Attributes

Name: Crystal
OS: Linux; MacOS; Windows
Version: 1.11.2

Code

<dl class="attributes">
  <dt>Name</dt>
  <dd>Crystal</dd>
  <dt>OS</dt>
  <dd>Linux</dd>
  <dd>MacOS</dd>
  <dd>Windows</dd>
  <dt>Version</dt>
  <dd>1.11.2</dd>
</dl>

Book Authors

Include partial: _includes/components/book-authors.html

Lorem ipsum dolor sit amet.

Lorem ipsum dolor sit amet consectetur, adipisicing elit. Quia quos autem veniam libero! Deleniti nemo quas optio voluptas voluptatibus sint ratione. Id vel error quia ipsam sit saepe hic at amet excepturi ea.

Code

<div class="book-authors">
    <div class="book-author">
      <img class="book-author-icon" src="/assets/learning/george.png" alt="Author's picture" />
      <p class="small">Lorem ipsum dolor sit amet.

      </p>
    </div>
    <div class="book-author">
      <img class="book-author-icon" src="/assets/learning/guilherme.jpg" alt="Author's picture" />
      <p class="small">Lorem ipsum dolor sit amet consectetur, adipisicing elit. Quia quos autem
veniam libero! Deleniti nemo quas optio voluptas voluptatibus sint ratione.
Id vel error quia ipsam sit saepe hic at amet excepturi ea.

      </p>
    </div>
</div>

Book Presenter

Include partial: _includes/components/book-presenter.html

Lorem ipsum dolor sit amet consectetur, adipisicing elit. Quia quos autem veniam libero! Deleniti nemo quas optio voluptas voluptatibus sint ratione. Id vel error quia ipsam sit saepe hic at amet excepturi ea.

You can get it from these vendors:

Buy on Amazon

Buy on Packt

Voluptas sunt ratione consequatur optio porro eaque nam quod ex illum modi id animi fugiat vero explicabo illo officiis assumenda nulla rerum, dignissimos sed dicta pariatur quis eum. Beatae ea cumque alias ducimus quos maxime sed, modi illum at repellendus, ex deleniti nesciunt tempore placeat in accusantium!

Code

<div class="book-presenter">
  <div class="cover">
    <img src="/assets/learning/crystal_programming.png" alt="" aria-label="Book cover" />
  </div>

  <div class="description">
    <p>Lorem ipsum dolor sit amet consectetur, adipisicing elit. Quia quos autem
veniam libero! Deleniti nemo quas optio voluptas voluptatibus sint ratione.
Id vel error quia ipsam sit saepe hic at amet excepturi ea.

    </p>

    <p>You can get it from these vendors:</p>
      <div class="link-item">
        <a class="link-item__main" href="https://www.amazon.com/Crystal-Programming-project-based-introduction-applications/dp/1801818673/ref=sr_1_2"><svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 -960 960 960">
  <path d="M240-80q-33 0-56.5-23.5T160-160v-640q0-33 23.5-56.5T240-880h480q33 0 56.5 23.5T800-800v640q0 33-23.5 56.5T720-80H240Zm0-80h480v-640h-80v280l-100-60-100 60v-280H240v640Zm0 0v-640 640Zm200-360 100-60 100 60-100-60-100 60Z"/>
</svg>

          Buy on Amazon</a>
      </div>
      <div class="link-item">
        <a class="link-item__main" href="https://www.packtpub.com/product/crystal-programming/9781801818674"><svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 -960 960 960">
  <path d="M240-80q-33 0-56.5-23.5T160-160v-640q0-33 23.5-56.5T240-880h480q33 0 56.5 23.5T800-800v640q0 33-23.5 56.5T720-80H240Zm0-80h480v-640h-80v280l-100-60-100 60v-280H240v640Zm0 0v-640 640Zm200-360 100-60 100 60-100-60-100 60Z"/>
</svg>

          Buy on Packt</a>
      </div>
  </div>

  <div class="details">Voluptas sunt ratione consequatur optio porro eaque nam quod ex illum modi
id animi fugiat vero explicabo illo officiis assumenda nulla rerum,
dignissimos sed dicta pariatur quis eum. Beatae ea cumque alias ducimus quos
maxime sed, modi illum at repellendus, ex deleniti nesciunt tempore placeat
in accusantium!

  </div>
</div>

Breadcrumbs

Include partial: _includes/site/breadcrumbs.html

Basic

Section Main

Non-link Item

No section

Code

<strong>Basic</strong>

<nav class="breadcrumbs" aria-label="Breadcrumbs"><span class="breadcrumb">
    <a href="/" rel="index up">Home</a>
  </span>

  <span aria-hidden="true">/</span>

      <div class="breadcrumb"><a href="/community/" rel="up">Community</a>
      </div>
</nav>

<nav class="section-links" aria-label="Section links"><ul>
    <li>
      <a href="/team/" 
        >Team</a>
    </li>
    <li>
      <a href="/sponsors/" 
        >Sponsors</a>
    </li>
    <li>
      <a href="/community/#events" 
        >Events</a>
    </li>
    <li>
      <a href="/used_in_prod/" 
        >Used in production</a>
    </li>
    <li>
      <a href="/community/governance/" 
        >Governance</a>
    </li>
</ul>

</nav>


<strong>Section Main</strong>

<nav class="breadcrumbs" aria-label="Breadcrumbs"><span class="breadcrumb">
    <a href="/" rel="index up">Home</a>
  </span>

  <span aria-hidden="true">/</span>

    <span class="breadcrumb">
      <a href="/community/" aria-current="page">Community</a>
    </span>
</nav>

<nav class="section-links" aria-label="Section links"><ul>
    <li>
      <a href="/team/" 
        >Team</a>
    </li>
    <li>
      <a href="/sponsors/" 
        >Sponsors</a>
    </li>
    <li>
      <a href="/community/#events" 
        >Events</a>
    </li>
    <li>
      <a href="/used_in_prod/" 
        >Used in production</a>
    </li>
    <li>
      <a href="/community/governance/" 
        >Governance</a>
    </li>
</ul>

</nav>


<strong>Non-link Item</strong>

<nav class="breadcrumbs" aria-label="Breadcrumbs"><span class="breadcrumb">
    <a href="/" rel="index up">Home</a>
  </span>

  <span aria-hidden="true">/</span>

      <div class="breadcrumb"><span>Archive</span>
      </div>
</nav>

<nav class="section-links" aria-label="Section links"><ul>
</ul>

</nav>


<strong>No section</strong>

<nav class="breadcrumbs" aria-label="Breadcrumbs"><span class="breadcrumb">
    <a href="/" rel="index up">Home</a>
  </span>

  
</nav>

<nav class="section-links" aria-label="Section links"><ul>
</ul>

</nav>

Card

Crystal

A language for humans and computers.

Version 1.7.3

Code

<div class="card">
  <img src="/assets/icon.svg" alt="">
  <a href="/" class="name">Crystal</a>

  <div>
    A language for humans and computers.
  </div>

  <div>
    Version 1.7.3
  </div>
</div>

Card list

Include partial: _includes/pages/sponsors/top_sponors.html

84codes €22,000 per month since Apr 1, 2018 €369,000
Manas.Tech $5,000 per month since Jun 19, 2009 $1,300,000
Buy Google Reviews $750 per month since Aug 7, 2024 $1,500
Buy Instagram Followers Thunderclapit $750 per month since Aug 7, 2024 $1,500

Code

<ul class="cards-list">
    <li class="sponsor-card">
      <a href="https://www.84codes.com/" class="name" rel="sponsored nofollow">84codes</a>
      <img src="/assets/sponsors/84.png" alt="Logo of 84codes">
      <span class="last-payment" title="Last payment">€22,000 per month since Apr 1, 2018</span>
      <span class="all-time" title="All-time total">€369,000</span>
    </li>
    <li class="sponsor-card">
      <a href="https://manas.tech/" class="name" rel="sponsored nofollow">Manas.Tech</a>
      <img src="/assets/manas-orange.svg" alt="Logo of Manas.Tech">
      <span class="last-payment" title="Last payment">$5,000 per month since Jun 19, 2009</span>
      <span class="all-time" title="All-time total">$1,300,000</span>
    </li>
    <li class="sponsor-card">
      <a href="https://buyreviewz.com/buy-google-reviews" class="name" rel="sponsored nofollow">Buy Google Reviews</a>
      <img src="/assets/sponsors/buy_google_reviews.jpg" alt="Logo of Buy Google Reviews">
      <span class="last-payment" title="Last payment">$750 per month since Aug 7, 2024</span>
      <span class="all-time" title="All-time total">$1,500</span>
    </li>
    <li class="sponsor-card">
      <a href="https://thunderclap.it/buy-instagram-followers" class="name" rel="sponsored nofollow">Buy Instagram Followers Thunderclapit</a>
      <img src="/assets/sponsors/buy_instagram_followers_thunderclapit.png" alt="Logo of Buy Instagram Followers Thunderclapit">
      <span class="last-payment" title="Last payment">$750 per month since Aug 7, 2024</span>
      <span class="all-time" title="All-time total">$1,500</span>
    </li>
</ul>

Copy Action

This component adds a copy button to an element (primarily intended for code blocks) which writes the content of the element to the clipboard.

puts "Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum
  has been the industry's standard dummy text ever since the 1500s, when an unknown printer."

Code

This component adds a copy button to an element (primarily intended for code blocks)
which writes the content of the element to the clipboard.

<div class="enable-copy-action">
{% highlight crystal %}
puts "Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum
  has been the industry's standard dummy text ever since the 1500s, when an unknown printer."
{% endhighlight %}
</div>

<script src="/assets/js/copy-action.js"></script>
<script>
document.querySelectorAll(".enable-copy-action pre").forEach(copy_action)
</script>

Image List

Include partial: _includes/components/image-list.html

Lorem ipsum dolor sit amet consectetur, adipisicing elit

Quia quos autem veniam libero!

Code

<div class="image-list">
    <div class="item"><div class="hex-icon">
  <div class="inner"><svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 -960 960 960">
  <path d="M664-160 440-384v-301L336-581l-57-57 201-201 200 200-57 57-103-103v269l200 200-56 56Zm-368 1-56-56 127-128 57 57-128 127Z"/>
</svg>

  </div>
</div>

      <div class="small">Lorem ipsum dolor sit amet consectetur, adipisicing elit
      </div>
    </div>
    <div class="item"><div class="hex-icon">
  <div class="inner"><svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 -960 960 960">
  <path d="M160-160q-33 0-56.5-23.5T80-240v-480q0-33 23.5-56.5T160-800h240l80 80h320q33 0 56.5 23.5T880-640v400q0 33-23.5 56.5T800-160H160Zm0-80h640v-400H447l-80-80H160v480Zm0 0v-480 480Z"/>
</svg>

  </div>
</div>

      <div class="small">Quia quos autem veniam libero!
      </div>
    </div>
</div>

Link Actions

A set of links which are displayed together. Attached icons are automatically derived from the target URL.

API Docs Changelog Source Nondescript Link

Linux

Code

<div class="link-actions">
  <a href="https://crystal-lang.org/api/">API Docs</a>
  <a href="https://github.com/crystal-lang/crystal/releases/tag/1.11.1">Changelog</a>
  <a href="https://github.com/crystal-lang/crystal/tree/1.11.1">Source</a>
  <a href="https://example.com/">Nondescript Link</a>
  <a href="#top"><img src="/assets/install/linux.svg" alt=""> Linux</a>
</div>

Link Item

News

Main link

Main Link (aux link)

Lorem ipsum dolor sit amet.

Link without highlight

Code

<div class="link-items">
  <h3>News</h3>

  <div class="link-item">
    <a class="link-item__main" href="#top">
      {%- include icons/newsletter.svg %}
      Main link
    </a>
  </div>

  <div class="link-item">
    <a class="link-item__main" href="#top">
      {%- include icons/rss.svg %}
      Main Link
    </a> (<a href="#top">aux link</a>)
    <p>Lorem ipsum dolor sit amet.</p>
  </div>

  <div class="link-item">
    <a href="#top">
      {%- include icons/announce.svg %}
      Link without highlight
    </a>
  </div>
</div>

Partner Images

Code

{% include components/partner-images.html images=page.partner_images2 %}

{% include components/partner-images.html images=page.partner_images3 %}

Post Card

84codes LavinMQ: Understanding code to get the best performance

Bright Security Crystal: the lingua franca at Bright

PlaceOS Automating smart buildings with Crystal

Code

{% include components/posts-list.html posts=site.categories.success limit=3 %}

Post Teaser

Include partial: _includes/posts/meta.html

13 Aug 2021

Johannes Müller Beta Ziliani

Installing specific versions of Crystal's binary packages

Lorem ipsum dolor sit amet consectatur elit.

Code

<div class="post-teaser"><time class="post-date" pubdate datetime="2021-08-13"
  >13 Aug 2021</time
>

<ul class="avatar-list" aria-hidden="true">
  <li>
    <a title="Johannes Müller">
      <img
        src="/assets/authors/straight-shoota.jpg"
        alt=""
      />
    </a>
  </li>
  <li>
    <a title="Beta Ziliani">
      <img
        src="/assets/authors/beta-ziliani.jpg"
        alt=""
      />
    </a>
  </li>
</ul>
<div class="author-names">
  <span class="author-name" title="straight-shoota">Johannes Müller</span>
  <span class="author-name" title="beta-ziliani">Beta Ziliani</span>
</div>

<div class="taxonomy">
</div>


  <a href="/2021/08/13/install-specific-versions/" class="post-title">Installing specific versions of Crystal's binary packages</a>
  <div class="excerpt">Lorem ipsum dolor sit amet consectatur elit.
</div>
</div>

Include partial: _includes/components/profile-card.html

Code

<div class="profile-card" itemscope itemtype="https://schema.org/Person">
  <strong class="name" itemprop="name">Beta Ziliani</strong>
  <span class="handle">@beta-ziliani</span>
  <img src="/assets/authors/beta-ziliani.jpg" itemprop="image" alt="Photo of Beta Ziliani" alt="Profile picture of " />

  <div class="roles">
    <span class="role" itemprop="jobTitle">Team lead, Steering Council</span>
    <span class="affiliation" itemprop="affiliation">Manas.Tech</span>
  </div>

  <div class="profiles">
    <a href="https://github.com/beta-ziliani" itemprop="url" title="beta-ziliani on GitHub" class="icon" aria-label="GitHub profile"><svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24.13 23.03">
  <path fill="currentColor" d="M12.11 0C5.61-.19.21 4.91 0 11.41c-.2 5.3 3.2 10 8.3 11.6.3.1.7-.1.8-.4v-2.2c-3.3.7-4-1.6-4-1.6-.2-.7-.7-1.3-1.3-1.7-1.1-.7.1-.7.1-.7.8.1 1.4.6 1.8 1.2.7 1.2 2.2 1.6 3.4 1 .1-.6.3-1.2.8-1.6-2.7-.3-5.5-1.3-5.5-5.8 0-1.2.4-2.3 1.2-3.2-.4-1-.3-2.1.1-3.1 0 0 1-.3 3.3 1.2 2-.5 4-.5 6 0 2.3-1.5 3.3-1.2 3.3-1.2.4 1 .5 2.1.1 3.1.8.9 1.2 2 1.2 3.2 0 4.5-2.8 5.5-5.5 5.8.6.6.9 1.4.8 2.2v3.2c0 .3.3.6.6.6h.3c6.2-1.9 9.7-8.5 7.8-14.7-1.49-5.1-6.19-8.5-11.49-8.31Z"/>
</svg>

    </a>
    <a href="https://forum.crystal-lang.org/u/beta-ziliani" itemprop="url" title="beta-ziliani on the Crystal Forum" class="icon" aria-label="Crystal Forum profile"><svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 40 39.95">
  <path d="M0 30V2.1c0-.47.22-.93.65-1.4S1.53 0 2 0h25.95c.5 0 .97.22 1.4.68.43.45.65.92.65 1.42v17.8c0 .47-.22.93-.65 1.4s-.9.7-1.4.7H8l-8 8Zm10.05 2c-.47 0-.93-.23-1.38-.7-.45-.47-.68-.93-.68-1.4V25h25V8h5c.47 0 .92.23 1.35.7.43.47.65.95.65 1.45v29.8L32.04 32H10.05Z"/>
</svg>

    </a>
  </div>
</div>

Side Section

Aside 1

BODY 1

Aside 2 (Reversed)

BODY 2

Code

<section class="side-section">
  <h2>Aside 1</h2>
  <aside class="info">
    <p>The Core Team manages the development of Crystal and its ecosystem.</p>
  </aside>

  <div style="background-color: #ddd; min-width: 35ch;">
    BODY 1
  </div>
</section>

<section class="side-section reversed">
  <h2>Aside 2 (Reversed)</h2>
  <div style="background-color: #ddd; min-width: 35ch;">
    BODY 2
  </div>
  <aside class="info">
    <p>The Core Team manages the development of Crystal and its ecosystem.</p>
  </aside>
</section>

Testimonial Profile

Include partial: _includes/components/testimonial-profile.html

Peter Schols, CEO, Diploid

Isaac Sloan, CIO & Software Architect, Nikola Motor Company

I love working with Crystal. It has a lot of the happiness value that Ruby had at the beginning, and the community is doing really amazing things.

Code

<div class="testimonial-profile">
  <img src="/assets/authors/peterschols.jpg" alt="Photo of Peter Schols">
  <p>Peter Schols, CEO, Diploid</p>
</div>


<div class="testimonial-profile">
  <img src="/assets/authors/elorest.jpg" alt="Photo of Isaac Sloan">
  <p>Isaac Sloan, CIO & Software Architect, Nikola Motor Company</p>
</div>


> I love working with Crystal. It has a lot of the happiness value that Ruby had at the beginning, and the community is doing really amazing things.

Topics

Sponsorship

Become a Crystal sponsor in only 3 simple steps via OpenCollective

Contribute

Enterprise support

Sponsoring Crystal creates a great springboard for your brand

Get Support

Hire us for your project

You can tap into the expertise of the very creators of the language to guide you in your implementation.

Hire Us

Code

{% include components/sponsorship.html %}

Hex Icon

Include partial: _includes/elements/hex-icon.html

Code

<div class="hex-icon">
  <div class="inner"><svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 -960 960 960">
  <path d="M160-160q-33 0-56.5-23.5T80-240v-480q0-33 23.5-56.5T160-800h240l80 80h320q33 0 56.5 23.5T880-640v400q0 33-23.5 56.5T800-160H160Zm0-80h640v-400H447l-80-80H160v480Zm0 0v-480 480Z" />
</svg>

  </div>
</div>

Hex Button

Get Crystal Now!!!

Code

<a href="/" class="hex">Get Crystal Now!!!</a>

<a href="/" class="hex bordered">Get Crystal Now!!!</a>

Basics

Crystal’s syntax is heavily inspired by Ruby’s.

So it feels natural to read and easy to write, and has the added benefit of a lower learning curve for experienced Ruby devs: cat [crystal](https://) > /dev/brain.

The slick syntax makes it easy to read for humans, but it’s also fast on machines.

On the Crystal Forum you can meet humans interested in Crystal.

Press Ctr+C to end the process.

Code

**Crystal’s** syntax is *heavily* inspired by [Ruby’s](https://ruby-lang.org/).

So it feels natural to read and ***easy*** to write, and has the added benefit of
a lower learning curve for experienced Ruby devs: `cat [crystal](https://) > /dev/brain`.

The **slick** syntax makes it easy to `read` for humans, but it's also [**fast** on machines](/).

On [the *Crystal Forum* you can meet `humans` interested in Crystal](https://forum.crystal-lang.org).

Press <kbd>Ctr+C</kbd> to end the process.

Blockquotes

Thank you! Crystal is awesome!

I am always happy to read the release notes. Awesome work, guys!

We are delivering a new release with several bugfixes and improvements. Below we list the most important or interesting changes, without mentioning several bugfixes and smaller enhancements. For more details, visit the changelog.

Breaking changes are marked with ⚠️.

Point 1

Point 2

Multi assign = heaven.

Code

> Thank you! [Crystal](https://crystal-lang.org) is awesome!

> I am always happy to read the release notes. Awesome work, guys!

> We are delivering a new release with several bugfixes and improvements. Below we list the most important or interesting changes, without mentioning several bugfixes and smaller enhancements. For more details, visit the [changelog](https://github.com/crystal-lang/crystal/releases/tag/1.3.0).
>
> Breaking changes are marked with ⚠️.
>
> * Point 1
> * Point 2

> `Multi assign = heaven`.

Callout: Generic (with title)

Important notice

To use this new release you will need to build shards from sources or use a nightly Crystal release until 1.0.0-pre1 is tagged.

Code

> **NOTE:** Important notice
> To use this new release you will need to build shards from sources or use a nightly Crystal release until 1.0.0-pre1 is tagged.

Callout: Generic

Note

Generic callout use this new release you will need to build shards from nightly Crystal release until 1.0.0-pre1 is tagged.

With nested blockquote. Ye’a!

NOTE: Attention No nested callout.

Code

> **NOTE:**
> Generic callout use this new release you will need to build shards from
> nightly Crystal release until 1.0.0-pre1 is tagged.
>
> > With nested blockquote. Ye’a!
>
> ---
>
> > **NOTE:** Attention
> > No nested callout.

Callout: Types

Note

Lorem ipsum dolor sit amet, consectetur adipiscing elit. Nulla et euismod nulla. Curabitur feugiat, tortor non consequat finibus, justo purus auctor massa, nec semper lorem quam in massa.

Warning

Lorem ipsum dolor sit amet, consectetur adipiscing elit. Nulla et euismod nulla. Curabitur feugiat, tortor non consequat finibus, justo purus auctor massa, nec semper lorem quam in massa.

Info

Lorem ipsum dolor sit amet, consectetur adipiscing elit. Nulla et euismod nulla. Curabitur feugiat, tortor non consequat finibus, justo purus auctor massa, nec semper lorem quam in massa.

Code

> **NOTE:**
> Lorem ipsum dolor sit amet, consectetur adipiscing elit. Nulla et euismod nulla.
> Curabitur feugiat, tortor non consequat finibus, justo purus auctor massa,
> nec semper lorem quam in massa.

> **WARNING:**
> Lorem ipsum dolor sit amet, consectetur adipiscing elit. Nulla et euismod nulla.
> Curabitur feugiat, tortor non consequat finibus, justo purus auctor massa,
> nec semper lorem quam in massa.

> **INFO:**
> Lorem ipsum dolor sit amet, consectetur adipiscing elit. Nulla et euismod nulla.
> Curabitur feugiat, tortor non consequat finibus, justo purus auctor massa,
> nec semper lorem quam in massa.

Code Block

# A very basic HTTP server
require "http/server"

server = HTTP::Server.new do |context|
  context.response.content_type = "text/plain"
  context.response.print "Hello world, got #{context.request.path}!"
end

puts "Listening on http://127.0.0.1:8080"
server.listen(8080)

name: my-project
version: 0.1
license: MIT

crystal: 1.3.0

dependencies:
  mysql:
    github: crystal-lang/crystal-mysql

All types are non-nilable in Crystal, and nilable variables are represented as a union between the type and nil.

if rand(2) > 0
  my_string = "hello world"
end

puts my_string.upcase

$ crystal build hello-world.cr
$ ./hello-world
Hello World!

class Object
  def has_instance_var?(name) : Bool{{ @type.instance_vars.map &.name.stringify }}.includes? name
  end
end

class Person
  property name : String

  def initialize(@name)
  end
end

person = Person.new "John"
p! person.has_instance_var?("name") # => true
p! person.has_instance_var?("birthday") # => false

Code

```crystal
# A very basic HTTP server
require "http/server"

server = HTTP::Server.new do |context|
  context.response.content_type = "text/plain"
  context.response.print "Hello world, got #{context.request.path}!"
end

puts "Listening on http://127.0.0.1:8080"
server.listen(8080)
```

```yaml
name: my-project
version: 0.1
license: MIT

crystal: 1.3.0

dependencies:
  mysql:
    github: crystal-lang/crystal-mysql
```

All types are non-nilable in Crystal, and nilable variables are represented as a union between the type and nil.

```
if rand(2) > 0
  my_string = "hello world"
end

puts my_string.upcase
```

```terminal
$ crystal build hello-world.cr
$ ./hello-world
Hello World!
```

```crystal
class Object
  def has_instance_var?(name) : Bool
    {{- "{{" }} @type.instance_vars.map &.name.stringify }}.includes? name
  end
end

class Person
  property name : String

  def initialize(@name)
  end
end

person = Person.new "John"
p! person.has_instance_var?("name") # => true
p! person.has_instance_var?("birthday") # => false
```

Figure

  tmp = some_exp1
  if tmp
    tmp
  else
    some_exp2
  end

Crystal code

Code

<figure markdown="1">

  ```crystal
  tmp = some_exp1
  if tmp
    tmp
  else
    some_exp2
  end
  ```

  <figcaption>Crystal code</figcaption>
</figure>

Footnotes

Lorem ipsum dolor sit amet consectetur adipisicing elit.¹ Quod labore suscipit animi² consequatur. Accusantium quibusdam dolorum at a, numquam deserunt.

Lorem ipsum dolor sit amet consectetur, adipisicing elit. Quia quos autem veniam libero!¹ Deleniti nemo quas optio voluptas voluptatibus sint ratione. Id vel error quia ipsam sit saepe hic at amet excepturi ea. Voluptas sunt ratione consequatur optio porro eaque nam quod ex illum modi id animi fugiat vero explicabo illo officiis assumenda nulla rerum, dignissimos sed dicta pariatur quis eum. Beatae ea cumque alias ducimus quos maxime sed, modi illum at repellendus, ex deleniti nesciunt tempore placeat in accusantium!

Lorem ipsum dolor, sit amet consectetur adipisicing elit. Amet voluptas dicta dolor. ↩ ↩²
Voluptas sunt ratione consequatur optio porro eaque nam quod ex illum modi. ↩

Code

Lorem ipsum dolor sit amet consectetur adipisicing elit.[^foo] Quod labore suscipit animi[^bar] consequatur. Accusantium quibusdam dolorum at a, numquam deserunt.

Lorem ipsum dolor sit amet consectetur, adipisicing elit. Quia quos autem veniam libero![^foo] Deleniti nemo quas optio voluptas voluptatibus sint ratione. Id vel error quia ipsam sit saepe hic at amet excepturi ea. Voluptas sunt ratione consequatur optio porro eaque nam quod ex illum modi id animi fugiat vero explicabo illo officiis assumenda nulla rerum, dignissimos sed dicta pariatur quis eum. Beatae ea cumque alias ducimus quos maxime sed, modi illum at repellendus, ex deleniti nesciunt tempore placeat in accusantium!

[^foo]: Lorem ipsum dolor, sit amet consectetur adipisicing elit. Amet voluptas dicta dolor.
[^bar]: Voluptas sunt ratione consequatur optio [porro eaque](#top) nam quod ex illum modi.

Headlines

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