Re: Dynamic loop counter on x3

Hi,

I wrote the code based on Seth's approach. I want to separate the
container that contains the result of parsing from repeat counting.
Because I don't always need 5th parameter for outputs result on
`phrase_parse()`.
And capturing variables is acceptable in my usecase. So my code is as follows:

http://melpon.org/wandbox/permlink/aWi42xXerFNjjNsu

#include <string>
#include <iostream>
#include <iomanip>

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

int main() {
    for (std::string const input :
        {
            "3 1 2 3", // correct
            "4 1 2 3", // too few
            "2 1 2 3", // too many
            //
            "   3 1 2 3   ",
        }) {
        std::cout << "Parsing " << std::left << std::setw(20) << ("'"
+ input + "':");

        using namespace boost::spirit::x3;

        struct index_size {
            std::size_t index = 0;
            std::size_t size = 0;
        };
        index_size index_size;

        auto more   = [&index_size](auto &ctx) { _pass(ctx) =
index_size.index++ < index_size.size; };
        auto done   = [&index_size](auto &ctx) { _pass(ctx) =
index_size.index == index_size.size + 1; };
        auto number = [&index_size](auto &ctx) {
            index_size.size = _attr(ctx);
        };

        std::vector<int> v;
        auto r =
            omit[uint_[number] ]
            >> *(eps[more] >> int_)
            >> eps[done];

        auto it = input.cbegin();
        auto end = input.cend();
        if (phrase_parse(it, end, r, space, v)) {
            std::copy(
                v.begin(),
                v.end(),
                std::ostream_iterator<int>(
                    std::cout << v.size() << " elements: ", " "
                )
            );
            if (std::size_t rest = std::distance(it, end)) {
                std::cout << "(" << rest << " bytes remaining.)";
            }
        }
        else {
            std::cout << "Parse failed";
        }
        std::cout << std::endl;
    }
}

Thanks,
Takatoshi Kondo

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