abt: New function abt_is_empty().

[pspp] / src / libpspp / abt.h

diff --git a/src/libpspp/abt.h b/src/libpspp/abt.h
index 24d7268a2d6543a383361c50914d796e52e7b6c1..f97d957e5251c70aeb55190f4b313b6eefea0799 100644 (file)
--- a/src/libpspp/abt.h
+++ b/src/libpspp/abt.h
@@ -1,5 +1,5 @@
 /* PSPP - a program for statistical analysis.
-   Copyright (C) 2007, 2009 Free Software Foundation, Inc.
+   Copyright (C) 2007, 2009, 2011 Free Software Foundation, Inc.
 
    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -34,10 +34,9 @@
 
    The ABT data structure partially abstracts augmentation.  The
    client passes in a "reaugmentation" function that accepts a
-   node and its left and right children.  This function must
-   recalculate the node's augmentation data based on its own
-   contents and the contents of its children, and store the new
-   augmentation data in the node.
+   node.  This function must recalculate the node's augmentation
+   data based on its own contents and the contents of its
+   children, and store the new augmentation data in the node.
 
    The ABT automatically calls the reaugmentation function
    whenever it can tell that a node's augmentation data might
@@ -104,19 +103,16 @@
      }
 
      // Recalculates the count for NODE's subtree by adding up the
-     // counts for its LEFT and RIGHT child subtrees.
+     // counts for its left and right child subtrees.
      static void
-     reaugment_elements (struct abt_node *node_,
-                         const struct abt_node *left,
-                         const struct abt_node *right,
-                         const void *aux)
+     reaugment_elements (struct abt_node *node_, const void *aux)
      {
        struct element *node = node_to_element (node_);
        node->count = 1;
-       if (left != NULL)
-         node->count += node_to_element (left)->count;
-       if (right != NULL)
-         node->count += node_to_element (right)->count;
+       if (node->node.down[0] != NULL)
+         node->count += node_to_element (node->node.down[0])->count;
+       if (node->node.down[1] != NULL)
+         node->count += node_to_element (node->node.down[1])->count;
      }
 
      // Finds and returns the element in ABT that is in the given
@@ -149,8 +145,9 @@
    code and links to other resources, such as the original AA
    tree paper.  */
 
+#include <stdbool.h>
 #include <stddef.h>
-#include <libpspp/cast.h>
+#include "libpspp/cast.h"
 
 /* Returns the data structure corresponding to the given NODE,
    assuming that NODE is embedded as the given MEMBER name in
@@ -173,12 +170,10 @@ typedef int abt_compare_func (const struct abt_node *a,
                               const struct abt_node *b,
                               const void *aux);
 
-/* Recalculates NODE's augmentation based on NODE's data and that
-   of its LEFT and RIGHT children, with the tree's AUX. */
-typedef void abt_reaugment_func (struct abt_node *node,
-                                 const struct abt_node *left,
-                                 const struct abt_node *right,
-                                 const void *aux);
+/* Recalculates NODE's augmentation based on NODE's data and that of its left
+   and right children NODE->down[0] and NODE[1], respectively, with the tree's
+   AUX. */
+typedef void abt_reaugment_func (struct abt_node *node, const void *aux);
 
 /* An augmented binary tree. */
 struct abt
@@ -192,6 +187,8 @@ struct abt
 void abt_init (struct abt *, abt_compare_func *, abt_reaugment_func *,
                const void *aux);
 
+static inline bool abt_is_empty (const struct abt *);
+
 struct abt_node *abt_insert (struct abt *, struct abt_node *);
 void abt_insert_after (struct abt *,
                        const struct abt_node *, struct abt_node *);
@@ -209,4 +206,12 @@ void abt_reaugmented (const struct abt *, struct abt_node *);
 struct abt_node *abt_changed (struct abt *, struct abt_node *);
 void abt_moved (struct abt *, struct abt_node *);
 
+/* Returns true if ABT contains no nodes, false if ABT contains at least one
+   node. */
+static inline bool
+abt_is_empty (const struct abt *abt)
+{
+  return abt->root == NULL;
+}
+
 #endif /* libpspp/abt.h */