/* __ *\
** ________ ___ / / ___ Scala API **
** / __/ __// _ | / / / _ | (c) 2003-2009, LAMP/EPFL **
** __\ \/ /__/ __ |/ /__/ __ | http://scala-lang.org/ **
** /____/\___/_/ |_/____/_/ | | **
** |/ **
\* */
// $Id$
// !!! todo: integrate in collections framework
package scala.collection.mutable;
private object Utils{
def growArray(x : Array[AnyRef]) = {
val y = new Array[AnyRef](x.length * 2);
Array.copy(x, 0, y, 0, x.length);
y;
}
def clone(x : Array[AnyRef]) = {
val y = new Array[AnyRef](x.length);
Array.copy(x, 0, y, 0, x.length);
y;
}
}
/**
* Simple stack class backed by an array. Should be significantly faster
* than the standard mutable stack.
*
* @author David MacIver
*/
@cloneable
class ArrayStack[T] private(private var table : Array[AnyRef],
private var index : Int) extends Iterable[T]{
def this() = this(new Array[AnyRef](1), 0);
/**
* Push an element onto the stack.
*
* @param x The element to push
*/
def push(x : T) = {
if (index == table.length) table = Utils.growArray(table);
table(index) = x.asInstanceOf[AnyRef];
index += 1;
}
/**
* Pop the top element off the stack.
*/
def pop = {
if (index == 0) error("Stack empty");
index -= 1;
val x = table(index).asInstanceOf[T];
table(index) = null;
x;
}
/** View the top element of the stack. */
@deprecated("use top instead")
def peek = top
/**
* View the top element of the stack.
*/
def top = table(index - 1).asInstanceOf[T]
/**
* Duplicate the top element of the stack.
*/
def dup = push(top);
/**
* Empties the stack.
*/
def clear = {
index = 0;
table = new Array(1);
}
/**
* Empties the stack, passing all elements on it in FIFO order to the
* provided function.
*
* @param f The function to drain to.
*/
def drain(f : T => Unit) = while(!isEmpty) f(pop);
/**
* Pushes all the provided elements onto the stack.
*
* @param x The source of elements to push
*/
def ++=(x : collection.Iterable[T]): this.type = { x.foreach(this +=(_)); this }
/**
* Pushes all the provided elements onto the stack.
*
* @param x The source of elements to push
*/
def ++=(x : Iterator[T]): this.type = { x.foreach(this +=(_)); this }
/**
* Alias for push.
*
* @param x The element to push
*/
def +=(x : T): this.type = { push(x); this }
/**
* Pop the top two elements off the stack, apply f to them and push the result
* back on to the stack.
*
* @param f The combining function
*/
def combine(f : (T, T) => T) = push(f(pop, pop));
/**
* Repeatedly combine the top elements of the stack until the stack contains only
* one element.
*/
def reduceWith(f : (T, T) => T) = while(size > 1) combine(f)
override def size = index;
/**
* Evaluates the expression, preserving the contents of the stack so that
* any changes the evaluation makes to the stack contents will be undone after
* it completes.
*
* @param action The action to run.
*/
def preserving[T](action : => T) = {
val oldIndex = index;
val oldTable = Utils.clone(table);
try{
action;
} finally {
index = oldIndex;
table = oldTable;
}
}
override def isEmpty = index == 0;
/**
* Iterates over the stack in LIFO order.
*/
def iterator: Iterator[T] = new Iterator[T]{
var currentIndex = index;
def hasNext = currentIndex > 0;
def next = {
currentIndex -= 1;
table(currentIndex).asInstanceOf[T];
}
}
override def foreach[U](f : T => U){
var currentIndex = index;
while(currentIndex > 0){
currentIndex -= 1;
f(table(currentIndex).asInstanceOf[T]);
}
}
override def clone = new ArrayStack[T](Utils.clone(table), index);
}