[ESS] elisp code: show function arguments

[Stephen Eglen]

A.J. Rossini writes:
 > I'm sure that if Sven provides explicit permission (GPL) in the file,
 > and it's legit, we can.
...
 > Not sure where the rest of ESS core is right now, though I've noticed
 > a bit of silence from them.  However, it's great to see some new
 > names, etc, hacking on ESS.


Dear Tony, and all,
I've just got back from a conference, apologies for delay.  This idea
of Sven's is great.  Emacs has a facility called "eldoc" to do this
functionality for elisp, with hooks for other code.  It might be worth
seeing how to make ESS available to eldoc, so that we make efficient
use of resources.

Best wishes, Stephen
eldoc.el commentary:

;;; Commentary:

;; This program was inspired by the behavior of the "mouse documentation
;; window" on many Lisp Machine systems; as you type a function's symbol
;; name as part of a sexp, it will print the argument list for that
;; function.  Behavior is not identical; for example, you need not actually
;; type the function name, you need only move point around in a sexp that
;; calls it.  Also, if point is over a documented variable, it will print
;; the one-line documentation for that variable instead, to remind you of
;; that variable's meaning.

;; One useful way to enable this minor mode is to put the following in your
;; .emacs:
;;
;;      (add-hook 'emacs-lisp-mode-hook 'turn-on-eldoc-mode)
;;      (add-hook 'lisp-interaction-mode-hook 'turn-on-eldoc-mode)
;;      (add-hook 'ielm-mode-hook 'turn-on-eldoc-mode)

;; Major modes for other languages may use Eldoc by defining an
;; appropriate function as the buffer-local value of
;; `eldoc-documentation-function'.