in scala/collection/immutable
class Tree

abstract class Tree[A,B](view: (A) => Ordered[A])
extends Object
with ScalaObject
with java.io.Serializable
Implementing classes or objects:
class TreeSet[A](view: (A) => Ordered[A])
class TreeMap[A,B](view: (A) => Ordered[A])

General Balanced Trees - highly efficient functional dictionaries. An efficient implementation of Prof. Arne Andersson's General Balanced Trees. These have no storage overhead compared to plain unbalanced binary trees, and their performance is in general better than AVL trees.

This implementation does not balance the trees after deletions. Since deletions don't increase the height of a tree, this should be OK in most applications. A balance method is provided for those cases where rebalancing is needed.

The tree consists of entries conatining a key with an order.

When instanciating the tree an order for the keys has to be supplied.

Author:
Erik Stenman, Michel Schinz
Version:
1.1, 2005-01-20

Field Summary
protected abstract type This
     The type returned when creating a new tree.
protected type aNode
     The type of nodes that the tree is build from.

Method Summary
protected abstract def New(sz: Int, t: GBTree[A,B]): This
     This abstract method should be defined by a concrete implementation C[T] as something like:
     override def New(sz:Int,t:aNode):This {
       new C[T](order) {
        override def size=sz;
        override protected def tree:aNode=t;
     }
    
The concrete implementation should also override the def of This override type This = C[T];
protected def add(key: A, entry: B): This
     A new tree with the entry added is returned, assuming that key is not in the tree.
  def balance: This
     Create a new balanced tree from the tree.
protected def deleteAny(key: A): This
     Removes the key from the tree.
protected def entries: Iterator[B]
     Gives you an iterator over all elements in the tree.
protected def findValue(key: A): Option[B]
     Check if this map maps key to a value and return the value if it exists.
protected abstract def getThis: This
  def size: Int
     The size of the tree, returns 0 (zero) if the tree is empty.
protected def tree: GBTree[A,B]
     The nodes in the tree.
protected def updateOrAdd(key: A, entry: B): This
     A new tree with the entry added is returned, if key is not in the tree, otherwise the key is updated with the new entry.

Methods inherited from java/lang/Object-class
clone, eq, equals, finalize, getClass, hashCode, ne, notify, notifyAll, synchronized, toString, wait, wait, wait

Methods inherited from scala/Any-class
!=, ==, asInstanceOf, isInstanceOf, match

Methods inherited from scala/ScalaObject-class
getScalaType

Field Detail

This

  protected abstract type This<:Tree[A,B]
The type returned when creating a new tree. This type should be defined by concrete implementations e.g.
   class C[T](...) extends Tree[A,B](...) {
     type This = C[T];
   

aNode

  protected type aNode = GBTree[A,B]
The type of nodes that the tree is build from.
Method Detail

getThis

  protected abstract def getThis: This

tree

  protected def tree: GBTree[A,B]
The nodes in the tree.

New

  protected abstract def New(sz: Int, t: GBTree[A,B]): This
This abstract method should be defined by a concrete implementation C[T] as something like:
     override def New(sz:Int,t:aNode):This {
       new C[T](order) {
        override def size=sz;
        override protected def tree:aNode=t;
     }
    
The concrete implementation should also override the def of This override type This = C[T];

size

  def size: Int
The size of the tree, returns 0 (zero) if the tree is empty.
Returns:
The number of nodes in the tree as an integer.

add

  protected def add(key: A, entry: B): This
A new tree with the entry added is returned, assuming that key is not in the tree.

updateOrAdd

  protected def updateOrAdd(key: A, entry: B): This
A new tree with the entry added is returned, if key is not in the tree, otherwise the key is updated with the new entry.

deleteAny

  protected def deleteAny(key: A): This
Removes the key from the tree.

findValue

  protected def findValue(key: A): Option[B]
Check if this map maps key to a value and return the value if it exists.
Parameters:
key - the key of the mapping of interest
Returns:
the value of the mapping, if it exists

entries

  protected def entries: Iterator[B]
Gives you an iterator over all elements in the tree. The iterator structure corresponds to the call stack of an in-order traversal. Note: The iterator itself has a state, i.e., it is not functional.

balance

  def balance: This
Create a new balanced tree from the tree. Might be useful to call after many deletions, since deletion does not rebalance the tree.