Question

我有这个功能：

(defn movies [directors]
  (->> directors
       (mapcat :movies)
       (group-by :genre)))

给了我这个输出：

{"Action" [{:title "Blade Runner 2049", :genre "Action", :year 2017}],
 "Drama"
 [{:title "Gladiator", :genre "Drama", :year 2000}
  {:title "Apocalypse Now", :genre "Drama", :year 1979}
  {:title "The Departed", :genre "Drama", :year 2006}
  {:title "The Aviator", :genre "Drama", :year 2004}],
 "Adventure" [{:title "Mars", :genre "Adventure", :year 2015}],
 "Crime"
 [{:title "American Gangster", :genre "Crime", :year 2007}
  {:title "The Godfather", :genre "Crime", :year 1972}
  {:title "GoodFellas", :genre "Crime", :year 1990}],
 "Comedy"
 [{:title "Jack", :genre "Comedy", :year 1996}
  {:title "The Wolf", :genre "Comedy", :year 2013}]}

我想在相同功能“电影”中使用减少或计数来计算每个类别中的电影数量

谢谢， R上。

Answer 1

(frequencies 
 (sequence (comp (mapcat :movies)
                 (map :genre)) 
           directors))

Answer 2

这只是计算每个:genre组中的数字：

(map #((juxt key (comp count val)) %) your-current-output)
;; => (["Action" 1] ["Drama" 4] ["Adventure" 1] ["Crime" 3] ["Comedy" 2])

所以对你的功能：

(defn movies [directors]
  (->> directors
       (mapcat :movies)
       (group-by :genre)
       (map #((juxt key (comp count val)) %))))

Answer 3

你真的需要在那里使用import UIKit class Line { var startPoint:CGPoint var endPoint:CGPoint init (start:CGPoint , end:CGPoint) { startPoint = start endPoint = end } } class AnnotationView: UIView { static internal let nibName = "AnnotationView" @IBOutlet weak var imageView: UIImageView! var lines :[Line] = [] var lastPoint:CGPoint! let drawingLayer = CAShapeLayer() override func awakeFromNib() { super.awakeFromNib() layer.addSublayer(drawingLayer) } required init?(coder aDecoder: NSCoder) { fatalError("init(coder:) has not been implemented") } override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) { lastPoint = touches.first?.location(in: self) } override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) { if let touch = touches.first { let newPoint = touch.location(in:self) lines.append(Line(start: lastPoint, end: newPoint)) lastPoint = newPoint updateDrawingOverlay() } } func updateDrawingOverlay() { let path = CGMutablePath() for line in lines { path.move(to: line.startPoint) path.addLine(to: line.endPoint) } drawingLayer.frame = imageView.frame drawingLayer.path = path drawingLayer.lineWidth = 5 drawingLayer.strokeColor = UIColor.black.cgColor setNeedsDisplay() } }吗？因为您可以使用reduce和map的组合来计算项目：

frequencies

Clojure减少/计算集合中元素的数量

3 个答案: