functions which return all the files or all of the directories contained within a Pathname

pathname_collections.rb

def collect_files(pn)
  if pn.file?
    return pn
  end
  pn.children.collect {|cn| collect_files(cn)}.flatten
end

def collect_directories(pn)
  if pn.directory?
    pn.children.collect {|cn| collect_directories(cn)}.flatten.reject{|i| i.nil?}.push(pn)
  end
end