jr@bbn.com (John Robinson) (12/21/88)
Here's an interactive greeting card. Eval the following and then M-X
surprise. May offend some non-Christians...
I picked this up originally in mocklisp, from I forget where.
;;; GNU Emacs code converted from Mocklisp
(defun show ()
(save-excursion
(goto-char (dot-min))
(sit-for 0)
))
(defun replace (from to)
(save-excursion
(while (search-forward from nil t)
(replace-match to))))
(defun re-replace (from to)
(save-excursion
(while (re-search-forward from nil t)
(replace-match to))))
(defun surprise (limit)
"Towers of Hanoi greeting"
(interactive "nValue (I suggest 3, 4 or 5): ")
(let ((i 1))
(pop-to-buffer "Surprise")
(erase-buffer)
(insert-string " . . . \n =|= | | \n")
(while (< i limit)
(goto-char (dot-max))
(forward-line -1)
(set-mark (dot-max))
(insert-string (buffer-substring (point) (mark)))
(goto-char (dot-min))
(replace " . " " . ")
(goto-char (dot-min))
(replace " =" " =")
(goto-char (dot-min))
(replace "= " "= ")
(goto-char (dot-min))
(replace " | " " | ")
(goto-char (dot-max))
(forward-line -1)
(replace " =" "==")
(replace "= " "==")
(setq i (1+ i)))
(goto-char (dot-min))
(replace "." " ")
(goto-char (dot-min))
(sit-for 2)
(do-it limit 1 2 3)
(goto-char (dot-min))
(search-forward "=|")
(previous-line 1)
(backward-char)
(insert-string "*")
(forward-line 1)
(set-mark (dot-min))
(let ((str (buffer-substring (point) (mark))))
(goto-char (dot-max))
(insert-string str))
(previous-line 1)
(save-excursion (delete-char 1) (replace "*" "y X") (sit-for 0))
(save-excursion (delete-char 1) (re-replace "y.X" "p\\&m") (sit-for 0))
(save-excursion (delete-char 1) (re-replace "p.*m" "p\\&a") (sit-for 0))
(save-excursion (delete-char 1) (re-replace "p.*a" "a\\&s") (sit-for 0))
(save-excursion (delete-char 1) (re-replace "a.*s" "H\\&!") (sit-for 0))
(goto-char (dot-min))
(search-forward "*")
(backward-char)))
(defun raise ()
(while (looking-at "=*|")
(let ((i 1))
(while (<= i 2)
(setq i (1+ i))
(while (looking-at "=")
(delete-char 1)
(insert-string " ")
(backward-char)
(previous-line 1)
(delete-char 1)
(insert-string "=")
(next-line 1))
(forward-char))
(previous-line 1)
(search-backward " =")
(forward-char)
(show))))
(defun lower ()
(next-line 1)
(while (not (or (looking-at "=") (eobp)))
(previous-line 1)
(let ((i 1))
(while (<= i 2)
(setq i (+ i 1))
(while (looking-at "=")
(delete-char 1)
(insert-string " ")
(backward-char)
(next-line 1)
(delete-char 1)
(insert-string "=")
(previous-line 1))
(forward-char))
(next-line 1)
(search-backward " =")
(forward-char)
(show)
(next-line 1))))
(defun jiggle (from to)
"Move a single ring for Hanoi program."
(interactive "nFrom: \nnTo: ")
(let ((replacement (if (< from to) " \\1" "\\1 ")))
(goto-char (dot-min))
(search-forward "|" nil nil from)
(backward-char 2)
(while (not (looking-at "="))
(next-line 1))
(search-backward " ")
(forward-char)
(raise)
(goto-char (dot-min))
(search-forward "|" nil nil to)
(backward-char)
(previous-line 1)
(while (not (looking-at "="))
(goto-char (dot-min))
(re-replace " \\(==* ==*\\) " replacement)
(show)
(search-forward "|" nil nil to)
(backward-char)
(previous-line 1))
(while (not (looking-at " "))
(goto-char (dot-min))
(re-replace " \\(==* ==*\\) " replacement)
(show)
(search-forward "|" nil nil to)
(backward-char)
(previous-line 1))
(search-backward " =")
(forward-char)
(lower)))
(defun do-it (level from to work)
(if (> level 0)
(progn
(do-it (- level 1) from work to)
(jiggle from to)
(do-it (- level 1) work to from)
)))
/jr
jr@bbn.com or bbn!jreichin@ATHENA.MIT.EDU ("Mark W. Eichin") (12/21/88)
>> From: John Robinson <jr@bbn.com> >> Subject: surprise >> Message-Id: <33736@bbn.COM> >> Organization: BBN Systems and Technologies Corporation, Cambridge MA >> Source-Info: From (or Sender) name not authenticated. >> Here's an interactive greeting card. Eval the following and then M-X >> surprise. May offend some non-Christians... Amusing... I haven't run it yet, of course, though I have glanced over it. Commemorating the second (third?) anniversary of CHRISTMA.EXEC, are we? [I do NOT mean to malign John Robinson, or imply that he would even THINK about propagating viral elisp code. However, the historical similarity was too amusing to be passed up...] Mark Eichin <eichin@athena.mit.edu> SIPB Member & Project Athena ``Watchmaker'' [And part-time Internet Virologist :-]
jr@bbn.com (John Robinson) (12/22/88)
In article <33614@bbn.COM>, dsill@RELAY-NSWC (Dave Sill) writes: >Current discussion on wizards brought up the subject of GNU Emacs' >local variables. Are you aware that arbitrary Lisp code can be >embedded in a file in such a manner that it is automatically executed >when the file is read in? Not only that, but there's a variable, >inhibit-local-variables, that, if non-nil, requires confirmation >before executing the commands BUT IT'S DEFAULT IS NIL? > >I can understand how such a capability could be quite handy, but >there's no excuse for it to be enabled by default. The posting >describing the problem on wizards even included an example that ran >kill-emacs. It boggles the mind to think what could be done with >this. It wouldn't take much of a lisper to write a viral mail message >or news posting. > >In fact, you may be reading such a message right now. > >Ha ha. > >========= In article <8812202329.AA10348@OLIVER.MIT.EDU>, eichin@ATHENA ("Mark W. Eichin") writes: >>> From: John Robinson <jr@bbn.com> >>> Here's an interactive greeting card. Eval the following and then M-X >>> surprise. May offend some non-Christians... > >Amusing... I haven't run it yet, of course, though I have glanced over >it. Commemorating the second (third?) anniversary of CHRISTMA.EXEC, >are we? > >[I do NOT mean to malign John Robinson, or imply that he would even >THINK about propagating viral elisp code. However, the historical >similarity was too amusing to be passed up...] > > Mark Eichin > <eichin@athena.mit.edu> > SIPB Member & Project Athena ``Watchmaker'' > [And part-time Internet Virologist :-] The point here, for those who may have missed it, it that when anyone sends you something and says "here, run this on your computer", bells and warning lights should go off in your head. CHRISTMA.EXEC refers to one such prank a few years back where a supposed Christmas greeting would do all sorts of damage to your account (if I remember correctly, this was the BTINET "virus" (actually worm) that is fairly widely docuemnted; Mark or soemone correct this if I have lied). The point about auto-execute code in a file that emacs reads is well-taken, and I agree that the default setting of the variable ought to be t. If you don't understand what this all means, you DEFINITELY should set it in your .emacs: (setq inhibit-local-variables t) And when you get the warning: Set local variables as specified at end of <file>? reply no. Once you understand the mechanism and see its advantages, you may want to be a little more willing to use it, though I am not sure you'd ever want to change inhibit-local-variables. One very important point that ought to be brought out in this forum is that distributing source is a powerful tool in deciding whether a program conceals a trojan horse. Sure, the code can be pretty opaque in source form, but it gives you the opportunity to look it over before you submit it to your compiler. I think this is a rather powerful argument for a part of the GNU manifesto - that all programs should be distributed with full source. The extra cautious should always recompile from scratch (and read over the code). Another point (now that I have your attention) is that an awful lot of what has been glued onto "computer virus attacks by hackers" stories in the news is actually malicious destruction of company data by disgruntled or deranged insiders, (ex-)employees etc. In fact, a not insignificant amount of this sort of attack has been perpetrated by so-called "security experts". Don't rely on the experts! Learn to read source and insist on it. Yikes, that got a little heavy. Happy New Year everyone. Now I feel better. -- /jr jr@bbn.com or bbn!jr