Chebyshev v2

cheb2.cpp

__forceinline double chebyshev_ryg(int n, double x)
{
  if (n == 0) return 1.0;
  if (n == 1) return x;

  double t = x, t1 = 1, t2;
  x += x;
  for (int i=1; i<n; i++) {
    t2 = t1;
    t1 = t;
    t = x * t1 - t2;
  }
  return t;
}