RE: LZ: matrices


RE: LZ: matrices

see changes....may help....or not

Brian Greer  <>

On Sat, 7 Dec 1996, Michael Wyman wrote:

> On Sat, 7 Dec 1996 15:19:52 -0600 (CST),
> Will Stokes wrote...
> >I'm really impacient about learning matrices and even though I mailed one
> >guy about them I can;t wait days to learn how since I'm going out of town
> >and wont have internet acces.
> >	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? How do I define it at the bottom of the screen? What about memory
> >allocation, i won;t have to define it at the top will I? It's like sprites
> >or pictures right? Any help appreciated as I would like the info soon so I
> >can work on this game and maybe finnish it over the winter break.
> >			Will Stokes
> So you're trying to have the calculator recall values from a 50 row x 5 
> column matrix, right?  Then define your matrix with .db's with your values 
> as follows:
> <Label>:
> ;     C1     C2     C3     C4     C5
> *db value, value, value, value, value ;row 1
> db value, value, value, value, value ;row 2
> etc. until you have all of your values stored.  To recall a value at 
> (MATX,MATY), have a loop such as follows:
> ld   hl, <Label>
> ld   de, (PROGRAM_ADDR)
> add  hl, de               ;hl points to begining of row 1 in matrix
> ld   a, MATY
> dec  a
> or   a                    ;If value needed is in row 1, skip loop
> jr   z, Done_With_Loop
> ld   b, a                 ;b is the counter
> Row_Loop:
> add  hl, $05              ;hl points to begining of next row

I couldn't get this part to compile so you might want to try:
  ld de,$05
  add hl,de
instead of just 'add hl,$05'  --just at thought

> djnz Row_Loop
> Done_With_Loop:
> dec  hl                   ;because we'll increase it at least once
> ld   b, MATX
> Column_Loop:
> inc  hl
> djnz Column_Loop
> ld   a, (hl)              ;acc should now hold the desired value!
> I have never tried this before, but I think that it should work.  If it 
> does, please let me know, and even if it does, please do!
> Hope I've helped!
> Michael Wyman - SeaHorse Software

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