Re: LZ-Adv: matrices

To: lz-adv@lists.ticalc.org
Subject: Re: LZ-Adv: matrices
From: "Jason C. Wenger" <jwenger@clinton.net>
Date: Sat, 07 Dec 1996 16:02:57 -0600
Posted-Date: Sat, 7 Dec 1996 16:08:16 -0600
References: <Pine.SOL.3.95.961207152452.4574A-100000@vertex.ucls.uchicago.edu>
Reply-To: lz-adv@lists.ticalc.org

>         Lets say I have a defined matrix at the bottom of a prog. that
> will not be changed but values will be take from it to calculate stuff in
> the prog depending on variable. In other words, a 5 by 50 matrix with
> preset values. How do i load the value of MATX (refering to 5) and MATY
> (refering to  50) posision in matrix into register a? in other words for
> values of MATX and MATY how do I load the appropriate value of the matrix
> into a?

Okay, right now you have:

[Code]

MatrixStart:
.db 6,2,5,2,6
.db 2,5,3,6,4
.db 7,2,5,8,4
(and so on)

here's the code you would use to load the value of a position in the
matrix into A. I use MatRow and MatCol for ease of interpretation.

   ld    b, (your MatRow)
   ld    c, (your MatCol)
CALL_(Ld_To_A)


-------  Somewhere else in the code

Ld_To_A:
   ld    a,b
   shl   a 
   shl   a
   add   b                ; This multiplies row (b) by 5 and puts it in
                          ; A, via a=4b+b and is much faster code than
                          ; multiplying

   add  c                 ; a=5b+c

   ld   de,(prog_Start)
   ld   bc,MatrixStart
   add  bc,de             ;bc=absolute address of beginning of matrix 

   ld   de,a
   add  bc,de             ;bc=address of (beginning + offset)

   ld   a,(bc)            ; a= value of memory location BC


This probably contains some syntax errors and the like,  but it should
give you a general idea.


>  How do I define it at the bottom of the screen?

huh???

> What about memory allocation, i won't have to define it at the top will I?

No. the bottom's okay.

>                         Will Stokes

Hope this helps,
Jason Wenger

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References:

LZ-Adv: matrices

From: Will Stokes <wstokes@vertex.ucls.uchicago.edu>