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From: edp@jareth.enet.dec.com (Eric Postpischil (Always mount a scratch monkey.))
Newsgroups: comp.sys.handhelds
Subject: HP-28 to HP-48 changes
Message-ID: <20898@shlump.nac.dec.com>
Date: 8 Mar 91 14:13:54 GMT
Sender: newsdaemon@shlump.nac.dec.com
Reply-To: edp@jareth.enet.dec.com (Eric Postpischil (Always mount a scratch monkey.))
Organization: Digital Equipment Corporation
Lines: 36

I'm curious about the changes from the 28 that HP made in the 48.  Some
of these are obvious, like the change in the integration parameters
(needed to handle symbolic integration) and the ability to recall
directories.  But some are a bit more subtle.

On the 28, doing something (like plotting) that caused PPAR to be
created caused the 28 to scan the equation and select the first variable
as the independent variable.  On the 48, X is always assumed.  Why did
HP make this change?  One guess is that algebraics can now contain local
variables (because of the "where" and integration operators), so the
first variable seen is not necessarily a free variable of the
expression.  Is this why they made the change?

Another change is that storage arithmetic has been generalized.  It used
to be that STO+ would accept only certain objects to be added (real and
complex numbers, I think).  Now any objects acceptable to + are
acceptable to STO+, and similarly for the other STO operators.  Okay,
that change provides more function, as do the evaluation of lists and 0
WAIT.

Two items that fit into the category of trying to improve behavior are
that STO checks for directly recursive definition (putting 'var' in
'var') and plotting 'variable=expression' plots only the expression
(unless flag setting is changed).

ABORT is gone.  0 DOERR is not the same thing -- why was this function deleted?

== and != now properly compare reals and algebraics.  On the 28, (0,0)
did not equal 0, according to ==, but on the 48 they do.

Has anybody noticed other changes?


				-- edp (Eric Postpischil)
				"Always mount a scratch monkey."
				edp@jareth.enet.dec.com