Extension on SequenceType to count the occurrence of an element.

CountElement.Swift

extension SequenceType where Generator.Element : Equatable {
    func count(other: Generator.Element) -> Int {
        var sum = 0
        for case other in self { sum++ }
        return sum
    }
}

func ~=<T>(pattern: T -> Bool, value: T) -> Bool {
    return pattern(value)
}

extension SequenceType where Generator.Element : Equatable {
    func count(predicate: Generator.Element -> Bool) -> Int {
        var sum = 0
        for case predicate in self { sum++ }
        return sum
    }
}