Program Listing for File drag_to.hpp

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#pragma once
#ifndef SGPL_ALGORITHM_DRAG_TO_HPP_INCLUDE
#define SGPL_ALGORITHM_DRAG_TO_HPP_INCLUDE

#include <algorithm>
#include <cassert>
#include <iterator>

namespace sgpl {

template<typename RandomIt>
RandomIt drag_to(const RandomIt first, const RandomIt last, const RandomIt to) {

  assert( first <= last );

  // adapted from https://youtu.be/W2tWOdzgXHA?t=778
  // slide backward
  if (to < first) {
    std::rotate(to, first, last);
    return to;
  }
  // slide forward
  else if (last < to) return std::rotate(first, last, to);
  else if (first == to) return first;
  // rotate (slide target is inside selection)
  else return std::rotate(
    first,
    std::next(first, std::distance(to, last) + 1),
    last
  );

}

} // namespace sgpl

#endif // #ifndef SGPL_ALGORITHM_DRAG_TO_HPP_INCLUDE