#include <boost/coroutine/all.hpp>
#include <functional>
#include <iostream>

using namespace boost::coroutines;


class Stmt
{
public:
    virtual ~Stmt()
    {
    }

    virtual void execute(coroutine<int>::push_type& sink) = 0;
};


class WhileStmt : public Stmt
{
public:
    void execute(coroutine<int>::push_type& sink) override
    {
        for (int n = 1; n <= 5; ++n)
            sink(n);

        sink(-1);
    }
};


class WhileStmt2 : public Stmt
{
public:
    void execute(coroutine<int>::push_type& sink) override
    {
        WhileStmt subStmt;
        coroutine<int>::pull_type subSource{
            std::bind(&WhileStmt::execute, subStmt, std::placeholders::_1)};

        while (subSource.get() != -1)
        {
            sink(subSource.get());

            for (int n = 1; n <= 2; ++n)
                sink(10);

            subSource();
        }

        sink(-1);
    }
};


int main()
{
    Stmt* stmt = new WhileStmt2();
    coroutine<int>::pull_type source{std::bind(&Stmt::execute, stmt, std::placeholders::_1)};

    while (source.get() != -1)
    {
        std::cout << source.get() << std::endl;
        source();
    }

    return 0;
}