### Impacto

### Downloads

Downloads per month over past year

López Fraguas, Francisco J. and Martín Martín, Enrique and Rodríguez Hortalá, Juan and Sánchez Hernández, Jaime
(2014)
*Rewriting and narrowing for constructor systems with call-time choice semantics.*
Theory and Practice of Logic Programming, March
(14.2).
pp. 165-213.
ISSN 1471-0684

Preview |
PDF
752kB |

## Abstract

Non-confluent and non-terminating constructor-based term rewrite systems are useful for the purpose of specification and programming. In particular, existing functional logic languages use such kind of rewrite systems to define possibly non-strict non-deterministic functions. The semantics adopted for non-determinism is call-time choice, whose combination with non-strictness is a non trivial issue, addressed years ago from a semantic point of view with the Constructor-based Rewriting Logic (CRWL), a well-known semantic framework commonly accepted as suitable semantic basis of modern functional logic languages. A drawback of CRWL is that it does not come with a proper notion of one-step reduction, which would be very useful to understand and reason about how computations proceed. In this paper we develop thoroughly the theory for the first order version of letrewriting, a simple reduction notion close to that of classical term rewriting, but extended with a let-binding construction to adequately express the combination of call-time choice with non-strict semantics. Let-rewriting can be seen as a particular textual presentation of term graph rewriting. We investigate the properties of let-rewriting, most remarkably their equivalence with respect to a conservative extension of the CRWL-semantics coping with let-bindings, and we show by some case studies that having two interchangeable formal views (reduction/semantics) of the same language is a powerful reasoning tool. After that, we provide a notion of let-narrowing which is adequate for call-time choice as proved by soundness and completeness results of let-narrowing with respect to letre writing. Moreover, we relate those let-rewriting and let-narrowing relations (and hence CRWL) with ordinary term rewriting and narrowing, providing in particular soundness and completeness of let-rewriting with respect to term rewriting for a class of programs which are deterministic in a semantic sense.

Item Type: | Article |
---|---|

Uncontrolled Keywords: | Term rewriting systems, constructor-based rewriting logic, narrowing, nondeterminism, call-time choice semantics, sharing, local bindings |

Subjects: | Sciences > Computer science > Programming languages (Electronic computers) Sciences > Computer science > Expert systems (Computer science) |

ID Code: | 36061 |

Deposited On: | 03 Mar 2016 11:39 |

Last Modified: | 01 Jun 2016 23:01 |

### Origin of downloads

Repository Staff Only: item control page