#include <vector>
#include <memory>
#include <iostream>
#include <ostream>

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

    virtual std::ostream& output(std::ostream& o) const { return o; }

    friend std::ostream& operator<<(std::ostream& o, const IConfig &c)
    {
        return o << c.output(o);
    }
};

class MultiConfig : public IConfig
{
public:
    virtual ~MultiConfig() { }

    virtual std::ostream& output(std::ostream& o) const
    {
        for (std::vector<std::string>::const_iterator cit = m_vals.begin();
             cit != m_vals.end(); cit ++)
             o << (*cit) << std::endl;
        return o;
    }

protected:
    std::vector<std::string> m_vals;
};

class SingleConfig : public IConfig
{
public:
    virtual ~SingleConfig() { }

    virtual std::ostream& output(std::ostream& o) const
    {
        return o << m_val;
    }
protected:
    std::string m_val;
};

class IndexConfig : public IConfig
{
public:
    virtual ~IndexConfig() { }

    virtual std::ostream& output(std::ostream& o) const
    {
        return o << m_val;
    }

protected:
    std::string m_val;
    int m_index;
};

class IpConfig : public SingleConfig
{
public:
    IpConfig() { m_val = "8.8.8.8"; }
    virtual ~IpConfig() { }
};

using ConfigPtr = std::shared_ptr<IConfig>;
using Configs = std::vector<ConfigPtr>;

int main(int argc, char* argv[])
{
    ConfigPtr c(new IpConfig());
    Configs s;
    s.push_back(c);
    for (Configs::const_iterator cit = s.begin(); cit != s.end(); cit++)
    std::cout << (**cit) << std::endl;
}