webLISP
© '98 Thomas Mahler

Why webLISP ?

Fun: Lisp is fun, Lisp on the web is more fun, Lisp in your own Browser is just ...

Research: webLISP is based on a parallel operating GraphReduction Machine. It is a showcase for JAVA-programming techniques and a Toolbox for experimenting with Lambda-calculus, Combinatory Logics, Parallel Processing and component software architecture.

Main Features

• Lisp-like Syntax, Lisp Interpreter User Interface
• Applet, Standalone and ActiveX Server versions included
• Incremental Compilation to Combinatory Logic Graphs
• Implements lazy evaluation (Normal order reduction)
• The efficient Graph reduction Machine detects strict Operations
  and performs parallel evaluation of the subgraphs
• Full AND/OR-Parallelism like in ParLisp
• Special P-Combinator for defining explicit parallel processes
• Save Printing of circular Expressions
• Interface layer to expose the webLISP virtual machine as an ActiveX Server

Introduction

webLISP is an experimental Implementation of reflective functional Programming. It contains a very simple Lexer and Parser for a lambda-calculus language in lisp-syntax. The Lambda terms are compiled to variablefree Combinator Graphs. The virtual Graph-Reduction-Machine that reduces the Combinator-graph distinguishes between strict and non-strict operations. Strict operations have to be evaluated even if we obey lazy evaluation and can thus be evaluated in parallel to the main computation. The parallel computations are added to a global task pool, which is maintained by a stochastic scheduler.

In addition to this basic implemenation a special Combinator P is introduced which performs an asyncronous parallelism of two given applications. P (app1 rator1) (app2 rator2) --> (quote parEval(app1 rator1) parEval(app2 rator2))

If rator1 and app2 point to the same object X, you get the funny result, that the same object is used simultaneously as Operand (by app1) and as Operator (for rator2), because both applications are evaluated in parallel: P (app1 X) (X rator2)

This special situation is quite ambigious and "dangerous" for it disturbs the predictability of computational systems. Although it looks a bit awkward and arises many problems in traditional calculi, this Relationship can be formalized by PolyContextural Logics (PCL), which describes it as the "Proemial relationship"

This Relationship is useful in formalizing self-referential, contradictory, autopoietic etc. systems. It is also quite helpful in the formalisation of meta-level architectures and computational reflection.

The aim of the webLISP project is to build a LISP-like Programming language which is capable of implementing such architectures. A short paper in English that provides a general overview is here. A detailed description of the approach and documentation of the implementation is only available in German.

As you will recognise, the implementation is rather small and includes until now only the most necessary features. However you can feel free to experiment with this toolbox, improve it, discard it... or give some feedback for further developments.

/****************************************************************************
Copyright (c) 1998 by Thomas Mahler. All rights reserved.

THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
OR IMPLIED. ANY USE IS AT YOUR OWN RISK.

Permission is hereby granted to use or copy this program for non-commercial
purpose, provided the above notices are retained on all copies.
Permission to modify the code is granted, provided the above notices
are retained. If you intend to distibrute modified versions of this code or
to use this program for commercial purposes contact the author
of this software for permission and further legal arrangements.

mailto:[email protected]
http://www.techno.net/pcl
****************************************************************************/

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