Data update

Task/Fast-Fourier-transform/PascalABC.NET/fast-fourier-transform.pas

@@ -0,0 +1,32 @@
+function fft(x: array of complex): array of complex;
+begin
+  var n := x.length;
+  if n = 0 then exit;
+
+  setlength(result, n);
+
+  if n = 1 then
+  begin
+    result[0] := x[0];
+    exit;
+  end;
+
+  var evens := x.Where((x, i) -> i mod 2 = 0).ToArray;
+  var odds := x.Where((x, i) -> i mod 2 = 1).ToArray;
+  var (even, odd) := (fft(evens), fft(odds));
+
+  var halfn := n div 2;
+
+  for var k := 0 to halfn - 1 do
+  begin
+    var a := exp(new Complex(0.0, -2 * Pi * k / n)) * odd[k];
+    result[k] := even[k] + a;
+    result[k + halfn] := even[k] - a;
+  end;
+end;
+
+begin
+  var test := |1.0, 1.0, 1.0, 1.0, 0.0, 0.0, 0.0, 0.0|;
+  foreach var x in fft(test.select(x -> new Complex(x, 0)).ToArray) do
+    println(x)
+end.