Author Topic: 3 byte vars? (Read 3948 times)

FinaleTI · « **on:** December 19, 2010, 06:35:14 pm »

I was looking at this page to see what kind of data structure I'd need for Pokemon TI, but for experience, it says a 3 byte var was used.
If someone could give me a routine for addition, subtraction, and displaying a 3 byte var (or 4 byte if necessary), I would greatly appreciate it.

Runer112 · « **Reply #1 on:** December 19, 2010, 06:54:46 pm »

An earlier thread asked how to do this too, so I have a bit of knowledge regarding this already. The following routines all accept inputs in the form of:
sub(___, Pointer to first argument, Pointer to second argument, Pointer to store answer to)

This routine adds 2 4-byte numbers and stores the result to another 4-byte number:

Code: (4-byte addition) [Select]

:Lbl ADD
:{r₁}ʳ→r₅+{r₂}ʳ→r₄
:<r₅+{r₁+2}ʳ+{r₂+2}ʳ
:→{r₄→{r₃}ʳ+1}ʳ
:Return

Here is a slightly modified version to work with 3-byte numbers instead:

Code: (3-byte addition) [Select]

:Lbl ADD
:{r₁}ʳ→r₅+{r₂}ʳ→r₄
:<r₅+{r₁+2}+{r₂+2}
:→{r₄→{r₃}ʳ+1}
:Return

And here are their subtraction counterparts:

Code: (4-byte subtraction) [Select]

:Lbl SUB
:{r₁}ʳ→r₄≥({r₂}ʳ→r₅)
:-1+{r₁+2}ʳ+{r₂+2}ʳ
:→{r₄-r₅→{r₃}ʳ+1}ʳ
:Return

Code: (3-byte subtraction) [Select]

:Lbl SUB
:{r₁}ʳ→r₄≥({r₂}ʳ→r₅)
:-1+{r₁+2}-{r₂+2}
:→{r₄-r₅→{r₃}ʳ+1}
:Return

FinaleTI · « **Reply #2 on:** December 19, 2010, 06:56:55 pm »

Awesome!
Now if anyone knows how to display a 3 byte var...

ztrumpet · « **Reply #3 on:** December 19, 2010, 07:00:02 pm »

I know there's a DCS routine to display a three byte var.

You may want to ask Kerm about it.

jnesselr · « **Reply #4 on:** December 19, 2010, 07:25:00 pm »

Let's see, addition of 3 byte vars. In Axe. Sounds like fun. Okay, let's see. Assuming A is the MSB, and B has the LSW. For the second number, C=MSB, and D has the LSW. Unsigned, I'm assuming. LSW=Least significant word (2-bytes). MSB=most significant byte. mSB=middle significant byte. LSB=Least significant byte.

It is essentially D+B is the LSW. And (D+B-65535)+A+B is the MSB. Note, that assumes D+B>65535. If it's not, then you get the wrong solution, so check that beforehand. Note, that with assembly, I can think of a better routine than that. Example: (Note, X >> 8 means shift X 8 bits to the right)
0xECD182. 0xEC=A 0xD182=B
0x9287F6. 0x92=C 0x87F6=D

B & 0x00FF = 0082h = E
D & 0x00FF = 00F6h = F
E+F = 0x0178 = G
G >> 8 = 0x0001 = H
B >> 8 = I
D >> 8 = J
H+I+J = 0x959 = K
K >> 8 = L
L+A+B = 0x0187 = M
(G&0x00FF)+(K<<8) = N
M is now your MSW, and N is the LSW.
So, your number is MN or 0x0187 5978.

I think that should work. Good luck with that. I don't know about subtraction, though. ;-)

EDIT: triple-ninja'd.

Runer112 · « **Reply #5 on:** December 19, 2010, 08:22:36 pm »

I'm guessing you would want the values displayed in their base-10 representations, but how would you want the resulting strings to be formatted? Would you want them:

Right-aligned in a block of 8 characters, padded with spaces? Like: " 12345"
Or would you want the string to have variable length with the leading zeros/spaces cut away? Like: "12345"

EDIT:

I went ahead under the assumption that you would want the second option. So I wrote up an Axe library that has everything you need: 3-byte addition, 3-byte subtraction, and 3-byte decimal display. The whole thing is somewhat large (371 bytes), but I optimized it as much as I could.

And since it isn't that much more of an extension, I also made an Axe library that has routines for 4-byte addition, subtraction, and decimal display (407 bytes). I figure even if you don't end up wanting it, I'm sure it could be very handy for other Axe programmers. I know at least a few others have actually made threads asking about using 4-byte numbers before.

Because this turned out to be a pretty nice tool for Axe programmers in general, I posted it in the Routines thread. You can find the post and download the library/libraries you want here.

Author Topic: 3 byte vars? (Read 3948 times)

FinaleTI

3 byte vars?

Runer112

Re: 3 byte vars?

FinaleTI

Re: 3 byte vars?

ztrumpet

Re: 3 byte vars?

jnesselr

Re: 3 byte vars?

Runer112

Re: 3 byte vars?