Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!uunet!mcsun!ukc!icdoc!zmact61
From: zmact61@doc.ic.ac.uk (D Spinellis)
Newsgroups: comp.graphics
Subject: Re: YACC grammar for HPGL wanted (please)
Summary: Yacc is an overkill
Keywords: YACC, HPGL, grammar
Message-ID: <1630@gould.doc.ic.ac.uk>
Date: 26 Feb 90 14:37:17 GMT
References: <1239@acadch.UUCP>
Sender: news@doc.ic.ac.uk
Reply-To: dds@cc.ic.ac.uk (Diomidis Spinellis)
Organization: Imperial College Department of Computing
Lines: 36

In article <1239@acadch.UUCP> jeremy@acadch.UUCP (Jeremy Tammik) writes:
>could somebody please send me a Yacc grammar for the HPGL
>plotter language? Thank you! 

/* Commands needing 0, 1, 2 and 4 arguments */
%token	tCOM0 tCOM1 tCOM2 tCOM4
%token	tTERMINATOR tARG
%start	command_file

%%
command_file	: /* Empty */
		| command_file command
		;

command		: tCOM0 tTERMINATOR
		| tCOM1 tARG tTERMINATOR
		| tCOM2 tARG tARG tTERMINATOR
		| tCOM4 tARG tARG tARG tARG tTERMINATOR
		;
%%

>Hints on using it efficiently
>to parse & convert & understand HPGL would also be appreciated.

DON'T USE IT.  HPGL can be parsed very easily by a finite state machine.
Using yacc to parse it is an overkill.  All commands are two characters
long and are terminated by a special character.  You can determine the
number of arguments a command uses by counting argument separators until
you encounter the command terminator.

Diomidis
--
Diomidis Spinellis                  Internet:                 dds@cc.ic.ac.uk
Department of Computing             UUCP:                    ...!ukc!iccc!dds
Imperial College                    JANET:                    dds@uk.ac.ic.cc
London SW7 2BZ                      #include "/dev/tty"