Depth first traversal

Tree<T>/Forest<T> can be converted to TreeWalk<T>/ForestWalk<T> which act like cursors for depth first traversal.

Keeping on get()-ing current node then forward()ing the cursor results in a depth first search sequence. The two operations are combined as next().

During traversal, the cursor can jump to_parent()/to_child()/to_sib() at any time. To restart DFS search of a node, use revisit().

Example

#![allow(unused)]
fn main() {
use trees::{tr, Visit, TreeWalk};

let tree = tr(0) /( tr(1)/tr(2)/tr(3) ) /( tr(4)/tr(5)/tr(6) );
let mut walk = TreeWalk::from( tree );
assert_eq!( walk.get(), Some( Visit::Begin(
    ( tr(0) /( tr(1)/tr(2)/tr(3) ) /( tr(4)/tr(5)/tr(6) ) )
    .root() )));

walk.forward();
assert_eq!( walk.get(), Some( Visit::Begin(
    ( tr(1) /tr(2)/tr(3) )
    .root() )));

walk.forward();
assert_eq!( walk.get(), Some( Visit::Leaf(
    tr(2)
    .root() )));

walk.forward();
assert_eq!( walk.get(), Some( Visit::Leaf(
    tr(3)
    .root() )));

walk.forward();
assert_eq!( walk.get(), Some( Visit::End(
    ( tr(1) /tr(2)/tr(3) )
    .root() )));

walk.forward();
assert_eq!( walk.get(), Some( Visit::Begin(
    ( tr(4) /tr(5)/tr(6) )
    .root() )));

walk.forward();
assert_eq!( walk.get(), Some( Visit::Leaf(
    tr(5)
    .root() )));

walk.forward();
assert_eq!( walk.get(), Some( Visit::Leaf(
    tr(6)
    .root() )));

walk.forward();
assert_eq!( walk.get(), Some( Visit::End(
    ( tr(4) /tr(5)/tr(6) )
    .root() )));

walk.forward();
assert_eq!( walk.get(), Some( Visit::End(
    ( tr(0) /( tr(1)/tr(2)/tr(3) ) /( tr(4)/tr(5)/tr(6) ) )
    .root() )));

walk.forward();
assert_eq!( walk.get(), None );

walk.forward();
assert_eq!( walk.get(), None );
}