A simple example of using bison++ and flex++

Dear All,


    I noticed that there is an interest in having an example of using bison++
and flex++. I also noticed that there is no concrete example in the web
(from my search). For this reason, this an example of how to use bison++
and flex++.


I am using bison++ Version 1.21-8 and flex++ version 2.5.4.


The files are:


============================================================
file name: parser.y


%name Parser
%define LSP_NEEDED
%define MEMBERS \
          virtual ~Parser() {} \
          private: \
                yyFlexLexer lexer;
%define LEX_BODY {return lexer.yylex();}
%define ERROR_BODY {cerr << "error encountered at line: "<<lexer.lineno()<<"
last word parsed:"<<lexer.YYText()<<"\n";}


%header{
#include <iostream>
#include <fstream>
#include <FlexLexer.h>
using namespace std;
%}


%union {
                int i_type;
}


%token UNKNOWN
%token <i_type> NUMBER


%type <i_type> number


%start number


%%
number
: NUMBER { $$ = atoi(lexer.YYText());std::cout << "Parser value
"<<$$<<std::endl;}
;


%%
====================================================================
file name: scanner.l
%option c++
%option noyywrap


%{
#include<sstream>
#include "parser.h"
#include <cstdlib>
//YY_CalcParser_STYPE val;
%}


DIGIT [0-9]
DIGIT1 [1-9]


%%


{DIGIT1}{DIGIT}* {
                                      std::cout <<"Lexer: "<< yytext <<std::endl;
                                      return Parser::NUMBER;
                                    }
. {
                                        return Parser::UNKNOWN;
                                    }
<<EOF>> {
                                        yyterminate();
                                    }


%%
======================================================================
file name: test.cpp
#include "parser.h"
#include <iostream>
using namespace std;
int main(int argc, char ** argv)
{
                Parser parser;
                parser.yyparse();
                return 0;
}
======================================================================


To generate cpp files use:
1. bison++ -d -hparser.h -o parser.cpp parser.y
2. flex++ -d -oscanner.cpp scanner.l


To compile the files user:
1. g++ -c parser.cpp
2. g++ -c scanner.cpp
3. g++ -c test.cpp


To link them all
1. g++ -o test test.o parser.o scanner.o


To test your parser/lexer use
1. echo "12345" | ./test


For more information about options and declarations in flex++ and
bison++, the man of flex++ and bison++ is an excellent source for
that.


With best regards.
Belaid Moa.

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