check balanced parentheses in ruby

check_balanced_parentheses.rb

# check balanced parentheses in ruby :
#
# $ ruby check_balanced_parentheses.rb
# Enter string : 
# ((()))
# true

def check_balanced_parentheses?(entered_string)
  stack = []
  entered_string.chars.each do |token|
    case token
      when '('
        stack.push '('
      when ')'
        if stack.empty? || stack.pop != '('
          return false
        end
    end
  end
  stack.empty?
end

puts "Enter string :"
entered_string = gets
puts check_balanced_parentheses?(entered_string)