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Merge pull request boostorg#47 from tzlaine/develop
Add find() variants.
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‎doc/algorithm.qbk

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@@ -64,6 +64,8 @@ Thanks to all the people who have reviewed this library and made suggestions for
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[section:Misc Other Algorithms]
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[include clamp-hpp.qbk]
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[include find_not.qbk]
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[include find_backward.qbk]
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[include gather.qbk]
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[include hex.qbk]
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[include is_palindrome.qbk]

‎doc/find_backward.qbk

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[/ File find_backward.qbk]
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[section:find_backward find_backward ]
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[/license
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Copyright (c) 2018 T. Zachary Laine
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Distributed under the Boost Software License, Version 1.0.
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(See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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]
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The header file 'find_backward.hpp' contains variants of the stl algorithm
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`find`. These variants are like `find`, except that the evaluate the elements
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of the given sequence in reverse order.
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Consider how finding the last element that is equal to `x` in a range is
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typically done:
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// Assume a valid range if elements delimited by [first, last).
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while (last-- != first) {
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if (*last == x) {
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// Use last here...
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}
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}
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Raw loops are icky though. Perhaps we should do a bit of extra work to allow
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the use of `std::find()`:
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auto rfirst = std::make_reverse_iterator(last);
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auto rlast = std::make_reverse_iterator(first);
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auto it = std::find(rfirst, rlast);
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// Use it here...
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That seems nicer in that there is no raw loop, but it has two major drawbacks.
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First, it requires an unpleasant amount of typing. Second, it is less
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efficient than forward-iterator `find` , since `std::reverse_iterator` calls
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its base-iterator's `operator--()` in most of its member functions before
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doing the work that the member function requires.
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[heading interface]
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template<typename BidiIter, typename T>
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BidiIter find_backward(BidiIter first, BidiIter last, const T & x);
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template<typename Range, typename T>
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boost::range_iterator<Range> find_backward(Range & range, const T & x);
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These overloads of `find_backward` return an iterator to the last element that
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is equal to `x` in `[first, last)` or `r`, respectively.
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template<typename BidiIter, typename T>
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BidiIter find_not_backward(BidiIter first, BidiIter last, const T & x);
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template<typename Range, typename T>
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boost::range_iterator<Range> find_not_backward(Range & range, const T & x);
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These overloads of `find_not_backward` return an iterator to the last element
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that is not equal to `x` in `[first, last)` or `r`, respectively.
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template<typename BidiIter, typename Pred>
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BidiIter find_if_backward(BidiIter first, BidiIter last, Pred p);
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template<typename Range, typename Pred>
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boost::range_iterator<Range> find_if_backward(Range & range, Pred p);
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These overloads of `find_if_backward` return an iterator to the last element
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for which `pred` returns `true` in `[first, last)` or `r`, respectively.
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template<typename BidiIter, typename Pred>
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BidiIter find_if_not_backward(BidiIter first, BidiIter last, Pred p);
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template<typename Range, typename Pred>
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boost::range_iterator<Range> find_if_not_backward(Range & range, Pred p);
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These overloads of `find_if_not_backward` return an iterator to the last
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element for which `pred` returns `false` in `[first, last)` or `r`,
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respectively.
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[heading Examples]
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Given the container `c1` containing `{ 2, 1, 2 }`, then
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find_backward ( c1.begin(), c1.end(), 2 ) --> --c1.end()
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find_backward ( c1.begin(), c1.end(), 3 ) --> c1.end()
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find_if_backward ( c1.begin(), c1.end(), [](int i) {return i == 2;} ) --> --c1.end()
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find_if_backward ( c1.begin(), c1.end(), [](int i) {return i == 3;} ) --> c1.end()
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find_not_backward ( c1.begin(), c1.end(), 2 ) --> std::prev(c1.end(), 2)
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find_not_backward ( c1.begin(), c1.end(), 1 ) --> c1.end()
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find_if_not_backward ( c1.begin(), c1.end(), [](int i) {return i == 2;} ) --> std::prev(c1.end(), 2)
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find_if_not_backward ( c1.begin(), c1.end(), [](int i) {return i == 1;} ) --> c1.end()
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[heading Iterator Requirements]
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All variants work on bidirectional iterators.
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[heading Complexity]
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Linear.
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[heading Exception Safety]
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All of the variants take their parameters by value and do not depend upon any
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global state. Therefore, all the routines in this file provide the strong
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exception guarantee.
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[heading Notes]
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All variants are `constexpr` in C++14 or later.
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[endsect]
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[/ File equal.qbk
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Copyright 2018 T. Zachary Laine
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Distributed under the Boost Software License, Version 1.0.
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(See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt).
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]

‎doc/find_not.qbk

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[/ File find_not.qbk]
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[section:find_not find_not ]
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[/license
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Copyright (c) 2018 T. Zachary Laine
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Distributed under the Boost Software License, Version 1.0.
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(See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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]
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The header file 'find_not.hpp' contains a variants of a the stl algorithm
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`find`. The algorithm finds the first value in the given sequence that is not
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equal to the given value.
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Consider this use of `find()`:
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auto std::vector<int> vec = { 1, 1, 2 };
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auto it = std::find(vec.begin(), vec.end(), 1);
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This gives us the first occurance of `1` in `vec`. What if we want to find
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the first occurrance of any number besides `1` in `vec`? We have to write an
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unfortunate amount of code:
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auto std::vector<int> vec = { 1, 1, 2 };
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auto it = std::find_if(vec.begin(), vec.end(), [](int i) { return i != 1; });
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With `find_not()` the code gets much more terse:
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auto std::vector<int> vec = { 1, 1, 2 };
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auto it = find_not(vec.begin(), vec.end(), 1);
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The existing `find` variants are: `find()`, `find_if()`, and `find_if_not()`.
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It seems natural to also have `find_not()`, for the very reason that we have
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`find_if_not()` -- to avoid having to write a lambda to wrap the negation of
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the find condition.
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[heading interface]
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template<typename InputIter, typename Sentinel, typename T>
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InputIter find_not(InputIter first, Sentinel last, const T & x);
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template<typename Range, typename T>
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boost::range_iterator<Range> find_not(Range & r, const T & x);
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These overloads of `find_not` return the first value that is not equal to `x`
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in the sequence `[first, last)` or `r`, respectively.
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[heading Examples]
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Given the container `c1` containing `{ 0, 1, 2 }`, then
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find_not ( c1.begin(), c1.end(), 1 ) --> c1.begin()
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find_not ( c1.begin(), c1.end(), 0 ) --> std::next(c1.begin())
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[heading Iterator Requirements]
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`find_not` works on all iterators except output iterators.
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The template parameter `Sentinel` is allowed to be different from `InputIter`,
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or they may be the same. For an `InputIter` `it` and a `Sentinel` `end`, `it
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== end` and `it != end` must be well-formed expressions.
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[heading Complexity]
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Linear.
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[heading Exception Safety]
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`find_not` takes its parameters by value and do not depend upon any global
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state. Therefore, it provides the strong exception guarantee.
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[heading Notes]
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`constexpr` in C++14 or later.
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[endsect]
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[/ File equal.qbk
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Copyright 2018 T. Zachary Laine
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Distributed under the Boost Software License, Version 1.0.
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(See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt).
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]

‎include/boost/algorithm/find_backward.hpp

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/*
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Copyright (c) T. Zachary Laine 2018.
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Distributed under the Boost Software License, Version 1.0. (See accompanying
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file LICENSE10.txt or copy at http://www.boost.org/LICENSE10.txt)
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*/
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#ifndef BOOST_ALGORITHM_FIND_BACKWARD_HPP
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#define BOOST_ALGORITHM_FIND_BACKWARD_HPP
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#include <boost/config.hpp>
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#include <boost/range/begin.hpp>
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#include <boost/range/end.hpp>
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#include <utility>
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namespace boost { namespace algorithm {
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template<typename BidiIter, typename T>
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BOOST_CXX14_CONSTEXPR
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BidiIter find_backward(BidiIter first, BidiIter last, const T & x)
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{
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BidiIter it = last;
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while (it != first) {
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if (*--it == x)
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return it;
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}
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return last;
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}
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template<typename Range, typename T>
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BOOST_CXX14_CONSTEXPR
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typename boost::range_iterator<Range>::type find_backward(Range & range, const T & x)
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{
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return ::boost::algorithm::find_backward(boost::begin(range), boost::end(range), x);
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}
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template<typename BidiIter, typename T>
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BOOST_CXX14_CONSTEXPR
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BidiIter find_not_backward(BidiIter first, BidiIter last, const T & x)
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{
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BidiIter it = last;
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while (it != first) {
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if (*--it != x)
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return it;
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}
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return last;
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}
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template<typename Range, typename T>
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BOOST_CXX14_CONSTEXPR
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typename boost::range_iterator<Range>::type find_not_backward(Range & range, const T & x)
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{
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return ::boost::algorithm::find_not_backward(boost::begin(range), boost::end(range), x);
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}
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template<typename BidiIter, typename Pred>
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BOOST_CXX14_CONSTEXPR
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BidiIter find_if_backward(BidiIter first, BidiIter last, Pred p)
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{
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BidiIter it = last;
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while (it != first) {
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if (p(*--it))
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return it;
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}
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return last;
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}
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template<typename Range, typename Pred>
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BOOST_CXX14_CONSTEXPR
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typename boost::range_iterator<Range>::type find_if_backward(Range & range, Pred p)
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{
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return ::boost::algorithm::find_if_backward(boost::begin(range), boost::end(range), p);
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}
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template<typename BidiIter, typename Pred>
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BOOST_CXX14_CONSTEXPR
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BidiIter find_if_not_backward(BidiIter first, BidiIter last, Pred p)
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{
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BidiIter it = last;
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while (it != first) {
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if (!p(*--it))
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return it;
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}
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return last;
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}
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template<typename Range, typename Pred>
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BOOST_CXX14_CONSTEXPR
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typename boost::range_iterator<Range>::type find_if_not_backward(Range & range, Pred p)
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{
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return ::boost::algorithm::find_if_not_backward(boost::begin(range), boost::end(range), p);
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}
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}} // namespace boost and algorithm
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#endif // BOOST_ALGORITHM_FIND_BACKWARD_HPP

‎include/boost/algorithm/find_not.hpp

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/*
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Copyright (c) T. Zachary Laine 2018.
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Distributed under the Boost Software License, Version 1.0. (See accompanying
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file LICENSE10.txt or copy at http://www.boost.org/LICENSE10.txt)
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*/
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#ifndef BOOST_ALGORITHM_FIND_NOT_HPP
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#define BOOST_ALGORITHM_FIND_NOT_HPP
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#include <boost/config.hpp>
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#include <boost/range/begin.hpp>
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#include <boost/range/end.hpp>
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#include <utility>
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namespace boost { namespace algorithm {
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template<typename InputIter, typename Sentinel, typename T>
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BOOST_CXX14_CONSTEXPR
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InputIter find_not(InputIter first, Sentinel last, const T & x)
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{
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for (; first != last; ++first) {
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if (*first != x)
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break;
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}
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return first;
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}
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template<typename Range, typename T>
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BOOST_CXX14_CONSTEXPR
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typename boost::range_iterator<Range>::type find_not(Range & r, const T & x)
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{
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return ::boost::algorithm::find_not(boost::begin(r), boost::end(r), x);
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}
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}} // namespace boost and algorithm
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#endif // BOOST_ALGORITHM_FIND_NOT_HPP

‎test/Jamfile.v2

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[ run is_partitioned_until_test.cpp unit_test_framework : : : : is_partitioned_until_test ]
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# Apply_permutation tests
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[ run apply_permutation_test.cpp unit_test_framework : : : : apply_permutation_test ]
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[ run apply_permutation_test.cpp unit_test_framework : : : : apply_permutation_test ]
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# Find tests
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[ run find_not_test.cpp unit_test_framework : : : : find_not_test ]
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[ run find_backward_test.cpp unit_test_framework : : : : find_backward_test ]
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;
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}
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