return binary_search(col.begin(), col.end(), r);
}
/** Set the matrix entry at row 'r' and column 'c'. */
void set(index_type r, index_type c, bool value) {
return binary_search(col.begin(), col.end(), r);
}
/** Set the matrix entry at row 'r' and column 'c'. */
void set(index_type r, index_type c, bool value) {