13514949
Programming Languages for Compressing Graphics
Images are programs. They are usually simple instructions to a very specialized interpreter that renders them on screen. Image formats therefore correspond to different programming languages, each with distinctive properties of program size and accuracy. Image-processing languages render large images from small pieces of code. We present Evolver, a language and toolkit that perform the reverse transformation.The toolkit accepts images in conventional graphics formats like JPEG and uses genetic algorithms to grow a program in the Evolver language that generates a similar image. Because the program it produces is often significantly smaller than the input image, Evolver can be used as a compression tool.The language balances the tradeoff between having many features, which improves compression, and fewer features, which improves searching. In addition, by being programmatic descriptions, the rendered images scale much better to multiple resolutions than fixed-size images. We have implemented this system and present examples of its use.
7017581
Multi-finger cursor techniques
The mouse cursor acts as a digital proxy for a finger on graphical displays. Our hands, however, have ten fingers and many degrees of freedom that we use to interact with the world. We posit that by creating graphical cursors that reflect more of the hand's physical properties, we can allow for richer and more fluid interaction. We demonstrate this idea with three new cursors that are controlled by the user's fingers using a multi-point touchpad. The first two techniques allow for simultaneous control of several properties of graphical objects, while the third technique makes several enhancements to object selection.
6477925
Constructive solid geometry for polyhedral objects
Constructive Solid Geometry (CSG) is a powerful way of describing solid objects for computer graphics and modeling. The surfaces of any primitive object (such as a cube, sphere or cylinder) can be approximated by polygons. Being abile to find the union, intersection or difference of these objects allows more interesting and complicated polygonal objects to be created. The algorithm presented here performs these set operations on objects constructed from convex polygons. These objects must bound a finite volume, but need not be convex. An object that results from one of these operations also contains only convex polygons, and bounds a finite volume; thus, it can be used in later combinations, allowing the generation of quite complicated objects. Our algorithm is robust and is presented in enough detail to be implemented.
2239491
Voice as sound: using non-verbal voice input for interactive control
We describe the use of non-verbal features in voice for direct control of interactive applications. Traditional speech recognition interfaces are based on an indirect, conversational model. First the user gives a direction and then the system performs certain operation. Our goal is to achieve more direct, immediate interaction like using a button or joystick by using lower-level features of voice such as pitch and volume. We are developing several prototype interaction techniques based on this idea, such as "control by continuous voice", "rate-based parameter control by pitch," and "discrete parameter control by tonguing." We have implemented several prototype systems, and they suggest that voice-as-sound techniques can enhance traditional voice recognition approach.
795737
Navigating documents with the virtual scroll ring
We present a technique for scrolling through documents that is simple to implement and requires no special hardware. This is accomplished by simulating a hardware scroll ring--a device that maps circular finger motion into vertical scrolling. The technique performs at least as well as a mouse wheel for medium and long distances, and is preferred by users. It can be particularly useful in portable devices where screen-space and space for peripherals is at a premium.
6983775
Modeling surfaces of arbitrary topology using manifolds
Manifolds describe complicated objects that are locally $\Re\sp{n}$ by defining a set of overlapping maps from the object to $\Re\sp{n}$. In this thesis we present a general technique for inverting that process: we define a complicated object from a set of overlapping subsets of $\Re\sp{n}$. We first present a constructive definition that describes how to perform such a construction in general. We then apply this construction to the particular problem of defining surfaces of arbitrary topology. The surface is built in two steps: we build a manifold with the correct topology then embed the manifold into $\Re\sp3$ using traditional spline techniques. The surface inherits many of the properties of B-splines: local control, a compact representation, and guaranteed continuity of arbitrary degree. The surface is specified using a polyhedral control mesh instead of a rectangular one; the resulting surface approximates the polyhedral mesh much as a B-spline approximates its rectangular control mesh. Like a B-spline, the surface is a single, continuous object.
42717421
Global variables in Haskell
Haskell today provides good support not only for a functional programming style, but also for an imperative one. Elements of imperative programming are needed in applications such as web servers, or to provide efficient implementations of well-known algorithms, such as many graph algorithms. However, one element of imperative programming, the global variable, is surprisingly hard to emulate in Haskell. We discuss several existing methods, none of which is really satisfactory, and finally propose a new approach based on implicit parameters. This approach is simple, safe, and efficient, although it does reveal weaknesses in Haskell's present type system.
958035
A Loop-Detecting Interpreter for Lazy, Higher-Order Programs
Interpreters that detect some forms of non-termination have a variety of applications, from abstract interpretation to partial evaluation. A simple and often used strategy is to test for a repeated state, but this cannot handle infinite values (such as first-class functions) or unevaluated states such as arise in lazy programs. In this paper we propose using Berry and Curien’s theory of sequential algorithms as a semantic foundation for loop detection: we obtain straightforwardly a loop detector for lazy higher-order functional programs, which is more effective than the simple strategy even for strict first order cases.
40448216
Multiple fault detection using single fault test sets
A simulation study of the 74LS181 4-b ALU (arithmetic logic unit) using 16 complete single stuck-at fault test sets demonstrated significantly higher multiple stuck-at fault coverage than predicted by previous theoretical studies. Analysis of the undetected multiple faults shows the effect of circuit and test set characteristics on fault coverage. A fault masking property, defined as self-masking, is observed for the undetected faults in the simulation study. A heuristic is described for evaluating the multiple fault coverage of single stuck-at fault test sets. A second heuristic generates augmented test sets, providing improved multiple stuck-at fault coverage with a minimal increase in test set development cost. >
40790646
A Type Specialisation Tutorial
The essence of partial evaluation is beautifully simple: we just take a program, together with values of some of its inputs; we perform the operations that depend only on known inputs, build a new program from the other operations, and finally obtain a residual program which solves the same problem as the original for a subclass of the cases. Work by Neil Jones and his group over the past decade and a half has demonstrated just how powerful this simple idea really is.
16084483
Why Functional Programming Matters
As software becomes more and more complex, it is more and more important to structure it well. Well-structured software is easy to write and to debug, and provides a collection of modules that can be reused to reduce future programming costs. In this paper we show that two features of functional languages in particular, higher-order functions and lazy evaluation, can contribute significantly to modularity. As examples, we manipulate lists and trees, program several numerical algorithms, and implement the alpha-beta heuristic (an algorithm from Artificial Intelligence used in game-playing programs). We conclude that since modularity is the key to successful programming, functional programming oers important advantages for software development.