Ruby 4.0 Box

rubybox.rb

# frozen_string_literal: true

X = 1

class Rubybox
  def self.x = X
  def x = ::X
end

# Usage:
#
# irb
# > box = Ruby::Box.new
# (irb):1:in 'Ruby::Box#initialize': Ruby Box is disabled. Set RUBY_BOX=1 environment variable to use Ruby::Box. (RuntimeError)
# > Ruby::Box.enabled?
# => false
#
# RUBY_BOX=1 irb
# /Users/dskecse/.rubies/ruby-4.0.0/bin/ruby: warning: Ruby::Box is experimental, and the behavior may change in the future!
# See https://docs.ruby-lang.org/en/4.0/Ruby/Box.html for known issues, etc.
# > box = Ruby::Box.new
# => #<Ruby::Box:3,user,optional>
# > box.require_relative("rubybox")
# => true
# > X = 2
# => 2
# > p X
# 2
# => 2
# > p ::X
# 2
# => 2
# > p box::Rubybox.x
# 1
# => 1
# > p box::Rubybox.new.x
# 1
# => 1
# > p box::X
# 1
# => 1
#
# > Ruby::Box.main
# => #<Ruby::Box:2,user,main>
# > Ruby::Box.root
# => #<Ruby::Box:1,root>
# > Ruby::Box.current
# => #<Ruby::Box:1,root>

https://docs.ruby-lang.org/en/master/Ruby/Box.html