Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!know!sdd.hp.com!hp-pcd!hpcvra.cv.hp.com!rnews!hpcvbbs!akcs.joehorn
From: akcs.joehorn@hpcvbbs.UUCP (Joseph K. Horn)
Newsgroups: comp.sys.handhelds
Subject: Re: Jekyll and Hyde
Message-ID: <274ae35f:1200.1comp.sys.handhelds;1@hpcvbbs.UUCP>
Date: 21 Nov 90 20:40:11 GMT
References: <1990Nov20.104639@ee.ubc.ca>
Lines: 27

John Paul Morrison writes:

> The library posted by HP was pretty cute, but no one has yet
> mentioned an obvious use for it, once someone disassembles it:
>
> The library posted hooks into the error handling. This provides
> a very nifty way of implementing an error handler, without an
> RPL program ever knowing that errors even ocurred.
>
> The built in IFERR structure is too  complicated: you wouldn't
> want to put IFERRs around every single operation. 

John, I doubt it.  Notice that HYDE does not only change error
messages, but ALL messages!  (Example: press I/O SETUP and look at
that bizarre I/O setup menu!)  "Strange Case 998" is not a error
handler, but a message translator.  A "nifty" and practical use
for this ability is the reason it's supported: foreign translation
libraries that turn the HP 48 into a French calculator, or any
language you please.

Of course, foreign versions of ROM cards are just as easily
implemented.

Notice that the 48 manuals do not mention all the messages; for
example, message #7 is normally "Warning:" but HYDE translates it
to "Hey you:".

--  Joseph K. Horn  --  (714) 858-0920  --  Peripheral Vision, Ltd.