rubyのpattern matchの実験

option.rb

class None
  def to_s
    'None'
  end
end

class Some
  def initialize(v)
    @v = v
  end

  def to_s
    "Some(#{@v})"
  end

  def deconstruct
    [@v]
  end
end

def double_opt(o)
  case o
  in None
    o
  in Some(v)
    Some.new(v * 2)
  end
end

puts None.new
puts double_opt(None.new)

puts Some.new(2)
puts double_opt(Some.new(2))