Header <boost/algorithm/minmax.hpp>

namespace boost {
  template<typename T> 
    tuple< T const &, T const & > minmax(T const & a, T const & b);
  template<typename T, typename BinaryPredicate> 
    tuple< T const &, T const & > 
    minmax(T const & a, T const & b, BinaryPredicate comp);
}