Iterating over edge differences
As with trees, the API provides a lending iterator over edge differences.
Each step of the iterator advances to the next tree in the tree sequence.
For each tree, a standard Iterator over removals and insertions is available:
if let Ok(mut edge_diff_iterator) = treeseq.edge_differences_iter() {
while let Some(diffs) = edge_diff_iterator.next() {
for edge_removal in diffs.edge_removals() {
println!("{}", edge_removal);
}
for edge_insertion in diffs.edge_insertions() {
println!("{}", edge_insertion);
}
}
} else {
panic!("creating edge diffs iterator failed");
}Edge differences are the basis of efficient algorithms based on the incremental updating of summaries of trees. The following example co-iterates over edge differences and trees. The edge differences are used to calculate the parent array for each tree:
let num_nodes = treeseq.nodes().num_rows().as_usize();
// num_nodes + 1 to reflect a "virtual root" present in
// the tree arrays
let mut parents = vec![NodeId::NULL; num_nodes + 1];
match treeseq.edge_differences_iter() {
Ok(mut ediff_iter) => match treeseq.tree_iterator(0) {
Ok(mut tree_iter) => {
while let Some(diffs) = ediff_iter.next() {
let tree = tree_iter.next().unwrap();
for edge_out in diffs.edge_removals() {
let c = edge_out.child();
parents[c.as_usize()] = NodeId::NULL;
}
for edge_in in diffs.edge_insertions() {
let c = edge_in.child();
parents[c.as_usize()] = edge_in.parent();
}
assert_eq!(tree.parent_array(), &parents);
}
}
Err(e) => panic!("error creating tree iter: {:?}", e),
},
Err(e) => panic!("error creating edge diff iter: {:?}", e),
}