![]() |
Home | Libraries | People | FAQ | More |
Returns the number of elements within a sequence with a type for which
a given unary function object evaluates to true.
template<
typename Sequence,
typename F
>
typename result_of::count_if<Sequence, F>::type count_if(
Sequence const& seq, F f);
Table 1.56. Parameters
|
Parameter |
Requirement |
Description |
|---|---|---|
|
|
A model of Forward
Sequence, |
The sequence to search |
|
|
A unary function object |
The search predicate |
count_if(seq, f)
Return type: int
Semantics: Returns the number of elements
in seq where f evaluates to true.
Linear. At most comparisons.
result_of::size<Sequence>::value
#include <boost/fusion/algorithm/query/count_if.hpp> #include <boost/fusion/include/count_if.hpp>
constvector<int,int,int> vec(1,2,3); assert(count_if(vec,odd()) == 2);