Enum indextree::NodeEdge

source ·

pub enum NodeEdge {
    Start(NodeId),
    End(NodeId),
}

Expand description

Indicator if the node is at a start or endpoint of the tree

Variants§

§

Start(NodeId)

Indicates that start of a node that has children.

Yielded by Traverse::next() before the node’s descendants. In HTML or XML, this corresponds to an opening tag like <div>.

§

End(NodeId)

Indicates that end of a node that has children.

Yielded by Traverse::next() after the node’s descendants. In HTML or XML, this corresponds to a closing tag like </div>

Implementations§

source §

impl NodeEdge

source

pub fn next_traverse<T>(self, arena: &Arena<T>) -> Option<Self>

Returns the next NodeEdge to be returned by forward depth-first traversal.

§Examples

// arena
// `-- 1
//     |-- 1_1
//     |   `-- 1_1_1
//     |-- 1_2
//     `-- 1_3

let steps = std::iter::successors(
    Some(NodeEdge::Start(n1)),
    |current| current.next_traverse(&arena)
)
    .collect::<Vec<_>>();
let traversed_by_iter = n1.traverse(&arena).collect::<Vec<_>>();
assert_eq!(
    steps,
    traversed_by_iter,
    "repeated `.next_traverse()`s emit same events as `NodeId::traverse()` iterator"
);

NodeEdge itself does not borrow an arena, so you can modify the nodes being traversed.

// arena: Arena<String>
// `-- 1
//     |-- 1_1
//     |   `-- 1_1_1
//     |-- 1_2
//     `-- 1_3

assert_eq!(*arena[n1].get(), "1");
assert_eq!(*arena[n1_1_1].get(), "1_1_1");
assert_eq!(*arena[n1_3].get(), "1_3");

let mut next = Some(NodeEdge::Start(n1));
let mut count = 0;
while let Some(current) = next {
    next = current.next_traverse(&arena);
    let current = match current {
        NodeEdge::Start(id) => id,
        NodeEdge::End(_) => continue,
    };

    arena[current].get_mut().push_str(&format!(" (count={})", count));
    count += 1;
}

assert_eq!(*arena[n1].get(), "1 (count=0)");
assert_eq!(*arena[n1_1_1].get(), "1_1_1 (count=2)");
assert_eq!(*arena[n1_3].get(), "1_3 (count=4)");

source

pub fn prev_traverse<T>(self, arena: &Arena<T>) -> Option<Self>

Returns the previous NodeEdge to be returned by forward depth-first traversal.

§Examples

// arena
// `-- 1
//     |-- 1_1
//     |   `-- 1_1_1
//     |-- 1_2
//     `-- 1_3

let steps = std::iter::successors(
    Some(NodeEdge::End(n1)),
    |current| current.prev_traverse(&arena)
)
    .collect::<Vec<_>>();
let traversed_by_iter = n1.reverse_traverse(&arena).collect::<Vec<_>>();
assert_eq!(
    steps,
    traversed_by_iter,
    "repeated `.prev_traverse()`s emit same events as \
     `NodeId::reverse_traverse()` iterator"
);

NodeEdge itself does not borrow an arena, so you can modify the nodes being traversed.

use indextree::{Arena, NodeEdge};

// arena: Arena<String>
// `-- 1
//     |-- 1_1
//     |   `-- 1_1_1
//     |-- 1_2
//     `-- 1_3

assert_eq!(*arena[n1_3].get(), "1_3");
assert_eq!(*arena[n1_1_1].get(), "1_1_1");
assert_eq!(*arena[n1].get(), "1");

let mut next = Some(NodeEdge::End(n1_3));
let mut count = 0;
while let Some(current) = next {
    next = current.prev_traverse(&arena);
    let current = match current {
        NodeEdge::Start(id) => id,
        NodeEdge::End(_) => continue,
    };

    arena[current].get_mut().push_str(&format!(" (count={})", count));
    count += 1;
}

assert_eq!(*arena[n1_3].get(), "1_3 (count=0)");
assert_eq!(*arena[n1_1_1].get(), "1_1_1 (count=2)");
assert_eq!(*arena[n1].get(), "1 (count=4)");