A preliminary model is presented that can serve as a starting point for more advanced systems. The model shows how touch sensors can be added to arbitrary points on a robot arm and used for providing reactive information, i.e. information about legal directions for movement when sensors are activated. More specifically, the model can provide detailed information about directions in configuration space that lead to decreasing contact between the arm and obstacles. The model is an extension of the D.H. Graf and W.R. LaLonde (1988) neuroplanar architecture

Object-oriented languages provide facilities for code reuse, abstraction, encapsulation, instantiation, polymorphism, and inheritance. Major differences between pure object-oriented languages like Smalltalk and hybrid languages like C++, Objective-C, and Object Pascal are discussed. It is argued that the inclusion of both pointer and nonpointer types and the lack of garbage collection in hybrid systems is a major impediment to reliability, correctness, and extensibility. Hybrid systems lack design environments that permit evolutionary code development, which is a major impediment to rapid, and therefore cost-effective, software development and to the development of reusable libraries.>

Designing data types in isolation is fundamentally different from designing them for integration into communities of data types, especially when inheritance is a fundamental issue. Moreover, we can distinguish between the design of families—integrated types that are variations of each other—and more general communities where totally different but cohesive collections of types support specific applications (e.g., a compiler). We are concerned with the design of integrated families of data types as opposed to individual data types; that is, on the issues that arise when the focus is intermediate between the design of individual data types and more general communities of data types. We argue that design at this level is not adequately served by systems providing only class-based inheritance hierarchies and that systems which additionally provide a coupled subtype specification hierarchy are still not adequate. We propose a system that provides an unlimited number of uncoupled specification hi erarchies and illustrate it with three: a subtype hierarchy, a specialization/generalization hierarchy, and a like hierarchy. We also resurrect a relatively unknown Smalltalk design methodology that we call programming-by-exemplars and argue that it is an important addition to a designer's grab bag of techniques. The methodology is used to show that the subtype hierarchy must be decoupled from the inheritance hierarchy, something that other researchers have also suggested. However, we do so in the context of exemplar-based systems to additionally show that they can already support the extensions required without modification and that they lead to a better separation between users and implementers, since classes and exemplars can be related in more flexible ways. We also suggest that class-based systems need the notion of private types if they are to surmount their current limitations. Our points are made in the guise of designing a family of List data types. Among these is a new variety of lists that have never been previously published: prefix-sharing lists. We also argue that there is a need for familial classes to serve as an intermediary between users and the members of a family.

We describe the design of a constraint-based window system for Smalltalk. This window system uses constraints to specify attributes of windows and relationships between them. Three classes of constraints are supported, one of which is implicit and not available for general use. The system extends the current Smalltalk system, providing support for both fixed-size and fixed-scale windows. It also provides the capability to dynamically reorganize the layout of a window. A goal of the design is to produce a system with real-time response that is fast enough to be substituted for the existing system. A prototype with response times of approximately 1/4 second has been implemented to demonstrate the feasibility of the design as well as to point out several important optimizations.

Languages like Snobol, Prolog, and Icon were designed with backtracking facilities from the outset and these facilities are deeply intertwined with the implementation. Retrofitting a backtracking facility in a language that wasn't designed for it has never been achieved. We report on an experiment to retrofit Smalltalk with a backtracking facility. The facility is provided through a small number of primitives written in the language (no modifications to the kernel were made). The ability to do this is a direct result of the power provided by the objectification of contexts.

Programming languages for robotics applications are continually being developed and extended as the applications become more sophisticated. Language evolution is proceeding along two directions: (1) providing more and better facilities for task-level as opposed to robot-level programming and (2) providing better facilities for simulation, graphics and symbolic manipulation. The trend makes it clear that the full capabilities of a general purpose programming language are needed. Instead of developing a new language from the ground up, it is easier and more productive to take an existing language with all the requisite general purpose facilities and specialize it for robotics. Because of its symbolic processing facilities, its object-oriented nature, its usefulness as a simulation language, and its sophisticated graphical interface, Smalltalk is an ideal candidate for specialization. We discuss in more detail why this is the case and we show how a programming language that approaches the power of AL can be imbedded in Smalltalk within 2-4 person-months of effort.

In recent years, object-oriented programming languages and object-oriented program design have become increasingly popular. Dialects of many popular programming languages are now available which support the major concepts of object-oriented programming; namely message-passing, classes, generic operations and inheritance. Experience in the paradigm is increasingly supporting the view that object-oriented programming may be to the 80's what structured programming was to the 70's in terms of its influence on software development.

article Free Access Share on Technical Correspondence: Comments on Soisalon-Soininen's ``Inessential Error Entries and Their Use in LR Parser Optimization'' Author: Wilf R. LaLonde School of Computer Science, Carleton University, Colonel By Drive, Ottawa, Canada K1S 5B6 School of Computer Science, Carleton University, Colonel By Drive, Ottawa, Canada K1S 5B6View Profile Authors Info & Claims ACM Transactions on Programming Languages and SystemsVolume 6Issue 3pp 432–439https://doi.org/10.1145/579.357255Published:01 July 1984Publication History 0citation244DownloadsMetricsTotal Citations0Total Downloads244Last 12 Months8Last 6 weeks2 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my AlertsNew Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteeReaderPDF

Although determinisitic pushdown automata and LR(k) parsers are formally equivalent, the latter (unlike the former) stack one symbol for each input symbol read.By relaxing this requirement, we obtain a class of LR parsers that can perform finite state recognition locally without associated stack manipulations.The definition and construction of such stack-controlling LR parsers is examined in detail along with some potential application areas.

A simple linear time and space algorithm that transforms a standardized tree representation of an arithmetic expression lacking operator precedence information into a tree containing it is presented.The approach has applications in modularizing compilers, since the transformations can be applied after the parsing phase.Moreover, it facilitates the compiling of languages that allow dynamic operator definition.

A chain production is a production of the form A→M where A is a nonterminal and M is either a terminal or nonterminal. Pager in [Pag5] has presented an algorithm which removes all chain reductions from LR(1) parsers after they have been constructed.