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