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C++11 Algorithms


The header file 'boost/algorithm/cxx11/all_of.hpp' contains four variants of a single algorithm, all_of. The algorithm tests all the elements of a sequence and returns true if they all share a property.

The routine all_of takes a sequence and a predicate. It will return true if the predicate returns true when applied to every element in the sequence.

The routine all_of_equal takes a sequence and a value. It will return true if every 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.


The function all_of returns true if the predicate returns true for every 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 all_of ( InputIterator first, InputIterator last, Predicate p );
template<typename Range, typename Predicate>
	bool all_of ( const Range &r, Predicate p );

The function all_of_equal is similar to all_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 all_of_equal ( InputIterator first, InputIterator last, V const &val );
template<typename Range, typename V>
	bool all_of_equal ( const Range &r, V const &val );


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;
all_of ( c, isOdd ) --> false
all_of ( c.begin (), c.end (), lessThan10 ) --> false
all_of ( c.begin (), c.begin () + 3, lessThan10 ) --> true
all_of ( c.end (), c.end (), isOdd ) --> true  // empty range
all_of_equal ( c, 3 ) --> false
all_of_equal ( c.begin () + 3, c.begin () + 4, 3 ) --> true
all_of_equal ( c.begin (), c.begin (), 99 ) --> true  // empty range

Iterator Requirements

all_of and all_of_equal work on all iterators except output iterators.


All of the variants of all_of and all_of_equal run in O(N) (linear) time; that is, they compare against each element in the list once. If any of the comparisons fail, the algorithm will terminate immediately, without examining the remaining members of the sequence.

Exception Safety

All of the variants of all_of and all_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.

  • The routine all_of is also available as part of the C++11 standard.
  • all_of and all_of_equal both return true for empty ranges, no matter what is passed to test against. When there are no items in the sequence to test, they all satisfy the condition to be tested against.
  • The second parameter to all_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 all elements in the sequence, the expression *iter == val evaluates to true (where iter is an iterator to each element in the sequence)