cadencii.fft.cftb040 C# (CSharp) Method

        static void cftb040( double* a ) {
            double x0r, x0i, x1r, x1i, x2r, x2i, x3r, x3i;

            x0r = a[0] + a[4];
            x0i = a[1] + a[5];
            x1r = a[0] - a[4];
            x1i = a[1] - a[5];
            x2r = a[2] + a[6];
            x2i = a[3] + a[7];
            x3r = a[2] - a[6];
            x3i = a[3] - a[7];
            a[0] = x0r + x2r;
            a[1] = x0i + x2i;
            a[2] = x1r + x3i;
            a[3] = x1i - x3r;
            a[4] = x0r - x2r;
            a[5] = x0i - x2i;
            a[6] = x1r - x3i;
            a[7] = x1i + x3r;
        }