Boost Spirit - How to match a string but not substrings [duplicate] - c++

Question

How can I prevent the Boost Spirit Symbol parser from accepting a keyword (symbol) when starts with a valid keyword (symbol). I would like the construct to fail parsing ‘ONEMORE’ as a whole and not succeed in parsing ‘ONE’ because that is a valid keyword and then fail on ‘MORE”.
Here is the actual output of the code below:
Keyword as a number: 1
Keyword as a number: 2
Keyword as a number: 1
Invalid keyword: MORETHREE
And this is what I like it to be:
Keyword as a number: 1
Keyword as a number: 2
Invalid keyword: ONEMORE
Keyword as a number: 3
The code is just a sample to get the point across.
#include <boost/config/warning_disable.hpp>
#include <boost/spirit/include/qi.hpp>
#include <iostream>
#include <string>
using namespace std;
namespace qi = boost::spirit::qi;
namespace ascii = boost::spirit::ascii;
void printNumber( unsigned u )
{
cout << "Keyword as a number: " << u << endl;
}
void printInvalidKeyword( const string &s )
{
cout << "Invalid keyword: " << s << endl;
}
template <typename Iterator>
struct keyword_parser : qi::grammar<Iterator, ascii::space_type>
{
struct mySymbols_ : qi::symbols<char, unsigned>
{
mySymbols_()
{
add
("ONE" , 1)
("TWO" , 2)
("THREE" , 2)
;
}
} mySymbols;
keyword_parser() : keyword_parser::base_type(start)
{
using qi::_1;
using qi::raw;
using ascii::char_;
start %= *(
mySymbols[&printNumber]
|
invalid[&printInvalidKeyword]
);
invalid = +char_;
}
qi::rule<Iterator, ascii::space_type> start;
qi::rule<Iterator, std::string(), ascii::space_type> invalid;
};
int main()
{
using boost::spirit::ascii::space;
typedef std::string::const_iterator iterator_type;
typedef keyword_parser<iterator_type> keyword_parser;
std::string s = "ONE TWO ONEMORE THREE";
iterator_type b = s.begin();
iterator_type e = s.end();
phrase_parse(b, e, keyword_parser(), space);
return 0;
}

Answer 1

Look at qi::repository::distinct or take some measures yourself:
start %= *(
keyword [cout << val("Keyword as a number: ") << _1 << endl]
| invalid [cout << val("Invalid keyword: ") << _1 << endl]
);
keyword = mySymbols >> !(char_("a-zA-Z0-9_"));
invalid = +ascii::graph;
The rules being declared as
qi::rule<Iterator, ascii::space_type> start;
// lexemes do not ignore embedded skippables
qi::rule<Iterator, int()> keyword;
qi::rule<Iterator, std::string()> invalid;
See it Live On Coliru
Prints:
Keyword as a number: 1
Keyword as a number: 2
Invalid keyword: ONEMORE
Keyword as a number: 2
Full source:
#include <boost/spirit/include/qi.hpp>
#include <boost/spirit/include/phoenix.hpp>
#include <iostream>
#include <string>
using namespace std;
namespace qi = boost::spirit::qi;
namespace phx = boost::phoenix;
namespace ascii = boost::spirit::ascii;
template <typename Iterator>
struct keyword_parser : qi::grammar<Iterator, ascii::space_type>
{
struct mySymbols_ : qi::symbols<char, unsigned>
{
mySymbols_()
{
add
("ONE" , 1)
("TWO" , 2)
("THREE" , 2)
;
}
} mySymbols;
keyword_parser() : keyword_parser::base_type(start)
{
using qi::_1;
using ascii::char_;
using phx::val;
start %= *(
keyword [cout << val("Keyword as a number: ") << _1 << endl]
| invalid [cout << val("Invalid keyword: ") << _1 << endl]
);
keyword = mySymbols >> !(char_("a-zA-Z0-9_"));
invalid = +ascii::graph;
}
qi::rule<Iterator, ascii::space_type> start;
// lexemes do not ignore embedded skippables
qi::rule<Iterator, int()> keyword;
qi::rule<Iterator, std::string()/*IMPLICIT LEXEME:, ascii::space_type*/> invalid;
};
int main()
{
using boost::spirit::ascii::space;
typedef std::string::const_iterator iterator_type;
typedef keyword_parser<iterator_type> keyword_parser;
std::string s = "ONE TWO ONEMORE THREE";
iterator_type b = s.begin();
iterator_type e = s.end();
phrase_parse(b, e, keyword_parser(), space);
return 0;
}