question about data_length

[diogoandrei]

Hello there all, what's up?

 

I am doing this small study on data arrays. I ran into a problem with the _lenght constant of the read-only data. My data has 12 elements and it's not returning this value. Here's the code:

 

 dim pixelPointer = a
dim pixelTimer = b
dim pixelX = c
dim pixelY = d

pixelPointer = $ff

COLUPF = $40
COLUBK = $00
scorecolor = $40

MainLoop

pixelTimer = pixelTimer + 1
if pixelTimer = 50 then pixelTimer = 0 : gosub pixelLocation

pfpixel pixelX pixelY on

rem ********************************************************************
rem TESTING VARIABLES

f = pixelData_length

score = 0
temp5 = f
if temp5 > 0 then for temp6 = 1 to temp5 : score = score + 1000 : next
temp5 = pixelY
if temp5 > 0 then for temp6 = 1 to temp5 : score = score + 1 : next

drawscreen
goto MainLoop

pixelLocation
pfpixel pixelX pixelY off
pixelPointer = pixelPointer + 1 : if pixelPointer = 12 then pixelPointer = 0
pixelX = pixelData[pixelPointer]
pixelPointer = pixelPointer + 1
pixelY = pixelData[pixelPointer]
return

data pixelData
1,1,2,2,3,3,4,4,5,5,6,6
end

 

Actually, when I test this:

 

 f = pixelData_length

score = 0
temp5 = f
if temp5 > 0 then for temp6 = 1 to temp5 : score = score + 1000 : next

 

...the playfield even changes color and the score shows 140.

 

So I had to hand code the value to avoid the pointers going beyond the number of elements...

 

if pixelPointer = 12 then pixelPointer = 0

 

Any help would be great! Thanks!

[RevEng]

Can you attach the .asm file that was generated when you compiled the basic file?

 

For some reason my bB version doesn't have _length attributes, but I did something equivalent in assembly and your code worked as expected. (012000, 012001, etc.)

[diogoandrei]

Hello RevEng, what's up?

 

Attached follows the .asm files (there was one for the project and one entitled bB.asm - I wasn't sure so I put both in there).

 

Regarding the _length attribute, I did read about it at Random Terrain, this section. From there I assumed it would be in bB. Can it be possible that this is a small bug?

 

Once again, thanks for your time and attention!

PF_pixels.zip

[RevEng]

Yeah, it's definitely a valid attribute. I just need to update my local bB, I guess.

 

I didn't learn anything from the PF_pixels.bas.asm. I guess the *_length constants are introduced in one of the included .asm files.

 

I do think this is probably a bB bug; my workaround produced correct results, so there aren't any bugs in your basic program.

 

Personally, I'd just workaround it by using your own constant. You could define it right above the data statement so you won't forget to update it if you update the values.

[diogoandrei]

Personally, I'd just workaround it by using your own constant. You could define it right above the data statement so you won't forget to update it if you update the values.

 

Yeah, I'll stick to that. Thx!

[RevEng]

You're welcome!

[diogoandrei]

Should I report this "may be a bug" to someone? What's the best thing to do when running into something like this?

[RevEng]

You can report it here: http://www.atariage.com/forums/topic/73160-bug-report-thread/

[+batari]

I posted about it in the bug report thread.

 

http://www.atariage.com/forums/topic/73160-bug-report-thread/page__st__150__gopid__2188545#entry2188545