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DPRG: Be Careful Recycling Old Code

Subject: DPRG: Be Careful Recycling Old Code
From: Douglas Kilgore dougkilgore at home.com
Date: Tue Nov 30 17:36:26 CST 1999

Subject:  Careless Code Recycling Causes Killer Kangaroos

     * From June 15, 1999 Defense Science and Technology
 Organization Lecture
     Series, Melbourne, Australia, and staff reports.


     Mutant Marsupials Take Up Arms Against Australian Air Force

     The reuse of some object-oriented code has caused tactical
 headaches for Australia's armed forces. As virtual reality simulators
 assume larger roles in helicopter combat training, programmers have
 gone to great lengths to increase the realism of their scenarios,
 including detailed landscapes and - in the case of the Northern
 Territory's Operation Phoenix - herds of kangaroos (since disturbed
 animals might well give away a helicopter's position).

     The head of the Defense Science & Technology Organization's
 Land Operations/Simulation division reportedly instructed developers to

 model the local marsupials' movements and reactions to helicopters.
 Being efficient programmers, they just re-appropriated some code
 originally used to model infantry detachment reactions under the same
 stimuli, changed the mapped icon from a soldier to a kangaroo, and
 increased the figures' speed of movement.

     Eager to demonstrate their flying skills for some visiting
 American pilots, the hotshot Aussies "buzzed" the virtual kangaroos in
 low flight during a simulation. The kangaroos scattered, as predicted,
 and the visiting Americans nodded appreciatively... then did a
 double-take as the kangaroos reappeared from behind a hill and launched

 a barrage of Stinger missiles at the hapless helicopter. (Apparently
 the programmers had forgotten to remove that part of the infantry
 coding.) The lesson?

     Objects are defined with certain attributes, and any new object
 defined in terms of an old one inherits all the attributes. The
 embarrassed programmers had learned to be careful when reusing
 object-oriented code, and the Yanks left with a newfound respect for
 Australian wildlife.

     Simulator supervisors report that pilots from that point onward
 have strictly avoided kangaroos, just as they were meant to.


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