CodeMirror

# Features of Crystal

# - Ruby-inspired syntax.

# - Statically type-checked but without having to specify the type of variables or method arguments.

# - Be able to call C code by writing bindings to it in Crystal.

# - Have compile-time evaluation and generation of code, to avoid boilerplate code.

# - Compile to efficient native code.

​

# A very basic HTTP server

require "http/server"

​

server = HTTP::Server.new(8080) do |request|

  HTTP::Response.ok "text/plain", "Hello world, got #{request.path}!"

end

​

puts "Listening on http://0.0.0.0:8080"

server.listen

​

module Foo

  def initialize(@foo); end

​

  abstract def abstract_method : String

​

  @[AlwaysInline]

  def with_foofoo

    with Foo.new(self) yield

  end

​

  struct Foo

    def initialize(@foo); end

​

    def hello_world

      @foo.abstract_method

    end

  end

end

​

class Bar

  include Foo

​

  @@foobar = 12345

​

  def initialize(@bar)

    super(@bar.not_nil! + 100)

  end

​

  macro alias_method(name, method)

    def {{ name }}(*args)

      {{ method }}(*args)

    end

  end

​

  def a_method

    "Hello, World"

  end

​

  alias_method abstract_method, a_method

​

  macro def show_instance_vars : Nil

    {% for var in @type.instance_vars %}

      puts "@{{ var }} = #{ @{{ var }} }"

    {% end %}

    nil

  end

end

​

class Baz < Bar; end

​

lib LibC

  fun c_puts = "puts"(str : Char*) : Int

end

​

$baz = Baz.new(100)

$baz.show_instance_vars

$baz.with_foofoo do

  LibC.c_puts hello_world

end

​