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From: edp@jareth.enet.dec.com (Eric Postpischil (Always mount a scratch monkey.))
Newsgroups: comp.sys.handhelds
Subject: Re: HP48 features -- what objects can be used?
Message-ID: <20065@shlump.nac.dec.com>
Date: 11 Feb 91 15:06:15 GMT
References: <1991Feb10.181833.16827@cs.dal.ca>
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Reply-To: edp@jareth.enet.dec.com (Eric Postpischil (Always mount a scratch monkey.))
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Organization: Digital Equipment Corporation
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In article <1991Feb10.181833.16827@cs.dal.ca>, silvert@cs.dal.ca (Bill Silvert)
writes:

>For example, consider rotation by an angle stored in variable THETA.
>I would love to be able to write equations like Y = A * X where X and Y
>are 2D vectors and A is the array whose elements are cos(THETA), etc.
>(Even better if I could solve for THETA!)

I think somebody wrote some routines to do algebraic manipulation with matrices.
I don't know how extensive or good they are, but I think I have them around
somewhere.  If you send mail asking, I will mail them to you.

Note that the specific example you give can be handled without matrices. 
Two-dimensional vectors can be represented with complex numbers.  The equation
you give can be written as 'Y=X*EXP(\Gh*i)'.  ("\Gh" is the Greek theta
character, or you can use any variable name.)

>Also, it would be nice to construct an array from two vectors like this:
[combining rows]

You can write a program to do that, or you can use the \GS+ command.  ("\GS" is
the capital Greek sigma.)

>I may have entered things wrong, but I can't even integrate a dot
>product of two vectors, which is after all a scalar!

You should be able to do a numerical integration on an expression involving dot
products, but the variable of integration must be real (the range you specify
for it must be a range of real numbers) and the value of the expression must be
real.


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