15 lines
495 B
D
15 lines
495 B
D
import std.stdio, std.algorithm, std.range, std.math;
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const(creal)[] fft(in creal[] x) pure /*nothrow*/ @safe {
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immutable N = x.length;
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if (N <= 1) return x;
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const ev = x.stride(2).array.fft;
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const od = x[1 .. $].stride(2).array.fft;
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auto l = iota(N / 2).map!(k => ev[k] + expi(-2*PI * k/N) * od[k]);
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auto r = iota(N / 2).map!(k => ev[k] - expi(-2*PI * k/N) * od[k]);
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return l.chain(r).array;
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}
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void main() @safe {
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[1.0L+0i, 1, 1, 1, 0, 0, 0, 0].fft.writeln;
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}
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