Question

我在Clojure Quil库中找出算法存在严重问题。我一直试图用功能中间件模式制作一些网络/植绒模式的图表，如this。我的问题是你如何在Quild中创建一个嵌套的“for循环”，以便将任何给定点连接到任何其他带有线的点？区别在于连接1-> 2 3-> 4 ...等的一组点和连接的组1-> 2 1-> 3 1-> 4 2-> 3 2 - →4 ...等

我的程序看起来像这样，虽然为了这个问题，我试图将它编辑为通用的。

(ns stack-question.core
  (:require [quil.core :as q]
            [quil.middleware :as m]))   

;how to draw the point
(defn draw-points [point]
  (q/point (:x point) (:y point)))

;the main data structure
(defn make-point [num]
  {:name num
   :x (rand 500.0)
   :y (rand 500.0)})    

;draws connections between two objects
(defn connections [p1 p2]
      (q/stroke 200 200 100 150)
      (q/line (:x p1) (:y  p1) (:x p2) (:y p2)))))

(defn setup []
  (q/frame-rate 30)
  {:points (map make-points (take 1000 (range)))})

;this function isn't important to the question 
;but let's just say that the points move position each frame 
(defn update-state [state]
  (update state :points move-group))

;this is the problem function here.
;I'm trying to map over the collection, but with a fixed head
;and do so for each element in the collection
(defn make-conts [coll]
  (loop [x coll]
    (when (not (empty? (rest coll)))
      (map (partial connections (first x)) (rest x))
      (recur (rest x)))))


(defn draw-state [state]
  (do
    ;(q/frame-rate 1)
    (q/background 0)
    (doseq [x (map draw-point (:points state))] x)
    (doseq [x (make-conts (:points state))] x)))

(q/defsketch stack-question
  :title "GL"
  :size [500 500]
  :setup setup
  :update update-state
  :draw draw-state
  :middleware [m/fun-mode]
  :renderer :opengl)

我希望这不是完全不透明的。

Answer 1

您的代码存在两个问题：

首先，您要在(rest coll)语句中检查(rest x)而不是when，从而导致无限循环。

第二个是map返回一个懒惰序列，这意味着对connections的调用没有发生。这可以通过使用map将调用包装到doall来修复，但由于您对副作用感兴趣而不是返回值，因此您应该使用doseq。

此版本的功能（多余的loop也已删除）应该有效：

(defn make-conts [coll]
    (when (not (empty? (rest coll)))
      (doseq [endpoint (rest coll)]
        (connections (first coll) endpoint))
      (recur (rest coll))))

您可以使用combinations中的clojure.math.combinatorics代替编写代码以自行生成组合：

(require '[clojure.math.combinatorics :as combi])

(defn make-conts [coll]
   (doseq [[p1 p2] (combi/combinations coll 2)]
     (connections p1 p2)))

Clojure Quil：绘制线条时嵌套循环

1 个答案: