piss

<p>My previous <a href="http://blog.cleancoder.com/uncle-bob/2023/01/18/functional-classes.html">blog</a> seemed only to continue the confusion regarding classes in Functional Programming. Indeed, many people got quite irate. So perhaps a bit of code will help.</p> <p><strong>Trigger Warning</strong>:</p> <ul> <li>Object Oriented Terminology.</li> <li>Dynamically Typed Language.</li> <li>Mixed Metaphors.</li> <li>Distracting Animations.</li> </ul> <blockquote> <p>To all the adherents of the <em>Statically Typed</em> Functional Programming religion: I know that you believe that <em>Static Typing</em> is an essential aspect of Functional Programming and that no mere dynamically typed language could ever begin to approach the heights and glory of <em>The One True and Holy TYPED Functional Apotheotic Paradigm</em>. But we lowly programmers quivering down here at the base of <em>Orthanc</em> can only hope to meekly subsist on the dregs that fall from on high.</p> </blockquote> <p>(R.I.P. Kirstie Alley</p> <p>OK, so, once again…</p> <blockquote> <p><em>A class is an intentionally named abstraction that consists of a set of narrowly cohesive functions that operate over an internally defined data structure.</em></p> </blockquote> <p>We do not need the <code class="language-plaintext highlighter-rouge">class</code> keyword. Nor do we need polymorphic dispatch. Nor do we need inheritance. A class is just a description, whether in full or in part, of an object.</p> <p>For example – it’s time we talked about clouds (which I have looked at from both sides now; and do, in fact, understand pretty well).</p> <p>So… Here come your father’s parentheses!</p> <p><img src="https://i.pinimg.com/originals/4f/1e/26/4f1e261d1afa9d58fd1125db5a5a4a12.jpg" /></p> <div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>(ns spacewar.game-logic.clouds (:require [clojure.spec.alpha :as s] [spacewar.geometry :as geo] [spacewar.game-logic.config :as glc])) (s/def ::x number?) (s/def ::y number?) (s/def ::concentration number?) (s/def ::cloud (s/keys :req-un [::x ::y ::concentration])) (s/def ::clouds (s/coll-of ::cloud)) (defn valid-cloud? [cloud] (let [valid (s/valid? ::cloud cloud)] (when (not valid) (println (s/explain-str ::cloud cloud))) valid)) (defn make-cloud ([] (make-cloud 0 0 0)) ([x y concentration] {:x x :y y :concentration concentration})) (defn harvest-dilithium [ms ship cloud] (let [ship-pos [(:x ship) (:y ship)] cloud-pos [(:x cloud) (:y cloud)]] (if (&lt; (geo/distance ship-pos cloud-pos) glc/dilithium-harvest-range) (let [max-harvest (* ms glc/dilithium-harvest-rate) need (- glc/ship-dilithium (:dilithium ship)) cloud-content (:concentration cloud) harvest (min max-harvest cloud-content need) ship (update ship :dilithium + harvest) cloud (update cloud :concentration - harvest)] [ship cloud]) [ship cloud]))) (defn update-dilithium-harvest [ms world] (let [{:keys [clouds ship]} world] (loop [clouds clouds ship ship harvested-clouds []] (if (empty? clouds) (assoc world :ship ship :clouds harvested-clouds) (let [[ship cloud] (harvest-dilithium ms ship (first clouds))] (recur (rest clouds) ship (conj harvested-clouds cloud))))))) (defn update-clouds-age [ms world] (let [clouds (:clouds world) decay (Math/pow glc/cloud-decay-rate ms) clouds (map #(update % :concentration * decay) clouds) clouds (filter #(&gt; (:concentration %) 1) clouds) clouds (doall clouds)] (assoc world :clouds clouds))) (defn update-clouds [ms world] (-&gt;&gt; world (update-clouds-age ms) (update-dilithium-harvest ms))) </code></pre></div></div> <p>Some years back I wrote a nice little <a href="http://blog.cleancoder.com/uncle-bob/2021/11/28/Spacewar.html">spacewar game</a> in Clojure. You can play it <a href="http://spacewar.fikesfarm.com/spacewar.html">here</a>. While playing, if you manage to blow up a Klingon, a sparkling cloud of <em>Dilithium Crystals</em> will remain behind, quickly dissipating. If you can guide your ship into the midst of that cloud, you will harvest some of that <em>Dilithium</em> and replenish your stores.</p> <p>The code you see above is the <em>class</em> that represents the <em>Dilithium Cloud</em>.</p> <p>The first thing to notice is that I defined the <em>TYPE</em> of the <code class="language-plaintext highlighter-rouge">cloud</code> <em>class</em> – <em>dynamically</em>.<br /> <img src="https://yt3.ggpht.com/a/AATXAJxJ07NzOxzlMLuiV6SGv808JXSCrALLJMXJ1w=s900-c-k-c0xffffffff-no-rj-mo" width="150" /></p> <p>A <code class="language-plaintext highlighter-rouge">cloud</code> is an object with an <code class="language-plaintext highlighter-rouge">x</code> and <code class="language-plaintext highlighter-rouge">y</code> coordinate, and a <code class="language-plaintext highlighter-rouge">concentration</code>; all of which must be numbers. I also created a little type checking function named <code class="language-plaintext highlighter-rouge">valid-cloud?</code> that is used by my unit tests (not shown) to make sure the <em>TYPE</em> is not violated by any of the <em>methods</em>.</p> <p>Next comes <code class="language-plaintext highlighter-rouge">make-cloud</code> the <em>constructor</em> of the <code class="language-plaintext highlighter-rouge">cloud</code> <em>class</em>.</p> <p><a href="https://giphy.com/gifs/theoffice-the-office-tv-frame-toby-vyTnNTrs3wqQ0UIvwE">via GIPHY</a></p> <p>There are two overloads of the <em>constructor</em>. The first takes no arguments and simply creates a <code class="language-plaintext highlighter-rouge">cloud</code> at (0,0) with no <em>Dilithium</em> in it. The second takes three arguments and loads the <em>instance variables</em> of the <em>class</em>.</p> <p><a href="https://giphy.com/gifs/monty-python-2yP1jNgjNAkvu">via GIPHY</a></p> <p>There are two primary <em>methods</em> of the <code class="language-plaintext highlighter-rouge">cloud</code> <em>class</em>: <code class="language-plaintext highlighter-rouge">update-clouds-age</code> and <code class="language-plaintext highlighter-rouge">update-dilithium-harvest</code>. The <code class="language-plaintext highlighter-rouge">update-clouds-age</code> <em>method</em> finds all the <code class="language-plaintext highlighter-rouge">cloud</code> <em>instances</em> in the <code class="language-plaintext highlighter-rouge">world</code> <em>object</em> and decreases their concentration by the <code class="language-plaintext highlighter-rouge">decay</code> factor – which is a function of the number of milliseconds (<code class="language-plaintext highlighter-rouge">ms</code>) since the last time they were updated. The <code class="language-plaintext highlighter-rouge">update-dilithium-harvest</code> <em>method</em> finds all the <code class="language-plaintext highlighter-rouge">cloud</code> <em>objects</em> that are within the <code class="language-plaintext highlighter-rouge">ship</code> <em>object</em>’s harvesting range and transfers <em>Dilithium</em> from those <code class="language-plaintext highlighter-rouge">cloud</code> <em>objects</em> to the <code class="language-plaintext highlighter-rouge">ship</code> <em>object</em>.</p> <p>Now, you might notice that these <em>methods</em> are not the traditional style of method you would find in a Java program. For one thing, they deal with a list of <code class="language-plaintext highlighter-rouge">cloud</code> <em>objects</em> rather than an individual <code class="language-plaintext highlighter-rouge">cloud</code> <em>object</em>. Secondly, there’s nothing polymorphic about them. Third, they are <em>functional</em>, because they return a new <code class="language-plaintext highlighter-rouge">world</code> <em>object</em> with new <code class="language-plaintext highlighter-rouge">cloud</code> <em>objects</em> and, in the case of <code class="language-plaintext highlighter-rouge">update-dilithium-harvest</code>, a new <code class="language-plaintext highlighter-rouge">ship</code> <em>object</em>.</p> <p>So are these really <em>methods</em> of the <code class="language-plaintext highlighter-rouge">cloud</code> <em>class</em>? Sure! Why not? They are a set of narrowly cohesive functions that manipulate an internal data structure within an intentionally named abstraction.</p> <p>For all intents and purposes <code class="language-plaintext highlighter-rouge">cloud</code> is a °°°°°° °°°°°°° <em>class</em>.</p> <p><a href="https://giphy.com/gifs/reaction-laughing-lotr-TcdpZwYDPlWXC">via GIPHY</a></p> <p>So there.</p>