Modified Preorder Tree Traversal アルゴリズムの理解とその実装はじめ

 #16

controllers/plugin_mptt.py

@@ -1,11 +1,49 @@
-# -*- coding: utf-8 -*-
-from plugin_solidtable import SOLIDTABLE
-from gluon.contrib.populate import populate
-
-db = DAL('sqlite:memory:') 
-db.define_table('product', Field('name'))
-populate(db.product, 10)
-
-def index():
-    table = SOLIDTABLE(db(db.product.id>0).select(), renderstyle=True)
-    return dict(table=table)
+'''
+Created on 2011/08/12
+
+@author: yusuke.kishita
+'''
+
+# -*- coding: utf-8 -*-
+from gluon import *
+
+db = DAL('sqlite:memory:')
+db.define_table('tree', 
+    Field('title'),  Field('left', 'integer'), 
+    Field('right', 'integer'),
+    )
+db.tree.insert(title='Food',left=1,right=2)
+
+def add_node(title,parent_title):
+    """
+    add_node('Fruit','Food')
+    add_node('Meat','Food')
+    add_node('Red','Food')
+    """
+    parent = db(db.tree.title == parent_title).select()[0]
+    db(db.tree.right >= parent.right).update(right = db.tree.right+2)
+    db(db.tree.left >= parent.right).update(left = db.tree.left+2)
+    db.tree.insert(title = title, left = parent.right, right = parent.right + 1)
+
+def ancestors(title, *fields):
+    """print ancestors('Red', db.tree.title)"""
+    node = db(db.tree.title == title).select()[0]
+    return db(db.tree.left < node.left)(db.tree.right > node.right).select(orderby = db.tree.left, *fields)  
+
+def descendants(title, *fields):
+    """print descendants('Fruit', db.tree.title)"""
+    node = db(db.tree.title == title).select()[0]
+    return db(db.tree.left > node.left)(db.tree.right < node.right).select(orderby=db.tree.left, *fields)
+
+def test():
+    print db().select(db.tree.ALL)
+    add_node('Fruit', 'Food')
+    print db().select(db.tree.ALL)
+    add_node('Meat', 'Food')
+    print db().select(db.tree.ALL)
+    add_node('Red', 'Food')
+    print db().select(db.tree.ALL)
+    print ancestors('Red', db.tree.title)
+    print descendants('Fruit', db.tree.title)
+
+test()