In applications with a complex structure of side effects, effects should be dealt with modularly: components should be programmed against abstract effect interfaces that other components can instantiate as required, and reusable effect patterns should be factored out from the rest of the application. In this paper, we study a new, general approach to achieve this in Haskell by combining effect polymorphism and the recently proposed coherent explicit dictionary applications. We demonstrate the elegance and generality of our approach in μVeriFast: a Haskell-based reimplementation of the semi-automatic separation-logic-based verification tool VeriFast. This implementation features a complex interplay of advanced side effects: a backtracking search of program paths with angelic and demonic non-determinism, interaction with an underlying off-the-shelf SMT solver, and mutable state that is either backtracked or not during the search. Our use of effect polymorphism improves over the current non-modular implementation of VeriFast, allows us to nicely factor out the backtracking search pattern as a new AssumeAssert monad, and enables advanced features involving effects, such as the non-intrusive addition of a graphical symbolic debugger based on delimited continuations.
{"title":"Modular effects in Haskell through effect polymorphism and explicit dictionary applications: a new approach and the μVeriFast verifier as a case study","authors":"Dominique Devriese","doi":"10.1145/3331545.3342589","DOIUrl":"https://doi.org/10.1145/3331545.3342589","url":null,"abstract":"In applications with a complex structure of side effects, effects should be dealt with modularly: components should be programmed against abstract effect interfaces that other components can instantiate as required, and reusable effect patterns should be factored out from the rest of the application. In this paper, we study a new, general approach to achieve this in Haskell by combining effect polymorphism and the recently proposed coherent explicit dictionary applications. We demonstrate the elegance and generality of our approach in μVeriFast: a Haskell-based reimplementation of the semi-automatic separation-logic-based verification tool VeriFast. This implementation features a complex interplay of advanced side effects: a backtracking search of program paths with angelic and demonic non-determinism, interaction with an underlying off-the-shelf SMT solver, and mutable state that is either backtracked or not during the search. Our use of effect polymorphism improves over the current non-modular implementation of VeriFast, allows us to nicely factor out the backtracking search pattern as a new AssumeAssert monad, and enables advanced features involving effects, such as the non-intrusive addition of a graphical symbolic debugger based on delimited continuations.","PeriodicalId":256081,"journal":{"name":"Proceedings of the 12th ACM SIGPLAN International Symposium on Haskell","volume":"410 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124363619","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}
Sebastian Ertel, Justus Adam, Norman A. Rink, Andrés Goens, J. Castrillón
Dataflow execution models are used to build highly scalable parallel systems. A programming model that targets parallel dataflow execution must answer the following question: How can parallelism between two dependent nodes in a dataflow graph be exploited? This is difficult when the dataflow language or programming model is implemented by a monad, as is common in the functional community, since expressing dependence between nodes by a monadic bind suggests sequential execution. Even in monadic constructs that explicitly separate state from computation, problems arise due to the need to reason about opaquely defined state. Specifically, when abstractions of the chosen programming model do not enable adequate reasoning about state, it is difficult to detect parallelism between composed stateful computations. In this paper, we propose a programming model that enables the composition of stateful computations and still exposes opportunities for parallelization. We also introduce smap, a higher-order function that can exploit parallelism in stateful computations. We present an implementation of our programming model and smap in Haskell and show that basic concepts from functional reactive programming can be built on top of our programming model with little effort. We compare these implementations to a state-of-the-art approach using monad-par and LVars to expose parallelism explicitly and reach the same level of performance, showing that our programming model successfully extracts parallelism that is present in an algorithm. Further evaluation shows that smap is expressive enough to implement parallel reductions and our programming model resolves short-comings of the stream-based programming model for current state-of-the-art big data processing systems.
{"title":"STCLang: state thread composition as a foundation for monadic dataflow parallelism","authors":"Sebastian Ertel, Justus Adam, Norman A. Rink, Andrés Goens, J. Castrillón","doi":"10.1145/3331545.3342600","DOIUrl":"https://doi.org/10.1145/3331545.3342600","url":null,"abstract":"Dataflow execution models are used to build highly scalable parallel systems. A programming model that targets parallel dataflow execution must answer the following question: How can parallelism between two dependent nodes in a dataflow graph be exploited? This is difficult when the dataflow language or programming model is implemented by a monad, as is common in the functional community, since expressing dependence between nodes by a monadic bind suggests sequential execution. Even in monadic constructs that explicitly separate state from computation, problems arise due to the need to reason about opaquely defined state. Specifically, when abstractions of the chosen programming model do not enable adequate reasoning about state, it is difficult to detect parallelism between composed stateful computations. In this paper, we propose a programming model that enables the composition of stateful computations and still exposes opportunities for parallelization. We also introduce smap, a higher-order function that can exploit parallelism in stateful computations. We present an implementation of our programming model and smap in Haskell and show that basic concepts from functional reactive programming can be built on top of our programming model with little effort. We compare these implementations to a state-of-the-art approach using monad-par and LVars to expose parallelism explicitly and reach the same level of performance, showing that our programming model successfully extracts parallelism that is present in an algorithm. Further evaluation shows that smap is expressive enough to implement parallel reductions and our programming model resolves short-comings of the stream-based programming model for current state-of-the-art big data processing systems.","PeriodicalId":256081,"journal":{"name":"Proceedings of the 12th ACM SIGPLAN International Symposium on Haskell","volume":"108 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115750976","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}
B. Finkbeiner, F. Klein, R. Piskac, Mark Santolucito
Functional Reactive Programming (FRP) is a paradigm that has simplified the construction of reactive programs. There are many libraries that implement incarnations of FRP, using abstractions such as Applicative, Monads, and Arrows. However, finding a good control flow, that correctly manages state and switches behaviors at the right times, still poses a major challenge to developers. An attractive alternative is specifying the behavior instead of programming it, as made possible by the recently developed logic: Temporal Stream Logic (TSL). However, it has not been explored so far how Control Flow Models (CFMs), resulting from TSL synthesis, are turned into executable code that is compatible with libraries building on FRP. We bridge this gap, by showing that CFMs are a suitable formalism to be turned into Applicative, Monadic, and Arrowized FRP. We demonstrate the effectiveness of our translations on a real-world kitchen timer application, which we translate to a desktop application using the Arrowized FRP library Yampa, a web application using the Monadic Threepenny-GUI library, and to hardware using the Applicative hardware description language ClaSH.
{"title":"Synthesizing functional reactive programs","authors":"B. Finkbeiner, F. Klein, R. Piskac, Mark Santolucito","doi":"10.1145/3331545.3342601","DOIUrl":"https://doi.org/10.1145/3331545.3342601","url":null,"abstract":"Functional Reactive Programming (FRP) is a paradigm that has simplified the construction of reactive programs. There are many libraries that implement incarnations of FRP, using abstractions such as Applicative, Monads, and Arrows. However, finding a good control flow, that correctly manages state and switches behaviors at the right times, still poses a major challenge to developers. An attractive alternative is specifying the behavior instead of programming it, as made possible by the recently developed logic: Temporal Stream Logic (TSL). However, it has not been explored so far how Control Flow Models (CFMs), resulting from TSL synthesis, are turned into executable code that is compatible with libraries building on FRP. We bridge this gap, by showing that CFMs are a suitable formalism to be turned into Applicative, Monadic, and Arrowized FRP. We demonstrate the effectiveness of our translations on a real-world kitchen timer application, which we translate to a desktop application using the Arrowized FRP library Yampa, a web application using the Monadic Threepenny-GUI library, and to hardware using the Applicative hardware description language ClaSH.","PeriodicalId":256081,"journal":{"name":"Proceedings of the 12th ACM SIGPLAN International Symposium on Haskell","volume":"318 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116290131","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}
{"title":"Proceedings of the 12th ACM SIGPLAN International Symposium on Haskell","authors":"","doi":"10.1145/3331545","DOIUrl":"https://doi.org/10.1145/3331545","url":null,"abstract":"","PeriodicalId":256081,"journal":{"name":"Proceedings of the 12th ACM SIGPLAN International Symposium on Haskell","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124909328","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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