void wavelet::partial_inverse(const vector<double>& in, vector<double>& out,
const int n) const
{
assert(in.size() == out.size());
assert(n <= in.size());
// trap calls where n is too small
if (n < 4)
return;
// initialise workspace (since out & in may be the same vector)
vector<double> b(n);
b = 0;
// set up some constants that we need
const int nh = n >> 1;
const int mask = n - 1;
const int ncof = g.size();
// do the transform
for (int i = 0; i < nh; i++)
for (int j = 0; j < ncof; j++)
{
const int k = ((i << 1) + j) & mask;
b(k) += g(j) * in(i) + h(j) * in(i + nh);
}
// copy the result back from workspace
out.copyfrom(b);
}
