| [/ QuickBook Document version 1.5 ] |
| [section:is_sorted is_sorted ] |
| |
| [/license |
| |
| Copyright (c) 2010-2012 Marshall Clow |
| |
| 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) |
| |
| ] |
| |
| |
| The header file `<boost/algorithm/cxx11/is_sorted.hpp>` contains functions for determining if a sequence is ordered. |
| |
| [heading is_sorted] |
| The function `is_sorted(sequence)` determines whether or not a sequence is completely sorted according so some criteria. If no comparison predicate is specified, then `std::less` is used (i.e, the test is to see if the sequence is non-decreasing) |
| |
| `` |
| namespace boost { namespace algorithm { |
| template <typename ForwardIterator, typename Pred> |
| bool is_sorted ( ForwardIterator first, ForwardIterator last, Pred p ); |
| |
| template <typename ForwardIterator> |
| bool is_sorted ( ForwardIterator first, ForwardIterator last ); |
| |
| |
| template <typename Range, typename Pred> |
| bool is_sorted ( const Range &r, Pred p ); |
| |
| template <typename Range> |
| bool is_sorted ( const Range &r ); |
| }} |
| `` |
| |
| Iterator requirements: The `is_sorted` functions will work forward iterators or better. |
| |
| [heading is_sorted_until] |
| |
| If `distance(first, last) < 2`, then `is_sorted ( first, last )` returns `last`. Otherwise, it returns the last iterator i in [first,last] for which the range [first,i) is sorted. |
| |
| In short, it returns the element in the sequence that is "out of order". If the entire sequence is sorted (according to the predicate), then it will return `last`. |
| |
| `` |
| namespace boost { namespace algorithm { |
| template <typename ForwardIterator, typename Pred> |
| FI is_sorted_until ( ForwardIterator first, ForwardIterator last, Pred p ); |
| |
| template <typename ForwardIterator> |
| ForwardIterator is_sorted_until ( ForwardIterator first, ForwardIterator last ); |
| |
| |
| template <typename Range, typename Pred> |
| typename boost::range_iterator<const R>::type is_sorted_until ( const Range &r, Pred p ); |
| |
| template <typename Range> |
| typename boost::range_iterator<const R>::type is_sorted_until ( const Range &r ); |
| }} |
| `` |
| |
| Iterator requirements: The `is_sorted_until` functions will work on forward iterators or better. Since they have to return a place in the input sequence, input iterators will not suffice. |
| |
| Complexity: |
| `is_sorted_until` will make at most ['N-1] calls to the predicate (given a sequence of length ['N]). |
| |
| Examples: |
| |
| Given the sequence `{ 1, 2, 3, 4, 5, 3 }`, `is_sorted_until ( beg, end, std::less<int>())` would return an iterator pointing at the second `3`. |
| |
| Given the sequence `{ 1, 2, 3, 4, 5, 9 }`, `is_sorted_until ( beg, end, std::less<int>())` would return `end`. |
| |
| |
| There are also a set of "wrapper functions" for is_ordered which make it easy to see if an entire sequence is ordered. These functions return a boolean indicating success or failure rather than an iterator to where the out of order items were found. |
| |
| To test if a sequence is increasing (each element at least as large as the preceding one): |
| `` |
| namespace boost { namespace algorithm { |
| template <typename Iterator> |
| bool is_increasing ( Iterator first, Iterator last ); |
| |
| template <typename R> |
| bool is_increasing ( const R &range ); |
| }} |
| `` |
| |
| To test if a sequence is decreasing (each element no larger than the preceding one): |
| |
| `` |
| namespace boost { namespace algorithm { |
| template <typename ForwardIterator> |
| bool is_decreasing ( ForwardIterator first, ForwardIterator last ); |
| |
| template <typename R> |
| bool is_decreasing ( const R &range ); |
| }} |
| `` |
| |
| To test if a sequence is strictly increasing (each element larger than the preceding one): |
| `` |
| namespace boost { namespace algorithm { |
| template <typename ForwardIterator> |
| bool is_strictly_increasing ( ForwardIterator first, ForwardIterator last ); |
| |
| template <typename R> |
| bool is_strictly_increasing ( const R &range ); |
| }} |
| `` |
| |
| To test if a sequence is strictly decreasing (each element smaller than the preceding one): |
| `` |
| namespace boost { namespace algorithm { |
| template <typename ForwardIterator> |
| bool is_strictly_decreasing ( ForwardIterator first, ForwardIterator last ); |
| |
| template <typename R> |
| bool is_strictly_decreasing ( const R &range ); |
| }} |
| `` |
| |
| Complexity: |
| Each of these calls is just a thin wrapper over `is_sorted`, so they have the same complexity as `is_sorted`. |
| |
| [heading Notes] |
| |
| * The routines `is_sorted` and `is_sorted_until` are part of the C++11 standard. When compiled using a C++11 implementation, the implementation from the standard library will be used. |
| |
| * `is_sorted` and `is_sorted_until` both return true for empty ranges and ranges of length one. |
| |
| [endsect] |