Poisson : Distribution équilibrée

//-------------
// Fast Fourier Transform ...
// v Reel
function fft(X) {
  const x = [...X];
  const N = x.length;
  if (N <= 1) {
    return x;
  }

  // var X = x.slice();
  const hN = N / 2;
  let even = [];
  let odd = [];
  even.length = hN;
  odd.length = hN;
  // on separe even/odd
  for (let i = 0; i < hN; ++i) {
    even[i] = x[i * 2];
    odd[i] = x[i * 2 + 1];
  }
  // on lance la recursivite
  even = fft(even);
  odd = fft(odd);
  // au retour on calcul ...
  const w = -2 * Math.PI;
  for (var k = 0; k < hN; ++k) {
    if (!(even[k] instanceof Complex))
      even[k] = new Complex(even[k], 0);
    if (!(odd[k] instanceof Complex))
      odd[k] = new Complex(odd[k], 0);
    let p = k/N;
    let Wk = new Complex(0,w*p);
    Wk.expW(Wk).mul(odd[k],Wk);
    x[k] = even[k].add(Wk, odd[k]);
    x[k + hN] = even[k].sub(Wk, even[k]);
  }
  return x;
}