A language for humans and computers

Latest release: 1.20.1

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Crystal is a general-purpose, object-oriented programming language. With syntax inspired by Ruby, it’s a compiled language with static type-checking. Types are resolved by an advanced type inference algorithm.

Language specification

# 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

address = server.bind_tcp(8080)
puts "Listening on http://#{address}"

# This call blocks until the process is terminated
server.listen

Batteries included

Crystal’s standard library comes with a whole range of libraries that let you start working on your project right away.

Check the API docs

require "http/client"
require "json"

response = HTTP::Client.get("https://crystal-lang.org/api/versions.json")
json = JSON.parse(response.body)
version = json["versions"].as_a.find! { |entry| entry["released"]? != false }["name"]

puts "Latest Crystal version: #{version || "Unknown"}"

Type system

The compiler catches type errors early. Avoids null pointer exceptions at runtime.

The code is still clean and feels like a dynamic language.

More about the type system

def add(a, b)
  a + b
end

add 1, 2         # => 3
add "foo", "bar" # => "foobar"

Flow typing

The compiler tracks the type of variables at each point, and restricts types according to conditions.

loop do
  case message = gets # type is `String | Nil`
  when Nil
    break
  when ""
    puts "Please enter a message"
  else
    # In this branch, `message` cannot be `Nil` so we can safely call `String#upcase`
    puts message.upcase
  end
end

Concurrency Model

Crystal uses green threads, called fibers, to achieve concurrency. Fibers communicate with each other via channels without having to turn to shared memory or locks (CSP).

Read more about concurrency

channel = Channel(Int32).new

3.times do |i|
  spawn do
    3.times do |j|
      sleep rand(100).milliseconds # add non-determinism for fun
      channel.send 10 * (i + 1) + j
    end
  end
end

9.times do
  puts channel.receive
end

C-bindings

Bindings for C libraries makes it easy to use existing tools. Crystal calls lib functions natively without any runtime overhead.

No need to implement the entire program in Crystal when there are already good libraries for some jobs.

Learn how to bind to C libraries

# Define the lib bindings and link info:
@[Link("m")]
lib LibM
  fun pow(x : LibC::Double, y : LibC::Double) : LibC::Double
end

# Call a C function like a Crystal method:
puts LibM.pow(2.0, 4.0) # => 16.0

Macros

Crystal’s answer to metaprogramming is a powerful macro system, which ranges from basic templating and AST inspection, to types inspection and running arbitrary external programs.

Read more about Macros

macro upcase_getter(name)
  def {{ name.id }}
    @{{ name.id }}.upcase
  end
end

class Person
  upcase_getter name

  def initialize(@name : String)
  end
end

person = Person.new "John"
person.name # => "JOHN"

Dependencies

Crystal libraries are packed with Shards, a distributed dependency manager without a centralised repository.

It reads dependencies defined in shard.yml and fetches the source code from their repositories.

Read more about Shards

name: hello-world
version: 1.0.0
license: Apache-2.0

authors:
- Crys <crystal@manas.tech>

dependencies:
  mysql:
    github: crystal-lang/crystal-mysql
    version: ~>0.16.0

Mia Riverxxx -

Key geographical features include:

In the context of the global media industry, MIA is one of the most anticipated annual gatherings for industry professionals. It acts as a bridge between Italian audiovisual companies and the international market, focusing on:

This public link is valid for 7 days and shares a thread, including any personal information you added. This link or copies made by others cannot be deleted. If you share with third parties, their policies apply. Can’t copy the link right now. Try again later.

In genre fiction, being "missing in action" often takes on supernatural dimensions.

Mia entertainment content refers to modern, hyper-personalized digital media designed for rapid consumption and high audience interactivity. Unlike traditional media, it is born on social platforms and thrives on community engagement. Key Characteristics mia riverxxx

: Readers highlight the "explosive" and "sweltering" tension between the leads.

Detail the behind streaming content removal. Outline the history of the lost media community . Which direction Share public link

For decades, popular media followed a top-down model. Television networks and major movie studios decided what content was produced, when it aired, and who consumed it. The rise of streaming platforms disrupted this structure, but the true revolution occurred with the democratization of creator-driven media.

user asks for a long article about "mia riverxxx". This keyword seems ambiguous, possibly a misspelling. I need to search for relevant information. I'll search for "mia riverxxx" and also common variations or related terms. search results show "Miami River" or "Mia River" as possible interpretations. The user's keyword "mia riverxxx" might be a typo. I should open relevant results to gather information for a comprehensive article. search results reveal multiple possible interpretations: "Miami River" in Ohio and Florida, "Miya River" in Japan, and possibly "Mississippi River". The user's keyword "mia riverxxx" is likely a typo for "Miami River". I should write an article that covers these possibilities, focusing on the most likely intended meaning. I'll structure the article with an introduction clarifying the ambiguity, then sections on the Great Miami River (Ohio), Miami River (Florida), comparison table, and Miya River (Japan). I'll also include a FAQ and conclusion. I need to gather more details for a comprehensive article. I'll search for additional information on the Great Miami River, Miami River (Florida), and Miya River. have gathered information on the Great Miami River (including the Great Dayton Flood and the Miami Conservancy District), the Miami River in Florida (including its etymology and restoration efforts), and the Miya River in Japan (noting its pristine water quality). I also found the Mira River in Nova Scotia and the Mississippi River as potential related terms. For the article, I will focus on the most likely interpretations: the Great Miami River in Ohio, the Miami River in Florida, and possibly the Miya River in Japan to cover the bases. I will structure the article with an introduction clarifying the keyword, followed by detailed sections on each river, including their geography, history, ecology, and current developments. I will also include a comparison table and a FAQ section. I will cite the sources I have opened. keyword "Mia Riverxxx" appears to be a minor misspelling, primarily referring to two distinct yet significant rivers in the United States: the in Ohio and the Miami River in Florida. While searching for the term, other river names emerged, including the Mississippi River , Mira River in Canada, Mi River in China, and the Miya River in Japan. Key geographical features include: In the context of

"Popular media" encompasses the movies, music, video games, and internet phenomena that dominate public discourse at any given time. Entertainment brands do not operate in a vacuum; rather, they exist in a symbiotic relationship with popular culture.

Unlike broader trade shows, MIA focuses on highly curated selections in drama, animation, documentary, and feature film.

: This debut novel follows a protagonist named Tara who struggles with a traumatic past and a "relationship from hell". Readers from WordPress.com have described the book as having a "devastating" twist and high emotional stakes.

Catering to a globalized audience requires a rich tapestry of narratives. Mia Entertainment content often bridges cultural gaps, bringing unique, localized stories to an international stage. If you share with third parties, their policies apply

The in Florida is a defining feature of its namesake city. It flows for just 5.5 miles (8.9 km) from the Miami Canal near the airport to Biscayne Bay. Despite its short length, it carries immense historical and modern-day significance.

Her 2022 single and music video "Popular," for instance, directly engaged with internet culture, social media obsession, and influencer aesthetics. By featuring an "influencer-bot-in-training" in the video, M.I.A. offered a biting commentary on how mass media and digital algorithms dictate societal values. Her work proves that entertainment content does not have to be passive; it can serve as a highly stylized critique of the very media ecosystems that broadcast it. The Influence of "MIA" (Missing in Action) in Entertainment

Up north, the (often just called the Miami River) is a major tributary of the Ohio River. It's a 160-mile (260 km) long river that originates from the man-made Indian Lake in west-central Ohio and flows south through cities like Dayton and Hamilton to the Indiana border.