The structure dir-streams defines procedures to represent and process
directories as streams of files and sub-directories.

(dir-stream-from-dir-name dir-name [chase?] [parent]) -> dir-stream

Constructor for dir-streams.


(dir-stream? thing) -> boolean

Type predicate for dir-streams.


(dir-stream-info dir-stream) -> fs-object

Returns the fs-object corresponding to the directory.


(fs-object? thing) -> boolean

Type predicate for file-objects.


(fs-object-parent fs-object) -> string

The parent directory of the fs-object.



(fs-object-name fs-object) -> string

The file name of the fs-object.



(fs-object-info fs-object) -> file-info

The file-info record of the fs-object.



(fs-object-file-name fs-object) -> string

The path to the fs-object.



(dir-stream-files-stream dir-steam) -> fs-object stream

A stream of the fs-objects of the files within the directory.



(dir-stream-subdir-stream dir-stream) -> dir-stream stream 

A stream of dir-streams of the subdirectories within the directory.


(dir-stream-filter dir-stream file-pred dir-pred) -> dir-stream

Applies the predicate DIR-PRED to all the subdirectories and FILE-PRED
to all the files within directory. The returned stream contains only
the files and subdirectories for which the predicates return #t.


(dir-stream-fold-right ds make-dir-stream
		       files-make-stream files-stream-empty 
		       subdirs-make-stream subdirs-empty) -> return type of make-dir-stream

Replaces the constructors of the dir-stream by the supplied procedures.
Example:
(define (disc-usage ds)
  (dir-stream-fold-right ds (lambda (fso sum subdirs) (list (fs-object-filename fso)
							    (apply + sum (map cadr subdirs))
							    subdirs))
			 (lambda (fso accu)
			   (+ accu (file-info:size (fs-object-info fso))))
			 0
			 cons
			 '()))


(dir-stream-map dir-stream-map-f dir-stream file-f dir-f)

TODO argument order

(dir-stream-filter-map dir-stream-map-f dir-stream file-f dir-f)


(dir-stream-for-each dir-stream file-f dir-f)