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|
/* __ *\
** ________ ___ / / ___ Scala API **
** / __/ __// _ | / / / _ | (c) 2003-2009, LAMP/EPFL **
** __\ \/ /__/ __ |/ /__/ __ | http://scala-lang.org/ **
** /____/\___/_/ |_/____/_/ | | **
** |/ **
\* */
// $Id$
package scala.collection.generic
import mutable.ListBuffer
// import immutable.{List, Nil, ::}
import generic._
import util.control.Breaks._
/** Class <code>Linear[A]</code> represents linear sequences of elements.
* For such sequences `isEmpty`, `head` and `tail` are guaranteed to be
* efficient constant time (or near so) operations.
* It does not add any methods to <code>Sequence</code> but overrides
* several methods with optimized implementations.
*
* @author Martin Odersky
* @author Matthias Zenger
* @version 1.0, 16/07/2003
*/
trait LinearSequenceTemplate[+A, +This <: LinearSequenceTemplate[A, This] with LinearSequence[A]] extends SequenceTemplate[A, This] { self =>
/** Abstract method to be implemented in a subclass */
def isEmpty: Boolean
/** Abstract method to be implemented in a subclass */
def head: A
/** Abstract method to be implemented in a subclass */
def tail: This
/** Returns the number of elements in the linear sequence.
*/
def length: Int = {
var these = self
var len = 0
while (!these.isEmpty) {
len += 1
these = these.tail
}
len
}
/** Returns the <code>n</code>-th element of this linear sequence. The first element
* (head of the linear sequence) is at position 0.
*
* @param n index of the element to return
* @return the element at position <code>n</code> in this linear sequence.
* @throws Predef.NoSuchElementException if the linear sequence is too short.
*/
def apply(n: Int): A = drop(n).head
/** Returns the elements in the sequence as an iterator
*/
override def iterator: Iterator[A] = new Iterator[A] {
var these = self
def hasNext: Boolean = !these.isEmpty
def next: A =
if (hasNext) {
val result = these.head; these = these.tail; result
} else Iterator.empty.next
override def toList: List[A] = these.toList
}
/** Apply the given function <code>f</code> to each element of this linear sequence
* (while respecting the order of the elements).
*
* @param f the treatment to apply to each element.
*/
override def foreach[B](f: A => B) {
var these = this
while (!these.isEmpty) {
f(these.head)
these = these.tail
}
}
/** Tests if the predicate <code>p</code> is satisfied by all elements
* in this list.
*
* @param p the test predicate.
* @return <code>true</code> iff all elements of this list satisfy the
* predicate <code>p</code>.
*/
override def forall(p: A => Boolean): Boolean = {
var these = this
while (!these.isEmpty) {
if (!p(these.head)) return false
these = these.tail
}
true
}
/** Tests the existence in this list of an element that satisfies the
* predicate <code>p</code>.
*
* @param p the test predicate.
* @return <code>true</code> iff there exists an element in this list that
* satisfies the predicate <code>p</code>.
*/
override def exists(p: A => Boolean): Boolean = {
var these = this
while (!these.isEmpty) {
if (p(these.head)) return true
these = these.tail
}
false
}
/** Count the number of elements in the iterable which satisfy a predicate.
*
* @param p the predicate for which to count
* @return the number of elements satisfying the predicate <code>p</code>.
*/
override def count(p: A => Boolean): Int = {
var these = this
var cnt = 0
while (!these.isEmpty) {
if (p(these.head)) cnt += 1
these = these.tail
}
cnt
}
/** Find and return the first element of the list satisfying a
* predicate, if any.
*
* @param p the predicate
* @return the first element in the list satisfying <code>p</code>,
* or <code>None</code> if none exists.
*/
override def find(p: A => Boolean): Option[A] = {
var these = this
while (!these.isEmpty) {
if (p(these.head)) return Some(these.head)
these = these.tail
}
None
}
/** Combines the elements of this list together using the binary
* function <code>f</code>, from left to right, and starting with
* the value <code>z</code>.
*
* @return <code>f(... (f(f(z, a<sub>0</sub>), a<sub>1</sub>) ...),
* a<sub>n</sub>)</code> if the list is
* <code>[a<sub>0</sub>, a<sub>1</sub>, ..., a<sub>n</sub>]</code>.
*/
override def foldLeft[B](z: B)(f: (B, A) => B): B = {
var acc = z
var these = this
while (!these.isEmpty) {
acc = f(acc, these.head)
these = these.tail
}
acc
}
/** Combines the elements of this list together using the binary
* function <code>f</code>, from right to left, and starting with
* the value <code>z</code>.
*
* @return <code>f(a<sub>0</sub>, f(a<sub>1</sub>, f(..., f(a<sub>n</sub>, z)...)))</code>
* if the list is <code>[a<sub>0</sub>, a1, ..., a<sub>n</sub>]</code>.
*/
override def foldRight[B](z: B)(f: (A, B) => B): B =
if (this.isEmpty) z
else f(head, tail.foldRight(z)(f))
/** Combines the elements of this list together using the binary
* operator <code>op</code>, from left to right
* @param op The operator to apply
* @return <code>op(... op(a<sub>0</sub>,a<sub>1</sub>), ..., a<sub>n</sub>)</code>
if the list has elements
* <code>a<sub>0</sub>, a<sub>1</sub>, ..., a<sub>n</sub></code>.
* @throws Predef.UnsupportedOperationException if the list is empty.
*/
override def reduceLeft[B >: A](f: (B, A) => B): B =
if (isEmpty) throw new UnsupportedOperationException("empty.reduceLeft")
else tail.foldLeft[B](head)(f)
/** Combines the elements of this iterable object together using the binary
* operator <code>op</code>, from right to left
* @note Will not terminate for infinite-sized collections.
* @param op The operator to apply
*
* @return <code>a<sub>0</sub> op (... op (a<sub>n-1</sub> op a<sub>n</sub>)...)</code>
* if the iterable object has elements <code>a<sub>0</sub>, a<sub>1</sub>, ...,
* a<sub>n</sub></code>.
*
* @throws Predef.UnsupportedOperationException if the iterator is empty.
*/
override def reduceRight[B >: A](op: (A, B) => B): B =
if (isEmpty) throw new UnsupportedOperationException("Nil.reduceRight")
else if (tail.isEmpty) head
else op(head, tail.reduceRight(op))
/** The last element of this linear sequence.
*
* @throws Predef.NoSuchElementException if the linear sequence is empty.
*/
override def last: A = {
if (isEmpty) throw new NoSuchElementException
var these = this
var nx = these.tail
while (!nx.isEmpty) {
these = nx
nx = nx.tail
}
these.head
}
override def take(n: Int): This = {
val b = newBuilder
var i = 0
var these = this
while (!these.isEmpty && i < n) {
i += 1
b += these.head
these = these.tail
}
b.result
}
override def drop(n: Int): This = {
var these: This = thisCollection
var count = n
while (!these.isEmpty && count > 0) {
these = these.tail
count -= 1
}
these
}
/** Returns the rightmost <code>n</code> elements from this iterable.
* @param n the number of elements to take
*/
override def dropRight(n: Int): This = {
val b = newBuilder
var these = this
var lead = this drop n
while (!lead.isEmpty) {
b += these.head
these = these.tail
lead = lead.tail
}
b.result
}
/** Returns a pair consisting of the longest prefix of the linear sequence whose
* elements all satisfy the given predicate, and the rest of the linear sequence.
*
* @param p the test predicate
*/
override def span(p: A => Boolean): (This, This) = {
var these: This = thisCollection
val b = newBuilder
while (!these.isEmpty && p(these.head)) {
b += these.head
these = these.tail
}
(b.result, these)
}
/** Returns true iff the other linear sequence contains the same elements as this one.
*
* @note will not terminate for two infinite-sized linear sequences.
* @param that the other linear sequence
*/
override def sameElements[B >: A](that: Iterable[B]): Boolean = that match {
case that1: LinearSequence[_] =>
var these = this
var those = that1
while (!these.isEmpty && !those.isEmpty && these.head == those.head) {
these = these.tail
those = those.tail
}
these.isEmpty && those.isEmpty
case _ => super.sameElements(that)
}
// Overridden methods from Sequence
/** Result of comparing <code>length</code> with operand <code>len</code>.
* returns <code>x</code> where
* <code>x < 0</code> iff <code>this.length < len</code>
* <code>x == 0</code> iff <code>this.length == len</code>
* <code>x > 0</code> iff <code>this.length > len</code>.
*/
override def lengthCompare(len: Int): Int = {
var i = 0
var these = self
while (!these.isEmpty && i <= len) {
i += 1
these = these.tail
}
i - len
}
/** Is this partial function defined for the index <code>x</code>?
*/
override def isDefinedAt(x: Int): Boolean = x >= 0 && lengthCompare(x) > 0
/** Returns length of longest segment starting from a start index `from`
* such that every element of the segment satisfies predicate `p`.
* @note may not terminate for infinite-sized collections.
* @param p the predicate
* @param from the start index
*/
override def segmentLength(p: A => Boolean, from: Int): Int = {
var i = 0
var these = this drop from
while (!these.isEmpty && p(these.head)) {
i += 1
these = these.tail
}
i
}
/** Returns index of the first element starting from a start index
* satisying a predicate, or -1, if none exists.
*
* @note may not terminate for infinite-sized linear sequences.
* @param p the predicate
* @param from the start index
*/
override def indexWhere(p: A => Boolean, from: Int): Int = {
var i = from
var these = this drop from
while (!these.isEmpty && !p(these.head)) {
i += 1
these = these.tail
}
if (these.isEmpty) -1 else i
}
/** Returns index of the last element satisying a predicate, or -1, if none exists.
*
* @param p the predicate
* @return the index of the last element satisfying <code>p</code>,
* or -1 if such an element does not exist
*/
override def lastIndexWhere(p: A => Boolean, end: Int): Int = {
var i = 0
var these = this
var last = -1
while (!these.isEmpty && i <= end) {
if (p(these.head)) last = i
these = these.tail
i += 1
}
last
}
override def equals(that: Any): Boolean = that match {
case that1: LinearSequence[a] =>
var these = this
var those = that1
while (!these.isEmpty && !those.isEmpty && these.head == those.head) {
these = these.tail
those = those.tail
}
these.isEmpty && those.isEmpty
case _ =>
super.equals(that)
}
}
|