Slicing.swift

extension Sequence {
    func eachPair() -> Zip2Sequence<Self, DropFirstSequence<Self>> {
        return zip(self, self.dropFirst())
    }
}

extension Collection {

    func indexed() -> [(index: Index, element: Element)] {
        return zip(indices, self).map({ (index: $0, element: $1) })
    }

    func slice(between predicate: (Element, Element) -> Bool) -> [SubSequence] {
        let innerSlicingPoints = self
            .indexed()
            .eachPair()
            .filter({ predicate($0.0.element, $0.1.element) })
            .lazy
            .map({ $0.1.index })

        let slicingPoints = [self.startIndex] + innerSlicingPoints + [self.endIndex]

        return slicingPoints
            .eachPair()
            .map({ self[$0..<$1] })
    }

    func slice(before predicate: (Element) -> Bool) -> [SubSequence] {
        return self.slice(between: { left, right in
            return predicate(right)
        })
    }

    func slice(after predicate: (Element) -> Bool) -> [SubSequence] {
        return self.slice(between: { left, right in
            return predicate(left)
        })
    }
}

let a = [1, 1, 2, 3, 3, 2, 3, 3, 4]
a.slice(between: !=)

let string1 = "AsdafTalk"
let b = string1.slice(before: { ("A"..."Z").contains($0) }).map({ String($0) })
b

let string2 = "slice.period."
let c = string2.slice(after: { $0 == "." }).map({ String($0) })
c