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/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
//! Helper functions for garbage collected doubly-linked trees.
/// The basic trait. This function is meant to encapsulate a clonable reference to a tree node.
pub trait TreeNodeRef<N> : Clone {
/// Borrows this node as immutable.
fn with_base<R>(&self, callback: &fn(&N) -> R) -> R;
/// Borrows this node as mutable.
fn with_mut_base<R>(&self, callback: &fn(&mut N) -> R) -> R;
}
/// The contents of a tree node.
pub trait TreeNode<NR> {
/// Returns the parent of this node.
fn parent_node(&self) -> Option<NR>;
/// Returns the first child of this node.
fn first_child(&self) -> Option<NR>;
/// Returns the last child of this node.
fn last_child(&self) -> Option<NR>;
/// Returns the previous sibling of this node.
fn prev_sibling(&self) -> Option<NR>;
/// Returns the next sibling of this node.
fn next_sibling(&self) -> Option<NR>;
/// Sets the parent of this node.
fn set_parent_node(&mut self, new_parent: Option<NR>);
/// Sets the first child of this node.
fn set_first_child(&mut self, new_first_child: Option<NR>);
/// Sets the last child of this node.
fn set_last_child(&mut self, new_last_child: Option<NR>);
/// Sets the previous sibling of this node.
fn set_prev_sibling(&mut self, new_prev_sibling: Option<NR>);
/// Sets the next sibling of this node.
fn set_next_sibling(&mut self, new_next_sibling: Option<NR>);
}
/// A set of helper functions useful for operating on trees.
pub trait TreeUtils {
/// Returns true if this node is disconnected from the tree or has no children.
fn is_leaf(&self) -> bool;
/// Adds a new child to the end of this node's list of children.
///
/// Fails unless `new_child` is disconnected from the tree.
fn add_child(&self, new_child: Self);
/// Removes the given child from this node's list of children.
///
/// Fails unless `child` is a child of this node. (FIXME: This is not yet checked.)
fn remove_child(&self, child: Self);
/// Iterates over all children of this node.
fn each_child(&self, callback: &fn(Self) -> bool) -> bool;
/// Iterates over this node and all its descendants, in preorder.
fn traverse_preorder(&self, callback: &fn(Self) -> bool) -> bool;
/// Iterates over this node and all its descendants, in postorder.
fn traverse_postorder(&self, callback: &fn(Self) -> bool) -> bool;
}
impl<NR:TreeNodeRef<N>,N:TreeNode<NR>> TreeUtils for NR {
fn is_leaf(&self) -> bool {
do self.with_base |this_node| {
this_node.first_child().is_none()
}
}
fn add_child(&self, new_child: NR) {
do self.with_mut_base |this_node| {
do new_child.with_mut_base |new_child_node| {
assert!(new_child_node.parent_node().is_none());
assert!(new_child_node.prev_sibling().is_none());
assert!(new_child_node.next_sibling().is_none());
match this_node.last_child() {
None => this_node.set_first_child(Some(new_child.clone())),
Some(last_child) => {
do last_child.with_mut_base |last_child_node| {
assert!(last_child_node.next_sibling().is_none());
last_child_node.set_next_sibling(Some(new_child.clone()));
new_child_node.set_prev_sibling(Some(last_child.clone()));
}
}
}
this_node.set_last_child(Some(new_child.clone()));
new_child_node.set_parent_node(Some((*self).clone()));
}
}
}
fn remove_child(&self, child: NR) {
do self.with_mut_base |this_node| {
do child.with_mut_base |child_node| {
assert!(child_node.parent_node().is_some());
match child_node.prev_sibling() {
None => this_node.set_first_child(child_node.next_sibling()),
Some(prev_sibling) => {
do prev_sibling.with_mut_base |prev_sibling_node| {
prev_sibling_node.set_next_sibling(child_node.next_sibling());
}
}
}
match child_node.next_sibling() {
None => this_node.set_last_child(child_node.prev_sibling()),
Some(next_sibling) => {
do next_sibling.with_mut_base |next_sibling_node| {
next_sibling_node.set_prev_sibling(child_node.prev_sibling());
}
}
}
child_node.set_prev_sibling(None);
child_node.set_next_sibling(None);
child_node.set_parent_node(None);
}
}
}
fn each_child(&self, callback: &fn(NR) -> bool) -> bool {
let mut maybe_current = self.with_base(|n| n.first_child());
while !maybe_current.is_none() {
let current = maybe_current.get_ref().clone();
if !callback(current.clone()) {
break;
}
maybe_current = current.with_base(|n| n.next_sibling());
}
true
}
fn traverse_preorder(&self, callback: &fn(NR) -> bool) -> bool {
if !callback((*self).clone()) {
return false;
}
for self.each_child |kid| {
// FIXME: Work around rust#2202. We should be able to pass the callback directly.
if !kid.traverse_preorder(|a| callback(a)) {
return false;
}
}
true
}
fn traverse_postorder(&self, callback: &fn(NR) -> bool) -> bool {
for self.each_child |kid| {
// FIXME: Work around rust#2202. We should be able to pass the callback directly.
if !kid.traverse_postorder(|a| callback(a)) {
return false;
}
}
callback((*self).clone())
}
}
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