A helper for comparing neighbors in an array

ForeEachAdjacent.swift

extension Array {
    
    func forEachAdjacent(do block: ((Element, Element))->()) {
        guard count > 1 else {
            return
        }
        var secondIndex = 1
        while secondIndex < count {
            let firstVal = self[secondIndex - 1]
            let secndVal = self[secondIndex]
            block(firstVal, secndVal)
            secondIndex += 1
        }
    }
    
    func adjacentMap<T>(_ block: (Element, Element)->T) -> [T] {
        var newArray = [T]()
        forEachAdjacent { (current, next) in
            let newElement = block(current, next)
            newArray.append(newElement)
        }
        return newArray
    }
    
}