Boost C++ Libraries

...one of the most highly regarded and expertly designed C++ library projects in the world. — Herb Sutter and Andrei Alexandrescu, C++ Coding Standards

Header <boost/algorithm/gather.hpp>

namespace boost {
  namespace algorithm {

    // iterator-based gather implementation 
    template<typename BidirectionalIterator, typename Pred> 
      std::pair< BidirectionalIterator, BidirectionalIterator > 
      gather(BidirectionalIterator first, BidirectionalIterator last, 
             BidirectionalIterator pivot, Pred pred);

    // range-based gather implementation 
    template<typename BidirectionalRange, typename Pred> 
      std::pair< typename boost::range_iterator< BidirectionalRange >::type, typename boost::range_iterator< BidirectionalRange >::type > 
      gather(BidirectionalRange & range, 
             typename boost::range_iterator< BidirectionalRange >::type pivot, 
             Pred pred);
  }
}