boost/libs/coroutine/example/cpp03/asymmetric/layout.cpp

//          Copyright Nat Goodspeed 2013.
// 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)

#include <iostream>
#include <iomanip>
#include <vector>
#include <string>
#include <utility>

#include <boost/assign/list_of.hpp>
#include <boost/bind.hpp>
#include <boost/coroutine/all.hpp>
#include <boost/range.hpp>

struct FinalEOL
{
    ~FinalEOL() { std::cout << std::endl; }
};

void layout(boost::coroutines::asymmetric_coroutine<std::string>::pull_type& in, int num, int width)
{
    // Finish the last line when we leave by whatever means
    FinalEOL eol;

    // Pull values from upstream, lay them out 'num' to a line
    for (;;)
    {
        for (int i = 0; i < num; ++i)
        {
            // when we exhaust the input, stop
            if (! in)
                return;

            std::cout << std::setw(width) << in.get();
            // now that we've handled this item, advance to next
            in();
        }
        // after 'num' items, line break
        std::cout << std::endl;
    }
}

int main(int argc, char *argv[])
{
    std::vector<std::string> words = boost::assign::list_of
        ("peas")
        ("porridge")
        ("hot")
        ("peas")
        ("porridge")
        ("cold")
        ("peas")
        ("porridge")
        ("in")
        ("the")
        ("pot")
        ("nine")
        ("days")
        ("old")
    ;

    boost::coroutines::asymmetric_coroutine<std::string>::push_type writer(
        boost::bind(layout, _1, 5, 15));

    std::copy(boost::begin(words), boost::end(words), boost::begin(writer));

    return 0;
}