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https://git.sr.ht/~rabbits/macintosh_cookbook
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63 lines
1.2 KiB
ObjectPascal
63 lines
1.2 KiB
ObjectPascal
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program ExampleJulia;
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{Program to compute and plot Julia set.}
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const
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scale = 0.01;
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R = 10;
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type
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complex = record
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r: Real;
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i: real
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end;
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var
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i, j, k, n, row, col, Nit: Integer;
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x, y: Real;
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z, znew, c: complex;
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done, gone: Boolean;
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procedure prod (a, b: complex; var c: complex);
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{Does complex multiplication: c = a bullet b}
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begin
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c.r := a.r * b.r - a.i * b.i;
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c.i := a.r * b.i + a.i * b.r;
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end;
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procedure add (a, b: complex; var c: complex);
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{Does complex addition: c = a + b}
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begin
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c.r := a.r + b.r;
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c.i := a.i + b.i;
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end;
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procedure plot (c, r: integer);
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{Procedure to pixel (c.r).}
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begin
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Moveto(c, r);
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Lineto(c, r);
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end;
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begin
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ShowText;
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writeLn('How many iterations at each point?');
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readLn(Nit);
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writeLn('Value of C: (Cr,Ci)?');
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ReadLn(c.r, c.i);
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showdrawing;
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ForeColor(blackColor);
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n := 0;
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for col := 1 to 400 do
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for row := 1 to 400 do
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begin
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z.r := (col - 200) * scale;
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z.i := (row - 200) * scale;
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repeat
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prod(z, z, znew);
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add(znew, c, z);
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gone := (z.r * z.r + z.i * z.i > R);
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n := n + 1;
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done := (n > Nit);
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until done or gone or button;
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if done then
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plot(col, row);
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n := 0;
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end;
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end.
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