any_of

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.

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.

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.

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.

interface

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.

namespace boost { namespace algorithm {
template<typename InputIterator, typename Predicate>
	bool any_of ( InputIterator first, InputIterator last, Predicate p );
template<typename Range, typename Predicate>
	bool any_of ( const Range &r, Predicate p );
}}

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.

namespace boost { namespace algorithm {
template<typename InputIterator, typename V>
	bool any_of_equal ( InputIterator first, InputIterator last, V const &val );
template<typename Range, typename V>
	bool any_of_equal ( const Range &r, V const &val );
}}

Examples

Given the container c containing { 0, 1, 2, 3, 14, 15 }, then

bool isOdd ( int i ) { return i % 2 == 1; }
bool lessThan10 ( int i ) { return i < 10; }

using boost::algorithm;
any_of ( c, isOdd ) --> true
any_of ( c.begin (), c.end (), lessThan10 ) --> true
any_of ( c.begin () + 4, c.end (), lessThan10 ) --> false
any_of ( c.end (), c.end (), isOdd ) --> false  // empty range
any_of_equal ( c, 3 ) --> true
any_of_equal ( c.begin (), c.begin () + 3, 3 ) --> false
any_of_equal ( c.begin (), c.begin (), 99 ) --> false  // empty range

Iterator Requirements

any_of and any_of_equal work on all iterators except output iterators.

Complexity

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.

Exception Safety

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.

Notes

The routine any_of is part of the C++11 standard. When compiled using a C++11 implementation, the implementation from the standard library will be used.
any_of and any_of_equal both return false for empty ranges, no matter what is passed to test against.
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)