Bullet code bug?

[turiqwalrus]

So, hellninjas and I have been trying to figure out some decent code for programming bullets, and we've pretty much got it down now- except for one bug.
when firing a new bullet, a picture of the bullet sprite bullet flashes briefly at the top of the screen.
Could someone find what's wrong?
Also, optimize if neccesary

Spoiler for code:

0->C+5 -> D
15 -> X -> Y
[18247EBDFFBDFFA5] -> Pic1
[183C3C3C3C240000] -> Pic2
Repeat getkey(15)
X+getKey(3)-getKey(2) --> X
Y+getKey(1)-getKey(4) --> Y
Pt-On(X,Y,Pic1
if getkey(54)
DS<(D,5)
X->{C+1*2+L1}
Y->{C+1*2+1+L1}     
C++
end
end
if C
for(L,0,C)
{L*2+1+L1}-1->{L*2+1+L1}
if {L*2+1+L1}>64
if C>0
Copy(C*2+L1,L*2+L1,2
end
C--
else
Pt-On({L*2+L1},{L*2+1+L1},Pic2
end
end
end
DispgraphClrdraw
end

[Runer112]

Your issue arises from this block of code:

Code: Select All | Copy To Clipboard

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If C For(L,0,C) .Snip End End

I see two issues with this. First, because of how you add bullets, the first bullet is located at L₁+2, whereas this loop structure treats L₁ as the location of the first bullet. Secondly, this loop will run 0 times if C equals 0, but it will run C+1 times if C doesn't equal 0. For instance, if C equals 1, the loop will iterate for L equals 0 and 1, for two iterations total. This extra iteration in combination with reading data at L₁ that's not a bullet is what's causing the issues you're seeing.

Thankfully, the fix for this is really easy. It even allows you to completely remove the If C block surrounding the for loop! Just change the lower bound of the for loop to 1.

Code: Select All | Copy To Clipboard

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For(L,1,C) .Snip End

Alternatively, the most optimized way to fix this is with your own loop structure.

Code: Select All | Copy To Clipboard

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C While →L .Snip L-1 End

And just for fun, here's my optimized version of the entire program. It's also attached.

Spoiler for Hidden:

Code: Select All | Copy To Clipboard

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.BULLET 0→C→D 15→X→Y [18247EBDFFBDFFA5]→Pic1 [183C3C3C3C240000]→Pic2 While 1  Pt-On(getKey(3)-getKey(2)+X→X,getKey(1)-getKey(4)+Y→Y,Pic1)  !If D   If getKey(54)    X→{Y→{C++*2-2+L1}+1}    4   End   +1  End  -1→D  C  While   -1→L   {*2+L1→P}--   Pt-On({}ʳʳ,/256,Pic2)   !If -L6    Copy(C--*2+L,P,2)   End   L  End  DispGraphClrDraw EndIf getKey(15)

If the code box is tiny, that's because Chrome fails. Click "Select All" and then press Ctrl+C to copy it, then just paste it into something like notepad to view it.