prog8/examples/mandelbrot.p8

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%import c64lib
%import c64utils
%import c64flt
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%zeropage basicsafe
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main {
const uword width = 30
const uword height = 20
const ubyte max_iter = 16
sub start() {
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c64scr.print("calculating mandelbrot fractal...")
c64.TIME_HI=0
c64.TIME_MID=0
c64.TIME_LO=0
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ubyte pixelx
ubyte pixely
for pixely in 0 to height-1 {
float yy = (pixely as float)/0.4/height - 1.0
for pixelx in 0 to width-1 {
float xx = (pixelx as float)/0.3/width - 2.2
float xsquared = 0.0
float ysquared = 0.0
float x = 0.0
float y = 0.0
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ubyte iter = 0
while (iter<max_iter and xsquared+ysquared<4.0) {
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y = x*y*2.0 + yy
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x = xsquared - ysquared + xx
xsquared = x*x
ysquared = y*y
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iter++
}
c64scr.setcc(pixelx+4, pixely+1, 160, max_iter-iter)
}
}
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float duration = ((c64.TIME_LO as float)
+ 256.0*(c64.TIME_MID as float)
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+ 65536.0*(c64.TIME_HI as float))/60.0
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c64scr.plot(0, 21)
c64scr.print("finished in ")
c64flt.print_f(duration)
c64scr.print(" seconds!\n")
check_eval_stack()
}
sub check_eval_stack() {
if X!=255 {
c64scr.print("stack x=")
c64scr.print_ub(X)
c64scr.print(" error!\n")
}
}
}