1[/ File one_of.qbk] 2 3[section:one_of one_of] 4 5[/license 6Copyright (c) 2010-2012 Marshall Clow 7 8Distributed under the Boost Software License, Version 1.0. 9(See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) 10] 11 12The header file 'boost/algorithm/cxx11/one_of.hpp' contains four variants of a single algorithm, `one_of`. The algorithm tests the elements of a sequence and returns true if exactly one of the elements in the sequence has a particular property. 13 14The routine `one_of` takes a sequence and a predicate. It will return true if the predicate returns true for one element in the sequence. 15 16The routine `one_of_equal` takes a sequence and a value. It will return true if one element in the sequence compares equal to the passed in value. 17 18Both 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. 19 20 21[heading interface] 22 23The function `one_of` returns true if the predicate returns true for one item in the sequence. There are two versions; one takes two iterators, and the other takes a range. 24 25`` 26namespace boost { namespace algorithm { 27template<typename InputIterator, typename Predicate> 28 bool one_of ( InputIterator first, InputIterator last, Predicate p ); 29template<typename Range, typename Predicate> 30 bool one_of ( const Range &r, Predicate p ); 31}} 32`` 33 34The function `one_of_equal` is similar to `one_of`, but instead of taking a predicate to test the elements of the sequence, it takes a value to compare against. 35 36`` 37namespace boost { namespace algorithm { 38template<typename InputIterator, typename V> 39 bool one_of_equal ( InputIterator first, InputIterator last, V const &val ); 40template<typename Range, typename V> 41 bool one_of_equal ( const Range &r, V const &val ); 42}} 43`` 44 45[heading Examples] 46 47Given the container `c` containing `{ 0, 1, 2, 3, 14, 15 }`, then 48`` 49bool isOdd ( int i ) { return i % 2 == 1; } 50bool lessThan10 ( int i ) { return i < 10; } 51 52using boost::algorithm; 53one_of ( c, isOdd ) --> false 54one_of ( c.begin (), c.end (), lessThan10 ) --> false 55one_of ( c.begin () + 3, c.end (), lessThan10 ) --> true 56one_of ( c.end (), c.end (), isOdd ) --> false // empty range 57one_of_equal ( c, 3 ) --> true 58one_of_equal ( c.begin (), c.begin () + 3, 3 ) --> false 59one_of_equal ( c.begin (), c.begin (), 99 ) --> false // empty range 60`` 61 62[heading Iterator Requirements] 63 64`one_of` and `one_of_equal` work on all iterators except output iterators. 65 66[heading Complexity] 67 68All of the variants of `one_of` and `one_of_equal` run in ['O(N)] (linear) time; that is, they compare against each element in the list once. If more than one of the elements in the sequence satisfy the condition, then algorithm will return false immediately, without examining the remaining members of the sequence. 69 70[heading Exception Safety] 71 72All of the variants of `one_of` and `one_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. 73 74[heading Notes] 75 76* `one_of` and `one_of_equal` both return false for empty ranges, no matter what is passed to test against. 77 78* The second parameter to `one_of_equal` 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 one element in the sequence, the expression `*iter == val` evaluates to true (where `iter` is an iterator to each element in the sequence) 79 80[endsect] 81 82[/ File one_of.qbk 83Copyright 2011 Marshall Clow 84Distributed under the Boost Software License, Version 1.0. 85(See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt). 86] 87 88