Boost C++ Libraries

...one of the most highly regarded and expertly designed C++ library projects in the world. Herb Sutter and Andrei Alexandrescu, C++ Coding Standards

This is the documentation for a snapshot of the develop branch, built from commit 55c1396b28.

libs/spirit/example/x3/complex_number.cpp

/*=============================================================================
    Copyright (c) 2002-2015 Joel de Guzman

    Distributed under the Boost Software License, Version 1.0. (See accompanying
    file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
=============================================================================*/
///////////////////////////////////////////////////////////////////////////////
//
//  A complex number micro parser.
//
//  [ JDG May 10, 2002 ]    spirit1
//  [ JDG May 9, 2007 ]     spirit2
//  [ JDG May 12, 2015 ]    spirit X3
//
///////////////////////////////////////////////////////////////////////////////

#include <boost/spirit/home/x3.hpp>

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

///////////////////////////////////////////////////////////////////////////////
//  Our complex number parser/compiler
///////////////////////////////////////////////////////////////////////////////
namespace client
{
    template <typename Iterator>
    bool parse_complex(Iterator first, Iterator last, std::complex<double>& c)
    {
        using boost::spirit::x3::double_;
        using boost::spirit::x3::_attr;
        using boost::spirit::x3::phrase_parse;
        using boost::spirit::x3::ascii::space;

        double rN = 0.0;
        double iN = 0.0;
        auto fr = [&](auto& ctx){ rN = _attr(ctx); };
        auto fi = [&](auto& ctx){ iN = _attr(ctx); };

        bool r = phrase_parse(first, last,

            //  Begin grammar
            (
                    '(' >> double_[fr]
                        >> -(',' >> double_[fi]) >> ')'
                |   double_[fr]
            ),
            //  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;
}