// If a page-count is requested, we use state_, which
// is indexed by page*system, for our dynamic programming
// intermediate storage. Otherwise, we use simple_state_,
// which is indexed only by system.
Matrix<Page_spacing_node> state_;
// If a page-count is requested, we use state_, which
// is indexed by page*system, for our dynamic programming
// intermediate storage. Otherwise, we use simple_state_,
// which is indexed only by system.
Matrix<Page_spacing_node> state_;