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90 lines
3.9 KiB
Plaintext
90 lines
3.9 KiB
Plaintext
[/ File any_of.qbk]
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[section:any_of any_of]
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[/license
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Copyright (c) 2010-2012 Marshall Clow
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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 'boost/algorithm/cxx11/any_of.hpp' contains four variants of a single algorithm, `any_of`. The algorithm tests the elements of a sequence and returns true if any of the elements has a particular property.
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The routine `any_of` takes a sequence and a predicate. It will return true if the predicate returns true for any element in the sequence.
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The routine `any_of_equal` takes a sequence and a value. It will return true if any element in the sequence compares equal to the passed in value.
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Both routines come in two forms; the first one takes two iterators to define the range. The second form takes a single range parameter, and uses Boost.Range to traverse it.
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[heading interface]
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The function `any_of` returns true if the predicate returns true any item in the sequence. There are two versions; one takes two iterators, and the other takes a range.
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``
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namespace boost { namespace algorithm {
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template<typename InputIterator, typename Predicate>
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bool any_of ( InputIterator first, InputIterator last, Predicate p );
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template<typename Range, typename Predicate>
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bool any_of ( const Range &r, Predicate p );
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}}
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``
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The function `any_of_equal` is similar to `any_of`, but instead of taking a predicate to test the elements of the sequence, it takes a value to compare against.
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``
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namespace boost { namespace algorithm {
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template<typename InputIterator, typename V>
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bool any_of_equal ( InputIterator first, InputIterator last, V const &val );
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template<typename Range, typename V>
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bool any_of_equal ( const Range &r, V const &val );
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}}
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``
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[heading Examples]
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Given the container `c` containing `{ 0, 1, 2, 3, 14, 15 }`, then
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``
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bool isOdd ( int i ) { return i % 2 == 1; }
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bool lessThan10 ( int i ) { return i < 10; }
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using boost::algorithm;
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any_of ( c, isOdd ) --> true
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any_of ( c.begin (), c.end (), lessThan10 ) --> true
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any_of ( c.begin () + 4, c.end (), lessThan10 ) --> false
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any_of ( c.end (), c.end (), isOdd ) --> false // empty range
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any_of_equal ( c, 3 ) --> true
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any_of_equal ( c.begin (), c.begin () + 3, 3 ) --> false
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any_of_equal ( c.begin (), c.begin (), 99 ) --> false // empty range
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``
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[heading Iterator Requirements]
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`any_of` and `any_of_equal` work on all iterators except output iterators.
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[heading Complexity]
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All of the variants of `any_of` and `any_of_equal` run in ['O(N)] (linear) time; that is, they compare against each element in the list once. If any of the comparisons succeed, the algorithm will terminate immediately, without examining the remaining members of the sequence.
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[heading Exception Safety]
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All of the variants of `any_of` and `any_of_equal` take their parameters by value or const reference, and do not depend upon any global state. Therefore, all the routines in this file provide the strong exception guarantee.
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[heading Notes]
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* The routine `any_of` is also available as part of the C++11 standard.
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* `any_of` and `any_of_equal` both return false for empty ranges, no matter what is passed to test against.
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* The second parameter to `any_of_value` is a template parameter, rather than deduced from the first parameter (`std::iterator_traits<InputIterator>::value_type`) because that allows more flexibility for callers, and takes advantage of built-in comparisons for the type that is pointed to by the iterator. The function is defined to return true if, for any element in the sequence, the expression `*iter == val` evaluates to true (where `iter` is an iterator to each element in the sequence)
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[endsect]
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[/ File any_of.qbk
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Copyright 2011 Marshall Clow
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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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