- let mut closure_cell = self.closure.borrow_mut();
- let mut closure = closure_cell.take();
- if closure.is_none() {
- closure = Some(self.compute_closure());
- }
- let result = op(closure.as_ref().unwrap());
- *closure_cell = closure;
- result
- }
-
- fn compute_closure(&self) -> BitMatrix<usize, usize> {
- let mut matrix = BitMatrix::new(self.elements.len(), self.elements.len());
- let mut changed = true;
- while changed {
- changed = false;
- for edge in &self.edges {
- // add an edge from S -> T
- changed |= matrix.insert(edge.source.0, edge.target.0);
-
- // add all outgoing edges from T into S
- changed |= matrix.union_rows(edge.target.0, edge.source.0);
- }
- }
- matrix