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From: dag@control.lth.se (Dag Bruck)
Newsgroups: comp.sources.wanted
Subject: Re: YACC++ LEX++
Message-ID: <1990Dec18.095629.5729@lth.se>
Date: 18 Dec 90 09:56:29 GMT
References: <5140@tahoe.unr.edu> <3706@atomic.trl.mei.co.jp>
Sender: newsuser@lth.se (LTH network news server)
Organization: Department of Automatic Control, Lund, Sweden
Lines: 68

Rebecca Hayhurst writes:
> I'm looking for information, source on a LEX and YACC to produce
> C++ code.  

I have successfully used the plain YACC and LEX supplied with our Sun
system.  YACC and LEX do not have any particular views on the contents
of the actions; the trick is to make the C parser/scanner skeletons
acceptable to the C++ compiler.

The two files that must be changed are (on a Sun):

	/usr/lib/yaccpar
	/usr/lib/lex/ncform

The following steps should bring you a long way:

	1.  Include the header file (enclosed below) in your .y and .l
	files.  The file contains some declarations that the C++
	compiler needs.

	2.  Modify the skeletons so they become legal C++ code. This
	essentially means that you will have to change the formal
	argument lists of the functions, etc.

	If you wrap your changes in #ifdef __cplusplus/#else/#endif,
	you will get a parser/scanner that is useful for *both* C
	and C++.

Please note that your parser/scanner skeleton may be different from
mine, so you may run into trouble I haven't discovered.  Here is my
header file:

	/* C++ definition for lex programs */

	#ifdef __cplusplus
	#include <malloc.h>

	extern int yydebug;
	extern int yylineno;
	extern int yynerrs;
	extern YYSTYPE yylval;
	
	extern void yyerror(const char *);

	extern int yylook();
	extern int yyparse();
	extern int yylex();
	extern "C" {
	        int yyless();
	        int yyreject();
	        int yywrap();
	        int yyback(int *, int);
	        int yyinput();
	        void yyoutput(int);
	        void yyunput(int);
	}
	#endif

The `extern "C"' routines are in the LEX runtime library.

Good luck.

Dag M. Bruck
--
Department of Automatic Control		E-mail: dag@control.lth.se
Lund Institute of Technology
P. O. Box 118				Phone:	+46 46-104287
S-221 00 Lund, SWEDEN			Fax:    +46 46-138118