Simple threading in Ruby

Output

$ ruby threadit.rb
> 2
> 1
> 0
> 3
> 4
> 5
> 6
  2 <
  0 <
  1 <
  3 <
  4 <
  5 <
  6 <

threadit.rb

def costly(id)
  print("> #{id}\n")
  sleep 0.2
  print("  #{id} <\n")
end

def run
  7.times.map do |id|
    Thread.new { costly(id) }
  end.each(&:join)
end

run()