A strong confluence result for Q*, a quantum λ-calculus with measurements, is proved. More precisely, confluence is shown to hold both for finite and infinite computations. The technique used in the ...confluence proof is syntactical but innovative. This makes Q* different from similar quantum lambda calculi, which are either measurement-free or provided with a reduction strategy.
Every needed strategy is normalizing in the λ-calculus. Here, we extend the result to the λσ-calculus, a λ-calculus with explicit substitutions. The extension requires considering rewriting systems ...with critical pairs, confluent or non-confluent, and developing for them a satisfactory theory of needed normalization. Our idea is to count for every term M the number of its normalizing paths, up to Lévy permutation equivalence. We deduce from standardization that every needed strategy normalizes when this number is finite. The number is zero or one in the λ-calculus, and we show that it is finite in the λσ-calculus.
The notion of confluence is studied on the context of bigraphs. Confluence will be important in modelling real-world systems, both natural (as in biology) and artificial (as in pervasive computing). ...The paper uses bigraphs in which names have multiple locality; this enables a formulation of the lambda calculus with explicit substitutions. The paper reports work in progress, seeking conditions on a bigraphical reactive system that are sufficient to ensure confluence; the conditions must deal with the way that bigraphical redexes can be intricately intertwined. The conditions should also be satisfied by the lambda calculus. After discussion of these issues, two conjectures are put forward.
La complexité implicite (ICC) vise à donner des caractérisations de classes de complexité dans des langages de programmation ou des logiques, sans faire référence à des bornes sur les ressources ...(temps, espace mémoire). Dans cette thèse, nous étudions l’approche de la logique linéaire à la complexité implicite. L’objectif est de donner des caractérisations de classes de complexité, à travers des variantes du lambda-calcul qui sont typables dans de tels systèmes. En particulier, nous considérons à la fois une perspective monovalente et une perspective polyvalente par rapport à l’ICC. Dans le premier cas, le but est de caractériser une hiérarchie de classes de complexité à travers un lambda-calcul élémentaire typé dans la logique linéaire élémentaire (ELL), où la complexité ne dépend que de l’interface d’un programme, c’est à dire son type. La deuxième approche rend compte à la fois des fonctions calculables en temps polynomial et de la normalisation forte, à travers des termes du lambda-calcul pur qui sont typés dans un système inspiré par la logique linéaire Soft (SLL); en particulier, par rapport à l’approche logique ordinaire, ici nous abandonnons la modalité “!” en faveur de l’emploi des types stratifiés, vus comme un raffinement des types intersection non associatifs, afin d’améliorer la typabilité et, en conséquence, l’expressivité. Enfin, nous explorons l’utilisation des types intersection, privés de certaines de leurs propriétés, vers une direction plus quantitative que l’approche qualitative habituelle, afin d’obtenir une borne sur le calcul de lambda-termes purs, en obtenant en plus une caractérisation de la normalisation forte.
In this thesis we explore the linear logic approach to implicit computational complexity, through the design of type assignment systems based on light linear logic, or heavily inspired by them, with the purpose of giving a characterization of one or more complexity classes, through variants of lambda-calculi which are typable in such systems. In particular, we consider both a monovalent and a polyvalent perspective with respect to ICC. In the first one the aim is to characterize a hierarchy of complexity classes through an elementary lambda-calculus typed in Elementary Linear Logic (ELL), where the complexity depends only on the interface of a term, namely its type. The second approach gives an account of both the functions computable in polynomial time and of strong normalization, through terms of pure lambda-calculus which are typed in a system inspired by Soft Linear Logic (SLL); in particular, with respect to the usual logical take, in the latter we give up the “!” modality in favor of employing stratified types as a refinement of non-associative intersection types, in order to improve typability and, as a consequence, expressivity.Finally we explore the use of intersection types, deprived of some of their usual properties, towards a more quantitative approach rather than the usual qualitative one, namely in order to compute a bound on the computation of pure lambda-terms, obtaining in addition a characterization of strong normalization.
Mainstream object-oriented languages often fail to provide complete powerful features altogether, such as, multiple inheritance, dynamic overloading and copy semantics of inheritance. In this paper ...we present a core object-oriented imperative language that integrates all these features in a formal framework. We define a static type system and a translation of the language into the meta-language λ_object,, in order to account for semantic issues and prove type safety of our proposal.
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