anchor.diff:  
   (defun mapdir (function pathspec)
     "Applies function to each entry in directory designated by
  -PATHSPEC in turn and returns a list of the results.  Binds
  +PATHSPEC in turn and returns a list of the results. Binds
   *DEFAULT-FILE-PATH-DEFAULTS* to the directory designated by
   pathspec round to function call.
   
  
positive.code: 
  (defun directory-exists-p (pathspec)
    "Checks whether the file named by the file-path designator
  PATHSPEC exists and is a directory.  Returns its truename
  if this is the case, NIL otherwise.  Follows symbolic links."
    (nth-value 0 (file-exists-p pathspec :directory)))
  
  (defun good-symlink-exists-p (pathspec)
  
negative.code:   "Creates hard LINK that points to TARGET.
  Returns the file-path of the link.
  
  Relative targets are resolved against the link. Relative links
  are resolved against *DEFAULT-FILE-PATH-DEFAULTS*.
  
  Signals an error if TARGET does not exist, or LINK exists already."
  