static void cftf040( 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;
}