reduce-with-inout.swift

extension Sequence {
    func reduce<A>(_ initial: A, combine: (inout A, Iterator.Element) -> ()) -> A {
        var result = initial
        for element in self {
            combine(&result, element)
        }
        return result
    }
}


// Example implementation of `filter` using `reduce`:
extension Sequence {
    func myFilter(condition: (Iterator.Element) -> Bool) -> [Iterator.Element] {
        return reduce([]) { (result: inout [Iterator.Element], element) in
            guard condition(element) else { return }
            result.append(element)
        }
    }
}