Limit the results of a Swift array filter to X for performance

Question

I have about 2000 elements in my array, and when it is filtered, I would like to end the filtering as soon as I have 5 elements in my filtered array.

Currently it i

Answer 1

The fastest solution in terms of execution time seems to be an explicit loop which adds matching elements until the limit is reached:

extension Sequence {
    public func filter(where isIncluded: (Iterator.Element) -> Bool, limit: Int) -> [Iterator.Element] {
        var result : [Iterator.Element] = []
        result.reserveCapacity(limit)
        var count = 0
        var it = makeIterator()

        // While limit not reached and there are more elements ...
        while count < limit, let element = it.next() {
            if isIncluded(element) {
                result.append(element)
                count += 1
            }
        }
        return result
    }
}

Example usage:

let numbers = Array(0 ..< 2000)
let result = numbers.filter(where: { $0 % 3 == 0 }, limit: 5)
print(result) // [0, 3, 6, 9, 12]