language: en

[Journal of Visual Languages and Computing (1992) 3, 221-236]

Hypertextual Concurrent Control of a Lisp Kernel

P. David Stotts Richard Furuta
Department of Computer and Department of Computer Science and Information Sciences Institute for Advanced Computer Studies University of Florida University of Maryland
Gainesville, FL 32611 College Park, MD 20742
Received 16 December 1991 and accepted 14 February 1992

Abstract Using the Trellis human/computer interaction model as an implementation vehicle, we demonstrate how to use concurrency-supporting hypertext to provide visual displays of the execution flows through a parallel Lisp program. In addition to displays, the hypertext interface allows injection of control flow into an otherwise functional computation, and therefore provides reader control over the order of evaluation of expressions. The resulting system, termed Trellis, can be thought of as a concurrent control flow browser for composing functional computations, providing a visual implementation of kernel-control decomposition. The advantages of Trellis are ease of exploring program side effects; ease of debugging parallel code; aid in teaching functional languages; and the ability to construct hypertext documents that have parallel execution semantics and flexible browsing behaviors. Key words: functional programming, parallelism, kernel-control decomposition, Lisp, hypertext, exe cution visualization.

1 Introduction