integer_range.cpp

template<typename ValueType>
class next_iterator
    : public std::iterator<std::forward_iterator_tag, ValueType>
{
public:
    next_iterator(ValueType current) : m_current(std::move(current)) {}
    next_iterator(next_iterator const&) = default;
    
    friend bool operator== (next_iterator const& lhs, next_iterator const& rhs)
    {
        return lhs.m_current == rhs.m_current;
    }
    
    friend bool operator!= (next_iterator const& lhs, next_iterator const& rhs)
    {
        return lhs.m_current != rhs.m_current;
    }
    
    ValueType operator*() const
    {
        return m_current;
    }
    
    next_iterator& operator++()
    {
        ++m_current;
        return *this;
    }
    
    next_iterator operator++(int)
    {
        next_iterator prev(*this);
        operator++();
        return prev;
    }

private:
    ValueType m_current;
};

template<typename ValueType>
class next_range
{
public:
    next_range(ValueType first, ValueType last)
        : m_first(std::move(first))
        , m_last(std::move(last))
    {}
    
    next_iterator<ValueType> begin() const
    {
        return next_iterator<ValueType>{m_first};
    }
    
    next_iterator<ValueType> end() const
    {
        return next_iterator<ValueType>{m_last};
    }
    
private:
    ValueType m_first;
    ValueType m_last;
};

template<typename ValueType>
next_range<ValueType> range(ValueType const& first, ValueType const& last)
{
    return next_range<ValueType>{first, last};
}