RosettaCodeData/Task/Julia-set/FreeBASIC/julia-set.basic

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#define pix 1./120
#define zero_x 320
#define zero_y 240
#define maxiter 250
type complex
r as double
i as double
end type
operator + (x as complex, y as complex) as complex
dim as complex ret
ret.r = x.r + y.r
ret.i = x.i + y.i
return ret
end operator
operator * (x as complex, y as complex) as complex
dim as complex ret
ret.r = x.r*y.r - x.i*y.i
ret.i = x.r*y.i + x.i*y.r
return ret
end operator
operator abs ( x as complex ) as double
return sqr(x.r*x.r + x.i*x.i)
end operator
dim as complex c, z
dim as integer x, y, iter
input "Real part of c? ", c.r
input "Imaginary part of c? ", c.i
screen 12
for x=0 to 639
for y=0 to 479
z.r = (x-zero_x)*pix
z.i = (y-zero_y)*pix
for iter=0 to maxiter
z = z*z + c
if abs(z)>2 then
pset(x,y),iter mod 16
goto cont
end if
next iter
pset(x,y),1
cont:
next y
next x
while inkey=""
wend
end