1,585 research outputs found
Developing a Generic Debugger for Advanced-Dispatching Languages
Programming-language research has introduced a considerable number of advanced-dispatching mechanisms in order to improve modularity. Advanced-dispatching mechanisms allow changing the behavior of a function without modifying their call sites and thus make the local behavior of code less comprehensible. Debuggers are tools, thus needed, which can help a developer to comprehend program behavior but current debuggers do not provide inspection of advanced-\ud
dispatching-related language constructs. In this paper, we present a debugger which extends a traditional Java debugger with the ability of debugging an advanced-dispatching language constructs and a user interface for inspecting this
Assessing the Efficiency of Mass Transit Systems in the United States
Frustrated with increased parking problems, unstable gasoline prices, and stifling traffic congestion, a growing number of metropolitan city dwellers consider utilizing the mass transit system. Reflecting this sentiment, a ridership of the mass transit system across the United States has been on the rise for the past several years. A growing demand for the mass transit system, however, necessitates the expansion of service offerings, the improvement of basic infrastructure/routes, and the additional employment of mass transit workers, including drivers and maintenance crews. Such a need requires the optimal allocation of financial and human resources to the mass transit system in times of shrinking budgets and government downsizing. Thus, the public transit authority is faced with the dilemma of âdoing more with less.â That is to say, the public transit authority needs to develop a âleanâ strategy which can maximize transit services with the minimum expenses. To help the public transit authority develop such a lean strategy, this report identifies the best-in-class practices in the U.S. transit service sector and proposes transit policy guidelines that can best exploit lean principles built upon best-in-class practices
Towards a Decoupled Context-Oriented Programming Language for the Internet of Things
Easily programming behaviors is one major issue of a large and reconfigurable
deployment in the Internet of Things. Such kind of devices often requires to
externalize part of their behavior such as the sensing, the data aggregation or
the code offloading. Most existing context-oriented programming languages
integrate in the same class or close layers the whole behavior. We propose to
abstract and separate the context tracking from the decision process, and to
use event-based handlers to interconnect them. We keep a very easy declarative
and non-layered programming model. We illustrate by defining an extension to
Golo-a JVM-based dynamic language
Implementing Electricity Restructuring: Policies, Potholes, and Prospects
Electricity is one of the last U.S. industries in which competition is replacing regulation. We briefly review the technology for producing and delivering power, the history of electricity policy, and recent state and international experience. We then outline the major questions facing policymakers as they decide whether, when, and how to implement restructuring. We conclude with some thoughts on the California electricity crisis and other political controversies. Although the California experience has come to define what it means for electricity markets to fail, most of the problems it raised are among those we know how to solve or prevent. The still unresolved make-or-break issue remains whether the cooperation necessary to maintain reliability is compatible with the degree of competition necessary to bring about greater efficiency and lower prices. This paper draws upon our forthcoming book, Alternating Curents: Electricity Markets and Public Policy.electricity restructuring, regulation, deregulation
Objects and polymorphism in system programming languages: a new approach
A low-level data structure always has a predefined representation which does not fit into an object of traditional object-oriented languages, where explicit type tag denotes its dynamic type. This is the main reason why the advanced features of object-oriented programming cannot be fully used at the lowest level. On the other hand, the hierarchy of low-level data structures is very similar to class-trees, but instead of an explicit tag-field the value of the object determines its dynamic type. Another peculiar requirement in system programming is that some classes have to be polymorphic by-value with their ancestor: objects must fit into the space of a superclass instance. In our paper we show language constructs which enable the system programmer to handle all data structures as objects, and exploit the advantages of object-oriented programming even at the lowest level. Our solution is based on Predicate Dispatching, but adopted to the special needs of system programming. The techniques we show also allow fo
r some classes to be polymorphic by-value with their super. We also describe how to implement these features without losing modularity
Multiple dispatch in practice
Multiple dispatch uses the run time types of more than one argument to a method call to determine which method body to run. While several languages over the last 20 years have provided multiple dispatch, most object-oriented languages still support only single dispatch â forcing programmers to implement multiple dispatch manually when required. This paper presents an empirical study of the use of multiple dispatch in practice, considering six languages that support multiple dispatch, and also investigating the potential for multiple dispatch in Java programs. We hope that this study will help programmers understand the uses and abuses of multiple dispatch; virtual machine implementors optimise multiple dispatch; and language designers to evaluate the choice of providing multiple dispatch in new programming languages
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Diversification, Diseconomies of Scope, and Vertical Contracting: Evidence From the Taxicab Industry
This paper studies how firms reorganize following diversification, proposing that firms use outsourcing, or vertical disintegration, to manage diseconomies of scope. We also consider the origins of scope diseconomies, showing how different underlying mechanisms generate contrasting predictions about the link between within-firm task heterogeneity and the incentive to outsource following diversification. We test these propositions using microdata on taxicab and limousine fleets from the Economic Census. The results show that taxicab firms outsource, by shifting the composition of their fleets toward owner-operator drivers, when they diversify into the limousine business. The magnitude of the shift toward driver ownership is larger in less urban markets, where the tasks performed by taxicab and limousine drivers are more similar. These findings suggest that (1) firms use outsourcing to manage diseconomies of scope at a particular point in the value chain and (2) interagent conflicts can be an important source of scope diseconomies
Efficiency and Effectiveness Impacts of a Computer-Assisted Scheduling and Dispatching System Implementation
Computer-assisted scheduling and dispatch (CASD) systems have been implemented in many paratransit systems in the United States to improve the effectiveness and efficiency of operations. This paper contributes to the limited literature of studies documenting the impact of such systems on paratransit operations based on the implementation of such a system in a small city in Illinois. The analysis provides evidence of small but measurable efficiency and effectiveness gains. This paper also provides evidence that proper CASD evaluation efforts should allow enough time after implementation so that not only familiarity with the system has been established, but also most or all of the necessary organizational changes related to the new technology have been completed
Efficiency and Effectiveness Impacts of a Computer-Assisted Scheduling and Dispatching System Implementation
Computer-assisted scheduling and dispatch (CASD) systems have been implemented in many paratransit systems in the United States to improve the effectiveness and efficiency of operations. This paper contributes to the limited literature of studies documenting the impact of such systems on paratransit operations based on the implementation of such a system in a small city in Illinois. The analysis provides evidence of small but measurable efficiency and effectiveness gains. This paper also provides evidence that proper CASD evaluation efforts should allow enough time after implementation so that not only familiarity with the system has been established, but also most or all of the necessary organizational changes related to the new technology have been completed
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