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<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>reveal.js - The HTML Presentation Framework</title>
<meta name="description" content="A framework for easily creating beautiful presentations using HTML">
<meta name="author" content="Hakim El Hattab">
<meta name="apple-mobile-web-app-capable" content="yes" />
<meta name="apple-mobile-web-app-status-bar-style" content="black-translucent" />
<meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=no, minimal-ui">
<link rel="stylesheet" href="css/reveal.css">
<link rel="stylesheet" href="css/theme/moon.css" id="theme">
<!-- Code syntax highlighting -->
<link rel="stylesheet" href="lib/css/monokai_sublime.css">
<!-- Printing and PDF exports -->
<script>
var link = document.createElement( 'link' );
link.rel = 'stylesheet';
link.type = 'text/css';
link.href = window.location.search.match( /print-pdf/gi ) ? 'css/print/pdf.css' : 'css/print/paper.css';
document.getElementsByTagName( 'head' )[0].appendChild( link );
</script>
<!--[if lt IE 9]>
<script src="lib/js/html5shiv.js"></script>
<![endif]-->
</head>
<body>
<div class="reveal">
<!-- Any section element inside of this container is displayed as a slide -->
<div class="slides">
<section data-markdown>
# ScalaLab
### Look Mama, I can Monad without hands!
</section>
<section data-background="#5C5609">
<section data-markdown>
## Building blocks
* A type constructor
* A unit function, apply method
* A binding operation, flatMap
</section>
<section data-markdown>
## The type constructor
* Option[+A]
* Either[+A, +B]
* Try[+T]
</section>
<section data-markdown>
##The unit function
<pre>
<code class="scala">
object Option {
def apply[A](x: A): Option[A] =
if (x == null) None else Some(x)
}
val opt = Option("String")
</code>
</pre>
</section>
<section data-markdown>
##The binding function
<pre>
<code class="scala">
abstract class Option[+A] {
def flatMap[B](f: A => Option[B]): Option[B]
}
</code>
</pre>
</section>
</section>
<section data-markdown>
##The Maybe Monad
We'll start by implementing the Maybe Monad.
Which is just an Option but with another name.
<pre>
<code class="scala">
sealed trait Maybe[+A]
case class Just[+A](value: A) extends Maybe[A]
case object Empty extends Maybe[Nothing]
</code>
</pre>
</section>
<section data-background="#360515">
<section data-markdown>
## Type system basics
* Covariance
* The bottom type
</section>
<section data-markdown>
##Covariance
Maybe[+A] - Maybe Monad is covariant on its type paramter.
Given
<pre>
<code class="scala">
trait Animal { def name: String }
case class Cat(name:String) extends Animal
</code>
</pre>
Then
<pre>
<code class="scala">
val maybeCat: Maybe[Cat] = Maybe(Cat("Felix"))
maybeCat.isInstanceOf[Maybe[Animal]] // returns true
</code>
</pre>
</section>
<section data-markdown>
## Nothing
The Scala 'Nothing' type is a sub-type of all existing types.
As a consequence:
<pre>
<code class="scala">
val empty = Empty
empty.isInstanceOf[Maybe[Animal]] // returns true
</code>
</pre>
but also...
<pre>
<code class="scala">
val empty = Empty
trait Foo
empty.isInstanceOf[Maybe[Foo]] // returns true
</code>
</pre>
</section>
</section>
<section data-markdown>
##The Monad laws
We won't talk about it in a slide.
We'll simply code and learn them!.
</section>
<section data-background="#0C5E75">
<section data-markdown>
##For comprehension
We have a Monad!
Let's run a for-comprehension
</section>
<section data-markdown>
#Ouch!!!
</section>
</section>
<section data-background="#360515">
<section data-markdown>
##Maybe is not a Functor yet!
A Functor is any 'Box' that allow us to
apply a function to its value.
<pre>
<code class="scala">
trait Maybe[+A] {
def map[B](f: A => B): Maybe[B]
}
</code>
</pre>
</section>
<section data-markdown>
##The Functor laws
We won't talk about it in a slide.
We'll simply code and learn them!.
</section>
</section>
<section data-markdown>
## Filtering
<pre>
<code class="scala">
def filter(f: A => Boolean): Maybe[A]
</code>
</pre>
</section>
<section data-markdown data-background="#5C5609">
##Monads and for-comprehension
Don't really need to be a Monad.
It should only have `flatMap`, `map` and `filter`.
Most of them don't abide to the Monad's laws.
</section>
</div>
</div>
<script src="lib/js/head.min.js"></script>
<script src="js/reveal.js"></script>
<script>
// Full list of configuration options available at:
// https://github.com/hakimel/reveal.js#configuration
Reveal.initialize({
controls: true,
progress: true,
history: true,
center: true,
transition: 'slide', // none/fade/slide/convex/concave/zoom
// Optional reveal.js plugins
dependencies: [
{ src: 'lib/js/classList.js', condition: function() { return !document.body.classList; } },
{ src: 'plugin/markdown/marked.js', condition: function() { return !!document.querySelector( '[data-markdown]' ); } },
{ src: 'plugin/markdown/markdown.js', condition: function() { return !!document.querySelector( '[data-markdown]' ); } },
{ src: 'plugin/highlight/highlight.js', async: true, condition: function() { return !!document.querySelector( 'pre code' ); }, callback: function() { hljs.initHighlightingOnLoad(); } },
{ src: 'plugin/zoom-js/zoom.js', async: true },
{ src: 'plugin/notes/notes.js', async: true }
]
});
</script>
</body>
</html>