Fast filled circle

[SMcNeill]

Thanks bplus for the excellent example.
It got me thinking about BF option; why is it there? It seems unneeded.

After experimenting, I found that the BF option, even with single line makes drawing the line 5x faster!
Against common sense I added the BF option to the line statements in my code and surprise... it was 5x faster also.

As I've explained to bplus and a few others before, it makes perfect sense once you take a second to think about it...

How do you calculate a vertical line??   A horizontalntal line?  Or a box?

for y = start to finish
    memfill (xpos,y) to (xpos2, y), color
next

......

Now, how do you calculate and plot a sloped line?
for y = start to finish step yslope
   for x = start to finish step xslope
        plot x, y, color
   next
next 

.....  The first, you just fill a whole chunk of memory with one set of values in a single pass...   For the second, you do a lot of math to calculate your slope and plot each point as you move upon that slope.


Now, which is going to be faster than the other?