%{
		#define WEB 0
		#define SPACE 1
		#define STRING 2	
%}

string_component [0-9a-zA-Z \t\.!#$%^&()*@_]

%%

"daniweb"		              {return WEB;}
[ \t\n]			{return SPACE;}
{string_component}+	{return STRING;}

%%

#include <iostream>
			
using namespace std;
		
int main()
{	
	cout<<yylex()<<endl;
	cout<<yylex()<<endl;

	return 0;
}

int yywrap(void){return 1;}

test_string daniweb

flex flex.l
g++ lex.yy.c
./a.out <example

#include <boost/spirit/core.hpp>
#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <boost/assign.hpp>
using namespace std ;
using namespace boost ;
using namespace boost::spirit ;
using namespace boost::assign ;
 
struct parse_it
{ 
  void operator() ( const string& str ) const
  {
    vector<string> tokens ;
    const char* cstr = str.c_str() ;
    size_t n = 0 ;
    while( n < str.size() )
      n += parse( cstr + n,
                  (+space_p) [  push_back_a( tokens, "SPACE" ) ] |
                  str_p("daniweb") [ push_back_a( tokens, "WEB" ) ] |
                  str_p("lexer") [ push_back_a( tokens, "LEX" ) ] |
                  str_p("tokenizer") [ push_back_a( tokens, "TOK" ) ] |
                  (+~space_p) [ push_back_a( tokens, "STRING" ) ]
                ).length ;
    cout << '\n' << "parsed: " << str << "\ntokens: " ;      
    copy( tokens.begin(), tokens.end(), 
               ostream_iterator<string>(cout," ") ) ;
    cout << '\n' ;      
  }
};
int main()
{
  vector<string> test_cases = list_of
                ( "test daniweb lexer xyz tokenizer lexer" )
                ( "daniweblexer tokenizerlexer abcd lexerlexer" )
                ( "daniwebtest lexerdaniweblexertest tokenizerxxx" ) ;
  for_each( test_cases.begin(), test_cases.end(), parse_it() ) ;
}
/**
>g++ -Wall -std=c++98 -I/usr/local/include keyword.cpp && ./a.out
 
parsed: test daniweb lexer xyz tokenizer lexer
tokens: STRING SPACE WEB SPACE LEX SPACE STRING SPACE TOK SPACE LEX
 
parsed: daniweblexer tokenizerlexer abcd lexerlexer
tokens: WEB LEX SPACE TOK LEX SPACE STRING SPACE LEX LEX
 
parsed: daniwebtest lexerdaniweblexertest tokenizerxxx
tokens: WEB STRING SPACE LEX WEB LEX STRING SPACE TOK STRING
*/