<!-- ##### SECTION Title ##### -->
N-ary Trees

<!-- ##### SECTION Short_Description ##### -->
trees of data with any number of branches.

<!-- ##### SECTION Long_Description ##### -->
<para>
The #GNode struct and its associated functions provide a N-ary tree data
structure, where nodes in the tree can contain arbitrary data.
</para>
<para>
To create a new tree use g_node_new().
</para>
<para>
To insert a node into a tree use g_node_insert(), g_node_insert_before(),
g_node_append() and g_node_prepend().
</para>
<para>
To create a new node and insert it into a tree use g_node_insert_data(), 
g_node_insert_data_before(), g_node_append_data() and g_node_prepend_data().
</para>
<para>
To reverse the children of a node use g_node_reverse_children().
</para>
<para>
To find a node use g_node_get_root(), g_node_find(), g_node_find_child(),
g_node_child_index(), g_node_child_position(), 
g_node_first_child(), g_node_last_child(),
g_node_nth_child(), g_node_first_sibling(), g_node_prev_sibling(),
g_node_next_sibling() or g_node_last_sibling().
</para>
<para>
To get information about a node or tree use G_NODE_IS_LEAF(),
G_NODE_IS_ROOT(), g_node_depth(), g_node_n_nodes(), g_node_n_children(),
g_node_is_ancestor() or g_node_max_height().
</para>
<para>
To traverse a tree, calling a function for each node visited in the
traversal, use g_node_traverse() or g_node_children_foreach().
</para>
<para>
To remove a node or subtree from a tree use g_node_unlink() or
g_node_destroy().
</para>

<!-- ##### SECTION See_Also ##### -->
<para>

</para>

<!-- ##### STRUCT GNode ##### -->
<para>
The <structname>GNode</structname> struct represents one node in a
<link linkend="glib-N-ary-Trees">N-ary Tree</link>.
The <structfield>data</structfield> field contains the actual data of the node.
The <structfield>next</structfield> and <structfield>prev</structfield>
fields point to the node's siblings (a sibling is another <structname>GNode</structname> with the
same parent).
The <structfield>parent</structfield> field points to the parent of the <structname>GNode</structname>,
or is %NULL if the <structname>GNode</structname> is the root of the tree.
The <structfield>children</structfield> field points to the first child of the
<structname>GNode</structname>. The other children are accessed by using the
<structfield>next</structfield> pointer of each child.
</para>

@data: 
@next: 
@prev: 
@parent: 
@children: 

<!-- ##### FUNCTION g_node_new ##### -->
<para>
Creates a new #GNode containing the given data.
Used to create the first node in a tree.
</para>

@data: the data of the new node.
@Returns: a new #GNode.


<!-- ##### FUNCTION g_node_copy ##### -->
<para>
Recursively copies a #GNode (but does not deep-copy the data inside the nodes,
since there's no way for GLib to know how to do that).
</para>

@node: a #GNode.
@Returns: a new #GNode containing the same data pointers.


<!-- ##### FUNCTION g_node_insert ##### -->
<para>
Inserts a #GNode beneath the parent at the given position.
</para>

@parent: the #GNode to place @node under.
@position: the position to place @node at, with respect to its siblings.
If position is -1, @node is inserted as the last child of @parent.
@node: the #GNode to insert.
@Returns: the inserted #GNode.


<!-- ##### FUNCTION g_node_insert_before ##### -->
<para>
Inserts a #GNode beneath the parent before the given sibling.
</para>

@parent: the #GNode to place @node under.
@sibling: the sibling #GNode to place @node before. If sibling is %NULL,
the node is inserted as the last child of @parent.
@node: the #GNode to insert.
@Returns: the inserted #GNode.


<!-- ##### FUNCTION g_node_insert_after ##### -->
<para>
Inserts a #GNode beneath the parent after the given sibling.
</para>

@parent: the #GNode to place @node under.
@sibling: the sibling #GNode to place @node after. If sibling is %NULL,
the node is inserted as the first child of @parent.
@node: the #GNode to insert.
@Returns: the inserted #GNode.


<!-- ##### MACRO g_node_append ##### -->
<para>
Inserts a #GNode as the last child of the given parent.
</para>

@parent: the #GNode to place the new #GNode under.
@node: the #GNode to insert.
@Returns: the inserted #GNode.


<!-- ##### FUNCTION g_node_prepend ##### -->
<para>
Inserts a #GNode as the first child of the given parent.
</para>

@parent: the #GNode to place the new #GNode under.
@node: the #GNode to insert.
@Returns: the inserted #GNode.


<!-- ##### MACRO g_node_insert_data ##### -->
<para>
Inserts a new #GNode at the given position.
</para>

@parent: the #GNode to place the new #GNode under.
@position: the position to place the new #GNode at.
If position is -1, the new #GNode is inserted as the last child of @parent.
@data: the data for the new #GNode.
@Returns: the new #GNode.


<!-- ##### MACRO g_node_insert_data_before ##### -->
<para>
Inserts a new #GNode before the given sibling.
</para>

@parent: the #GNode to place the new #GNode under.
@sibling: the sibling #GNode to place the new #GNode before.
@data: the data for the new #GNode.
@Returns: the new #GNode.


<!-- ##### MACRO g_node_append_data ##### -->
<para>
Inserts a new #GNode as the last child of the given parent.
</para>

@parent: the #GNode to place the new #GNode under.
@data: the data for the new #GNode.
@Returns: the new #GNode.


<!-- ##### MACRO g_node_prepend_data ##### -->
<para>
Inserts a new #GNode as the first child of the given parent.
</para>

@parent: the #GNode to place the new #GNode under.
@data: the data for the new #GNode.
@Returns: the new #GNode.


<!-- ##### FUNCTION g_node_reverse_children ##### -->
<para>
Reverses the order of the children of a #GNode.
(It doesn't change the order of the grandchildren.)
</para>

@node: a #GNode.


<!-- ##### FUNCTION g_node_traverse ##### -->
<para>
Traverses a tree starting at the given root #GNode.
It calls the given function for each node visited.
The traversal can be halted at any point by returning %TRUE from @func.
</para>

@root: the root #GNode of the tree to traverse.
@order: the order in which nodes are visited - %G_IN_ORDER, %G_PRE_ORDER,
%G_POST_ORDER, or %G_LEVEL_ORDER.
@flags: which types of children are to be visited, one of %G_TRAVERSE_ALL,
%G_TRAVERSE_LEAFS and %G_TRAVERSE_NON_LEAFS.
@max_depth: the maximum depth of the traversal. Nodes below this
depth will not be visited. If max_depth is -1 all nodes in the tree are
visited. If depth is 1, only the root is visited. If depth is 2, the root
and its children are visited. And so on.
@func: the function to call for each visited #GNode.
@data: user data to pass to the function.


<!-- ##### ENUM GTraverseFlags ##### -->
<para>
Specifies which nodes are visited during several of the tree functions,
including g_node_traverse() and g_node_find().
</para>

@G_TRAVERSE_LEAFS: only leaf nodes should be visited.
@G_TRAVERSE_NON_LEAFS: only non-leaf nodes should be visited.
@G_TRAVERSE_ALL: all nodes should be visited.
@G_TRAVERSE_MASK: 

<!-- ##### USER_FUNCTION GNodeTraverseFunc ##### -->
<para>
Specifies the type of function passed to g_node_traverse().
The function is called with each of the nodes visited, together with the
user data passed to g_node_traverse().
If the function returns %TRUE, then the traversal is stopped.
</para>

@node: a #GNode.
@data: user data passed to g_node_traverse().
@Returns: %TRUE to stop the traversal.


<!-- ##### FUNCTION g_node_children_foreach ##### -->
<para>
Calls a function for each of the children of a #GNode.
Note that it doesn't descend beneath the child nodes.
</para>

@node: a #GNode.
@flags: which types of children are to be visited, one of %G_TRAVERSE_ALL,
%G_TRAVERSE_LEAFS and %G_TRAVERSE_NON_LEAFS.
@func: the function to call for each visited node.
@data: user data to pass to the function.


<!-- ##### USER_FUNCTION GNodeForeachFunc ##### -->
<para>
Specifies the type of function passed to g_node_children_foreach().
The function is called with each child node, together with the user data
passed to g_node_children_foreach().
</para>

@node: a #GNode.
@data: user data passed to g_node_children_foreach().


<!-- ##### FUNCTION g_node_get_root ##### -->
<para>
Gets the root of a tree.
</para>

@node: a #GNode.
@Returns: the root of the tree.


<!-- ##### FUNCTION g_node_find ##### -->
<para>
Finds a #GNode in a tree.
</para>

@root: the root #GNode of the tree to search.
@order: the order in which nodes are visited - %G_IN_ORDER, %G_PRE_ORDER,
%G_POST_ORDER, or %G_LEVEL_ORDER.
@flags: which types of children are to be searched, one of %G_TRAVERSE_ALL,
%G_TRAVERSE_LEAFS and %G_TRAVERSE_NON_LEAFS.
@data: the data to find.
@Returns: the found #GNode, or %NULL if the data is not found.


<!-- ##### FUNCTION g_node_find_child ##### -->
<para>
Finds the first child of a #GNode with the given data.
</para>

@node: a #GNode.
@flags: which types of children are to be searched, one of %G_TRAVERSE_ALL,
%G_TRAVERSE_LEAFS and %G_TRAVERSE_NON_LEAFS.
@data: the data to find.
@Returns: the found child #GNode, or %NULL if the data is not found.


<!-- ##### FUNCTION g_node_child_index ##### -->
<para>
Gets the position of the first child of a #GNode which contains the given data.
</para>

@node: a #GNode.
@data: the data to find.
@Returns: the index of the child of @node which contains @data, or -1
if the data is not found.


<!-- ##### FUNCTION g_node_child_position ##### -->
<para>
Gets the position of a #GNode with respect to its siblings.
@child must be a child of @node.
The first child is numbered 0, the second 1, and so on.
</para>

@node: a #GNode.
@child: a child of @node.
@Returns: the position of @child with respect to its siblings.


<!-- ##### MACRO g_node_first_child ##### -->
<para>
Gets the first child of a #GNode.
</para>

@node: a #GNode.
@Returns: the last child of @node, or %NULL if @node is %NULL or has no children.


<!-- ##### FUNCTION g_node_last_child ##### -->
<para>
Gets the last child of a #GNode.
</para>

@node: a #GNode (must not be %NULL).
@Returns: the last child of @node, or %NULL if @node has no children.


<!-- ##### FUNCTION g_node_nth_child ##### -->
<para>
Gets a child of a #GNode, using the given index.
The first child is at index 0. If the index is too big, %NULL is returned.
</para>

@node: a #GNode.
@n: the index of the desired child.
@Returns: the child of @node at index @n.


<!-- ##### FUNCTION g_node_first_sibling ##### -->
<para>
Gets the first sibling of a #GNode.
This could possibly be the node itself.
</para>

@node: a #GNode.
@Returns: the first sibling of @node.


<!-- ##### MACRO g_node_next_sibling ##### -->
<para>
Gets the next sibling of a #GNode.
</para>

@node: a #GNode.
@Returns: the next sibling of @node, or %NULL if @node is %NULL.


<!-- ##### MACRO g_node_prev_sibling ##### -->
<para>
Gets the previous sibling of a #GNode.
</para>

@node: a #GNode.
@Returns: the previous sibling of @node, or %NULL if @node is %NULL.


<!-- ##### FUNCTION g_node_last_sibling ##### -->
<para>
Gets the last sibling of a #GNode.
This could possibly be the node itself.
</para>

@node: a #GNode.
@Returns: the last sibling of @node.


<!-- ##### MACRO G_NODE_IS_LEAF ##### -->
<para>
Returns %TRUE if a #GNode is a leaf node.
</para>

@node: a #GNode.
@Returns: %TRUE if the #GNode is a leaf node (i.e. it has no children).


<!-- ##### MACRO G_NODE_IS_ROOT ##### -->
<para>
Returns %TRUE if a #GNode is the root of a tree.
</para>

@node: a #GNode.
@Returns: %TRUE if the #GNode is the root of a tree (i.e. it has no parent
or siblings).


<!-- ##### FUNCTION g_node_depth ##### -->
<para>
Gets the depth of a #GNode.
</para>
<para>
If @node is %NULL the depth is 0.
The root node has a depth of 1.
For the children of the root node the depth is 2. And so on.
</para>

@node: a #GNode.
@Returns: the depth of the #GNode.


<!-- ##### FUNCTION g_node_n_nodes ##### -->
<para>
Gets the number of nodes in a tree.
</para>

@root: a #GNode.
@flags: which types of children are to be counted, one of %G_TRAVERSE_ALL,
%G_TRAVERSE_LEAFS and %G_TRAVERSE_NON_LEAFS.
@Returns: the number of nodes in the tree.


<!-- ##### FUNCTION g_node_n_children ##### -->
<para>
Gets the number of children of a #GNode.
</para>

@node: a #GNode.
@Returns: the number of children of @node.


<!-- ##### FUNCTION g_node_is_ancestor ##### -->
<para>
Returns %TRUE if @node is an ancestor of @descendant.
This is true if node is the parent of @descendant, or if node is the
grandparent of @descendant etc.
</para>

@node: a #GNode.
@descendant: a #GNode.
@Returns: %TRUE if @node is an ancestor of @descendant.


<!-- ##### FUNCTION g_node_max_height ##### -->
<para>
Gets the maximum height of all branches beneath a #GNode.
This is the maximum distance from the #GNode to all leaf nodes.
</para>
<para>
If @root is %NULL, 0 is returned. If @root has no children, 1 is returned.
If @root has children, 2 is returned. And so on.
</para>

@root: a #GNode.
@Returns: the maximum height of the tree beneath @root.


<!-- ##### FUNCTION g_node_unlink ##### -->
<para>
Unlinks a #GNode from a tree, resulting in two separate trees.
</para>

@node: the #GNode to unlink, which becomes the root of a new tree.


<!-- ##### FUNCTION g_node_destroy ##### -->
<para>
Removes the #GNode and its children from the tree, freeing any memory
allocated.
</para>

@root: the root of the tree/subtree to destroy.


<!-- ##### FUNCTION g_node_push_allocator ##### -->
<para>
Sets the allocator to use to allocate #GNode elements.
Use g_node_pop_allocator() to restore the previous allocator.
</para>

@allocator: the #GAllocator to use when allocating #GNode elements.


<!-- ##### FUNCTION g_node_pop_allocator ##### -->
<para>
Restores the previous #GAllocator, used when allocating #GNode elements.
</para>



