Pub Date : 2022-12-23DOI: 10.1017/S0956796822000144
G. Hutton
The λ -calculus is considered the paradigmatic model for functional programming languages, and it is based on a rewriting mechanism. It comes with a beautiful mathematical theory, which has been studied and improved for more than 80 years. Rewriting expressions is common in computer science, but it is not the way in which programs are executed by the hardware. While the semantics of programs remains unaltered during compilation, the use of resources, in particular time and space, is more difficult to track. Slot and van Emde Boas Invariance Thesis states some requirements for a computational model to be reasonable . The rationale is that under the Invariance Thesis, complexity classes such as LOGSPACE and PTIME, become robust, i.e
{"title":"PhD Abstracts","authors":"G. Hutton","doi":"10.1017/S0956796822000144","DOIUrl":"https://doi.org/10.1017/S0956796822000144","url":null,"abstract":"The λ -calculus is considered the paradigmatic model for functional programming languages, and it is based on a rewriting mechanism. It comes with a beautiful mathematical theory, which has been studied and improved for more than 80 years. Rewriting expressions is common in computer science, but it is not the way in which programs are executed by the hardware. While the semantics of programs remains unaltered during compilation, the use of resources, in particular time and space, is more difficult to track. Slot and van Emde Boas Invariance Thesis states some requirements for a computational model to be reasonable . The rationale is that under the Invariance Thesis, complexity classes such as LOGSPACE and PTIME, become robust, i.e","PeriodicalId":15874,"journal":{"name":"Journal of Functional Programming","volume":null,"pages":null},"PeriodicalIF":1.1,"publicationDate":"2022-12-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49640448","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-12-22DOI: 10.1017/S0956796822000119
Cheng-En Chuang, Grant Iraci, Lukasz Ziarek
Abstract In this paper, we introduce a tiered-priority scheme for a synchronous message-passing language with support for selective communication and first-class communication protocols. Crucially, our scheme allows higher priority threads to communicate with lower priority threads, providing the ability to express programs that would be rejected by classic priority mechanisms that disallow any (potentially) blocking interactions between threads of differing priorities. We formalize our scheme in a novel semantic framework featuring a collection of actions to represent possible communications. Utilizing our formalism, we prove several important and desirable properties of our priority scheme. We also provide a prototype implementation of our tiered-priority scheme capable of expressing Concurrent ML and built in the MLton SML compiler and runtime. We evaluate the viability of our implementation through three case studies: a prioritized buyer-seller protocol and predictable shutdown mechanisms in the Swerve web server and eXene windowing toolkit. Our experiments show that priority can be easily added to existing CML programs without degrading performance. Our system exhibits negligible overheads on more modest workloads.
{"title":"Send to me first: Priority in synchronous message-passing","authors":"Cheng-En Chuang, Grant Iraci, Lukasz Ziarek","doi":"10.1017/S0956796822000119","DOIUrl":"https://doi.org/10.1017/S0956796822000119","url":null,"abstract":"Abstract In this paper, we introduce a tiered-priority scheme for a synchronous message-passing language with support for selective communication and first-class communication protocols. Crucially, our scheme allows higher priority threads to communicate with lower priority threads, providing the ability to express programs that would be rejected by classic priority mechanisms that disallow any (potentially) blocking interactions between threads of differing priorities. We formalize our scheme in a novel semantic framework featuring a collection of actions to represent possible communications. Utilizing our formalism, we prove several important and desirable properties of our priority scheme. We also provide a prototype implementation of our tiered-priority scheme capable of expressing Concurrent ML and built in the MLton SML compiler and runtime. We evaluate the viability of our implementation through three case studies: a prioritized buyer-seller protocol and predictable shutdown mechanisms in the Swerve web server and eXene windowing toolkit. Our experiments show that priority can be easily added to existing CML programs without degrading performance. Our system exhibits negligible overheads on more modest workloads.","PeriodicalId":15874,"journal":{"name":"Journal of Functional Programming","volume":null,"pages":null},"PeriodicalIF":1.1,"publicationDate":"2022-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44356963","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-09-29DOI: 10.1017/S0956796822000107
O. Danvy
Abstract Fold–unfold lemmas complement the rewrite tactic in the Coq Proof Assistant to reason about recursive functions, be they defined locally or globally. Each of the structural cases gives rise to a fold–unfold lemma that equates a call to this function in that case with the corresponding case branch. As such, they are “boilerplate” and can be generated mechanically, though stating them by hand is a learning experience for a beginner, to say nothing about explaining them. Their proof is generic. Their use is precise (e.g., in terms with multiple calls) and they scale seamlessly (e.g., to continuation-passing style and to various patterns of recursion), be the reasoning equational or relational. In the author’s experience, they prove effective in the classroom, considering the clarity of discourse in the subsequent term reports and oral exams, and beyond the classroom, considering their subsequent use when continuing to work with the Coq Proof Assistant. Fold–unfold lemmas also provide a measure of understanding as well as of control about what is cut short when one uses a shortcut, i.e., an automated simplification tactic. Since Version 8.0, the functional-induction plugin provides them for functions that are defined globally, i.e., recursive equations, and so does the Equations plugin now, both for global and for local declarations, a precious help for advanced users.
{"title":"Fold–unfold lemmas for reasoning about recursive programs using the Coq proof assistant","authors":"O. Danvy","doi":"10.1017/S0956796822000107","DOIUrl":"https://doi.org/10.1017/S0956796822000107","url":null,"abstract":"Abstract Fold–unfold lemmas complement the rewrite tactic in the Coq Proof Assistant to reason about recursive functions, be they defined locally or globally. Each of the structural cases gives rise to a fold–unfold lemma that equates a call to this function in that case with the corresponding case branch. As such, they are “boilerplate” and can be generated mechanically, though stating them by hand is a learning experience for a beginner, to say nothing about explaining them. Their proof is generic. Their use is precise (e.g., in terms with multiple calls) and they scale seamlessly (e.g., to continuation-passing style and to various patterns of recursion), be the reasoning equational or relational. In the author’s experience, they prove effective in the classroom, considering the clarity of discourse in the subsequent term reports and oral exams, and beyond the classroom, considering their subsequent use when continuing to work with the Coq Proof Assistant. Fold–unfold lemmas also provide a measure of understanding as well as of control about what is cut short when one uses a shortcut, i.e., an automated simplification tactic. Since Version 8.0, the functional-induction plugin provides them for functions that are defined globally, i.e., recursive equations, and so does the Equations plugin now, both for global and for local declarations, a precious help for advanced users.","PeriodicalId":15874,"journal":{"name":"Journal of Functional Programming","volume":null,"pages":null},"PeriodicalIF":1.1,"publicationDate":"2022-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47518255","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-09-16DOI: 10.1017/S0956796822000090
Paulette Koronkevich, Ramon Rakow, Amal J. Ahmed, W. J. Bowman
Abstract Many programmers use dependently typed languages such as Coq to machine-verify high-assurance software. However, existing compilers for these languages provide no guarantees after compiling, nor when linking after compilation. Type-preserving compilers preserve guarantees encoded in types and then use type checking to verify compiled code and ensure safe linking with external code. Unfortunately, standard compiler passes do not preserve the dependent typing of commonly used (intensional) type theories. This is because assumptions valid in simpler type systems no longer hold, and intensional dependent type systems are highly sensitive to syntactic changes, including compilation. We develop an A-normal form (ANF) translation with join-point optimization—a standard translation for making control flow explicit in functional languages—from the Extended Calculus of Constructions (ECC) with dependent elimination of booleans and natural numbers (a representative subset of Coq). Our dependently typed target language has equality reflection, allowing the type system to encode semantic equality of terms. This is key to proving type preservation and correctness of separate compilation for this translation. This is the first ANF translation for dependent types. Unlike related translations, it supports the universe hierarchy, and does not rely on parametricity or impredicativity.
{"title":"ANF preserves dependent types up to extensional equality","authors":"Paulette Koronkevich, Ramon Rakow, Amal J. Ahmed, W. J. Bowman","doi":"10.1017/S0956796822000090","DOIUrl":"https://doi.org/10.1017/S0956796822000090","url":null,"abstract":"Abstract Many programmers use dependently typed languages such as Coq to machine-verify high-assurance software. However, existing compilers for these languages provide no guarantees after compiling, nor when linking after compilation. Type-preserving compilers preserve guarantees encoded in types and then use type checking to verify compiled code and ensure safe linking with external code. Unfortunately, standard compiler passes do not preserve the dependent typing of commonly used (intensional) type theories. This is because assumptions valid in simpler type systems no longer hold, and intensional dependent type systems are highly sensitive to syntactic changes, including compilation. We develop an A-normal form (ANF) translation with join-point optimization—a standard translation for making control flow explicit in functional languages—from the Extended Calculus of Constructions (ECC) with dependent elimination of booleans and natural numbers (a representative subset of Coq). Our dependently typed target language has equality reflection, allowing the type system to encode semantic equality of terms. This is key to proving type preservation and correctness of separate compilation for this translation. This is the first ANF translation for dependent types. Unlike related translations, it supports the universe hierarchy, and does not rely on parametricity or impredicativity.","PeriodicalId":15874,"journal":{"name":"Journal of Functional Programming","volume":null,"pages":null},"PeriodicalIF":1.1,"publicationDate":"2022-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44281455","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-08-08DOI: 10.1017/S0956796822000065
Wouter Swierstra
Abstract Vectors—or length-indexed lists—are classic example of a dependent type. Yet, most tutorials stay clear of any function on vectors whose definition requires non-trivial equalities between natural numbers to type check. This pearl shows how to write functions, such as vector reverse, that rely on monoidal equalities to be type correct without having to write any additional proofs. These techniques can be applied to many other functions over types indexed by a monoid, written using an accumulating parameter, and even be used to decide arbitrary equalities over monoids ‘for free.’
{"title":"A well-known representation of monoids and its application to the function ‘vector reverse’","authors":"Wouter Swierstra","doi":"10.1017/S0956796822000065","DOIUrl":"https://doi.org/10.1017/S0956796822000065","url":null,"abstract":"Abstract Vectors—or length-indexed lists—are classic example of a dependent type. Yet, most tutorials stay clear of any function on vectors whose definition requires non-trivial equalities between natural numbers to type check. This pearl shows how to write functions, such as vector reverse, that rely on monoidal equalities to be type correct without having to write any additional proofs. These techniques can be applied to many other functions over types indexed by a monoid, written using an accumulating parameter, and even be used to decide arbitrary equalities over monoids ‘for free.’","PeriodicalId":15874,"journal":{"name":"Journal of Functional Programming","volume":null,"pages":null},"PeriodicalIF":1.1,"publicationDate":"2022-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41761242","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-07-05DOI: 10.1017/S0956796822000041
S. Perna, V. Tannen, L. Wong
Abstract Modern programming languages typically provide some form of comprehension syntax which renders programs manipulating collection types more readable and understandable. However, comprehension syntax corresponds to nested loops in general. There is no simple way of using it to express efficient general synchronized iterations on multiple ordered collections, such as linear-time algorithms for low-selectivity database joins. Synchrony fold is proposed here as a novel characterization of synchronized iteration. Central to this characterization is a monotonic isBefore predicate for relating the orderings on the two collections being iterated on and an antimonotonic canSee predicate for identifying matching pairs in the two collections to synchronize and act on. A restriction is then placed on Synchrony fold, cutting its extensional expressive power to match that of comprehension syntax, giving us Synchrony generator. Synchrony generator retains sufficient intensional expressive power for expressing efficient synchronized iteration on ordered collections. In particular, it is proved to be a natural generalization of the database merge join algorithm, extending the latter to more general database joins. Finally, Synchrony iterator is derived from Synchrony generator as a novel form of iterator. While Synchrony iterator has the same extensional and intensional expressive power as Synchrony generator, the former is better dovetailed with comprehension syntax. Thereby, algorithms requiring synchronized iterations on multiple ordered collections, including those for efficient general database joins, become expressible naturally in comprehension syntax.
{"title":"Iterating on multiple collections in synchrony","authors":"S. Perna, V. Tannen, L. Wong","doi":"10.1017/S0956796822000041","DOIUrl":"https://doi.org/10.1017/S0956796822000041","url":null,"abstract":"Abstract Modern programming languages typically provide some form of comprehension syntax which renders programs manipulating collection types more readable and understandable. However, comprehension syntax corresponds to nested loops in general. There is no simple way of using it to express efficient general synchronized iterations on multiple ordered collections, such as linear-time algorithms for low-selectivity database joins. Synchrony fold is proposed here as a novel characterization of synchronized iteration. Central to this characterization is a monotonic isBefore predicate for relating the orderings on the two collections being iterated on and an antimonotonic canSee predicate for identifying matching pairs in the two collections to synchronize and act on. A restriction is then placed on Synchrony fold, cutting its extensional expressive power to match that of comprehension syntax, giving us Synchrony generator. Synchrony generator retains sufficient intensional expressive power for expressing efficient synchronized iteration on ordered collections. In particular, it is proved to be a natural generalization of the database merge join algorithm, extending the latter to more general database joins. Finally, Synchrony iterator is derived from Synchrony generator as a novel form of iterator. While Synchrony iterator has the same extensional and intensional expressive power as Synchrony generator, the former is better dovetailed with comprehension syntax. Thereby, algorithms requiring synchronized iterations on multiple ordered collections, including those for efficient general database joins, become expressible naturally in comprehension syntax.","PeriodicalId":15874,"journal":{"name":"Journal of Functional Programming","volume":null,"pages":null},"PeriodicalIF":1.1,"publicationDate":"2022-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45861238","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-01-20DOI: 10.1017/S0956796821000277
H. Iwasaki, Kento Emoto, Akimasa Morihata, Kiminori Matsuzaki, Zhenjiang Hu
Abstract The vertex-centric programming model is now widely used for processing large graphs. User-defined vertex programs are executed in parallel over every vertex of a graph, but the imperative and explicit message-passing style of existing systems makes defining a vertex program unintuitive and difficult. This article presents Fregel, a purely functional domain-specific language for processing large graphs and describes its model, design, and implementation. Fregel is a subset of Haskell, so Haskell tools can be used to test and debug Fregel programs. The vertex-centric computation is abstracted using compositional programming that uses second-order functions on graphs provided by Fregel. A Fregel program can be compiled into imperative programs for use in the Giraph and Pregel+ vertex-centric frameworks. Fregel’s functional nature without side effects enables various transformations and optimizations during the compilation process. Thus, the programmer is freed from the burden of program optimization, which is manually done for existing imperative systems. Experimental results for typical examples demonstrated that the compiled code can be executed with reasonable and promising performance.
{"title":"Fregel: a functional domain-specific language for vertex-centric large-scale graph processing","authors":"H. Iwasaki, Kento Emoto, Akimasa Morihata, Kiminori Matsuzaki, Zhenjiang Hu","doi":"10.1017/S0956796821000277","DOIUrl":"https://doi.org/10.1017/S0956796821000277","url":null,"abstract":"Abstract The vertex-centric programming model is now widely used for processing large graphs. User-defined vertex programs are executed in parallel over every vertex of a graph, but the imperative and explicit message-passing style of existing systems makes defining a vertex program unintuitive and difficult. This article presents Fregel, a purely functional domain-specific language for processing large graphs and describes its model, design, and implementation. Fregel is a subset of Haskell, so Haskell tools can be used to test and debug Fregel programs. The vertex-centric computation is abstracted using compositional programming that uses second-order functions on graphs provided by Fregel. A Fregel program can be compiled into imperative programs for use in the Giraph and Pregel+ vertex-centric frameworks. Fregel’s functional nature without side effects enables various transformations and optimizations during the compilation process. Thus, the programmer is freed from the burden of program optimization, which is manually done for existing imperative systems. Experimental results for typical examples demonstrated that the compiled code can be executed with reasonable and promising performance.","PeriodicalId":15874,"journal":{"name":"Journal of Functional Programming","volume":null,"pages":null},"PeriodicalIF":1.1,"publicationDate":"2022-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44834519","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-01-05DOI: 10.1017/s0956796821000289
Derek Dreyer, Benjamin C. Pierce
Abstract The Robert Harper Festschrift includes articles by three of Bob’s students and colleagues—Karl Crary, Andrzej Filinski, and Jonathan Sterling. Each of these articles touches on themes that are central to Bob’s research: module system design, proof-directed program development, and (to use Bob’s term) “computational trinitarianism”. In this foreword to the Festschrift, we have additionally compiled reminiscences of Bob Harper from his PhD students. We invited them to reflect on their experiences working with and learning from Bob. We believe these reminiscences, presented in chronological order of dissertation date, deliver a most fitting tribute to Bob in honor of his 64th birthday.
{"title":"On being a PhD student of Robert Harper","authors":"Derek Dreyer, Benjamin C. Pierce","doi":"10.1017/s0956796821000289","DOIUrl":"https://doi.org/10.1017/s0956796821000289","url":null,"abstract":"Abstract The Robert Harper Festschrift includes articles by three of Bob’s students and colleagues—Karl Crary, Andrzej Filinski, and Jonathan Sterling. Each of these articles touches on themes that are central to Bob’s research: module system design, proof-directed program development, and (to use Bob’s term) “computational trinitarianism”. In this foreword to the Festschrift, we have additionally compiled reminiscences of Bob Harper from his PhD students. We invited them to reflect on their experiences working with and learning from Bob. We believe these reminiscences, presented in chronological order of dissertation date, deliver a most fitting tribute to Bob in honor of his 64th birthday.","PeriodicalId":15874,"journal":{"name":"Journal of Functional Programming","volume":null,"pages":null},"PeriodicalIF":1.1,"publicationDate":"2022-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45642955","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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