bisonpp version 0.3

Bisonpp is a simple script that simplifies writing parsers using C++. Bisonpp calls bison, it has been tested with bison v.1.25. The commandline is

bisonpp [--help] [--class class-name] [bison-option].. file

• File is an ordinary bison input file.
• If no class-name is specified, it defaults to Parser.
• Any bison options may be specified but one should be aware of the fact that bisonpp will call bison with the yacc-compatibility option -y, which forces bison to call its output files y.tab.c and y.tab.h. The bisonpp script relies on this (and it makes bisonpp easy to use for automake: simply define YACC=bisonpp.

Bisonpp uses a slightly modified version of bison.simple, called bisonpp.simple. The main differences are that the definitions of the following ``global'' variables have been removed

int             yynerrs;
int             yychar;
YYSTYPE         yylval;
void    	yyerror(const char* msg);

int @CLASS@::yyparse()

All this implies that the user must include a declaration of a class class-name in the first section of the bison input file. Typically, this will be done by an include directive, like

#include parser.h

where parser.h might look like this (in the example, the
class-name is ExpParser:
#ifndef	EXPPARSER_H
#define	EXPPARSER_H

#include	
#include	"explexer.h"
#include	"y.tab.h"

class ExpParser {
public:
private:
	ExpLexer	_lexer;

	// yynerrs, yychar, yylval, yyerror *must* be defined
	// because they are used by the bison-generated yyparse()
	// function

	int		yynerrs;
	int		yychar;
	YYSTYPE		yylval;

	void	yyerror(const char* msg) { 
		cerr << "yyerror: " << msg << endl; }

	int	yylex() { return _lexer.yylex(yylval); }

public:
	ExpParser(istream& is): _lexer(&is) {}
	
	int	yyparse();
};

#endif

Example
Here is complete example using flex and bisonpp
to build a small program that evaluates the command line arguments
as a simple arithmetic expression.

makefile
expparser.h, the ExpParser class declaration.
expparser.y, the bisonpp input file.
explexer.h, the ExpLexer class declaration.
explexer.l, the flex input file.
calc.C, the main program.

Download
Bisonpp is available from tinf2.vub.ac.be