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diff --git a/static/talks/fp-js/index.html b/static/talks/fp-js/index.html deleted file mode 100644 index e90650c..0000000 --- a/static/talks/fp-js/index.html +++ /dev/null @@ -1,431 +0,0 @@ -<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" -"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> -<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en"> -<head> -<!-- 2017-10-16 Mon 10:10 --> -<meta http-equiv="Content-Type" content="text/html;charset=utf-8" /> -<meta name="viewport" content="width=device-width, initial-scale=1" /> -<title>Functional Programming in JavaScript</title> -<meta name="generator" content="Org mode" /> -<meta name="author" content="Alan Pearce" /> -<meta name="version" content="S5 1.2a2" /> -<meta name='defaultView' content='slideshow' /> -<meta name='controlVis' content='hidden' /> -<!-- style sheet links --> -<link rel='stylesheet' href='ui/default/outline.css' type='text/css' media='screen' id='outlineStyle' /> -<link rel='stylesheet' href='ui/default/print.css' type='text/css' media='print' id='slidePrint' /> -<link rel='stylesheet' href='ui/default/opera.css' type='text/css' media='projection' id='operaFix' /> -<link rel='stylesheet' href='ui/default/slides.css' type='text/css' media='screen' id='slideProj' /> -<!-- S5 JS --> -<script src='ui/default/slides.js' type='text/javascript'></script> - - -</head> -<body> -<div class="layout"> -<div id="controls"><!-- no edit --></div> -<div id="currentSlide"><!-- no edit --></div> -<div id="header" class="status"> -  -</div> - -<div id="footer" class="status"> -<h1>Alan Pearce - Functional Programming in JavaScript</h1> -</div> - -</div> -<div id="content" class="presentation"> -<div id='title-slide' class='slide'> -<h1>Functional Programming in JavaScript</h1> -<h2></h2> -<h2>Alan Pearce</h2> -<h3><a href="mailto:alan@alanpearce.eu">alan@alanpearce.eu</a></h3> -<h4></h4> -</div> -<div id='table-of-contents' class='slide'> -<h1>Table of Contents</h1> -<div id="text-table-of-contents"> -<ul> -<li>1. Why?</li> -<li>2. Concepts</li> -<li>3. Further concepts</li> -<li>4. First-class functions</li> -<li>5. Higher-order functions</li> -<li>6. Higher-order functions (cont.)</li> -<li>7. Pure functions</li> -<li>8. Recursion</li> -<li>9. Partial application</li> -<li>10. Partial application (cont.)</li> -<li>11. Currying</li> -<li>12. Easy Currying</li> -<li>13. Practical Currying</li> -<li>14. Functional composition</li> -<li>15. Functional composition (cont.)</li> -<li>16. pipe</li> -<li>17. Point-free programming</li> -<li>18. Further Resources</li> -</ul> -</div> -</div> - -<div id="outline-container-org05e10f9" class="outline-1 slide"> -<h1 id="org05e10f9"><span class="section-number-1">1</span> Why?</h1> -<div class="outline-text-1" id="text-1"> -<p> -Imperative programming is concerned with <b>how</b> -</p> - -<p> -Functional programming is concerned with <b>what</b> -</p> -</div> -</div> - -<div id="outline-container-org14fa5d9" class="outline-1 slide"> -<h1 id="org14fa5d9"><span class="section-number-1">2</span> Concepts</h1> -<div class="outline-text-1" id="text-2"> -<ul class="org-ul"> -<li>First-class Functions</li> -<li>Higher-order Functions</li> -<li>Recursion</li> -<li>Pure functions</li> -<li>Currying & Partial Application</li> -</ul> -</div> -</div> - -<div id="outline-container-orgd930436" class="outline-1 slide"> -<h1 id="orgd930436"><span class="section-number-1">3</span> Further concepts</h1> -<div class="outline-text-1" id="text-3"> -<ul class="org-ul"> -<li>Lazy Evaluation</li> -<li>Types & Data Structures</li> -<li>Category Theory</li> -</ul> -</div> -</div> - -<div id="outline-container-orgbd39891" class="outline-1 slide"> -<h1 id="orgbd39891"><span class="section-number-1">4</span> First-class functions</h1> -<div class="outline-text-1" id="text-4"> -<ul class="org-ul"> -<li>Are values</li> -<li>Have no restriction on their use</li> -<li>Enable the use of callback functions in JavaScript</li> -</ul> - -<p> - -</p> - -<div class="org-src-container"> -<pre><code class="src src-js">var fn = function () { - return 2 -} -</code></pre> -</div> -</div> -</div> - - -<div id="outline-container-org8d1ee8a" class="outline-1 slide"> -<h1 id="org8d1ee8a"><span class="section-number-1">5</span> Higher-order functions</h1> -<div class="outline-text-1" id="text-5"> -<p> -Functions that operate on other functions are higher-order functions -</p> - -<p> - -</p> - -<div class="org-src-container"> -<pre><code class="src src-js">var succ = function (x) { - return x + 1 -} - -var arr = [1, 2, 3, 4] - -arr.map(succ) -</code></pre> -</div> - -<p> -Here, <code>Array.prototype.map</code> is the higher-order function -</p> -</div> -</div> - -<div id="outline-container-org3bbf4ac" class="outline-1 slide"> -<h1 id="org3bbf4ac"><span class="section-number-1">6</span> Higher-order functions (cont.)</h1> -<div class="outline-text-1" id="text-6"> -<p> -Functions that return functions are also higher-order functions -</p> - -<p> - -</p> - -<div class="org-src-container"> -<pre><code class="src src-js">function <span style="font-weight: bold;">adder</span> (n) { - return function (x) { - return n + x - } -} - -var add1 = adder(1) -</code></pre> -</div> - -<p> -<code>adder</code> is a higher-order function -</p> -</div> -</div> - -<div id="outline-container-orgfb6eee2" class="outline-1 slide"> -<h1 id="orgfb6eee2"><span class="section-number-1">7</span> Pure functions</h1> -<div class="outline-text-1" id="text-7"> -<p> -Functions without side-effects -</p> - -<div class="org-src-container"> -<pre><code class="src src-js">var succ = (x) => x + 1 - -console.log(succ(succ(1))) - -<span style="color: #b8b8b8; background-color: #f8f8f8; font-style: italic;">// </span><span style="color: #b8b8b8; background-color: #f8f8f8; font-style: italic;">could be optimised away by a compiler, e.g.:</span> - -console.log(3) -</code></pre> -</div> -</div> -</div> - -<div id="outline-container-org16e9966" class="outline-1 slide"> -<h1 id="org16e9966"><span class="section-number-1">8</span> Recursion</h1> -<div class="outline-text-1" id="text-8"> -<p> -Functions that call themselves -</p> - -<div class="org-src-container"> -<pre><code class="src src-js">function <span style="font-weight: bold;">fibonacci</span> (n) { - switch (n) { - case 0: - case 1: - return 1 - default: - return fibonacci(n - 1) + fibonacci(n - 2) - } -} -</code></pre> -</div> -</div> -</div> - -<div id="outline-container-org1b7b0af" class="outline-1 slide"> -<h1 id="org1b7b0af"><span class="section-number-1">9</span> Partial application</h1> -<div class="outline-text-1" id="text-9"> -<p> -The infamous <code>Function.prototype.bind</code> in JavaScript -</p> - -<div class="org-src-container"> -<pre><code class="src src-js">function <span style="font-weight: bold;">add</span> (x, y) { - return x + y -} - -var add1 = add.bind(add, 1) - -add1(3) <span style="color: #b8b8b8; background-color: #f8f8f8; font-style: italic;">// </span><span style="color: #b8b8b8; background-color: #f8f8f8; font-style: italic;">= 4</span> -</code></pre> -</div> -</div> -</div> - -<div id="outline-container-org796e6d3" class="outline-1 slide"> -<h1 id="org796e6d3"><span class="section-number-1">10</span> Partial application (cont.)</h1> -<div class="outline-text-1" id="text-10"> -<p> -After ES6 introduced arrow functions, partial application has become -more popular -</p> - -<div class="org-src-container"> -<pre><code class="src src-js">var add = x => y => x + y -</code></pre> -</div> -</div> -</div> - -<div id="outline-container-orgeb4d67b" class="outline-1 slide"> -<h1 id="orgeb4d67b"><span class="section-number-1">11</span> Currying</h1> -<div class="outline-text-1" id="text-11"> -<p> -Related to partial application, but more implicit and general -</p> - -<p> -Translates <b><i>1</i> function of arity <i>n</i></b> to <b><i>n</i> functions of arity <i>1</i></b> -</p> - -<div class="org-src-container"> -<pre><code class="src src-js">function <span style="font-weight: bold;">volume</span> (w, d, h) { - return w * d * h -} - -var vol = curry(volume) -vol(10)(20)(30) -<span style="color: #b8b8b8; background-color: #f8f8f8; font-style: italic;">// </span><span style="color: #b8b8b8; background-color: #f8f8f8; font-style: italic;">is strictly equivalent to</span> -volume(10, 20, 30) -</code></pre> -</div> -</div> -</div> - -<div id="outline-container-orgdfd8353" class="outline-1 slide"> -<h1 id="orgdfd8353"><span class="section-number-1">12</span> Easy Currying</h1> -<div class="outline-text-1" id="text-12"> -<p> -In order to make currying (and partial application) easier to use, -move the <b>most important</b> argument to a function to the end: -</p> - -<div class="org-src-container"> -<pre><code class="src src-js">var badMap = (arr, fn) => arr.map(fn) -var goodMap = (fn, arr) => arr.map(fn) -var curriedBadMap = curry(badmap) -var curriedGoodMap = curry(goodMap) - -var goodDoubleArray = goodMap(x => x * 2) -var badDoubleArray = badMap(_, x => x * 2) -</code></pre> -</div> - -<p> -The bad version requires the curry function to support a magic -placeholder argument and doesn't look as clean. -</p> -</div> -</div> - -<div id="outline-container-org30accd5" class="outline-1 slide"> -<h1 id="org30accd5"><span class="section-number-1">13</span> Practical Currying</h1> -<div class="outline-text-1" id="text-13"> -<p> -Currying is not automatic in JavaScript, as in other languages -</p> - -<p> -External tools aren't (so far) able to statically analyse curried -functions -</p> - -<p> -Solution: Don't expose curried functions -Instead, write functions as if currying were automatic -</p> - -<p> -If consumers want to curry, they can. If they don't, their editor or -language server will show them the arguments -</p> -</div> -</div> - -<div id="outline-container-org5f352dc" class="outline-1 slide"> -<h1 id="org5f352dc"><span class="section-number-1">14</span> Functional composition</h1> -<div class="outline-text-1" id="text-14"> -<p> -Creating functions from other functions -</p> - -<p> -Usually provided by <code>compose</code> (right-to-left) and <code>pipe</code> (left-to-right) -</p> - -<p> -A very simple definition of <code>compose</code> for only two functions would look like this -</p> - -<div class="org-src-container"> -<pre><code class="src src-js">function <span style="font-weight: bold;">compose</span> (f, g) { - return function (...args) { - return f(g(...args)) - } -} -</code></pre> -</div> -</div> -</div> - -<div id="outline-container-org0c2c4f9" class="outline-1 slide"> -<h1 id="org0c2c4f9"><span class="section-number-1">15</span> Functional composition (cont.)</h1> -<div class="outline-text-1" id="text-15"> -<div class="org-src-container"> -<pre><code class="src src-js">var plusOne = x => x + 1 -var timesTwo = x => x * 2 - -var plusOneTimesTwo = compose(timesTwo, plusOne) -var timesTwoPlusOne = compose(plusOne, timesTwo) - -nextDoubled(3) <span style="color: #b8b8b8; background-color: #f8f8f8; font-style: italic;">// </span><span style="color: #b8b8b8; background-color: #f8f8f8; font-style: italic;">= (3 + 1) * 2 = 8</span> -doubledPlusOne(3) <span style="color: #b8b8b8; background-color: #f8f8f8; font-style: italic;">// </span><span style="color: #b8b8b8; background-color: #f8f8f8; font-style: italic;">= (3 * 2) + 1 = 7</span> -</code></pre> -</div> -</div> -</div> - -<div id="outline-container-orgddc61f6" class="outline-1 slide"> -<h1 id="orgddc61f6"><span class="section-number-1">16</span> pipe</h1> -<div class="outline-text-1" id="text-16"> -<p> -What about <code>pipe</code>? -</p> - -<p> -<code>pipe</code> does the same thing, but runs the functions the other way around -</p> - -<p> -<code>pipe(f, g)</code> is the same as <code>compose(g, f)</code> -</p> -</div> -</div> - -<div id="outline-container-org7426c58" class="outline-1 slide"> -<h1 id="org7426c58"><span class="section-number-1">17</span> Point-free programming</h1> -<div class="outline-text-1" id="text-17"> -<p> -With currying and higher-order functions, we (often) don't need to declare function arguments -</p> - -<div class="org-src-container"> -<pre><code class="src src-js">var modulo = a => b => b % a -var eq = a => b => a === b - -var isEven = x => eq(0)(modulo(2)(x)) -var isEvenPointFree = compose(eq(0), modulo(2)) -</code></pre> -</div> -</div> -</div> - -<div id="outline-container-org8868cfb" class="outline-1 slide"> -<h1 id="org8868cfb"><span class="section-number-1">18</span> Further Resources</h1> -<div class="outline-text-1" id="text-18"> -<ul class="org-ul"> -<li><a href="https://drboolean.gitbooks.io/mostly-adequate-guide/content/">Mostly adequate guide to FP (in javascript)</a></li> -<li><a href="http://ramdajs.com/">Ramda</a>, a general-purpose FP library</li> -<li><a href="https://sanctuary.js.org/">Sanctuary</a>, a JavaScript library for Haskellers</li> -</ul> -</div> -</div> - - -</div> -</body> -</html> |