functional and Constraint Logic Programming

作者： Almendros-Jimenez, Jesus M. Caballero, Rafael Garcia-Ruiz, Yolanda Saenz-Perez, Fernando Univ Almeria Dpto Lenguajes & Computac Almeria Spain Univ Complutense Madrid Dept Sistemas Informat & Computac E-28040 Madrid Spain Univ Complutense Madrid Dept Ingn Software Int Artificial Madrid Spain

ISBN: (纸本)9783642225307;9783642225314

This paper presents an encoding of the XML query language XQuery in the functional-logic language TOY. The encoding is based on the definition of for-let-where-return constructors by means of TOY functions, and uses the recently proposed XPath implementation for this language as a basis. XQuery expressions can be executed in TOY obtaining sequences of XML elements as answers. Our setting exploits the non-deterministic nature of TOY by retrieving the elements of the XML tree once at a time when necessary. We show that one of the advantages of using a rewriting-based language for implementing XQuery is that it can be used for optimizing XQuery expressions by query rewriting. With this aim, XQuery expressions are converted into higher order patterns that can be analyzed and modified by TOY functions.

关键词： Functional-Logic Programming non-deterministic functions XQuery Higher-Order Patterns

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XPath Query Processing in a Functional-Logic Language

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ELECTRONIC NOTES IN THEORETICAL COMPUTER SCIENCE 2012年 282卷 19-34页

作者： Almendros-Jimenez, J. M. Caballerob, R. Garcia-Ruiz, Y. Saenz-Perez, F. Univ Almeria Dpto Lenguajes & Computac Almeria Spain Univ Complutense Madrid Dpto Sistemas Informat & Computac Madrid Spain Univ Complutense Madrid Dpto Ingn Software & Inteligencia Artificial Madrid Spain

XPath is a well-known query language for finding and extracting information from XML documents. This paper shows how the characteristics of this domain-specific language fits very well into the functional-logic paradigm. The proposed framework allows the user to write XPath-like queries as first-class citizens of the functional-logic language TOY, using higher-order combinators for constructing the queries and non-determinism in order to obtain the different answers that XPath queries can return. The result is a very good example of cross-fertilization of two different areas. In the case of TOY, the users can now integrate XML queries in their programs without using any external library or ad hoc interface. In the case of XPath, the use of higher-order patterns allow us to define functions for easily processing the queries. In particular, the paper shows how to trace and debug erroneous queries, and how to detect that a query is a refinement of another query, which can be useful for improving the efficiency of query processing.

关键词： Functional-Logic Programming non-deterministic functions XPath Higher-Order Patterns

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