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Reference Counting as a Computational Interpretation of Linear Logic
 Journal of Functional Programming
, 1996
"... We develop formal methods for reasoning about memory usage at a level of abstraction suitable for establishing or refuting claims about the potential applications of linear logic for static analysis. In particular, we demonstrate a precise relationship between type correctness for a language based o ..."
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We develop formal methods for reasoning about memory usage at a level of abstraction suitable for establishing or refuting claims about the potential applications of linear logic for static analysis. In particular, we demonstrate a precise relationship between type correctness for a language based on linear logic and the correctness of a referencecounting interpretation of the primitives that the language draws from the rules for the `of course' operation. Our semantics is `lowlevel' enough to express sharing and copying while still being `highlevel ' enough to abstract away from details of memory layout. This enables the formulation and proof of a result describing the possible runtime reference counts of values of linear type. Contents 1 Introduction 1 2 Operational Semantics with Memory 4 3 A Programming Language Based on Linear Logic 9 4 Semantics 14 5 Properties of the Semantics 24 6 Linear Logic and Memory 27 7 Discussion 32 A Proofs of the Main Theorems 36 Acknowledgements...
Games and full abstraction for nondeterministic languages
, 1999
"... Abstract Nondeterminism is a pervasive phenomenon in computation. Often it arises as an emergent property of a complex system, typically as the result of contention for access to shared resources. In such circumstances, we cannot always know, in advance, exactly what will happen. In other circumstan ..."
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Abstract Nondeterminism is a pervasive phenomenon in computation. Often it arises as an emergent property of a complex system, typically as the result of contention for access to shared resources. In such circumstances, we cannot always know, in advance, exactly what will happen. In other circumstances, nondeterminism is explicitly introduced as a means of abstracting away from implementation details such as precise command scheduling and control flow. However, the kind of behaviours exhibited by nondeterministic computations can be extremely subtle in comparison to those of their deterministic counterparts and reasoning about such programs is notoriously tricky as a result. It is therefore important to develop semantic tools to improve our understanding of, and aid our reasoning about, such nondeterministic programs. In this thesis, we extend the framework of game semantics to encompass nondeterministic computation. Game semantics is a relatively recent development in denotational semantics; its main novelty is that it views a computation not as a static entity, but rather as a dynamic process of interaction. This perspective makes the theory wellsuited to modelling many aspects of computational processes: the original use of game semantics in modelling the simple functional language PCF has subsequently been extended to handle more complex control structures such as references and continuations.
Specification and Verification of ObjectOriented Programs
, 1997
"... Interface specifications should express program properties in a formal, declarative, and implementationindependent way. To achieve implementationindependency, interface specifications have to support data abstraction. Program verification should enable to prove implementations correct w.r.t. suc ..."
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Interface specifications should express program properties in a formal, declarative, and implementationindependent way. To achieve implementationindependency, interface specifications have to support data abstraction. Program verification should enable to prove implementations correct w.r.t. such interface specifications. The presented work bridges the gap between existing specification and verification techniques for objectoriented programs. The integration is done within a formal framework for interface specifications and programming language semantics. Interface specification techniques are enhanced to support the specification of data structure sharing and destructive updating of shared variables. These extensions are necessary for the specification of real life software libraries. Moreover this generalization is needed for intermediate steps in correctness proofs. For verification, Hoare logic is extended to capture recursive classes and subtyping. Based on this extended logic, techniques are presented for proving typing properties, class and method invariants. The new
A rational deconstruction of Landin’s SECD machine
 Implementation and Application of Functional Languages, 16th International Workshop, IFL’04, number 3474 in Lecture Notes in Computer Science
, 2004
"... Abstract. Landin’s SECD machine was the first abstract machine for applicative expressions, i.e., functional programs. Landin’s J operator was the first control operator for functional languages, and was specified by an extension of the SECD machine. We present a family of evaluation functions corre ..."
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Abstract. Landin’s SECD machine was the first abstract machine for applicative expressions, i.e., functional programs. Landin’s J operator was the first control operator for functional languages, and was specified by an extension of the SECD machine. We present a family of evaluation functions corresponding to this extension of the SECD machine, using a series of elementary transformations (transformation into continuationpassing style (CPS) and defunctionalization, chiefly) and their left inverses (transformation into direct style and refunctionalization). To this end, we modernize the SECD machine into a bisimilar one that operates in lockstep with the original one but that (1) does not use a data stack and (2) uses the callersave rather than the calleesave convention for environments. We also identify that the dump component of the SECD machine is managed in a calleesave way. The callersave counterpart of the modernized SECD machine precisely corresponds to Thielecke’s doublebarrelled continuations and to Felleisen’s encoding of J in terms of call/cc. We then variously characterize the J operator in terms of CPS and in terms of delimitedcontrol operators in the CPS hierarchy. As a byproduct, we also present several reduction semantics for applicative expressions
What Is an Algorithm?
, 2000
"... Machines and Recursive Definitions 2.1 Abstract Machines The bestknown model of mechanical computation is (still) the first, introduced by Turing [18], and after half a century of study, few doubt the truth of the fundamental ChurchTuring Thesis : A function f : N # N on the natural numbers (o ..."
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Machines and Recursive Definitions 2.1 Abstract Machines The bestknown model of mechanical computation is (still) the first, introduced by Turing [18], and after half a century of study, few doubt the truth of the fundamental ChurchTuring Thesis : A function f : N # N on the natural numbers (or, more generally, on strings from a finite alphabet) is computable in principle exactly when it can be computed by a Turing Machine. The ChurchTuring Thesis grounds proofs of undecidability and it is essential for the most important applications of logic. On the other hand, it cannot be argued seriously that Turing machines model faithfully all algorithms on the natural numbers. If, for example, we code the input n in binary (rather than unary) notation, then the time needed for the computation of f(n) can sometimes be considerably shortened; and if we let the machine use two tapes rather than one, then (in some cases) we may gain a quadratic speedup of the computation, see [8]. This mea...
A Formal Semantics for the C Programming Language
, 1998
"... educational and research purposes, provided that the source is acknowledged and the present ..."
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educational and research purposes, provided that the source is acknowledged and the present
Defunctionalized interpreters for programming languages
, 2008
"... This document illustrates how functional implementations of formal semantics (structural operational semantics, reduction semantics, smallstep and bigstep abstract machines, natural semantics, and denotational semantics) can be transformed into each other. These transformations were foreshadowed ..."
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This document illustrates how functional implementations of formal semantics (structural operational semantics, reduction semantics, smallstep and bigstep abstract machines, natural semantics, and denotational semantics) can be transformed into each other. These transformations were foreshadowed by Reynolds in Definitional Interpreters for HigherOrder Programming Languages for functional implementations of denotational semantics, natural semantics, and bigstep abstract machines using closure conversion, CPS transformation, and defunctionalization. Over the last few years, the author and his students have further observed that machines are related using fusion by xedpoint promotion and that functional implementations of reduction semantics and of smallstep abstract machines are related using refocusing and transition
Correspondence between Operational and Denotational Semantics
 Handbook of Logic in Computer Science
, 1995
"... This course introduces the operational and denotational semantics of PCF and examines the relationship between the two. Topics: Syntax and operational semantics of PCF, Activity Lemma, undefinability of parallel or; Context Lemma (first principles proof) and proof by logical relations Denotational ..."
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This course introduces the operational and denotational semantics of PCF and examines the relationship between the two. Topics: Syntax and operational semantics of PCF, Activity Lemma, undefinability of parallel or; Context Lemma (first principles proof) and proof by logical relations Denotational semantics of PCF induced by an interpretation; (standard) Scott model, adequacy, weak adequacy and its proof (by a computability predicate) Domain Theory up to SFP and Scott domains; non full abstraction of the standard model, definability of compact elements and full abstraction for PCFP (PCF + parallel or), properties of orderextensional (continuous) models of PCF, Milner's model and Mulmuley's construction (excluding proofs) Additional topics (time permitting): results on pure simplytyped lambda calculus, Friedman 's Completeness Theorem, minimal model, logical relations and definability, undecidability of lambda definability (excluding proof), dIdomains and stable functions Homepa...
Realizability semantics of parametric polymorphism, general references, and recursive types
, 2010
"... Abstract. We present a realizability model for a callbyvalue, higherorder programming language with parametric polymorphism, general firstclass references, and recursive types. The main novelty is a relational interpretation of open types (as needed for parametricity reasoning) that include gener ..."
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Abstract. We present a realizability model for a callbyvalue, higherorder programming language with parametric polymorphism, general firstclass references, and recursive types. The main novelty is a relational interpretation of open types (as needed for parametricity reasoning) that include general reference types. The interpretation uses a new approach to modeling references. The universe of semantic types consists of worldindexed families of logical relations over a universal predomain. In order to model general reference types, worlds are finite maps from locations to semantic types: this introduces a circularity between semantic types and worlds that precludes a direct definition of either. Our solution is to solve a recursive equation in an appropriate category of metric spaces. In effect, types are interpreted using a Kripke logical relation over a recursively defined set of worlds. We illustrate how the model can be used to prove simple equivalences between different implementations of imperative abstract data types. 1
On the equivalence between smallstep and bigstep abstract machines: a simple application of lightweight fusion
 Inf. Process. Lett
, 2008
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