Proxies are a powerful approach to implement meta-objects in object-oriented languages without having to resort to metacircular interpretation. We introduce such a meta-level API based on proxies for Javascript. We simultaneously introduce a set of design principles that characterize such APIs in general, and compare similar APIs of other languages in terms of these principles. We highlight how principled proxy-based APIs improve code robustness by avoiding interference between base and meta-level code that occur in more common reflective intercession mechanisms.
{"title":"Proxies: design principles for robust object-oriented intercession APIs","authors":"T. V. Cutsem, Mark S. Miller","doi":"10.1145/1869631.1869638","DOIUrl":"https://doi.org/10.1145/1869631.1869638","url":null,"abstract":"Proxies are a powerful approach to implement meta-objects in object-oriented languages without having to resort to metacircular interpretation. We introduce such a meta-level API based on proxies for Javascript. We simultaneously introduce a set of design principles that characterize such APIs in general, and compare similar APIs of other languages in terms of these principles. We highlight how principled proxy-based APIs improve code robustness by avoiding interference between base and meta-level code that occur in more common reflective intercession mechanisms.","PeriodicalId":344101,"journal":{"name":"Dynamic Languages Symposium","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129220906","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}
First-class classes add expressive power to class-based object-oriented languages. Most importantly, programmers can abstract over common scenarios with first-class classes. When it comes to behavioral software contracts, however, first-class classes pose significant challenges. In this paper, we present the first contract system for a programming language with first-class classes. The design has been implemented for Racket, which supports first-class classes and which implements mixins and traits as syntactic sugar. We expect that our experience also applies to languages with native mixins and/or traits.
{"title":"Contracts for first-class classes","authors":"T. Strickland, M. Felleisen","doi":"10.1145/1869631.1869642","DOIUrl":"https://doi.org/10.1145/1869631.1869642","url":null,"abstract":"First-class classes add expressive power to class-based object-oriented languages. Most importantly, programmers can abstract over common scenarios with first-class classes. When it comes to behavioral software contracts, however, first-class classes pose significant challenges. In this paper, we present the first contract system for a programming language with first-class classes. The design has been implemented for Racket, which supports first-class classes and which implements mixins and traits as syntactic sugar. We expect that our experience also applies to languages with native mixins and/or traits.","PeriodicalId":344101,"journal":{"name":"Dynamic Languages Symposium","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132768896","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}
Dynamic mixin is a construct available in Ruby and other dynamic languages. It can be used as a base to implement a range of programming paradigms, such as dynamic aspect-oriented programming and context-oriented programming. However, the performance characteristics of current implementation of dynamic mixin in Ruby leaves much to be desired under condition of frequent dynamic mixin operations, global method cache and inline cache misses incur significant overhead. In this work we implemented fine-grained state tracking for CRuby 1. and were able to improve performance by more than six times on the microbenchmark exercising extreme case flowing 4 times to global method cache clearing, 28% to fine-grained state tracking and further 12% to inline cache miss elimination by caching alternating states. We demonstrated a small application using dynamic mixins that gets 48% improvement in performance from our techniques. We also implemented in C a more general delegation object models and proposed an algorithm of thread-local caching, which allows to reduce inline cache misses while permitting thread-local delegation changes.
{"title":"Optimizing dynamic dispatch with fine-grained state tracking","authors":"Salikh Zakirov, S. Chiba, Etsuya Shibayama","doi":"10.1145/1869631.1869634","DOIUrl":"https://doi.org/10.1145/1869631.1869634","url":null,"abstract":"Dynamic mixin is a construct available in Ruby and other dynamic languages. It can be used as a base to implement a range of programming paradigms, such as dynamic aspect-oriented programming and context-oriented programming. However, the performance characteristics of current implementation of dynamic mixin in Ruby leaves much to be desired under condition of frequent dynamic mixin operations, global method cache and inline cache misses incur significant overhead. In this work we implemented fine-grained state tracking for CRuby 1. and were able to improve performance by more than six times on the microbenchmark exercising extreme case flowing 4 times to global method cache clearing, 28% to fine-grained state tracking and further 12% to inline cache miss elimination by caching alternating states. We demonstrated a small application using dynamic mixins that gets 48% improvement in performance from our techniques. We also implemented in C a more general delegation object models and proposed an algorithm of thread-local caching, which allows to reduce inline cache misses while permitting thread-local delegation changes.","PeriodicalId":344101,"journal":{"name":"Dynamic Languages Symposium","volume":"54 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114622383","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}
Eyvind W. Axelsen, Stein Krogdahl, B. Møller-Pedersen
In addition to traditional object-oriented (OO) concepts such as inheritance and polymorphism, several modularization and composition mechanisms like e.g. traits, mixins and virtual classes have emerged. The Package Template mechanism is another attempt at providing a flexible mechanism for modularization, composition and adaption. Dynamic languages have traditionally employed strong support for meta-programming, with hooks to control OO concepts such as method invocation and object construction, by utilizing meta-classes and meta-object protocols. In this work, we attempt to bring a corresponding degree of meta-level control to composition primitives, with a concrete starting point in the package template mechanism as developed for the dynamic language Groovy. We wish to support a wide range of possible composition semantics, and to make such choices available to the developer through a meta-level API. This API should be extensible, and the semantic variations should be applied within well-defined scopes.
{"title":"Controlling dynamic module composition through an extensible meta-level API","authors":"Eyvind W. Axelsen, Stein Krogdahl, B. Møller-Pedersen","doi":"10.1145/1869631.1869641","DOIUrl":"https://doi.org/10.1145/1869631.1869641","url":null,"abstract":"In addition to traditional object-oriented (OO) concepts such as inheritance and polymorphism, several modularization and composition mechanisms like e.g. traits, mixins and virtual classes have emerged. The Package Template mechanism is another attempt at providing a flexible mechanism for modularization, composition and adaption.\u0000 Dynamic languages have traditionally employed strong support for meta-programming, with hooks to control OO concepts such as method invocation and object construction, by utilizing meta-classes and meta-object protocols.\u0000 In this work, we attempt to bring a corresponding degree of meta-level control to composition primitives, with a concrete starting point in the package template mechanism as developed for the dynamic language Groovy. We wish to support a wide range of possible composition semantics, and to make such choices available to the developer through a meta-level API. This API should be extensible, and the semantic variations should be applied within well-defined scopes.","PeriodicalId":344101,"journal":{"name":"Dynamic Languages Symposium","volume":"113 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129662824","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 design of the Icon programming language's expression evaluation system, which can perform limited backtracking, was unique amongst imperative programming languages when created. In this paper I explain and critique the original Icon design and show how a similar system can be integrated into a modern dynamically typed language. Finally I detail my experiences of this system and offer suggestions for the lessons to be learned from it.
{"title":"Experiences with an icon-like expression evaluation system","authors":"L. Tratt","doi":"10.1145/1869631.1869640","DOIUrl":"https://doi.org/10.1145/1869631.1869640","url":null,"abstract":"The design of the Icon programming language's expression evaluation system, which can perform limited backtracking, was unique amongst imperative programming languages when created. In this paper I explain and critique the original Icon design and show how a similar system can be integrated into a modern dynamically typed language. Finally I detail my experiences of this system and offer suggestions for the lessons to be learned from it.","PeriodicalId":344101,"journal":{"name":"Dynamic Languages Symposium","volume":"96 3","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121012471","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}
Traditional treatment of scoping in programming languages considers two opposite semantics: static scoping, where the scope of a binding is a block of program text, and dynamic scoping, where a binding is in effect during the whole reduction of an expression to a value. Static scoping and dynamic scoping are however but two points in the design space of scoping mechanisms. As a result, most proposed language mechanisms that rely on some notion of scoping, such as variable bindings of course, but also more exotic ones like aspects and mixin layers, adopt either one or the other semantics. As it turns out, these two semantics are sometimes too extreme, and a mixture of both is needed. To achieve this, language designers and/or programmers have to resort to ad hoc solutions. We present a general scoping model that simply expresses static and dynamic scoping, and that goes further by allowing fine-grained exploration of the design space of scoping. The model, called scoping strategies, gives precise control over propagation and activation of language mechanisms. While we have already studied it for aspects, we hereby show that the model is not restricted to aspects, by treating in depth its application to the most standard kind of adaptation: variable bindings. We also briefly discuss its application to mixin layers, and program monitoring. We believe that research in programming language constructs can benefit from a more flexible notion of scoping that goes beyond the static/dynamic dichotomy.
{"title":"Beyond static and dynamic scope","authors":"É. Tanter","doi":"10.1145/1640134.1640137","DOIUrl":"https://doi.org/10.1145/1640134.1640137","url":null,"abstract":"Traditional treatment of scoping in programming languages considers two opposite semantics: static scoping, where the scope of a binding is a block of program text, and dynamic scoping, where a binding is in effect during the whole reduction of an expression to a value. Static scoping and dynamic scoping are however but two points in the design space of scoping mechanisms. As a result, most proposed language mechanisms that rely on some notion of scoping, such as variable bindings of course, but also more exotic ones like aspects and mixin layers, adopt either one or the other semantics. As it turns out, these two semantics are sometimes too extreme, and a mixture of both is needed. To achieve this, language designers and/or programmers have to resort to ad hoc solutions. We present a general scoping model that simply expresses static and dynamic scoping, and that goes further by allowing fine-grained exploration of the design space of scoping. The model, called scoping strategies, gives precise control over propagation and activation of language mechanisms. While we have already studied it for aspects, we hereby show that the model is not restricted to aspects, by treating in depth its application to the most standard kind of adaptation: variable bindings. We also briefly discuss its application to mixin layers, and program monitoring. We believe that research in programming language constructs can benefit from a more flexible notion of scoping that goes beyond the static/dynamic dichotomy.","PeriodicalId":344101,"journal":{"name":"Dynamic Languages Symposium","volume":"27 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-10-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116977063","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}
Behavioral software contracts express properties concerning the flow of values across component (modules, classes, etc) interfaces. These properties are often beyond the reach of theorem provers and are therefore monitored at run-time. When the monitor discovers a contract violation, it raises an exception that simultaneously pinpoints the contract violator and explains the nature of the violation. Currently contract monitoring assumes static module interfaces. Specifically, the contract compiler partitions a contract into disjoint obligations for the static modules that communicate to an interface. At run-time, the information is used for catching and explaining contract violations. While static modules suffice for many situations, first-class modules - such as the units provided by PLT Scheme - support the dynamic and multiple linking that is often required in open software systems. The problem is, of course, that in such a world, it becomes impossible to tell from the source program alone which components have agreed to which contracts. In this paper, we develop the semantic framework of monitoring contracts for dynamic modules. We establish the internal consistency of the semantics, and we sketch an implementation based on our experience of equipping PLT Scheme with such contracts.
{"title":"Contracts for first-class modules","authors":"T. Strickland, M. Felleisen","doi":"10.1145/1640134.1640140","DOIUrl":"https://doi.org/10.1145/1640134.1640140","url":null,"abstract":"Behavioral software contracts express properties concerning the flow of values across component (modules, classes, etc) interfaces. These properties are often beyond the reach of theorem provers and are therefore monitored at run-time. When the monitor discovers a contract violation, it raises an exception that simultaneously pinpoints the contract violator and explains the nature of the violation.\u0000 Currently contract monitoring assumes static module interfaces. Specifically, the contract compiler partitions a contract into disjoint obligations for the static modules that communicate to an interface. At run-time, the information is used for catching and explaining contract violations. While static modules suffice for many situations, first-class modules - such as the units provided by PLT Scheme - support the dynamic and multiple linking that is often required in open software systems. The problem is, of course, that in such a world, it becomes impossible to tell from the source program alone which components have agreed to which contracts.\u0000 In this paper, we develop the semantic framework of monitoring contracts for dynamic modules. We establish the internal consistency of the semantics, and we sketch an implementation based on our experience of equipping PLT Scheme with such contracts.","PeriodicalId":344101,"journal":{"name":"Dynamic Languages Symposium","volume":"86 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-10-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114839925","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}
Software transactional memory (STM) is a promising approach for coordinating concurrent threads, for which many implementation strategies are currently being researched. Although some first steps exist to ease experimenting with different strategies, this still remains a relatively complex and cumbersome task. The reason is that software transactions require STM-specific dynamic crosscutting adaptations, but this is not accounted for in current STM implementations. This paper presents CSTM, an STM framework based on Context-oriented Progamming, in which transactions are modelled as dynamically scoped layer activations. It enables expressing transactional variable accesses as user-defined crosscutting concerns, without requiring invasive changes in the rest of a program. This paper presents a proof-of-concept implementation based on ContextL for Common Lisp, along with example STM strategies and preliminary benchmarks, and introduces some of ContextL's unique features for context-dependent variable accesses.
{"title":"Context-oriented software transactional memory in common lisp","authors":"Pascal Costanza, Charlotte Herzeel, T. D'Hondt","doi":"10.1145/1640134.1640144","DOIUrl":"https://doi.org/10.1145/1640134.1640144","url":null,"abstract":"Software transactional memory (STM) is a promising approach for coordinating concurrent threads, for which many implementation strategies are currently being researched. Although some first steps exist to ease experimenting with different strategies, this still remains a relatively complex and cumbersome task. The reason is that software transactions require STM-specific dynamic crosscutting adaptations, but this is not accounted for in current STM implementations. This paper presents CSTM, an STM framework based on Context-oriented Progamming, in which transactions are modelled as dynamically scoped layer activations. It enables expressing transactional variable accesses as user-defined crosscutting concerns, without requiring invasive changes in the rest of a program. This paper presents a proof-of-concept implementation based on ContextL for Common Lisp, along with example STM strategies and preliminary benchmarks, and introduces some of ContextL's unique features for context-dependent variable accesses.","PeriodicalId":344101,"journal":{"name":"Dynamic Languages Symposium","volume":"30 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-10-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122066841","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}
Ruby is a popular, dynamic scripting language that aims to "feel natural to programmers" and give users the "freedom to choose" among many different ways of doing the same thing. While this arguably makes programming in Ruby easier, it makes it hard to build analysis and transformation tools that operate on Ruby source code. In this paper, we present the Ruby Intermediate Language (RIL), a Ruby front-end and intermediate representation that addresses these. RIL includes an extensible GLR parser for Ruby, and an automatic translation into an easy-to-analyze intermediate form. This translation eliminates redundant language constructs, unravels the often subtle ordering among side effecting operations, and makes implicit interpreter operations explicit. We also describe several additional useful features of RIL, such as a dynamic instrumentation library for profiling source code and a dataflow analysis engine. We demonstrate the usefulness of RIL by presenting a static and dynamic analysis to eliminate null pointer errors in Ruby programs. We hope that RIL's features will enable others to more easily build analysis tools for Ruby, and that our design will inspire the of similar frameworks for other dynamic languages.
{"title":"The ruby intermediate language","authors":"Michael Furr, Jong-hoon An, J. Foster, M. Hicks","doi":"10.1145/1640134.1640148","DOIUrl":"https://doi.org/10.1145/1640134.1640148","url":null,"abstract":"Ruby is a popular, dynamic scripting language that aims to \"feel natural to programmers\" and give users the \"freedom to choose\" among many different ways of doing the same thing. While this arguably makes programming in Ruby easier, it makes it hard to build analysis and transformation tools that operate on Ruby source code. In this paper, we present the Ruby Intermediate Language (RIL), a Ruby front-end and intermediate representation that addresses these. RIL includes an extensible GLR parser for Ruby, and an automatic translation into an easy-to-analyze intermediate form. This translation eliminates redundant language constructs, unravels the often subtle ordering among side effecting operations, and makes implicit interpreter operations explicit. We also describe several additional useful features of RIL, such as a dynamic instrumentation library for profiling source code and a dataflow analysis engine. We demonstrate the usefulness of RIL by presenting a static and dynamic analysis to eliminate null pointer errors in Ruby programs. We hope that RIL's features will enable others to more easily build analysis tools for Ruby, and that our design will inspire the of similar frameworks for other dynamic languages.","PeriodicalId":344101,"journal":{"name":"Dynamic Languages Symposium","volume":"122 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-10-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129820333","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}
Yit Phang Khoo, M. Hicks, J. Foster, Vibha Sazawal
JavaScript programmers make extensive use of event-driven programming to help build responsive web applications. However, standard approaches to sequencing events are messy, and often lead to code that is difficult to understand and maintain. We have found that arrows, a generalization of monads, are an elegant solution to this problem. Arrows allow us to easily write asynchronous programs in small, modular units of code, and flexibly compose them in many different ways, while nicely abstracting the details of asynchronous program composition. In this paper, we present Arrowlets, a new JavaScript library that offers arrows to the everyday JavaScript programmer. We show how to use Arrowlets to construct a variety of state machines, including state machines that branch and loop. We also demonstrate how Arrowlets separate computation from composition with examples such as a drag-and-drop handler and a bubblesort animation.
{"title":"Directing JavaScript with arrows","authors":"Yit Phang Khoo, M. Hicks, J. Foster, Vibha Sazawal","doi":"10.1145/1640134.1640143","DOIUrl":"https://doi.org/10.1145/1640134.1640143","url":null,"abstract":"JavaScript programmers make extensive use of event-driven programming to help build responsive web applications. However, standard approaches to sequencing events are messy, and often lead to code that is difficult to understand and maintain. We have found that arrows, a generalization of monads, are an elegant solution to this problem. Arrows allow us to easily write asynchronous programs in small, modular units of code, and flexibly compose them in many different ways, while nicely abstracting the details of asynchronous program composition. In this paper, we present Arrowlets, a new JavaScript library that offers arrows to the everyday JavaScript programmer. We show how to use Arrowlets to construct a variety of state machines, including state machines that branch and loop. We also demonstrate how Arrowlets separate computation from composition with examples such as a drag-and-drop handler and a bubblesort animation.","PeriodicalId":344101,"journal":{"name":"Dynamic Languages Symposium","volume":"31 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-10-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114338811","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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