Support for collapsible text?

[bill <bill_knight2@yahoo.com>]

Is there a programming mode that supports "collapsible" blocks?  For
example, if I have source code like this:

(defun find-file (filename &optional wildcards)
  "Edit file FILENAME.
Switch to a buffer visiting file FILENAME,
creating one if none already exists.
Interactively, or if WILDCARDS is non-nil in a call from Lisp,
expand wildcards (if any) and visit multiple files."
  (interactive "FFind file: \np")
  (let ((value (find-file-noselect filename nil nil wildcards)))
    (if (listp value)
	(mapcar 'switch-to-buffer (nreverse value))
      (switch-to-buffer value))))

(defun find-file-other-window (filename &optional wildcards)
  "Edit file FILENAME, in another window.
May create a new window, or reuse an existing one.
See the function `display-buffer'.
Interactively, or if WILDCARDS is non-nil in a call from Lisp,
expand wildcards (if any) and visit multiple files."
  (interactive "FFind file in other window: \np")
  (let ((value (find-file-noselect filename nil nil wildcards)))
    (if (listp value)
	(progn
	  (setq value (nreverse value))
	  (switch-to-buffer-other-window (car value))
	  (mapcar 'switch-to-buffer (cdr value)))
      (switch-to-buffer-other-window value))))

...it would be nice to be able to collapse some of this text, to
something like:

(defun find-file ... )

(defun find-file-other-window ... )



Partial expansion of collapsed text would also be nice:

(defun find-file-other-window (filename &optional wildcards)
  "Edit file FILENAME, in another window.
May create a new window, or reuse an existing one.
See the function `display-buffer'.
Interactively, or if WILDCARDS is non-nil in a call from Lisp,
expand wildcards (if any) and visit multiple files."
  (interactive ... )
  (let ... ))


Thanks,

bill