Optimal Union-Find in Constraint Handling Rules

Constraint Handling Rules (CHR) is a committed-choice rule-based language that was originally intended for writing constraint solvers. In this paper we show that it is also possible to write the classic union-find algorithm and variants in CHR. The programs neither compromise in declarativeness nor efficiency. We study the time complexity of our programs: they match the almost-linear complexity of the best known imperative implementations. This fact is illustrated with experimental results.Comment: 12 pages, 3 figures, to appear in Theory and Practice of Logic Programming (TPLP

Who rules the rules?

How pupils are to learn a second or a foreign language, especially grammatical elements, has been much debated the last couple of decades. This study is a qualitative analysis of teaching materials published between 1966 and 2007, used when teaching English in Swedish schools. The focus is on grammar exercises and the grammatical element relative pronouns. The exercises devoted to relative pronouns are analysed and contrasted in connection with the steering documents published in the early sixties (Lgr -60), the early eighties (Lgr -80) and the ones used today (Lpo -94). Results in short show that the exercises look roughly the same with introductory example sentences and so called fill-in-the-gaps exercises. The teaching materials, except one, use an inductive approach to grammar and the closer we get to the new millennium the more contrastive the exercises and explanations get

Visiting Rules and Regulations: A Preliminary Study

A revised version of this paper was published as: Schafer, N.E. (1989). "Prison Visiting: Is It Time to Review the Rules?" Federal Probation 53(4): 25–30 (Dec 1989). (http://heinonline.org/HOL/LandingPage?collection=journals&handle=hein.journals/fedpro53&div=57&id=&page=; )Visiting rules and regulations from 71 long-term adult correctional facilities from 31 states were collected for review. The rules are divided into five areas: visitor application, visitor processing, contraband, conduct, and dress codes. They are reviewed in the light of recent standards which stress the importance of encouraging visits. Suggestions and recommendations for change are included.Abstract / [Introduction] / The Visiting Rules / Becoming a Visitor / Visitor Processing / Contraband / Conduct / Dress Codes / Reference

Rules and risk in the euro area

Anna Iara and Guntram Wolff develop a model of sovereign spreads that are determined by the probability of default in interaction with the level of risk aversion. Estimation of the model confirms the central predictions. The legal basis for the rules, and mechanisms for enforcing them, are the most important dimensions of rulesbased fiscal governance.