module Regexp::Parser

def self.free_space(token)
  case token.token
  when :comment
    @node << Comment.new(token)
  when :whitespace
    if @node.last and @node.last.is_a?(WhiteSpace)
      @node.last.merge(WhiteSpace.new(token))
    else
      @node << WhiteSpace.new(token)
    end
  else
    raise UnknownTokenError.new('FreeSpace', token)
  end
end