# File lib/highline.rb, line 183
  def agree( yes_or_no_question, character = nil )
    ask(yes_or_no_question, lambda { |yn| yn.downcase[0] == ?y}) do |q|
      q.validate                 = /\Ay(?:es)?|no?\Z/i
      q.responses[:not_valid]    = 'Please enter "yes" or "no".'
      q.responses[:ask_on_error] = :question
      q.character                = character
      
      yield q if block_given?
    end
  end