A preliminary set of file and directory facilities are provided.
| file-mtime | (filename|<str> => <flo>) | M | 
|  | return the last modification time of a file in seconds (relative to the
n       GOOepoch) as a floating point number. |  | 
| file-exists? | (filename|<str> => <log>) | M | 
|  | return true if and only if a file (or a directory, etc.) exists with
       the given name. |  | 
| file-type | (filename|<str> => <sym>) | M | 
|  | return 'file, 'directory or some other symbol, 
       depending on the type of the file. |  | 
| create-directory | (filename|<str> => <sym>) | M | 
|  | create a directory with the given name.  The parent directory must
       already exist, and must contain no item with the given name. |  | 
| parent-directory | (name|<str> => <str>) | M | 
|  | find the parent directory of the current filename. |  | 
| probe-directory | (name|<str> => <str>) | M | 
|  | make sure that the named directory exists. |  | 
|  |