Decidable structures between Church-style and Curry-style

It is well-known that the type-checking and type-inference problems are undecidable for second order lambda-calculus in Curry-style, although those for Church-style are decidable. What causes the differences in decidability and undecidability on the problems? We examine crucial conditions on terms for the (un)decidability property from the viewpoint of partially typed terms, and what kinds of type annotations are essential for (un)decidability of type-related problems. It is revealed that there exists an intermediate structure of second order lambda-terms, called a style of hole-application, between Church-style and Curry-style, such that the type-related problems are decidable under the structure. We also extend this idea to the omega-order polymorphic calculus F-omega, and show that the type-checking and type-inference problems then become undecidable

Strong Normalization of MLF via a Calculus of Coercions

MLF is a type system extending ML with first-class polymorphism as in system F. The main goal of the present paper is to show that MLF enjoys strong normalization, i.e. it has no infinite reduction paths. The proof of this result is achieved in several steps. We first focus on xMLF, the Church-style version of MLF, and show that it can be translated into a calculus of coercions: terms are mapped into terms and instantiations into coercions. This coercion calculus can be seen as a decorated version of system F, so that the simulation results entails strong normalization of xMLF through the same property of system F. We then transfer the result to all other versions of MLF using the fact that they can be compiled into xMLF and showing there is a bisimulation between the two. We conclude by discussing what results and issues are encountered when using the candidates of reducibility approach to the same problem

Determining code choice: written slogans during Egyptian revolution-January 2011

This qualitative study aims at depicting the phenomenon of the written code switching between Modern Standard Arabic (MSA) and Egyptian colloquial Arabic (ECA) in the written slogans during the Egyptian revolution January 2011. Findings show that ECA clauses comprise a significant percentage as observed from the survey done through the questionnaire and application of Myers-Scotton\u27s (1993) theoretical framework of Matrix Language Frame (MLF). These findings shed light on 1) Merging between MSA and ECA is a distinctive feature in Arabic in many domains 2)The best ways to benefit from this phenomenon in AFL teaching 3)The importance of the event in documenting the Arabic language and its varieties in face of future language change;and 4) Building on Bassiouney\u27s (2010) idea that code switching and role are related, this thesis demonstrates that the protestors chose ECA code when they wanted to express their anger and embrace their new role or identity as having power over the regime

On the Power of Coercion Abstraction

International audienceErasable coercions in System F-eta, also known as retyping functions, are well-typed eta-expansions of the identity. They may change the type of terms without changing their behavior and can thus be erased before reduction. Coercions in F-eta can model subtyping of known types and some displacement of quantifiers, but not subtyping assumptions nor certain forms of delayed type instantiation. We generalize F-eta by allowing abstraction over retyping functions. We follow a general approach where computing with coercions can be seen as computing in the lambda-calculus but keeping track of which parts of terms are coercions. We obtain a language where coercions do not contribute to the reduction but may block it and are thus not erasable. We recover erasable coercions by choosing a weak reduction strategy and restricting coercion abstraction to value-forms or by restricting abstraction to coercions that are polymorphic in their domain or codomain. The latter variant subsumes F-eta, F-sub, and MLF in a unified framework

Diglossic code-switching in Kuwaiti newspapers

Phd ThesisThe present study investigates the phenomenon of diglossic code-switching between Standard Arabic, as a High variety, and Kuwaiti Arabic, as a Low variety, in Kuwaiti newspaper articles. The study was precipitated by the paucity of research on the linguistic characteristics of newspaper discourse generated within this region as well as Kuwaiti perceptions towards this medium of communication. The frameworks adopted in this research were extended to novel contexts and were also utilised to gain new insights into several dimensions of diglossia, most of which have never been explored before. The findings of this study indeed revealed important insights into how diglosia is changing and how participants both use and perceive diglossic code-switching. The investigation was carried out to explore three main dimensions of code-switching in newspaper articles in Kuwait: changes in attitudes and frequency of code-switching use, the social motivations for it and the morphosyntactic constraints associated with it in this context. The first involves the study of changes in both language attitudes and in the frequency of code-switching in newspaper articles over the last 29-30 years. The second part of the study offers a social motivations’ analysis of code-switching in newspaper articles by appealing to the ideas captured in the Markedness Model (MM), proposed by Myers-Scotton 1993a. The primary goal of this element of the research was to seek explanations for the diglossic code-switching strategies identified in a sample of twelve newspaper articles. The third aspect explored in the research relates to the testing of the Matrix Language Frame (MLF) model which applies specifically to the morphosyntactic constraints thought to operate in spoken code-switching contexts (Myers-Scotton 1993b, 2002). A key objective of the research overall was to evaluate the models themselves which have not, to my knowledge, been appraised heretofore using written data of this kind. In general terms, my findings regarding attitudinal change and code-switching frequency suggest that, despite the differences exhibited by a range of social variables, the nature of the attitudes expressed by the readers and columnists alike still reflect the traditional diglossic situation in Kuwait. Moreover, an analysis of language attitudes, ix employing the ‘apparent time’ hypothesis, shows that there is indeed a change in language attitudes in Kuwait between one generation and the next. This change, however, is contrary to predictions as it actually shows a favouring effect within the community at large for the H variety, i.e. SA. Non-parametric statistical analyses (specifically the Wilcoxon Signed Ranks, Mann-Whitney and Kruskal-Wallis tests) were selected as most appropriate for discriminating quantitative distinctions in the analysis of attitudes. Furthermore, an investigation of how common code-switching has become over the last three decades reveals that there is, in fact, static code-switching frequency, indicating that the practice of code-switching has remained relatively stable between 1985 and 2014-15. As for the second and third dimensions of the research, it was shown that the MM offers a very useful explanation of the linguistic behaviour of columnists and reveals the intricacies of their code-switching strategies which can be related to their understanding of community perceptions towards diglossic codeswitching in Kuwait as captured in other aspects of the research. A key finding with respect to the testing of the MLF model itself was how difficult it actually was to diglossic code-switching in a written context. My research clearly shows that the MLF approach does not, in fact, provide as much insight into the dynamics of the phenomenon as it clearly does when applied to conversational exchanges and this is partially due to the problems identified in my thesis regarding the analysis of Arabic code-switching in writing

On the Power of Coercion Abstraction

Erasable coercions in System F-eta, also known as retyping functions, are well-typed eta-expansions of the identity. They may change the type of terms without changing their behavior and can thus be erased before reduction. Coercions in F-eta can model subtyping of known types and some displacement of quantifiers, but not subtyping assumptions nor certain forms of delayed type instantiation. We generalize F-eta by allowing abstraction over retyping functions. We follow a general approach where computing with coercions can be seen as computing in the lambda-calculus but keeping track of which parts of terms are coercions. We obtain a language where coercions do not contribute to the reduction but may block it and are thus not erasable. We recover erasable coercions by choosing a weak reduction strategy and restricting coercion abstraction to value-forms or by restricting abstraction to coercions that are polymorphic in their domain or codomain. The latter variant subsumes F-eta, F-sub, and MLF in a unified framework.Les coercions effaçables dans le Système F-eta, aussi connues sous le nom de fonctions de retypage, sont des eta-expansions de l'identité. Elles peuvent changer le type des termes sans en changer leur comportement et peuvent donc être effacées avant la réduction. Les coercions de F-eta peuvent modéliser le sous-typage entre types connus ou le déplacement de quantificateurs, mais elles ne permettent pas certaines formes d'instanciation retardée ni de raisonner sous des hypothèses de sous-typage. Nous généralisons F-eta en introduisant l'abstraction des fonctions de retypage. Nous suivons une approche générale où le calcul avec des coercions peut être vu comme une réduction dans le lambda-calcul gardant trace de la partie des termes qui sont des coercions. Nous obtenons un langage où les coercions ne contribuent pas au calcul, mais peuvent le bloquer et ne sont donc pas effaçables. Nous retrouvons des coercions effaçables en choisissant une stratégie de réduction faible et en restreignant l'abstraction de coercions aux valeurs ou bien en restreignant l'abstraction aux coercions qui sont polymorphes en leur domaine ou en leur codomaine. Cette seconde variante généralise F-eta, MLF et F-sub dans un cadre unifié

Evidence Normalization in System FC (Invited Talk)

System FC is an explicitly typed language that serves as the target language for Haskell source programs. System FC is based on System F with the addition of erasable but explicit type equality proof witnesses. Equality proof witnesses are generated from type inference performed on source Haskell programs. Such witnesses may be very large objects, which causes performance degradation in later stages of compilation, and makes it hard to debug the results of type inference and subsequent program transformations. In this paper we present an equality proof simplification algorithm, implemented in GHC, which greatly reduces the size of the target System FC programs

Spartan Daily, February 25, 1981

Volume 76, Issue 21https://scholarworks.sjsu.edu/spartandaily/6725/thumbnail.jp

Casco Bay Weekly : 18 April 1991

https://digitalcommons.portlandlibrary.com/cbw_1991/1016/thumbnail.jp