Writing accurate numerical software is hard because of many sources of unavoidable uncertainties, including finite numerical precision of implementations. We present a programming model where the user writes a program in a real-valued implementation and specification language that explicitly includes different types of uncertainties. We then present a compilation algorithm that generates a finite-precision implementation that is guaranteed to meet the desired precision with respect to real numbers. Our compilation performs a number of verification steps for different candidate precisions. It generates verification conditions that treat all sources of uncertainties in a unified way and encode reasoning about finite-precision roundoff errors into reasoning about real numbers. Such verification conditions can be used as a standardized format for verifying the precision and the correctness of numerical programs. Due to their non-linear nature, precise reasoning about these verification conditions remains difficult and cannot be handled using state-of-the art SMT solvers alone. We therefore propose a new procedure that combines exact SMT solving over reals with approximate and sound affine and interval arithmetic. We show that this approach overcomes scalability limitations of SMT solvers while providing improved precision over affine and interval arithmetic. Our implementation gives promising results on several numerical models, including dynamical systems, transcendental functions, and controller implementations.
{"title":"Sound compilation of reals","authors":"Eva Darulova, Viktor Kunčak","doi":"10.1145/2535838.2535874","DOIUrl":"https://doi.org/10.1145/2535838.2535874","url":null,"abstract":"Writing accurate numerical software is hard because of many sources of unavoidable uncertainties, including finite numerical precision of implementations. We present a programming model where the user writes a program in a real-valued implementation and specification language that explicitly includes different types of uncertainties. We then present a compilation algorithm that generates a finite-precision implementation that is guaranteed to meet the desired precision with respect to real numbers. Our compilation performs a number of verification steps for different candidate precisions. It generates verification conditions that treat all sources of uncertainties in a unified way and encode reasoning about finite-precision roundoff errors into reasoning about real numbers. Such verification conditions can be used as a standardized format for verifying the precision and the correctness of numerical programs. Due to their non-linear nature, precise reasoning about these verification conditions remains difficult and cannot be handled using state-of-the art SMT solvers alone. We therefore propose a new procedure that combines exact SMT solving over reals with approximate and sound affine and interval arithmetic. We show that this approach overcomes scalability limitations of SMT solvers while providing improved precision over affine and interval arithmetic. Our implementation gives promising results on several numerical models, including dynamical systems, transcendental functions, and controller implementations.","PeriodicalId":20683,"journal":{"name":"Proceedings of the 41st ACM SIGPLAN-SIGACT Symposium on Principles of Programming Languages","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2013-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85368702","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract separation logics are a family of extensions of Hoare logic for reasoning about programs that mutate memory. These logics are "abstract" because they are independent of any particular concrete memory model. Their assertion languages, called propositional abstract separation logics, extend the logic of (Boolean) Bunched Implications (BBI) in various ways. We develop a modular proof theory for various propositional abstract separation logics using cut-free labelled sequent calculi. We first extend the cut-fee labelled sequent calculus for BBI of Hou et al to handle Calcagno et al's original logic of separation algebras by adding sound rules for partial-determinism and cancellativity, while preserving cut-elimination. We prove the completeness of our calculus via a sound intermediate calculus that enables us to construct counter-models from the failure to find a proof. We then capture other propositional abstract separation logics by adding sound rules for indivisible unit and disjointness, while maintaining completeness and cut-elimination. We present a theorem prover based on our labelled calculus for these logics.
{"title":"Proof search for propositional abstract separation logics via labelled sequents","authors":"Zhé Hóu, Ranald Clouston, R. Goré, Alwen Tiu","doi":"10.1145/2535838.2535864","DOIUrl":"https://doi.org/10.1145/2535838.2535864","url":null,"abstract":"Abstract separation logics are a family of extensions of Hoare logic for reasoning about programs that mutate memory. These logics are \"abstract\" because they are independent of any particular concrete memory model. Their assertion languages, called propositional abstract separation logics, extend the logic of (Boolean) Bunched Implications (BBI) in various ways. We develop a modular proof theory for various propositional abstract separation logics using cut-free labelled sequent calculi. We first extend the cut-fee labelled sequent calculus for BBI of Hou et al to handle Calcagno et al's original logic of separation algebras by adding sound rules for partial-determinism and cancellativity, while preserving cut-elimination. We prove the completeness of our calculus via a sound intermediate calculus that enables us to construct counter-models from the failure to find a proof. We then capture other propositional abstract separation logics by adding sound rules for indivisible unit and disjointness, while maintaining completeness and cut-elimination. We present a theorem prover based on our labelled calculus for these logics.","PeriodicalId":20683,"journal":{"name":"Proceedings of the 41st ACM SIGPLAN-SIGACT Symposium on Principles of Programming Languages","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2013-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89050867","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Thomas Dinsdale-Young, L. Birkedal, Philippa Gardner, Matthew J. Parkinson, Hongseok Yang
Compositional abstractions underly many reasoning principles for concurrent programs: the concurrent environment is abstracted in order to reason about a thread in isolation; and these abstractions are composed to reason about a program consisting of many threads. For instance, separation logic uses formulae that describe part of the state, abstracting the rest; when two threads use disjoint state, their specifications can be composed with the separating conjunction. Type systems abstract the state to the types of variables; threads may be composed when they agree on the types of shared variables. In this paper, we present the "Concurrent Views Framework", a metatheory of concurrent reasoning principles. The theory is parameterised by an abstraction of state with a notion of composition, which we call views. The metatheory is remarkably simple, but highly applicable: the rely-guarantee method, concurrent separation logic, concurrent abstract predicates, type systems for recursive references and for unique pointers, and even an adaptation of the Owicki-Gries method can all be seen as instances of the Concurrent Views Framework. Moreover, our metatheory proves each of these systems is sound without requiring induction on the operational semantics.
{"title":"Views: compositional reasoning for concurrent programs","authors":"Thomas Dinsdale-Young, L. Birkedal, Philippa Gardner, Matthew J. Parkinson, Hongseok Yang","doi":"10.1145/2429069.2429104","DOIUrl":"https://doi.org/10.1145/2429069.2429104","url":null,"abstract":"Compositional abstractions underly many reasoning principles for concurrent programs: the concurrent environment is abstracted in order to reason about a thread in isolation; and these abstractions are composed to reason about a program consisting of many threads. For instance, separation logic uses formulae that describe part of the state, abstracting the rest; when two threads use disjoint state, their specifications can be composed with the separating conjunction. Type systems abstract the state to the types of variables; threads may be composed when they agree on the types of shared variables.\u0000 In this paper, we present the \"Concurrent Views Framework\", a metatheory of concurrent reasoning principles. The theory is parameterised by an abstraction of state with a notion of composition, which we call views. The metatheory is remarkably simple, but highly applicable: the rely-guarantee method, concurrent separation logic, concurrent abstract predicates, type systems for recursive references and for unique pointers, and even an adaptation of the Owicki-Gries method can all be seen as instances of the Concurrent Views Framework. Moreover, our metatheory proves each of these systems is sound without requiring induction on the operational semantics.","PeriodicalId":20683,"journal":{"name":"Proceedings of the 41st ACM SIGPLAN-SIGACT Symposium on Principles of Programming Languages","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2013-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73250331","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
C. Fournet, N. Swamy, Juan Chen, Pierre-Évariste Dagand, Pierre-Yves Strub, B. Livshits
Many tools allow programmers to develop applications in high-level languages and deploy them in web browsers via compilation to JavaScript. While practical and widely used, these compilers are ad hoc: no guarantee is provided on their correctness for whole programs, nor their security for programs executed within arbitrary JavaScript contexts. This paper presents a compiler with such guarantees. We compile an ML-like language with higher-order functions and references to JavaScript, while preserving all source program properties. Relying on type-based invariants and applicative bisimilarity, we show full abstraction: two programs are equivalent in all source contexts if and only if their wrapped translations are equivalent in all JavaScript contexts. We evaluate our compiler on sample programs, including a series of secure libraries.
{"title":"Fully abstract compilation to JavaScript","authors":"C. Fournet, N. Swamy, Juan Chen, Pierre-Évariste Dagand, Pierre-Yves Strub, B. Livshits","doi":"10.1145/2429069.2429114","DOIUrl":"https://doi.org/10.1145/2429069.2429114","url":null,"abstract":"Many tools allow programmers to develop applications in high-level languages and deploy them in web browsers via compilation to JavaScript. While practical and widely used, these compilers are ad hoc: no guarantee is provided on their correctness for whole programs, nor their security for programs executed within arbitrary JavaScript contexts. This paper presents a compiler with such guarantees. We compile an ML-like language with higher-order functions and references to JavaScript, while preserving all source program properties. Relying on type-based invariants and applicative bisimilarity, we show full abstraction: two programs are equivalent in all source contexts if and only if their wrapped translations are equivalent in all JavaScript contexts. We evaluate our compiler on sample programs, including a series of secure libraries.","PeriodicalId":20683,"journal":{"name":"Proceedings of the 41st ACM SIGPLAN-SIGACT Symposium on Principles of Programming Languages","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2013-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80003157","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Benjamin Delaware, Bruno C. d. S. Oliveira, Tom Schrijvers
Formalizing meta-theory, or proofs about programming languages, in a proof assistant has many well-known benefits. Unfortunately, the considerable effort involved in mechanizing proofs has prevented it from becoming standard practice. This cost can be amortized by reusing as much of existing mechanized formalizations as possible when building a new language or extending an existing one. One important challenge in achieving reuse is that the inductive definitions and proofs used in these formalizations are closed to extension. This forces language designers to cut and paste existing definitions and proofs in an ad-hoc manner and to expend considerable effort to patch up the results. The key contribution of this paper is the development of an induction technique for extensible Church encodings using a novel reinterpretation of the universal property of folds. These encodings provide the foundation for a framework, formalized in Coq, which uses type classes to automate the composition of proofs from modular components. This framework enables a more structured approach to the reuse of meta-theory formalizations through the composition of modular inductive definitions and proofs. Several interesting language features, including binders and general recursion, illustrate the capabilities of our framework. We reuse these features to build fully mechanized definitions and proofs for a number of languages, including a version of mini-ML. Bounded induction enables proofs of properties for non-inductive semantic functions, and mediating type classes enable proof adaptation for more feature-rich languages.
{"title":"Meta-theory à la carte","authors":"Benjamin Delaware, Bruno C. d. S. Oliveira, Tom Schrijvers","doi":"10.1145/2429069.2429094","DOIUrl":"https://doi.org/10.1145/2429069.2429094","url":null,"abstract":"Formalizing meta-theory, or proofs about programming languages, in a proof assistant has many well-known benefits. Unfortunately, the considerable effort involved in mechanizing proofs has prevented it from becoming standard practice. This cost can be amortized by reusing as much of existing mechanized formalizations as possible when building a new language or extending an existing one. One important challenge in achieving reuse is that the inductive definitions and proofs used in these formalizations are closed to extension. This forces language designers to cut and paste existing definitions and proofs in an ad-hoc manner and to expend considerable effort to patch up the results.\u0000 The key contribution of this paper is the development of an induction technique for extensible Church encodings using a novel reinterpretation of the universal property of folds. These encodings provide the foundation for a framework, formalized in Coq, which uses type classes to automate the composition of proofs from modular components. This framework enables a more structured approach to the reuse of meta-theory formalizations through the composition of modular inductive definitions and proofs.\u0000 Several interesting language features, including binders and general recursion, illustrate the capabilities of our framework. We reuse these features to build fully mechanized definitions and proofs for a number of languages, including a version of mini-ML. Bounded induction enables proofs of properties for non-inductive semantic functions, and mediating type classes enable proof adaptation for more feature-rich languages.","PeriodicalId":20683,"journal":{"name":"Proceedings of the 41st ACM SIGPLAN-SIGACT Symposium on Principles of Programming Languages","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2013-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76475109","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We investigate impure, call-by-value programming languages. Our first language only has variables and let-binding. Its equational theory is a variant of Lambek's theory of multicategories that omits the commutativity axiom. We demonstrate that type constructions for impure languages --- products, sums and functions --- can be characterized by universal properties in the setting of 'premulticategories', multicategories where the commutativity law may fail. This leads us to new, universal characterizations of two earlier equational theories of impure programming languages: the premonoidal categories of Power and Robinson, and the monad-based models of Moggi. Our analysis thus puts these earlier abstract ideas on a canonical foundation, bringing them to a new, syntactic level.
{"title":"Universal properties of impure programming languages","authors":"S. Staton, P. Levy","doi":"10.1145/2429069.2429091","DOIUrl":"https://doi.org/10.1145/2429069.2429091","url":null,"abstract":"We investigate impure, call-by-value programming languages. Our first language only has variables and let-binding. Its equational theory is a variant of Lambek's theory of multicategories that omits the commutativity axiom.\u0000 We demonstrate that type constructions for impure languages --- products, sums and functions --- can be characterized by universal properties in the setting of 'premulticategories', multicategories where the commutativity law may fail. This leads us to new, universal characterizations of two earlier equational theories of impure programming languages: the premonoidal categories of Power and Robinson, and the monad-based models of Moggi. Our analysis thus puts these earlier abstract ideas on a canonical foundation, bringing them to a new, syntactic level.","PeriodicalId":20683,"journal":{"name":"Proceedings of the 41st ACM SIGPLAN-SIGACT Symposium on Principles of Programming Languages","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2013-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81229576","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A great deal of research on sanitizer placement, sanitizer correctness, checking path validity, and policy inference, has been done in the last five to ten years, involving type systems, static analysis and runtime monitoring and enforcement. However, in pretty much all work thus far, the burden of sanitizer placement has fallen on the developer. However, sanitizer placement in large-scale applications is difficult, and developers are likely to make errors, and thus create security vulnerabilities. This paper advocates a radically different approach: we aim to fully automate the placement of sanitizers by analyzing the ow of tainted data in the program. We argue that developers are better off leaving out sanitizers entirely instead of trying to place them. This paper proposes a fully automatic technique for sanitizer placement. Placement is static whenever possible, switching to run time when necessary. Run-time taint tracking techniques can be used to track the source of a value, and thus apply appropriate sanitization. However, due to the runtime overhead of run-time taint tracking, our technique avoids it wherever possible.
{"title":"Towards fully automatic placement of security sanitizers and declassifiers","authors":"B. Livshits, Stephen Chong","doi":"10.1145/2429069.2429115","DOIUrl":"https://doi.org/10.1145/2429069.2429115","url":null,"abstract":"A great deal of research on sanitizer placement, sanitizer correctness, checking path validity, and policy inference, has been done in the last five to ten years, involving type systems, static analysis and runtime monitoring and enforcement. However, in pretty much all work thus far, the burden of sanitizer placement has fallen on the developer. However, sanitizer placement in large-scale applications is difficult, and developers are likely to make errors, and thus create security vulnerabilities.\u0000 This paper advocates a radically different approach: we aim to fully automate the placement of sanitizers by analyzing the ow of tainted data in the program. We argue that developers are better off leaving out sanitizers entirely instead of trying to place them.\u0000 This paper proposes a fully automatic technique for sanitizer placement. Placement is static whenever possible, switching to run time when necessary. Run-time taint tracking techniques can be used to track the source of a value, and thus apply appropriate sanitization. However, due to the runtime overhead of run-time taint tracking, our technique avoids it wherever possible.","PeriodicalId":20683,"journal":{"name":"Proceedings of the 41st ACM SIGPLAN-SIGACT Symposium on Principles of Programming Languages","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2013-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84709591","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Tiark Rompf, Arvind K. Sujeeth, Nada Amin, Kevin J. Brown, V. Jovanovic, HyoukJoong Lee, Manohar Jonnalagedda, K. Olukotun, Martin Odersky
High level data structures are a cornerstone of modern programming and at the same time stand in the way of compiler optimizations. In order to reason about user- or library-defined data structures compilers need to be extensible. Common mechanisms to extend compilers fall into two categories. Frontend macros, staging or partial evaluation systems can be used to programmatically remove abstraction and specialize programs before they enter the compiler. Alternatively, some compilers allow extending the internal workings by adding new transformation passes at different points in the compile chain or adding new intermediate representation (IR) types. None of these mechanisms alone is sufficient to handle the challenges posed by high level data structures. This paper shows a novel way to combine them to yield benefits that are greater than the sum of the parts. Instead of using staging merely as a front end, we implement internal compiler passes using staging as well. These internal passes delegate back to program execution to construct the transformed IR. Staging is known to simplify program generation, and in the same way it can simplify program transformation. Defining a transformation as a staged IR interpreter is simpler than implementing a low-level IR to IR transformer. With custom IR nodes, many optimizations that are expressed as rewritings from IR nodes to staged program fragments can be combined into a single pass, mitigating phase ordering problems. Speculative rewriting can preserve optimistic assumptions around loops. We demonstrate several powerful program optimizations using this architecture that are particularly geared towards data structures: a novel loop fusion and deforestation algorithm, array of struct to struct of array conversion, object flattening and code generation for heterogeneous parallel devices. We validate our approach using several non trivial case studies that exhibit order of magnitude speedups in experiments.
{"title":"Optimizing data structures in high-level programs: new directions for extensible compilers based on staging","authors":"Tiark Rompf, Arvind K. Sujeeth, Nada Amin, Kevin J. Brown, V. Jovanovic, HyoukJoong Lee, Manohar Jonnalagedda, K. Olukotun, Martin Odersky","doi":"10.1145/2429069.2429128","DOIUrl":"https://doi.org/10.1145/2429069.2429128","url":null,"abstract":"High level data structures are a cornerstone of modern programming and at the same time stand in the way of compiler optimizations. In order to reason about user- or library-defined data structures compilers need to be extensible. Common mechanisms to extend compilers fall into two categories. Frontend macros, staging or partial evaluation systems can be used to programmatically remove abstraction and specialize programs before they enter the compiler. Alternatively, some compilers allow extending the internal workings by adding new transformation passes at different points in the compile chain or adding new intermediate representation (IR) types. None of these mechanisms alone is sufficient to handle the challenges posed by high level data structures. This paper shows a novel way to combine them to yield benefits that are greater than the sum of the parts.\u0000 Instead of using staging merely as a front end, we implement internal compiler passes using staging as well. These internal passes delegate back to program execution to construct the transformed IR. Staging is known to simplify program generation, and in the same way it can simplify program transformation. Defining a transformation as a staged IR interpreter is simpler than implementing a low-level IR to IR transformer. With custom IR nodes, many optimizations that are expressed as rewritings from IR nodes to staged program fragments can be combined into a single pass, mitigating phase ordering problems. Speculative rewriting can preserve optimistic assumptions around loops.\u0000 We demonstrate several powerful program optimizations using this architecture that are particularly geared towards data structures: a novel loop fusion and deforestation algorithm, array of struct to struct of array conversion, object flattening and code generation for heterogeneous parallel devices. We validate our approach using several non trivial case studies that exhibit order of magnitude speedups in experiments.","PeriodicalId":20683,"journal":{"name":"Proceedings of the 41st ACM SIGPLAN-SIGACT Symposium on Principles of Programming Languages","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2013-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79913915","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We exploit the apparent similarity between (discrete-time) stream processing and (continuous-time) signal processing and transfer a deductive verification framework from the former to the latter. Our development is based on rigorous semantics that relies on nonstandard analysis (NSA). Specifically, we start with a discrete framework consisting of a Lustre-like stream processing language, its Kahn-style fixed point semantics, and a program logic (in the form of a type system) for partial correctness guarantees. This stream framework is transferred as it is to one for hyperstreams---streams of streams, that typically arise from sampling (continuous-time) signals with progressively smaller intervals---via the logical infrastructure of NSA. Under a certain continuity assumption we identify hyperstreams with signals; our final outcome thus obtained is a deductive verification framework of signals. In it one verifies properties of signals using the (conventionally discrete) proof principles, like fixed point induction.
{"title":"Hyperstream processing systems: nonstandard modeling of continuous-time signals","authors":"Kohei Suenaga, Hiroyoshi Sekine, I. Hasuo","doi":"10.1145/2429069.2429120","DOIUrl":"https://doi.org/10.1145/2429069.2429120","url":null,"abstract":"We exploit the apparent similarity between (discrete-time) stream processing and (continuous-time) signal processing and transfer a deductive verification framework from the former to the latter. Our development is based on rigorous semantics that relies on nonstandard analysis (NSA).\u0000 Specifically, we start with a discrete framework consisting of a Lustre-like stream processing language, its Kahn-style fixed point semantics, and a program logic (in the form of a type system) for partial correctness guarantees. This stream framework is transferred as it is to one for hyperstreams---streams of streams, that typically arise from sampling (continuous-time) signals with progressively smaller intervals---via the logical infrastructure of NSA. Under a certain continuity assumption we identify hyperstreams with signals; our final outcome thus obtained is a deductive verification framework of signals. In it one verifies properties of signals using the (conventionally discrete) proof principles, like fixed point induction.","PeriodicalId":20683,"journal":{"name":"Proceedings of the 41st ACM SIGPLAN-SIGACT Symposium on Principles of Programming Languages","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2013-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73662754","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Reynolds' relational parametricity provides a powerful way to reason about programs in terms of invariance under changes of data representation. A dazzling array of applications of Reynolds' theory exists, exploiting invariance to yield "free theorems", non-inhabitation results, and encodings of algebraic datatypes. Outside computer science, invariance is a common theme running through many areas of mathematics and physics. For example, the area of a triangle is unaltered by rotation or flipping. If we scale a triangle, then we scale its area, maintaining an invariant relationship between the two. The transformations under which properties are invariant are often organised into groups, with the algebraic structure reflecting the composability and invertibility of transformations. In this paper, we investigate programming languages whose types are indexed by algebraic structures such as groups of geometric transformations. Other examples include types indexed by principals--for information flow security--and types indexed by distances--for analysis of analytic uniform continuity properties. Following Reynolds, we prove a general Abstraction Theorem that covers all these instances. Consequences of our Abstraction Theorem include free theorems expressing invariance properties of programs, type isomorphisms based on invariance properties, and non-definability results indicating when certain algebraically indexed types are uninhabited or only inhabited by trivial programs. We have fully formalised our framework and most examples in Coq.
{"title":"Abstraction and invariance for algebraically indexed types","authors":"R. Atkey, Patricia Johann, A. Kennedy","doi":"10.1145/2429069.2429082","DOIUrl":"https://doi.org/10.1145/2429069.2429082","url":null,"abstract":"Reynolds' relational parametricity provides a powerful way to reason about programs in terms of invariance under changes of data representation. A dazzling array of applications of Reynolds' theory exists, exploiting invariance to yield \"free theorems\", non-inhabitation results, and encodings of algebraic datatypes. Outside computer science, invariance is a common theme running through many areas of mathematics and physics. For example, the area of a triangle is unaltered by rotation or flipping. If we scale a triangle, then we scale its area, maintaining an invariant relationship between the two. The transformations under which properties are invariant are often organised into groups, with the algebraic structure reflecting the composability and invertibility of transformations.\u0000 In this paper, we investigate programming languages whose types are indexed by algebraic structures such as groups of geometric transformations. Other examples include types indexed by principals--for information flow security--and types indexed by distances--for analysis of analytic uniform continuity properties. Following Reynolds, we prove a general Abstraction Theorem that covers all these instances. Consequences of our Abstraction Theorem include free theorems expressing invariance properties of programs, type isomorphisms based on invariance properties, and non-definability results indicating when certain algebraically indexed types are uninhabited or only inhabited by trivial programs. We have fully formalised our framework and most examples in Coq.","PeriodicalId":20683,"journal":{"name":"Proceedings of the 41st ACM SIGPLAN-SIGACT Symposium on Principles of Programming Languages","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2013-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90674075","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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