Function combine

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#### Function combine

The `combine` function is used to make one range from multiple ranges. The `combine` function returns a `combined_range` which is an `iterator_range` of a `zip_iterator` from the Boost.Iterator library.

##### Synopsis

    namespace boost
    {
        namespace range
        {

    template<typename IterTuple>
    class combined_range
        : public iterator_range<zip_iterator<IterTuple> >
    {
    public:
        combined_range(IterTuple first, IterTuple last);
    };

    template<typename... Ranges>
    auto combine(Ranges&&... rngs) ->
        combined_range<decltype(boost::make_tuple(boost::begin(rngs)...))>

        } // namespace range
    } // namespace boost

- Precondition: For each type `r` in `Ranges`, `r` is a model of Single Pass Range or better.
- Return Type: `combined_range<tuple<typename range_iterator<Ranges>::type...> >`
- Returned Range Category: The minimum of the range category of every range `r` in `Ranges`.

##### Example

    #include <boost/range/combine.hpp>
    #include <boost/foreach.hpp>
    #include <iostream>
    #include <vector>
    #include <list>

    int main(int, const char*[])
    {
        std::vector<int> v;
        std::list<char> l;
        for (int i = 0; i < 5; ++i)
        {
            v.push_back(i);
            l.push_back(static_cast<char>(i) + 'a');
        }

        int ti;
        char tc;
        BOOST_FOREACH(boost::tie(ti, tc), boost::combine(v, l))
        {
            std::cout << '(' << ti << ',' << tv << ')' << '\n';
        }

        return 0;
    }

This produces the output:

    (0,a)
    (1,b)
    (2,c)
    (3,d)
    (4,e)