In this paper we describe the architecture of the Utrecht Haskell Compiler (UHC). UHC is a new Haskell compiler, that supports most (but not all) Haskell 98 features, plus some experimental extensions. It targets multiple backends, including a bytecode interpreter backend and a whole-program analysis backend, both via C. The implementation is rigorously organized as stepwise transformations through some explicit intermediate languages. The tree walks of all transformations are expressed as an algebra, with the aid of an Attribute Grammar based preprocessor. The compiler is just one materialization of a framework that supports experimentation with language variants, thanks to an aspect-oriented internal organization.
{"title":"The architecture of the Utrecht Haskell compiler","authors":"A. Dijkstra, Jeroen D. Fokker, S. Swierstra","doi":"10.1145/1596638.1596650","DOIUrl":"https://doi.org/10.1145/1596638.1596650","url":null,"abstract":"In this paper we describe the architecture of the Utrecht Haskell Compiler (UHC).\u0000 UHC is a new Haskell compiler, that supports most (but not all) Haskell 98 features, plus some experimental extensions. It targets multiple backends, including a bytecode interpreter backend and a whole-program analysis backend, both via C. The implementation is rigorously organized as stepwise transformations through some explicit intermediate languages. The tree walks of all transformations are expressed as an algebra, with the aid of an Attribute Grammar based preprocessor. The compiler is just one materialization of a framework that supports experimentation with language variants, thanks to an aspect-oriented internal organization.","PeriodicalId":188691,"journal":{"name":"ACM SIGPLAN Symposium/Workshop on Haskell","volume":"35 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125365035","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}
Refactorings are source-to-source program transformations which change program structure and organisation, but not program functionality. Documented in catalogues and supported by tools, refactoring provides the means to adapt and improve the design of existing code, and has thus enabled the trend towards modern agile software development processes. Refactoring has taken a prominent place in software development and maintenance, but most of this recent success has taken place in the OO and XP communities.In our project, we explore the prospects for 'Refactoring Functional Programs', taking Haskell as a concrete case-study. This paper discusses the variety of pragmatic and implementation issues raised by our work on the Haskell Refactorer. We briefly introduce the ideas behind refactoring, and a set of elementary functional refactorings. The core of the paper then outlines the main challenges that arise from our aim to produce practical tools for a decidedly non-toy language, summarizes our experience in trying to establish the necessary meta-programming infrastructure and gives an implementation overview of our current prototype refactoring tool. Using Haskell as our implementation language, we also offer some preliminary comments on Haskell programming-in-the-large.
{"title":"Tool support for refactoring functional programs","authors":"Huiqing Li, S. Thompson","doi":"10.1145/871895.871899","DOIUrl":"https://doi.org/10.1145/871895.871899","url":null,"abstract":"Refactorings are source-to-source program transformations which change program structure and organisation, but not program functionality. Documented in catalogues and supported by tools, refactoring provides the means to adapt and improve the design of existing code, and has thus enabled the trend towards modern agile software development processes. Refactoring has taken a prominent place in software development and maintenance, but most of this recent success has taken place in the OO and XP communities.In our project, we explore the prospects for 'Refactoring Functional Programs', taking Haskell as a concrete case-study. This paper discusses the variety of pragmatic and implementation issues raised by our work on the Haskell Refactorer. We briefly introduce the ideas behind refactoring, and a set of elementary functional refactorings. The core of the paper then outlines the main challenges that arise from our aim to produce practical tools for a decidedly non-toy language, summarizes our experience in trying to establish the necessary meta-programming infrastructure and gives an implementation overview of our current prototype refactoring tool. Using Haskell as our implementation language, we also offer some preliminary comments on Haskell programming-in-the-large.","PeriodicalId":188691,"journal":{"name":"ACM SIGPLAN Symposium/Workshop on Haskell","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117276504","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}
The Haskell definition and implementation of read is far from perfect. In the first place read is not able to handle the associativities defined for infix operators. Furthermore, it puts constraints on the way show is defined, and especially forces it to generate far more parentheses than expected. Lastly, it may give rise to exponential parsing times. All this is due to the compositionality requirement for read functions, which imposes a top-down parsing strategy. We propose a different approach, based on typed abstract syntax, in which grammars describing the data types are composed dynamically. Using the transformation libraries described in a companion paper these syntax descriptions are combined and transformed into parsers at runtime, from which the required read function are constructed. In this way we obtain linear parsing times, achieve consistency with the defined associativities, and may use a version of show which generates far fewer parentheses, thus improving readability of printed values. The described transformation algorithms can be incorporated in a Haskell compiler, thus moving most of the work involved to compile time.
{"title":"Haskell, do you read me?: constructing and composing efficient top-down parsers at runtime","authors":"Marcos Viera, S. Swierstra, Eelco Lempsink","doi":"10.1145/1411286.1411296","DOIUrl":"https://doi.org/10.1145/1411286.1411296","url":null,"abstract":"The Haskell definition and implementation of read is far from perfect. In the first place read is not able to handle the associativities defined for infix operators. Furthermore, it puts constraints on the way show is defined, and especially forces it to generate far more parentheses than expected. Lastly, it may give rise to exponential parsing times. All this is due to the compositionality requirement for read functions, which imposes a top-down parsing strategy.\u0000 We propose a different approach, based on typed abstract syntax, in which grammars describing the data types are composed dynamically. Using the transformation libraries described in a companion paper these syntax descriptions are combined and transformed into parsers at runtime, from which the required read function are constructed. In this way we obtain linear parsing times, achieve consistency with the defined associativities, and may use a version of show which generates far fewer parentheses, thus improving readability of printed values.\u0000 The described transformation algorithms can be incorporated in a Haskell compiler, thus moving most of the work involved to compile time.","PeriodicalId":188691,"journal":{"name":"ACM SIGPLAN Symposium/Workshop on Haskell","volume":"84 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116073417","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 present Haskell libraries that statically ensure the safe use of resources such as file handles. We statically prevent accessing an already closed handle or forgetting to close it. The libraries can be trivially extended to other resources such as database connections and graphic contexts. Because file handles and similar resources are scarce, we want to not just assure their safe use but further deallocate them soon after they are no longer needed. Relying on Fluet and Morrisett's [4] calculus of nested regions, we contribute a novel, improved, and extended implementation of the calculus in Haskell, with file handles as resources. Our library supports region polymorphism and implicit region subtyping, along with higher-order functions, mutable state, recursion, and run-time exceptions. A program may allocate arbitrarily many resources and dispose of them in any order, not necessarily LIFO. Region annotations are part of an expression's inferred type. Our new Haskell encoding of monadic regions as monad transformers needs no witness terms. It assures timely deallocation even when resources have markedly different lifetimes and the identity of the longest-living resource is determined only dynamically. For contrast, we also implement a Haskell library for manual resource management, where deallocation is explicit and safety is assured by a form of linear types. We implement the linear typing in Haskell with the help of phantom types and a parameterized monad to statically track the type-state of resources.
{"title":"Lightweight monadic regions","authors":"O. Kiselyov, Chung-chieh Shan","doi":"10.1145/1411286.1411288","DOIUrl":"https://doi.org/10.1145/1411286.1411288","url":null,"abstract":"We present Haskell libraries that statically ensure the safe use of resources such as file handles. We statically prevent accessing an already closed handle or forgetting to close it. The libraries can be trivially extended to other resources such as database connections and graphic contexts.\u0000 Because file handles and similar resources are scarce, we want to not just assure their safe use but further deallocate them soon after they are no longer needed. Relying on Fluet and Morrisett's [4] calculus of nested regions, we contribute a novel, improved, and extended implementation of the calculus in Haskell, with file handles as resources.\u0000 Our library supports region polymorphism and implicit region subtyping, along with higher-order functions, mutable state, recursion, and run-time exceptions. A program may allocate arbitrarily many resources and dispose of them in any order, not necessarily LIFO. Region annotations are part of an expression's inferred type.\u0000 Our new Haskell encoding of monadic regions as monad transformers needs no witness terms. It assures timely deallocation even when resources have markedly different lifetimes and the identity of the longest-living resource is determined only dynamically.\u0000 For contrast, we also implement a Haskell library for manual resource management, where deallocation is explicit and safety is assured by a form of linear types. We implement the linear typing in Haskell with the help of phantom types and a parameterized monad to statically track the type-state of resources.","PeriodicalId":188691,"journal":{"name":"ACM SIGPLAN Symposium/Workshop on Haskell","volume":"62 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116087519","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}
Eight years ago, functional dependencies, a concept from the theory of relational databases, were proposed as a mechanism for avoiding common problems with multiple parameter type classes in Haskell. In this context, functional dependencies give programmers a means to specify the semantics of a type class more precisely, and to obtain more accurate inferred types as a result. As time passed, however, several issues were uncovered - both in the design of a language to support functional dependencies, and in the ways that programmers use them - that led some to search for new, better alternatives. This paper focusses on two related aspects of design for functional dependencies: (i) the design of language/type system extensions that implement them; and (ii) the design of programs that use them. Our goal is to clarify the issues of what functional dependencies are, how they should be used, and how the problems encountered with initial proposals and implementations can be addressed.
{"title":"Language and program design for functional dependencies","authors":"Mark P. Jones, Iavor S. Diatchki","doi":"10.1145/1411286.1411298","DOIUrl":"https://doi.org/10.1145/1411286.1411298","url":null,"abstract":"Eight years ago, functional dependencies, a concept from the theory of relational databases, were proposed as a mechanism for avoiding common problems with multiple parameter type classes in Haskell. In this context, functional dependencies give programmers a means to specify the semantics of a type class more precisely, and to obtain more accurate inferred types as a result. As time passed, however, several issues were uncovered - both in the design of a language to support functional dependencies, and in the ways that programmers use them - that led some to search for new, better alternatives.\u0000 This paper focusses on two related aspects of design for functional dependencies: (i) the design of language/type system extensions that implement them; and (ii) the design of programs that use them. Our goal is to clarify the issues of what functional dependencies are, how they should be used, and how the problems encountered with initial proposals and implementations can be addressed.","PeriodicalId":188691,"journal":{"name":"ACM SIGPLAN Symposium/Workshop on Haskell","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129460308","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}
Monads as an organizing principle for programming and semantics are notoriously difficult to grasp, yet they are a central and powerful abstraction in Haskell. This paper introduces a domain-specific language, MonadLab, that simplifies the construction of monads, and describes its implementation in Template Haskell. MonadLab makes monad construction truly first class, meaning that arcane theoretical issues with respect to monad transformers are completely hidden from the programmer. The motivation behind the design of MonadLab is to make monadic programming in Haskell simpler while providing a tool for non-Haskell experts that will assist them in understanding this powerful abstraction.
{"title":"Making monads first-class with template haskell","authors":"Pericles S. Kariotis, A. Procter, W. Harrison","doi":"10.1145/1411286.1411300","DOIUrl":"https://doi.org/10.1145/1411286.1411300","url":null,"abstract":"Monads as an organizing principle for programming and semantics are notoriously difficult to grasp, yet they are a central and powerful abstraction in Haskell. This paper introduces a domain-specific language, MonadLab, that simplifies the construction of monads, and describes its implementation in Template Haskell. MonadLab makes monad construction truly first class, meaning that arcane theoretical issues with respect to monad transformers are completely hidden from the programmer. The motivation behind the design of MonadLab is to make monadic programming in Haskell simpler while providing a tool for non-Haskell experts that will assist them in understanding this powerful abstraction.","PeriodicalId":188691,"journal":{"name":"ACM SIGPLAN Symposium/Workshop on Haskell","volume":"30 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128113036","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}
The zipper is a well known design pattern for providing a cursor-like interface to a data structure. However, the classic treatise by Huet (1) only scratches the surface of some of the potential applications of the zipper. In this work we have taken inspiration from Huet, and built a library suitable as an underpinning for a structured editor for programming languages. We consider a zipper structure that is suitable for traversing heterogeneous data types, encoding routes to other places in the tree (for bookmark or quick-jump functionality), expressing lexically bound information using contexts, and traversals for rendering a program indicating where the cursor is currently focused in the whole.
{"title":"Clase: cursor library for a structured editor","authors":"T. O. R. Allwood, S. Eisenbach","doi":"10.1145/1411286.1411302","DOIUrl":"https://doi.org/10.1145/1411286.1411302","url":null,"abstract":"The zipper is a well known design pattern for providing a cursor-like interface to a data structure. However, the classic treatise by Huet (1) only scratches the surface of some of the potential applications of the zipper. In this work we have taken inspiration from Huet, and built a library suitable as an underpinning for a structured editor for programming languages. We consider a zipper structure that is suitable for traversing heterogeneous data types, encoding routes to other places in the tree (for bookmark or quick-jump functionality), expressing lexically bound information using contexts, and traversals for rendering a program indicating where the cursor is currently focused in the whole.","PeriodicalId":188691,"journal":{"name":"ACM SIGPLAN Symposium/Workshop on Haskell","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126595323","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}
The quality of a programming language itself is only one component in the ability of application writers to get the job done. Programming languages can succeed or fail based on the breadth and quality of their library collection. Over the last few years, the Haskell community has risen to the task of building the library infrastructure necessary for Haskell to succeed as a programming language suitable for writing real-world applications. This on-going work, the Cabal and Hackage effort, is built on the open source model of distributed development, and have resulted in a flowering of development in the language with more code produced and reused now than at any point in the community's history. It is easier to obtain and use Haskell code, in a wider range of environments, than ever before. This demonstration describes the infrastructure and process of Haskell development inside the Cabal/Hackage framework, including the build system, library dependency resolution, centralised publication, documentation and distribution, and how the code escapes outward into the wider software community. We survey the benefits and trade-offs in a distributed, collaborative development ecosystem and look at a proposed Haskell Platform that envisages a complete Haskell development environment, batteries included.
{"title":"Haskell: batteries included","authors":"Duncan Coutts, Isaac Potoczny-Jones, Don Stewart","doi":"10.1145/1411286.1411303","DOIUrl":"https://doi.org/10.1145/1411286.1411303","url":null,"abstract":"The quality of a programming language itself is only one component in the ability of application writers to get the job done. Programming languages can succeed or fail based on the breadth and quality of their library collection. Over the last few years, the Haskell community has risen to the task of building the library infrastructure necessary for Haskell to succeed as a programming language suitable for writing real-world applications.\u0000 This on-going work, the Cabal and Hackage effort, is built on the open source model of distributed development, and have resulted in a flowering of development in the language with more code produced and reused now than at any point in the community's history. It is easier to obtain and use Haskell code, in a wider range of environments, than ever before.\u0000 This demonstration describes the infrastructure and process of Haskell development inside the Cabal/Hackage framework, including the build system, library dependency resolution, centralised publication, documentation and distribution, and how the code escapes outward into the wider software community.\u0000 We survey the benefits and trade-offs in a distributed, collaborative development ecosystem and look at a proposed Haskell Platform that envisages a complete Haskell development environment, batteries included.","PeriodicalId":188691,"journal":{"name":"ACM SIGPLAN Symposium/Workshop on Haskell","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123791558","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}
This paper describes two Haskell libraries for property-based testing. Following the lead of QuickCheck, these testing libraries SmallCheck and Lazy SmallCheck also use type-based generators to obtain test-sets of finite values for which properties are checked, and report any counter-examples found. But instead of using a sample of randomly generated values they test properties for all values up to some limiting depth, progressively increasing this limit. The paper explains the design and implementation of both libraries and evaluates them in comparison with each other and with QuickCheck.
{"title":"Smallcheck and lazy smallcheck: automatic exhaustive testing for small values","authors":"C. Runciman, Matthew Naylor, Fredrik Lindblad","doi":"10.1145/1411286.1411292","DOIUrl":"https://doi.org/10.1145/1411286.1411292","url":null,"abstract":"This paper describes two Haskell libraries for property-based testing. Following the lead of QuickCheck, these testing libraries SmallCheck and Lazy SmallCheck also use type-based generators to obtain test-sets of finite values for which properties are checked, and report any counter-examples found. But instead of using a sample of randomly generated values they test properties for all values up to some limiting depth, progressively increasing this limit. The paper explains the design and implementation of both libraries and evaluates them in comparison with each other and with QuickCheck.","PeriodicalId":188691,"journal":{"name":"ACM SIGPLAN Symposium/Workshop on Haskell","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127634898","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 describe an automated analysis of Haskell 98 programs to check statically that, despite the possible use of partial (or non-exhaustive) pattern matching, no pattern-match failure can occur. Our method is an iterative backward analysis using a novel form of pattern-constraint to represent sets of data values. The analysis is defined for a core first-order language to which Haskell 98 programs are reduced. Our analysis tool has been successfully applied to a range of programs, and our techniques seem to scale well. Throughout the paper, methods are represented much as we have implemented them in practice, again in Haskell.
{"title":"Not all patterns, but enough: an automatic verifier for partial but sufficient pattern matching","authors":"Neil Mitchell, C. Runciman","doi":"10.1145/1411286.1411293","DOIUrl":"https://doi.org/10.1145/1411286.1411293","url":null,"abstract":"We describe an automated analysis of Haskell 98 programs to check statically that, despite the possible use of partial (or non-exhaustive) pattern matching, no pattern-match failure can occur. Our method is an iterative backward analysis using a novel form of pattern-constraint to represent sets of data values. The analysis is defined for a core first-order language to which Haskell 98 programs are reduced. Our analysis tool has been successfully applied to a range of programs, and our techniques seem to scale well. Throughout the paper, methods are represented much as we have implemented them in practice, again in Haskell.","PeriodicalId":188691,"journal":{"name":"ACM SIGPLAN Symposium/Workshop on Haskell","volume":"115 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133475024","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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