count

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##### count

###### Prototype

    template<class SinglePassRange, class Value>
    typename range_difference<SinglePassRange>::type
    count(SinglePassRange& rng, const Value& val);

    template<class SinglePassRange, class Value>
    typename range_difference<const SinglePassRange>::type
    count(const SinglePassRange& rng, const Value& val);

###### Description

`count` returns the number of elements `x` in `rng` where `x == val` is `true`.

###### Definition

Defined in the header file `boost/range/algorithm/count.hpp`

###### Requirements

- `SinglePassRange` is a model of the Single Pass Range Concept.
- `Value` is a model of the `EqualityComparableConcept`.
- `SinglePassRange`'s value type is a model of the `EqualityComparableConcept`.
- An object of `SinglePassRange`'s value type can be compared for equality with an object of type `Value`.

###### Complexity

Linear. Exactly `distance(rng)` comparisons.