forked from boostorg/range
33 lines
839 B
Plaintext
33 lines
839 B
Plaintext
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[section:count_if count_if]
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[heading Prototype]
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``
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template<class SinglePassRange, class UnaryPredicate>
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typename range_difference<const SinglePassRange>::type
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count_if(const SinglePassRange& rng, UnaryPredicate pred);
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``
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[heading Description]
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`count_if` returns the number of elements `x` in `rng` where `pred(x)` is `true`.
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[heading Definition]
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Defined in the header file `boost/range/algorithm/count_if.hpp`
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[heading Requirements]
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* `SinglePassRange` is a model of the __single_pass_range__ Concept.
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* `UnaryPredicate` is a model of the `UnaryPredicateConcept`.
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* `SinglePassRange`'s value type is a model of the `EqualityComparableConcept`.
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* The value type of `SinglePassRange` is convertible to the argument type of `UnaryPredicate`.
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[heading Complexity]
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Linear. Exactly `distance(rng)` invocations of `pred`.
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[endsect]
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