iter_util.hh

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// vi: set ts=2 noet:
//
// (c) Copyright Rosetta Commons Member Institutions.
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// (c) The Rosetta software is developed by the contributing members of the Rosetta Commons.
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/// @file utility/iter_util.hh
/// @author Christopher Miles (cmiles@uw.edu)

#ifndef INCLUDED_UTILITY_ITER_UTIL_hh
#define INCLUDED_UTILITY_ITER_UTIL_hh

// C/C++ headers
#include <algorithm>
#include <iterator>

namespace utility {

/// @brief Returns an iterator on the sorted range [first, last) nearest
/// to value. If value is equidistant between adjacent elements, the
/// lesser is returned.
template <typename BidirectionalIterator, typename T>
BidirectionalIterator find_closest(BidirectionalIterator first,
  BidirectionalIterator last,
  const T& value) {
  BidirectionalIterator before = std::lower_bound(first, last, value);

  if ( before == first ) return first;
  if ( before == last )  return --last; // iterator must be bidirectional

  BidirectionalIterator after = before;
  --before;

  return (*after - value) < (value - *before) ? after : before;
}

}  // namespace utility

#endif  // INCLUDED_UTILITY_ITER_UTIL_hh