Path: utzoo!yunexus!geac!daveb
From: daveb@geac.UUCP (David Collier-Brown)
Newsgroups: comp.software-eng
Subject: Re: Soft-Eng Digest v5n13
Summary: Sidebar on Deterministic Finite Automaton compilers.
Message-ID: <2859@geac.UUCP>
Date: 13 Jun 88 12:35:31 GMT
Article-I.D.: geac.2859
References: <8806082028.AA14514@pcsc-sun.mitre.org> <5444@pucc.Princeton.EDU>
Reply-To: daveb@geac.UUCP (David Collier-Brown)
Organization: The Geac "Its Tough To Be Green" Department
Lines: 106


| In article <8806082028.AA14514@pcsc-sun.mitre.org>, nigam@pcsc-sun (Alok Nigam) writes:
| (6) I am currently modifying some code based on an undocumented and
|     erroneous Finite State Machine -- ARRRGH


In article <5444@pucc.Princeton.EDU> EGNILGES@pucc.Princeton.EDU writes:
| You have my sympathy, but if you replace the string "Finite State
| Machine", the "ARRRGH" is still valid!  

  For mere humans, there is a good FSA compiler in the Kermit
distribution, called "wart".  Use of it makes
	1) the notation a fair bit easier to follow, and
	2) the ugly generated/required code irrelevant.
  I have an upgraded version, available by mail for anyone with a C
compiler.  Please note that Wart does not have to genrate C: FORTRAN
II would probably be ok.  You need a C compiler to compile Wart
itself.

  A short description follows:

WART(1)

        NAME
                  wart -- a dfa compiler

        SYNOPSIS
                  wart [file]

        DESCRIPTION
                 Wart is a program which takes a yacc-like file of code
             and directives and generates a c program from it.  The
             directives define a deterministic finite automaton (DFA),
             and are primarily for producing protocol engines, such as
             are used by C-Kermit.

                 The format of the file is:

                  lines to be copied
                  %states <list of state names>
                  %events <list of event names>
                  %%
                  event               { block of code to be executed }
                  ...
                  <state[,state]> event    { block of code to be executed }
                  <state> event       { more code... }
                  ...
                  %%
                  more lines to be copied

                 Wart therefor implements a small subset of the Unix
             'lex' lexical analyzer generator.  Unlike lex, wart may be
             distributed without requirement for a Unix license.
                 Wart is intended for production of state table switch-
             ers.  It allows a set of states to be defined, along with a
             function for getting input, and a table of state transi-
             tions.  A C program is generated which performs actions and
             switches states based on the current state and the input.

[...]

        HISTORY
                 Wart was written by Jeff Damens of the Columbia Center
             for Computing Activities, November, 1985, to facilitate
             development of Unix Kermit.  It was updated by David Brown
             of Tesseract Technologies in February, 1986.
                 The program is Copyright (C) 1985, the Trustees of
             Columbia University in the City of New York.
                 The earlier version assumed that the event would be a
             single ascii character, and did not support the "%events"
             directive.
























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-- 
 David Collier-Brown.  {mnetor yunexus utgpu}!geac!daveb
 Geac Computers Ltd.,  | "His Majesty made you a major 
 350 Steelcase Road,   |  because he believed you would 
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