possible problem with bits 3 & 5 of a variable

[InsaneSonikkuFan]

so i've been trying to write asteroids, and i'm running across a problem where bits 3 and 5 of variable c are unsetting themselves. let me explain the way the variable works:

[0] UP FAST [1] UP SLOW

[2] DOWN FAST [3] DOWN SLOW

[4] LEFT FAST [5] LEFT SLOW

[6] RIGHT FAST [7] RIGHT SLOW

 

so if you run the code, moving up and/or right drift correctly. however, moving left or down (from a stop) causes the screen to flicker, the ship to only move one tick and then stop, and what seems to be bits 3 and 5 turning from 1 to 0.

i've attached my code. i'm using bB bleeding edge 99b. am i overlooking something totally obvious, or is there an actual problem? thanks.

asteroids.bas

[+batari]

so i've been trying to write asteroids, and i'm running across a problem where bits 3 and 5 of variable c are unsetting themselves. let me explain the way the variable works:

[0] UP FAST [1] UP SLOW

[2] DOWN FAST [3] DOWN SLOW

[4] LEFT FAST [5] LEFT SLOW

[6] RIGHT FAST [7] RIGHT SLOW

 

so if you run the code, moving up and/or right drift correctly. however, moving left or down (from a stop) causes the screen to flicker, the ship to only move one tick and then stop, and what seems to be bits 3 and 5 turning from 1 to 0.

i've attached my code. i'm using bB bleeding edge 99b. am i overlooking something totally obvious, or is there an actual problem? thanks.

Bit access uses {}. [] are for arrays - so by using c[2] for instance, you are actually accessing e.

 

I went ahead and fixed it - I literally did a global search and replace and everything seems to work now.

asteroids.bas

[SeaGtGruff]

so i've been trying to write asteroids, and i'm running across a problem where bits 3 and 5 of variable c are unsetting themselves. let me explain the way the variable works:

[0] UP FAST [1] UP SLOW

[2] DOWN FAST [3] DOWN SLOW

[4] LEFT FAST [5] LEFT SLOW

[6] RIGHT FAST [7] RIGHT SLOW

 

so if you run the code, moving up and/or right drift correctly. however, moving left or down (from a stop) causes the screen to flicker, the ship to only move one tick and then stop, and what seems to be bits 3 and 5 turning from 1 to 0.

i've attached my code. i'm using bB bleeding edge 99b. am i overlooking something totally obvious, or is there an actual problem? thanks.

It looks like the only thing c is ever set to is 0 or 1. The square brackets ([ and ]) that you think you're using for the bit operations are actually for variable arrays. To do bit operations, use the curly set brackets ({ and }). Also, checking the bit settings in an if...then is done a little differently-- you can't use an equals sign or you'll get compile errors, so you just say "if c{3} then" or "if !c{3} then" (or whatever variable and bit you're checking), where the first case means "equals 1" (or is "true"), and the second case means "equals 0" (or is "not true"). I've made the appropriate changes in your code so you can see how to do it.

 

Michael Rideout

 

asteroids.bas

[SeaGtGruff]

I went ahead and fixed it - I literally did a global search and replace and everything seems to work now.

Heh, I guess we were doing it at the same time!

 

Michael Rideout

[+batari]

I went ahead and fixed it - I literally did a global search and replace and everything seems to work now.

Heh, I guess we were doing it at the same time!

 

Michael Rideout

And it looks like both .bas files will produce exactly the same binary...

 

BTW, your explanation is better, as I left out the part about how to use a bit operation in an if-then statement.

[InsaneSonikkuFan]

d'oh.

 

thanks a ton, guys.