1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
|
############################################################################
#
# File: julia1.icn
#
# Subject: Program to display the Julia set
#
# Author: Ralph E. Griswold
#
# Date: June 17, 1994
#
############################################################################
#
# This file is in the public domain.
#
############################################################################
#
# This is a barebones version of a display of the Julia set. It
# has deliberately been left simple and free of options so that the
# basic idea is clear and so that it can be used as the basis of
# more capable versions.
#
# This program is based on material given in "Chaos, Fractals,
# and Dynamics", Robert L. Devaney, Addison-Wesley, 1990.
#
# The point in the complex plane for which the Julia set is computed
# is given on the command line, as in
#
# julia1 .360284 .100376
#
# which displays the Julia set for the complex number .360284 + .100376i.
#
############################################################################
#
# Requires: Version 9 graphics
#
############################################################################
#
# Links: wopen
#
############################################################################
link wopen
procedure main(argl)
local c1, c2, extent, half, quarter, m, n, x0, y0, x, y
local x1, y1, i, z
c1 := real(argl[1]) | -1.0 # default is -1.0 + 0.0i
c2 := real(argl[2]) | 0.0
extent := 200
half := 200 / 2
quarter := real(extent) / 4
WOpen("label=julia", "height=" || extent, "width=" || extent) |
stop("*** cannot open window")
every m := 0 to extent do {
x0 := -2 + m / quarter
every n := 0 to half do {
y0 := 2 - n / quarter
x := x0
y := y0
every i := 1 to 20 do { # compute orbit
x1 := x ^ 2 - y ^ 2 + c1
y1 := 2 * x * y + c2
x := x1
y := y1
z := x ^ 2 + y ^ 2
if z > 4 then break next # if escaping, forget it
}
DrawPoint(m, n)
DrawPoint(extent - m, extent - n)
}
}
Event()
end
|
