[ESS] Use of up arrow and down arrow keys

[Martin Maechler]

>>>>> "StEgl" == Stephen Eglen <S.J.Eglen at damtp.cam.ac.uk>
>>>>>     on Fri, 8 Jul 2005 10:35:52 +0100 writes:

    StEgl> John Maindonald writes:
    >> [I forgot to say that I am using ess-5.2.8]
    >> 
    >> I've just now moved to using Aquaemacs (Mac OS X), from
    >> 
    >> http://aquamacs.org/
    >> 
    >> I've had code in my .emacs file that binds the up arrow
    >> key to <ESC>P, etc.  This does not work with Aquaemacs; I
    >> get the message: "Symbol's value as variable is void:
    >> xemacs-flag" Is there some way to make the up and down
    >> arrow (cursor) keys work, with my setup?
    >> 
    StEgl> Should be possible, but there's a bug somewhere that
    StEgl> we'll need your help tracking down.  Do as the info
    StEgl> pages for ESS suggest:

    StEgl> ---- If Emacs reports an error, backtraces can help
    StEgl> us debug the problem.  Type "M-x set-variable RET
    StEgl> debug-on-error RET t RET".  Then run the command that
    StEgl> causes the error and you should see a *Backtrace*
    StEgl> buffer containing debug information; send us that
    StEgl> buffer.  ----

(maybe the above is not necessary)

    StEgl> Also, does the text "xemacs-flag" occur in your
    StEgl> .emacs?

I think that's the crucial question :

John: You need to define  xemacs-flag somewhere, since your
functions rely on it .

BTW, a more usual name for such a variable is  
'xemacsp' (defined in GNU emacs) or 
'xemacs-p'  as defined here locally :

(defconst xemacs-p
  (not (null (save-match-data (string-match "XEmacs\\|Lucid" emacs-version)))))

the "p" meaning ``property'' is a convention in lisp-programming
for such logical variables.

Martin