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From: edp@jareth.enet.dec.com (Eric Postpischil (Always mount a scratch monkey.))
Newsgroups: comp.sys.handhelds
Subject: Re: Boy, does the 48 have a steep learning curve, or what!
Message-ID: <16561@shlump.nac.dec.com>
Date: 22 Oct 90 14:09:27 GMT
References: <1990Oct18.135213.22920@uunet!unhd>
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: 70

In article <1990Oct18.135213.22920@uunet!unhd>, rg@uunet!unhd (Roger Gonzalez )
writes:

>1)  Going from solver to plot and back to the solver.  There are times that
>I have an equation with several variables, and would like to plot it several
>times with different values in the non-plotted variables.  Is there an easy
>way to do this?

You might write a little program that takes several numbers from the stack and
stores them in your variables.  Then you could call it between plots.  Or you
could write a program that stores one value, plots, stores another value, plots,
and so on.

>2)  Creating equations seems to fill up the VAR menu very quickly.  Is this 
>because I am creating them as global variables?

I'm not sure what you mean by filling up the VAR menu.  NEXT and PREV will let
you step through many pages.  Do you just mean you're collecting a lot of
variables which makes them hard to find?

To organize your directories, you might try putting a set of equations for one
problem in one directory and equations for other problems in other directories. 
Typically, it is useful to keep all the programs and variables in one directory,
although there are exceptions.  One exception is when you have some things that
do not change often (like basic equations) and some things that do change often
(like values).  Then you can put the infrequently-changing things in a parent
directory and keep the changing things in a subdirectory.  That cuts down
clutter in the current directory.  The things in the parent directory don't
appear on the VAR menu.  But you can make them accessible by putting them in a
custom menu.

Another thing to put in parent directories is things that are common to several
subdirectories, such as equations that are common to several different
problems.

>3)  Is the algebraic manipulator actually worth anything?  I haven't
>investigated too closely, but it seems that it would be faster to just do
>it on paper before you input the equation.

Generally, I do not think it is found to be very useful.    It has a few nice
things in it, like the definitions for trigonmetric functions in terms of
exponentials.  And you can use it occasionally to fiddle with a reduction or
adjustment that COLCT won't make.  But otherwise I don't think it gets much
use.

>4)  Flag -19 seems to dictate how complex numbers are represented; in ()
>form or in [] form.  When would I want to use it in [] form? 

Page 167 of the Owner's Manual describes the differences.  "The main advantages
of using complex numbers are that they are allowed as elements of vectors and
matrices and that most real number operations work on them.  The main
disadvantages of using complex numbers are that they are limited to two
dimensions and that vector operations like DOT and CROSS don't apply to them."

>5)  Is there a good way to get a complex number input that contains a
>(for example) square root term as one of the numbers?

You can type in algebraic expressions for the elements of complex numbers.  Type
' to start an algebraic.  For example, ' ( 2 , sqrt 9 ENTER will give you
'2+sqrt(9)*i'.  You can leave it in that form or use ->NUM to get (2,3).  You
could also enter 'real+imaginary*i' yourself.

>6)  Is there a quick and dirty way to factor a polynomial?  Have it spew
>out the real/complex roots?  No?  Drat. 

Various polynomial routines have appeared in this group.  Check out the FTP
sites mentioned from time to time.


				-- edp