module RDoc::RI::Paths

def self.each system, site, home, gems, *extra_dirs # :yields: directory, type
  extra_dirs.each do |dir|
    yield dir, :extra
  end
  yield SYSDIR,  :system if system
  yield SITEDIR, :site   if site
  yield HOMEDIR, :home   if home
  gemdirs.each do |dir|
    yield dir, :gem
  end if gems
  nil
end