count_if

Boost C++ Libraries

count_if

Prototype

template<class SinglePassRange, class UnaryPredicate>
typename range_difference<const SinglePassRange>::type
count_if(const SinglePassRange& rng, UnaryPredicate pred);

Description

count_if returns the number of elements x in rng where pred(x) is true.

Definition

Defined in the header file boost/range/algorithm/count_if.hpp

Requirements

SinglePassRange is a model of the Single Pass Range Concept.
UnaryPredicate is a model of the UnaryPredicateConcept.
SinglePassRange's value type is a model of the EqualityComparableConcept.
The value type of SinglePassRange is convertible to the argument type of UnaryPredicate.

Complexity

Linear. Exactly distance(rng) invocations of pred.