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User-changeable visibility: Resolving unanticipated name clashes in traits

acm sigplan NOTICES 2007年第10期42卷 171-190页

作者： Ducasse, Stephane Wuyts, Roel Bergel, Alexandre INRIA Futurs LISTIC Univ Savoie Language & Software evolut Le Bourget Du Lac France IMEC Louvain Belgium Univ Libre Bruxelles Brussels Belgium LERO Trinity Coll Dublin Ireland

A trait is a unit of behaviour that can be composed with other traits and used by classes. Traits offer an alternative to multiple inheritance. Conflict resolution of traits, while flexible, does not completely handle accidental method name conflicts: if a trait with method m is composed with another trait defining a different method m then resolving the conflict may prove delicate or infeasible in cases where both versions of m are still needed. In this paper we present freezeable traits, which provide an expressive composition mechanism to support unanticipated method composition conflicts. Our solution introduces private trait methods and lets the class composer change method visibility at composition time (from public to private and vice versa). Moreover two class composers may use different composition policies for the same trait, something which is not possible in mainstream languages. This approach respects the two main design principles of traits: the class composer is empowered and traits can be flattened away. We present an implementation of freezable traits in Smalltalk. As a side-effect of this implementation we introduced private (early-bound and invisible) methods to Smalltalk by distinguishing object-sends from self-sends. Our implementation uses compile-time bytecode manipulation and, as such, introduces no run-time penalties.

关键词： languages dynamic typing traits encapsulation information hiding composition

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PADS/ML: A functional data description language 07

PADS/ML: A functional data description language

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34th acm sigplan-SIGACT Symposium on Principles of programming languages

作者： Mandelbaum, Yitzhak Fisher, Kathleen Walker, David Fernandez, Mary Gleyzer, Artem Princeton Univ Princeton NJ 08544 USA

ISBN: (纸本)9781595935755

Massive amounts of useful data are stored and processed in ad hoc formats for which common tools like parsers, printers, query engines and format converters are not readily available. In this paper, we explain the design and implementation of PADS/ML, a new language and system that facilitates the generation of data processing tools for ad hoc formats. The PADS/ML design includes features such as dependent, polymorphic and recursive datatypes, which allow programmers to describe the syntax and semantics of ad hoc data in a concise, easy-to-read notation. The PADS/ML implementation compiles these descriptions into ML structures and functors that include types for parsed data, functions for parsing and printing, and auxiliary support for user-specified, format-dependent and format-independent tool generation.

关键词： languages data description languages domain-specific languages functional programming dependent types ML modules parsing printing

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Component NextGen: A sound and expressive component framework for Java

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acm sigplan NOTICES 2007年第10期42卷 153-170页

作者： Sasitorn, James Cartwright, Robert Rice Univ Houston TX 77251 USA

Developing a general component system for a statically typed, object-oriented language is a challenging design problem for two reasons. First, mutually recursive references across components are common in object-oriented programs - an issue that has proven troublesome in the context of component systems for functional and procedural languages. Second, inheritance across component boundaries can cause accidental method overrides. Our recent research shows that a component framework can be constructed for a nominally typed object-oriented language supporting first-class(1) generic types simply by adding appropriate annotations, syntactic sugar, and component-level type-checking. The fundamental semantic building blocks for constructing, type-checking and manipulating components are provided by the underlying first-class generic type system. To demonstrate the simplicity and utility of this approach we have designed and implemented an extension of Java called Component NEXTGEN (CGEN). CGEN, which is based on the Sun Java 5.0 javac compiler, is backwards compatible with existing Java binary code and runs on current Java Virtual Machines. The primary contribution of this paper is a technical analysis of the subtle design issues involved in building a component framework for a nominally typed object-oriented language supporting first-class generics. In contrast to component systems for structurally typed languages, mutual recursion among components is accommodated in the type system and semantics without incorporating any special machinery. Our analysis includes a presentation of Core CGEN (CCG), a small, core language modeling the CGEN framework. It is based on Featherweight GJ and incorporates some ideas from MIXGEN. CCG adds the essential features to support components, but nothing more. Our discussion includes the type rules and semantics for CCG, as well as a proof of type safety.

关键词： design language first-class generics Java implementation custom class loader modules components signatures

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The exo VM system for automatic VM and application reduction 07

The exo VM system for automatic VM and application reduction

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conference on programming language design and implementation

作者： Titzer, Ben L. Auerbach, Joshua Bacon, David F. Palsberg, Jens Univ Calif Los Angeles Compilers Grp Los Angeles CA 90025 USA

ISBN: (纸本)9781595936332

Embedded systems pose unique challenges to Java application developers and virtual machine designers. Chief among these challenges is the memory footprint of both the virtual machine and the applications that run within it. With the rapidly increasing set of features provided by the Java language, virtual machine designers are often forced to build custom implementations that make various tradeoffs between the footprint of the virtual machine and the subset of the Java language and class libraries that are supported. In this paper, we present the Exo VM, a system in which an application is initialized in a fully featured virtual machine, and then the code, data, and virtual machine features necessary to execute it are packaged into a binary image. Key to this process is feature analysis, a technique for computing the reachable code and data of a Java program and its implementation inside the VM simultaneously. The Exo VM reduces the need to develop customized embedded virtual machines by reusing a single VM infrastructure and automatically eliding the implementation of unused Java features on a per-program basis. We present a constraint-based instantiation of the analysis technique, an implementation in IBM's J9 Java VM, experiments evaluating our technique for the EEMBC benchmark suite, and some discussion of the individual costs of some of Java's features. Our evaluation shows that our system can reduce the non-heap memory allocation of the virtual machine by as much as 75%. We discuss VM and language design decisions that our work shows are important in targeting embedded systems, supporting the long-term goal of a common VM infrastructure spanning from motes to large servers.

关键词： pre-initialization embedded systems persistence dead code elimination static compilation static analysis VM design VM modularity feature analysis

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Fault-tolerant typed assembly language

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acm sigplan NOTICES 2007年第6期42卷 42-53页

作者： Perry, Frances Mackey, Lester Reis, George A. Ligatti, Jay August, David I. Walker, David Princeton Univ Dept Comp Sci & Elect Engn Princeton NJ 08544 USA Univ S Florida Dept Comp Sci & Comp Engn Tampa FL 33620 USA

A transient hardware fault occurs when an energetic particle strikes a transistor, causing it to change state. Although transient faults do not permanently damage the hardware, they may corrupt computations by altering stored values and signal transfers. In this paper, we propose a new scheme for provably safe and reliable computing in the presence of transient hardware faults. In our scheme, software computations are replicated to provide redundancy while special instructions compare the independently computed results to detect errors before writing critical data. In stark contrast to any previous efforts in this area, we have analyzed our fault tolerance scheme from a formal, theoretical perspective. To be specific, first, we provide an operational semantics for our assembly language, which includes a precise formal definition of our fault model. Second, we develop an assembly-level type system designed to detect reliability problems in compiled code. Third, we provide a formal specification for program fault tolerance under the given fault model and prove that all well-typed programs are indeed fault tolerant. In addition to the formal analysis, we evaluate our detection scheme and show that it only takes 34% longer to execute than the unreliable version.

关键词： languages reliability theory verification transient hardware faults soft faults fault tolerance type systems typed assembly language

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EXOCHI: Architecture and programming environment for a heterogeneous multi-core multithreaded system

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acm sigplan NOTICES 2007年第6期42卷 156-166页

作者： Wang, Perry H. Collins, Jamison D. Chinya, Gautham N. Hong Jiang Xinmin Tian Girkar, Milind Yang, Nick Y. Lueh, Guei-Yuan Wang, Hong Intel Corp Microprocessor Technol Labs Microarchitecture Res Lab Santa Clara CA 95051 USA Intel Corp Chipset Grp Santa Clara CA 95051 USA Intel Corp Software Solut Corp Intel Compiler Lab Santa Clara CA 95051 USA

Future mainstream microprocessors will likely integrate specialized accelerators, such as GPUs, onto a single die to achieve better performance and power efficiency. However, it remains a keen challenge to program such a heterogeneous multi-core platform, since these specialized accelerators feature ISAs and functionality that are significantly different from the general purpose CPU cores. In this paper, we present EXOCHI: (1) Exoskeleton Sequencer (EXO), an architecture to represent heterogeneous accelerators as ISA-based MIMD architecture resources, and a shared virtual memory heterogeneous multithreaded program execution model that tightly couples specialized accelerator cores with general purpose CPU cores, and (2) C for Heterogeneous Integration (CHI), an integrated C/C++ programming environment that supports accelerator-specific inline assembly and domain-specific languages. The CHI compiler extends the OpenMP pragma for heterogeneous multithreading programming, and produces a single fat binary with code sections corresponding to different instruction sets. The runtime can judiciously spread parallel computation across the heterogeneous cores to optimize performance and power. We have prototyped the EXO architecture on a physical heterogeneous platform consisting of an Intel (R) Core (TM) 2 Duo processor and an 8-core 32-thread Intel (R) Graphics Media Accelerator X3000. In addition, we have implemented the CHI integrated programming environment with the Intel (R) C++ Compiler, runtime toolset, and debugger. On the EXO prototype system, we have enhanced a suite of production-quality media kernels for video and image processing to utilize the accelerator through the CHI programming interface, achieving significant speedup (1.41X to 10.97X) over execution on the IA32 CPU alone.

关键词： performance design languages heterogeneous multi-cores GPU OpenMP

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Can programming be liberated from the two-level style?: Multi-level programming with DeepJava 07

Can programming be liberated from the two-level style?: Mult...

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22nd International conference on Object-Oriented programming, Systems, languages and Applications

作者： Kuehne, Thomas Schreiber, Daniel Tech Univ Darmstadt Darmstadt Germany

ISBN: (纸本)9781595937865

Since the introduction of object-oriented programming few programming languages have attempted to provide programmers with more than objects and classes, i.e., more than two levels. Those that did, almost exclusively aimed at describing language properties - i. e., their metaclasses exert linguistic control on language concepts and mechanisms often in order to make the language extensible. In terms of supporting logical domain classification levels, however, they are still limited to two levels. In this paper we conservatively extend the object-oriented programming paradigm to feature an unbounded number of domain classification levels. We can therefore avoid the introduction of accidental complexity into programs caused by accommodating multiple domain levels within only two programming levels. We present a corresponding language design featuring "deep instantiation" and demonstrate its features with a running example. Finally, we outline the implementation of our compiler prototype and discuss the potentials of further developing our language design.

关键词： languages design domain metatypes ontological metamodeling deep characterization

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Modula-2 and Oberon

Modula-2 and Oberon

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3rd acm sigplan History of programming languages conference, HOPL-III

作者： Wirth, Niklaus ETH Zurich

ISBN: (纸本)9781595937667

This is an account of the development of the languages Modula-2 and Oberon. Together with their ancestors ALGOL 60 and Pascal they form a family called Algol-like languages. Pascal (1970) reflected the ideas of structured programming, Modula-2 (1979) added those of modular system design, and Oberon (1988) catered to the object-oriented style. Thus they mirror the essential programming paradigms of the past decades. Here the major language properties are outlined, followed by an account of the respective implementation efforts. The conditions and the environments in which the languages were created are elucidated. We point out that simplicity of design was the most essential guiding principle. Clarity of concepts, economy of features, efficiency and reliability of implementations were its consequences. © 2007 acm.

关键词： Computer programming languages

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Fault-tolerant typed assembly language 07

Fault-tolerant typed assembly language

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conference on programming language design and implementation

ISBN: (纸本)9781595936332

关键词： languages reliability theory verification transient hardware faults soft faults fault tolerance type systems typed assembly language

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Adding delimited and composable control to a production programming environment

Adding delimited and composable control to a production prog...

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12th acm sigplan International conference on Functional programming

作者： Flatt, Matthew Yu, Gang Findler, Robert Bruce Felleisen, Matthias Univ Utah Salt Lake City UT 84112 USA Chinese Acad Sci Inst Software Beijing 100864 Peoples R China Univ Chicago Chicago IL 60637 USA Northeastern Univ Boston MA 02115 USA

ISBN: (纸本)9781595938152

Operators for delimiting control and for capturing composable continuations litter the landscape of theoretical programming language research. Numerous papers explain their advantages, how the operators explain each other (or don't), and other aspects of the operators' existence. Production programming languages, however, do not support these operators, partly because their relationship to existing and demonstrably useful constructs-such as exceptions and dynamic binding-remains relatively unexplored. In this paper, we report on our effort of translating the theory of delimited and composable control into a viable implementation for a production system. The report shows how this effort involved a substantial design element, including work with a formal model, as well as significant practical exploration and engineering. The resulting version of PLT Scheme incorporates the expressive combination of delimited and composable control alongside dynamic-wind, dynamic binding, and exception handling. None of the additional operators subvert the intended benefits of existing control operators, so that programmers can freely mix and match control operators.

关键词： design languages

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