Generatorで植木算(https://twitter.com/takasek/status/716551378240299008)をリファクタ。 #CodePiece #cswift

CodePiece.swift

func uekizanGenerator<S: SequenceType>(sources: S, insert margin: S.Generator.Element) -> AnyGenerator<S.Generator.Element> {
    var gen = sources.generate()

    var isMargin = false
    var preserved: S.Generator.Element? = gen.next()

    func getMargin() -> S.Generator.Element? {
        guard preserved != nil else { return nil }
        return margin
    }
    func getElement() -> S.Generator.Element? {
        defer { preserved = gen.next() }
        return preserved
    }
    return anyGenerator {
        defer { isMargin = !isMargin }
        return isMargin ? getMargin() : getElement()
    }
}

for i in uekizanGenerator([10, 20, 30], insert: 7) {
    print(i)
}