Liberal Typing for Functional Logic Programs

We propose a new type system for functional logic programming which is more liberal than the classical Damas-Milner usually adopted, but it is also restrictive enough to ensure type soundness. Starting from Damas-Milner typing of expressions we propose a new notion of well-typed program that adds support for type-indexed functions, existential types, opaque higher-order patterns and generic functions-as shown by an extensive collection of examples that illustrate the possibilities of our proposal. In the negative side, the types of functions must be declared, and therefore types are checked but not inferred. Another consequence is that parametricity is lost, although the impact of this flaw is limited as "free theorems" were already compromised in functional logic programming because of non-determinism

Overview of recent TJ-II stellarator results

The main results obtained in the TJ-II stellarator in the last two years are reported. The most important topics investigated have been modelling and validation of impurity transport, validation of gyrokinetic simulations, turbulence characterisation, effect of magnetic configuration on transport, fuelling with pellet injection, fast particles and liquid metal plasma facing components. As regards impurity transport research, a number of working lines exploring several recently discovered effects have been developed: the effect of tangential drifts on stellarator neoclassical transport, the impurity flux driven by electric fields tangent to magnetic surfaces and attempts of experimental validation with Doppler reflectometry of the variation of the radial electric field on the flux surface. Concerning gyrokinetic simulations, two validation activities have been performed, the comparison with measurements of zonal flow relaxation in pellet-induced fast transients and the comparison with experimental poloidal variation of fluctuations amplitude. The impact of radial electric fields on turbulence spreading in the edge and scrape-off layer has been also experimentally characterized using a 2D Langmuir probe array. Another remarkable piece of work has been the investigation of the radial propagation of small temperature perturbations using transfer entropy. Research on the physics and modelling of plasma core fuelling with pellet and tracer-encapsulated solid-pellet injection has produced also relevant results. Neutral beam injection driven Alfvénic activity and its possible control by electron cyclotron current drive has been examined as well in TJ-II. Finally, recent results on alternative plasma facing components based on liquid metals are also presented. ISSN:0029-5515 ISSN:1741-432

Failure and Equality in Functional Logic Programming1 1Work partially supported by the Spanish project TIC2002-01167 ‘MELODIAS’

AbstractConstructive failure has been proposed recently as a programming construct useful for functional logic programming, playing a role similar to that of constructive negation in logic programming. On the other hand, almost any functional logic program requires the use of some kind of equality test between expressions. We face in this work in a rigorous way the interaction of failure and equality (even for non-ground expressions), which is a non trivial issue, requiring in particular the use of disequality conditions at the level of the operational mechanism of constructive failure. As an interesting side product, we develop a novel treatment of equality and disequality in functional logic programming, by giving them a functional status, which is better suited for practice than previous proposals

A Fully Abstract Semantics for Constructor Systems

Constructor-based term rewriting systems are a useful subclass of TRS, in particular for programming purposes. In this kind of systems constructors determine a universe of values, which are the expected output of the computations. Then it would be natural to think of a semantics associating each expression to the set of its reachable values. Somehow surprisingly, the resulting semantics has poor properties, for it is not compositional nor fully abstract when non-confluent systems are considered. In this paper we propose a novel semantics for expressions in constructor systems, which is compositional and fully abstract (with respect to sensible observation functions, in particular the set of reachable values for an expression), and therefore can serve as appropriate basis for semantic based analysis or manipulation of such kind of rewrite systems

Proving Failure in Functional Logic Programs

Abstract. How to extract negative information from programs is an important issue in logic programming. Here we address the problem for functional logic programs, from a proof-theoretic perspective. The starting point of our work is CRWL (Constructor based ReWriting Logic), a well established theoretical framework for functional logic programming, whose fundamental notion is that of non-strict non-deterministic function. We present a proof calculus, CRWLF, which is able to deduce negative information from CRWL-programs. In particular, CRWLF is able to prove ‘finite ’ failure of reduction within CRWL.

Skin cancer in survivors of childhood and adolescent cancer.

The incidence of basal cell carcinoma (BCC) has been related to ionizing radiation, particularly for exposure occurring at young age. In this study, we considered the incidence of second skin neoplasms in long-term survivors from childhood cancer. We considered second primary cancers occurring among 776 subjects (436 males, 340 females) with first primary cancer diagnosed before age 20 years, between 1974 and 2001, in the Swiss Cantons of Vaud and Neuchâtel (786,000 inhabitants). Five BCC were observed versus 0.43 expected (standardized incidence ratio: 11.6, 95% confidence interval: 3.7-27.1). No case of cutaneous squamous cell carcinoma, nor of malignant melanoma was observed. The estimated radiation doses at 1mm through the skin ranged between 7 and 27 Sv. These data confirm that BCC are strongly related to ionizing radiation exposure in childhood. All the BCC were located within the radiation field, thus indicating that ionizing radiation is the key aetiological factor, even in the absence of any meaningful interaction with UV