void add_to(view<T> out) const
{
if (out.size() != (size_t)in_.rows())
throw size_mismatch();
typename eigen<T>::col_map out_map(out.data(), out.size());
out_map += in_;
}
void add_to(view<T> out) const
{
if (out.size() != in_.size())
throw size_mismatch();
for (size_t i = 0; i != in_.size(); ++i)
out.data()[i] += in_[i];
}
void add_to(view<T> out) const
{
if (out.size() != 1)
throw size_mismatch();
out.data()[0] += in_;
}