<!-- ##### SECTION Title ##### -->
Balanced Binary Trees

<!-- ##### SECTION Short_Description ##### -->
a sorted collection of key/value pairs optimised for searching
and traversing in order.

<!-- ##### SECTION Long_Description ##### -->
<para>
The #GTree structure and its associated functions provide a sorted collection
of key/value pairs optimised for searching and traversing in order.
</para>
<para>
To create a new #GTree use g_tree_new().
</para>
<para>
To insert a key/value pair into a #GTree use g_tree_insert().
</para>
<para>
To lookup the value corresponding to a given key, use g_tree_lookup().
</para>
<para>
To find out the number of nodes in a #GTree, use g_tree_nnodes().
To get the height of a #GTree, use g_tree_height().
</para>
<para>
To traverse a #GTree, calling a function for each node visited in the
traversal, use g_tree_traverse().
</para>
<para>
To remove a key/value pair use g_tree_remove().
</para>
<para>
To destroy a #GTree, use g_tree_destroy().
</para>

<!-- ##### STRUCT GTree ##### -->
<para>
The #GTree struct is an opaque data structure representing a
<link linkend="glib-Balanced-Binary-Trees">Balanced Binary Tree</link>.
It should be accessed only by using the following functions.
</para>


<!-- ##### FUNCTION g_tree_new ##### -->
<para>
Creates a new GTree.
</para>

@key_compare_func: the function used to order the nodes in the #GTree.
It should return values similar to the standard <function>strcmp()</function>
function -
0 if the two arguments are equal, a negative value if the first argument comes
before the second, or a positive value if the first argument comes after the
second.
@Returns: a new #GTree.

<!-- ##### FUNCTION g_tree_insert ##### -->
<para>
Inserts a key/value pair into a #GTree.
If the given key already exists in the #GTree it is set to the new value.
(If you are using dynamically allocated keys and values you should be careful
to ensure that the old values are freed.)
</para>
<para>
The tree is automatically 'balanced' as new key/value pairs are added,
so that the distance from the root to every leaf is as small as possible.
</para>

@tree: a #GTree.
@key: the key to insert.
@value: the value corresponding to the key.

<!-- ##### FUNCTION g_tree_remove ##### -->
<para>
Removes a key/value pair from a #GTree.
If the key or value is dynamically allocated you must remember to free them
yourself.
</para>

@tree: a #GTree.
@key: the key to remove.

<!-- ##### FUNCTION g_tree_destroy ##### -->
<para>
Destroys the #GTree, freeing all of the memory allocated.
But it doesn't free keys or values.
</para>

@tree: a #GTree.

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

@tree: a #GTree.
@Returns: the number of nodes in the #GTree.

<!-- ##### FUNCTION g_tree_height ##### -->
<para>
Gets the height of a #GTree.
</para>
<para>
If the #GTree contains no nodes, the height is 0.
If the #GTree contains only one root node the height is 1.
If the root node has children the height is 2, etc.
</para>

@tree: a #GTree.
@Returns: the height of the #GTree.

<!-- ##### FUNCTION g_tree_lookup ##### -->
<para>
Gets the value corresponding to the given key.
Since a #GTree is automatically balanced as key/value pairs are
added, key lookup is very fast.
</para>

@tree: a #GTree.
@key: the key to look up.
@Returns: the value corresponding to the key.

<!-- ##### FUNCTION g_tree_search ##### -->
<para>
Searches a #GTree using an alternative form of the comparison function.
</para>
<para>
This function is not as useful as it sounds.
It allows you to use a different function for performing the lookup of
a key. However, since the tree is ordered according to the @key_compare_func
function passed to g_tree_new(), the function you pass to g_tree_search() must
return exactly the same value as would be returned by the comparison function,
for each pair of tree nodes, or the search will not work.
</para>
<para>
To search for a specific value, you can use g_tree_traverse().
</para>

@tree: a #GTree.
@search_func: the comparison function used to search the #GTree.
@data: the data passed as the second argument to the @search_func function.
@Returns: the value corresponding to the found key, or NULL if the key is
not found.

<!-- ##### USER_FUNCTION GSearchFunc ##### -->
<para>
Specifies the type of function passed to g_tree_search().
</para>

@key: a key from a #GTree.
@data: the data to compare with the key.
@Returns: 0 if the desired key has been found, a negative number if the
desired key comes before @key in the sort order of the #GTree, or a positive
value if the desired key comes after @key.

<!-- ##### FUNCTION g_tree_traverse ##### -->
<para>
Calls the given function for each node in the GTree.
</para>

@tree: a #GTree.
@traverse_func: the function to call for each node visited. If this function
returns TRUE, the traversal is stopped.
@traverse_type: the order in which nodes are visited, one of %G_IN_ORDER,
%G_PRE_ORDER and %G_POST_ORDER.
@data: user data to pass to the traverse function.

<!-- ##### USER_FUNCTION GTraverseFunc ##### -->
<para>
Specifies the type of function passed to g_tree_traverse().
It is passed the key and value of each node, together with
the @user_data parameter passed to g_tree_traverse().
If the function returns TRUE, the traversal is stopped.
</para>

@key: a key of a #GTree node.
@value: the value corresponding to the key.
@data: user data passed to g_tree_traverse().
@Returns: TRUE to stop the traversal.

<!-- ##### ENUM GTraverseType ##### -->
<para>
Specifies the type of traveral performed by g_tree_traverse(),
g_node_traverse() and g_node_find().
<itemizedlist>
<listitem><para>
%G_PRE_ORDER visits a node, then its children.
</para></listitem>
<listitem><para>
%G_IN_ORDER vists a node's left child first, then the node itself, then its
right child. This is the one to use if you want the output sorted according
to the compare function.
</para></listitem>
<listitem><para>
%G_POST_ORDER visits the node's children, then the node itself.
</para></listitem>
<listitem><para>
%G_LEVEL_ORDER is not implemented for
<link linkend="glib-Balanced-Binary-Trees">Balanced Binary Trees</link>.
For <link linkend="glib-N-ary-Trees">N-ary Trees</link>
it calls the function for each child of the node, then it recursively visits
each child.
</para></listitem>
</itemizedlist>
</para>


