function 
    /usr/local/lib/janet/spork/sh.janet  on  line  88 , column  1 
    (scan-directory  dir  func )
    Scan  a  directory  recursively , applying  the  given  function  on  all  
    files  and  directories  in  a  depth-first  manner.  This  function  has  no  
    effect  if  the  directory  does  not  exist.