More Array Extensions flattened, unwrapped, all and any.

ArrayExtension.swift

extension Array {
    func flattened<T>() -> [T] where Element == [T] {
        return self.flatMap({ $0 })
    }    
    
    func all(_ pred: (Element) -> Bool) -> Bool {
        return self.reduce(true, { acc, v in acc && pred(v) })
    }
    
    func any(_ pred: (Element) -> Bool) -> Bool {
        return self.reduce(false, { acc, v in acc || pred(v) })
    }

    subscript(safe index: Int) -> Element? {
        guard index < self.count && index >= 0 else {
            return nil
        }
        return self[index]
    }
}


extension Array {
    func groupBy(_ f: (Element, Element) -> Bool) -> [[Element]]  {
        guard let firstElement = first else {
            return []
        }

        return reduce(into: [[]], { acc, next in
            guard let lastGroup = acc.last else {
                acc.append([next])
                return
            }

            let previous = lastGroup.last ?? firstElement

            if f(previous, next) {
                var previousGroup = lastGroup
                previousGroup.append(next)
                let count = acc.count
                acc[count - 1] = previousGroup
            } else {
                acc.append([next])
            }
        })
    }
}