forked from boostorg/algorithm
556 lines
17 KiB
C++
556 lines
17 KiB
C++
// (C) Copyright Herve Bronnimann 2004.
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//
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// Distributed under the Boost Software License, Version 1.0. (See accompanying
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// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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/*
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Revision history:
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1 July 2004
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Split the code into two headers to lessen dependence on
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Boost.tuple. (Herve)
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26 June 2004
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Added the code for the boost minmax library. (Herve)
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*/
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#ifndef BOOST_ALGORITHM_MINMAX_ELEMENT_HPP
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#define BOOST_ALGORITHM_MINMAX_ELEMENT_HPP
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/* PROPOSED STANDARD EXTENSIONS:
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*
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* minmax_element(first, last)
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* Effect: std::make_pair( std::min_element(first, last),
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* std::max_element(first, last) );
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*
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* minmax_element(first, last, comp)
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* Effect: std::make_pair( std::min_element(first, last, comp),
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* std::max_element(first, last, comp) );
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*/
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#include <utility> // for std::pair and std::make_pair
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#include <boost/config.hpp>
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namespace boost {
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namespace detail { // for obtaining a uniform version of minmax_element
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// that compiles with VC++ 6.0 -- avoid the iterator_traits by
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// having comparison object over iterator, not over dereferenced value
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template <typename Iterator>
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struct less_over_iter {
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bool operator()(Iterator const& it1,
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Iterator const& it2) const { return *it1 < *it2; }
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};
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template <typename Iterator, class BinaryPredicate>
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struct binary_pred_over_iter {
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explicit binary_pred_over_iter(BinaryPredicate const& p ) : m_p( p ) {}
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bool operator()(Iterator const& it1,
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Iterator const& it2) const { return m_p(*it1, *it2); }
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private:
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BinaryPredicate m_p;
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};
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// common base for the two minmax_element overloads
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template <typename ForwardIter, class Compare >
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std::pair<ForwardIter,ForwardIter>
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basic_minmax_element(ForwardIter first, ForwardIter last, Compare comp)
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{
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if (first == last)
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return std::make_pair(last,last);
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ForwardIter min_result = first;
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ForwardIter max_result = first;
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// if only one element
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ForwardIter second = first; ++second;
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if (second == last)
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return std::make_pair(min_result, max_result);
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// treat first pair separately (only one comparison for first two elements)
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ForwardIter potential_min_result = last;
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if (comp(first, second))
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max_result = second;
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else {
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min_result = second;
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potential_min_result = first;
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}
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// then each element by pairs, with at most 3 comparisons per pair
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first = ++second; if (first != last) ++second;
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while (second != last) {
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if (comp(first, second)) {
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if (comp(first, min_result)) {
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min_result = first;
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potential_min_result = last;
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}
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if (comp(max_result, second))
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max_result = second;
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} else {
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if (comp(second, min_result)) {
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min_result = second;
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potential_min_result = first;
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}
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if (comp(max_result, first))
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max_result = first;
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}
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first = ++second;
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if (first != last) ++second;
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}
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// if odd number of elements, treat last element
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if (first != last) { // odd number of elements
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if (comp(first, min_result)) {
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min_result = first;
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potential_min_result = last;
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}
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else if (comp(max_result, first))
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max_result = first;
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}
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// resolve min_result being incorrect with one extra comparison
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// (in which case potential_min_result is necessarily the correct result)
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if (potential_min_result != last
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&& !comp(min_result, potential_min_result))
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min_result = potential_min_result;
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return std::make_pair(min_result,max_result);
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}
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} // namespace detail
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template <typename ForwardIter>
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std::pair<ForwardIter,ForwardIter>
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minmax_element(ForwardIter first, ForwardIter last)
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{
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return detail::basic_minmax_element(first, last,
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detail::less_over_iter<ForwardIter>() );
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}
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template <typename ForwardIter, class BinaryPredicate>
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std::pair<ForwardIter,ForwardIter>
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minmax_element(ForwardIter first, ForwardIter last, BinaryPredicate comp)
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{
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return detail::basic_minmax_element(first, last,
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detail::binary_pred_over_iter<ForwardIter,BinaryPredicate>(comp) );
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}
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}
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/* PROPOSED BOOST EXTENSIONS
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* In the description below, [rfirst,rlast) denotes the reversed range
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* of [first,last). Even though the iterator type of first and last may
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* be only a Forward Iterator, it is possible to explain the semantics
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* by assuming that it is a Bidirectional Iterator. In the sequel,
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* reverse(ForwardIterator&) returns the reverse_iterator adaptor.
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* This is not how the functions would be implemented!
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*
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* first_min_element(first, last)
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* Effect: std::min_element(first, last);
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*
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* first_min_element(first, last, comp)
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* Effect: std::min_element(first, last, comp);
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*
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* last_min_element(first, last)
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* Effect: reverse( std::min_element(reverse(last), reverse(first)) );
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*
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* last_min_element(first, last, comp)
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* Effect: reverse( std::min_element(reverse(last), reverse(first), comp) );
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*
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* first_max_element(first, last)
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* Effect: std::max_element(first, last);
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*
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* first_max_element(first, last, comp)
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* Effect: max_element(first, last);
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*
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* last_max_element(first, last)
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* Effect: reverse( std::max_element(reverse(last), reverse(first)) );
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*
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* last_max_element(first, last, comp)
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* Effect: reverse( std::max_element(reverse(last), reverse(first), comp) );
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*
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* first_min_first_max_element(first, last)
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* Effect: std::make_pair( first_min_element(first, last),
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* first_max_element(first, last) );
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*
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* first_min_first_max_element(first, last, comp)
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* Effect: std::make_pair( first_min_element(first, last, comp),
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* first_max_element(first, last, comp) );
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*
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* first_min_last_max_element(first, last)
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* Effect: std::make_pair( first_min_element(first, last),
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* last_max_element(first, last) );
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*
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* first_min_last_max_element(first, last, comp)
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* Effect: std::make_pair( first_min_element(first, last, comp),
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* last_max_element(first, last, comp) );
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*
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* last_min_first_max_element(first, last)
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* Effect: std::make_pair( last_min_element(first, last),
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* first_max_element(first, last) );
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*
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* last_min_first_max_element(first, last, comp)
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* Effect: std::make_pair( last_min_element(first, last, comp),
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* first_max_element(first, last, comp) );
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*
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* last_min_last_max_element(first, last)
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* Effect: std::make_pair( last_min_element(first, last),
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* last_max_element(first, last) );
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*
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* last_min_last_max_element(first, last, comp)
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* Effect: std::make_pair( last_min_element(first, last, comp),
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* last_max_element(first, last, comp) );
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*/
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namespace boost {
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// Min_element and max_element variants
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namespace detail { // common base for the overloads
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template <typename ForwardIter, class BinaryPredicate>
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ForwardIter
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basic_first_min_element(ForwardIter first, ForwardIter last,
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BinaryPredicate comp)
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{
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if (first == last) return last;
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ForwardIter min_result = first;
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while (++first != last)
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if (comp(first, min_result))
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min_result = first;
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return min_result;
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}
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template <typename ForwardIter, class BinaryPredicate>
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ForwardIter
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basic_last_min_element(ForwardIter first, ForwardIter last,
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BinaryPredicate comp)
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{
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if (first == last) return last;
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ForwardIter min_result = first;
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while (++first != last)
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if (!comp(min_result, first))
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min_result = first;
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return min_result;
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}
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template <typename ForwardIter, class BinaryPredicate>
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ForwardIter
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basic_first_max_element(ForwardIter first, ForwardIter last,
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BinaryPredicate comp)
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{
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if (first == last) return last;
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ForwardIter max_result = first;
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while (++first != last)
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if (comp(max_result, first))
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max_result = first;
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return max_result;
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}
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template <typename ForwardIter, class BinaryPredicate>
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ForwardIter
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basic_last_max_element(ForwardIter first, ForwardIter last,
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BinaryPredicate comp)
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{
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if (first == last) return last;
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ForwardIter max_result = first;
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while (++first != last)
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if (!comp(first, max_result))
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max_result = first;
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return max_result;
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}
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} // namespace detail
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template <typename ForwardIter>
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ForwardIter
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first_min_element(ForwardIter first, ForwardIter last)
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{
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return detail::basic_first_min_element(first, last,
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detail::less_over_iter<ForwardIter>() );
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}
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template <typename ForwardIter, class BinaryPredicate>
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ForwardIter
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first_min_element(ForwardIter first, ForwardIter last, BinaryPredicate comp)
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{
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return detail::basic_first_min_element(first, last,
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detail::binary_pred_over_iter<ForwardIter,BinaryPredicate>(comp) );
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}
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template <typename ForwardIter>
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ForwardIter
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last_min_element(ForwardIter first, ForwardIter last)
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{
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return detail::basic_last_min_element(first, last,
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detail::less_over_iter<ForwardIter>() );
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}
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template <typename ForwardIter, class BinaryPredicate>
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ForwardIter
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last_min_element(ForwardIter first, ForwardIter last, BinaryPredicate comp)
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{
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return detail::basic_last_min_element(first, last,
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detail::binary_pred_over_iter<ForwardIter,BinaryPredicate>(comp) );
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}
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template <typename ForwardIter>
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ForwardIter
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first_max_element(ForwardIter first, ForwardIter last)
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{
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return detail::basic_first_max_element(first, last,
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detail::less_over_iter<ForwardIter>() );
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}
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template <typename ForwardIter, class BinaryPredicate>
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ForwardIter
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first_max_element(ForwardIter first, ForwardIter last, BinaryPredicate comp)
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{
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return detail::basic_first_max_element(first, last,
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detail::binary_pred_over_iter<ForwardIter,BinaryPredicate>(comp) );
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}
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template <typename ForwardIter>
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ForwardIter
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last_max_element(ForwardIter first, ForwardIter last)
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{
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return detail::basic_last_max_element(first, last,
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detail::less_over_iter<ForwardIter>() );
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}
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template <typename ForwardIter, class BinaryPredicate>
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ForwardIter
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last_max_element(ForwardIter first, ForwardIter last, BinaryPredicate comp)
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{
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return detail::basic_last_max_element(first, last,
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detail::binary_pred_over_iter<ForwardIter,BinaryPredicate>(comp) );
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}
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// Minmax_element variants -- comments removed
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namespace detail {
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template <typename ForwardIter, class BinaryPredicate>
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std::pair<ForwardIter,ForwardIter>
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basic_first_min_last_max_element(ForwardIter first, ForwardIter last,
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BinaryPredicate comp)
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{
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if (first == last)
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return std::make_pair(last,last);
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ForwardIter min_result = first;
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ForwardIter max_result = first;
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ForwardIter second = ++first;
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if (second == last)
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return std::make_pair(min_result, max_result);
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if (comp(second, min_result))
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min_result = second;
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else
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max_result = second;
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first = ++second; if (first != last) ++second;
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while (second != last) {
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if (!comp(second, first)) {
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if (comp(first, min_result))
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min_result = first;
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if (!comp(second, max_result))
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max_result = second;
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} else {
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if (comp(second, min_result))
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min_result = second;
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if (!comp(first, max_result))
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max_result = first;
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}
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first = ++second; if (first != last) ++second;
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}
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if (first != last) {
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if (comp(first, min_result))
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min_result = first;
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else if (!comp(first, max_result))
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max_result = first;
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}
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return std::make_pair(min_result, max_result);
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}
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template <typename ForwardIter, class BinaryPredicate>
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std::pair<ForwardIter,ForwardIter>
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basic_last_min_first_max_element(ForwardIter first, ForwardIter last,
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BinaryPredicate comp)
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{
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if (first == last) return std::make_pair(last,last);
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ForwardIter min_result = first;
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ForwardIter max_result = first;
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ForwardIter second = ++first;
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if (second == last)
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return std::make_pair(min_result, max_result);
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if (comp(max_result, second))
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max_result = second;
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else
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min_result = second;
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first = ++second; if (first != last) ++second;
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while (second != last) {
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if (comp(first, second)) {
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if (!comp(min_result, first))
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min_result = first;
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if (comp(max_result, second))
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max_result = second;
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} else {
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if (!comp(min_result, second))
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min_result = second;
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if (comp(max_result, first))
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max_result = first;
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}
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first = ++second; if (first != last) ++second;
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}
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if (first != last) {
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if (!comp(min_result, first))
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min_result = first;
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else if (comp(max_result, first))
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max_result = first;
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}
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return std::make_pair(min_result, max_result);
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}
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template <typename ForwardIter, class BinaryPredicate>
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std::pair<ForwardIter,ForwardIter>
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basic_last_min_last_max_element(ForwardIter first, ForwardIter last,
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BinaryPredicate comp)
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{
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if (first == last) return std::make_pair(last,last);
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ForwardIter min_result = first;
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ForwardIter max_result = first;
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ForwardIter second = first; ++second;
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if (second == last)
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return std::make_pair(min_result,max_result);
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ForwardIter potential_max_result = last;
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if (comp(first, second))
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max_result = second;
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else {
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min_result = second;
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potential_max_result = second;
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}
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first = ++second; if (first != last) ++second;
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while (second != last) {
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if (comp(first, second)) {
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if (!comp(min_result, first))
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min_result = first;
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if (!comp(second, max_result)) {
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max_result = second;
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potential_max_result = last;
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}
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} else {
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if (!comp(min_result, second))
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min_result = second;
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if (!comp(first, max_result)) {
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max_result = first;
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potential_max_result = second;
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}
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}
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first = ++second;
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if (first != last) ++second;
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}
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if (first != last) {
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if (!comp(min_result, first))
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min_result = first;
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if (!comp(first, max_result)) {
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max_result = first;
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potential_max_result = last;
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}
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}
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if (potential_max_result != last
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&& !comp(potential_max_result, max_result))
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max_result = potential_max_result;
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return std::make_pair(min_result,max_result);
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}
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} // namespace detail
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template <typename ForwardIter>
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inline std::pair<ForwardIter,ForwardIter>
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first_min_first_max_element(ForwardIter first, ForwardIter last)
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{
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return minmax_element(first, last);
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}
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template <typename ForwardIter, class BinaryPredicate>
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inline std::pair<ForwardIter,ForwardIter>
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first_min_first_max_element(ForwardIter first, ForwardIter last,
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BinaryPredicate comp)
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{
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return minmax_element(first, last, comp);
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}
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template <typename ForwardIter>
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std::pair<ForwardIter,ForwardIter>
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first_min_last_max_element(ForwardIter first, ForwardIter last)
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{
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return detail::basic_first_min_last_max_element(first, last,
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detail::less_over_iter<ForwardIter>() );
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}
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template <typename ForwardIter, class BinaryPredicate>
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inline std::pair<ForwardIter,ForwardIter>
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first_min_last_max_element(ForwardIter first, ForwardIter last,
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BinaryPredicate comp)
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{
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return detail::basic_first_min_last_max_element(first, last,
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detail::binary_pred_over_iter<ForwardIter,BinaryPredicate>(comp) );
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}
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template <typename ForwardIter>
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std::pair<ForwardIter,ForwardIter>
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last_min_first_max_element(ForwardIter first, ForwardIter last)
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{
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return detail::basic_last_min_first_max_element(first, last,
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detail::less_over_iter<ForwardIter>() );
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}
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template <typename ForwardIter, class BinaryPredicate>
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inline std::pair<ForwardIter,ForwardIter>
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last_min_first_max_element(ForwardIter first, ForwardIter last,
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BinaryPredicate comp)
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{
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return detail::basic_last_min_first_max_element(first, last,
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detail::binary_pred_over_iter<ForwardIter,BinaryPredicate>(comp) );
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}
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template <typename ForwardIter>
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std::pair<ForwardIter,ForwardIter>
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last_min_last_max_element(ForwardIter first, ForwardIter last)
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{
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return detail::basic_last_min_last_max_element(first, last,
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detail::less_over_iter<ForwardIter>() );
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}
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template <typename ForwardIter, class BinaryPredicate>
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inline std::pair<ForwardIter,ForwardIter>
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last_min_last_max_element(ForwardIter first, ForwardIter last,
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BinaryPredicate comp)
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{
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return detail::basic_last_min_last_max_element(first, last,
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detail::binary_pred_over_iter<ForwardIter,BinaryPredicate>(comp) );
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}
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} // namespace boost
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#endif // BOOST_ALGORITHM_MINMAX_ELEMENT_HPP
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