33 lines
711 B
ObjectPascal
33 lines
711 B
ObjectPascal
function fft(x: array of complex): array of complex;
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begin
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var n := x.length;
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if n = 0 then exit;
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setlength(result, n);
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if n = 1 then
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begin
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result[0] := x[0];
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exit;
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end;
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var evens := x.Where((x, i) -> i mod 2 = 0).ToArray;
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var odds := x.Where((x, i) -> i mod 2 = 1).ToArray;
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var (even, odd) := (fft(evens), fft(odds));
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var halfn := n div 2;
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for var k := 0 to halfn - 1 do
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begin
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var a := exp(new Complex(0.0, -2 * Pi * k / n)) * odd[k];
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result[k] := even[k] + a;
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result[k + halfn] := even[k] - a;
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end;
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end;
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begin
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var test := |1.0, 1.0, 1.0, 1.0, 0.0, 0.0, 0.0, 0.0|;
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foreach var x in fft(test.select(x -> new Complex(x, 0)).ToArray) do
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println(x)
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end.
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