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#include <boost/spirit.hpp>
#include <boost/spirit/actor.hpp>
#include <string>
#include <iostream>
 
using namespace std;
using namespace boost::spirit;
 
int main()
{
    string input;
 
    cout << "Input a line.\n";
    getline(cin, input);
 
    cout << "Got '" << input << "'.\n";
 
    unsigned count = 0;
 
 /*  
    Next line parses the input (input.c_str()),
        using a parser constructed with the following semantics
        (identation matches source for clarity):
 
     Zero or more occurrences of (
          literal string "cat" ( when matched, increment the counter "count" )
      or  any character (to move on finding the next occurrence of "cat")
     )
 */
     parse(input.c_str(),
        *(  str_p("cat") [ increment_a(count) ]
          | anychar_p
         ));
 /*
     The parser is constructed by the compiler using operator
     overloading and template matching, so the actual work is
     done within spirit::parse(), and the expression starting
     with * only initializes the rule object that the parse
     function uses.
  */
 
    // last, show results.
    cout << "The input had " << count
              << " occurrences of 'cat'\n";
    return 0;
}

Code: Select all

#include <boost/config/warning_disable.hpp>
#include <boost/spirit/include/qi.hpp>
#include <boost/spirit/include/phoenix_core.hpp>
#include <boost/spirit/include/phoenix_operator.hpp>

#include <iostream>
#include <string>
#include <complex>

///////////////////////////////////////////////////////////////////////////////
//  Our complex number parser/compiler
///////////////////////////////////////////////////////////////////////////////
//[tutorial_complex_number
namespace client
{
    template <typename Iterator>
    bool parse_complex(Iterator first, Iterator last, std::complex<double>& c)
    {
        using boost::spirit::qi::double_;
        using boost::spirit::qi::_1;
        using boost::spirit::qi::phrase_parse;
        using boost::spirit::ascii::space;
        using boost::phoenix::ref;

        double rN = 0.0;
        double iN = 0.0;
        bool r = phrase_parse(first, last,

            //  Begin grammar
            (
                    '(' >> double_[ref(rN) = _1]
                        >> -(',' >> double_[ref(iN) = _1]) >> ')'
                |   double_[ref(rN) = _1]
            ),
            //  End grammar

            space);

        if (!r || first != last) // fail if we did not get a full match
            return false;
        c = std::complex<double>(rN, iN);
        return r;
    }
}
//]

////////////////////////////////////////////////////////////////////////////
//  Main program
////////////////////////////////////////////////////////////////////////////
int
main()
{
    std::cout << "/////////////////////////////////////////////////////////\n\n";
    std::cout << "\t\tA complex number micro parser for Spirit...\n\n";
    std::cout << "/////////////////////////////////////////////////////////\n\n";

    std::cout << "Give me a complex number of the form r or (r) or (r,i) \n";
    std::cout << "Type [q or Q] to quit\n\n";

    std::string str;
    while (getline(std::cin, str))
    {
        if (str.empty() || str[0] == 'q' || str[0] == 'Q')
            break;

        std::complex<double> c;
        if (client::parse_complex(str.begin(), str.end(), c))
        {
            std::cout << "-------------------------\n";
            std::cout << "Parsing succeeded\n";
            std::cout << "got: " << c << std::endl;
            std::cout << "\n-------------------------\n";
        }
        else
        {
            std::cout << "-------------------------\n";
            std::cout << "Parsing failed\n";
            std::cout << "-------------------------\n";
        }
    }

    std::cout << "Bye... :-) \n\n";
    return 0;
}