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/* __ *\
** ________ ___ / / ___ Scala API **
** / __/ __// _ | / / / _ | (c) 2003-2013, LAMP/EPFL **
** __\ \/ /__/ __ |/ /__/ __ | http://scala-lang.org/ **
** /____/\___/_/ |_/____/_/ | | **
** |/ **
\* */
package scala
package collection
import generic._
import immutable.{ List, Stream }
import scala.annotation.unchecked.uncheckedVariance
/** A template trait for iterable collections of type `Iterable[A]`.
* $iterableInfo
* @define iterableInfo
* This is a base trait for all $mutability Scala collections that define an `iterator`
* method to step through one-by-one the collection's elements.
* Implementations of this trait need to provide a concrete method with
* signature:
* {{{
* def iterator: Iterator[A]
* }}}
* They also need to provide a method `newBuilder`
* which creates a builder for collections of the same kind.
*
* This trait implements `Iterable`'s `foreach`
* method by stepping through all elements using `iterator`.
* Subclasses should re-implement `foreach` with something more efficient,
* if possible.
* This trait adds methods `iterator`, `sameElements`,
* `takeRight`, `dropRight` to the methods inherited
* from trait <a href="../Traversable.html" target="ContentFrame">
* `Traversable`</a>.
* Note: This trait replaces every method that uses `break` in
* `TraversableLike` by an iterator version.
*
* @author Martin Odersky
* @version 2.8
* @since 2.8
* @tparam A the element type of the collection
* @tparam Repr the type of the actual collection containing the elements.
*
* @define Coll Iterable
* @define coll iterable collection
*/
trait IterableLike[+A, +Repr] extends Any with Equals with TraversableLike[A, Repr] with GenIterableLike[A, Repr] {
self =>
override protected[this] def thisCollection: Iterable[A] = this.asInstanceOf[Iterable[A]]
override protected[this] def toCollection(repr: Repr): Iterable[A] = repr.asInstanceOf[Iterable[A]]
/** Creates a new iterator over all elements contained in this iterable object.
*
* @return the new iterator
*/
def iterator: Iterator[A]
/** Applies a function `f` to all elements of this $coll.
*
* Note: this method underlies the implementation of most other bulk operations.
* Subclasses should re-implement this method if a more efficient implementation exists.
*
* @usecase def foreach(f: A => Unit): Unit
* @inheritdoc
*/
def foreach[U](f: A => U): Unit =
iterator.foreach(f)
override /*TraversableLike*/ def forall(p: A => Boolean): Boolean =
iterator.forall(p)
override /*TraversableLike*/ def exists(p: A => Boolean): Boolean =
iterator.exists(p)
override /*TraversableLike*/ def find(p: A => Boolean): Option[A] =
iterator.find(p)
override /*TraversableLike*/ def isEmpty: Boolean =
!iterator.hasNext
override /*TraversableLike*/ def foldRight[B](z: B)(op: (A, B) => B): B =
iterator.foldRight(z)(op)
override /*TraversableLike*/ def reduceRight[B >: A](op: (A, B) => B): B =
iterator.reduceRight(op)
override /*TraversableLike*/ def toIterable: Iterable[A] =
thisCollection
override /*TraversableLike*/ def toIterator: Iterator[A] =
iterator
override /*TraversableLike*/ def head: A =
iterator.next
override /*TraversableLike*/ def slice(from: Int, until: Int): Repr = {
val lo = math.max(from, 0)
val elems = until - lo
val b = newBuilder
if (elems <= 0) b.result
else {
b.sizeHintBounded(elems, this)
var i = 0
val it = iterator drop lo
while (i < elems && it.hasNext) {
b += it.next
i += 1
}
b.result
}
}
override /*TraversableLike*/ def take(n: Int): Repr = {
val b = newBuilder
if (n <= 0) b.result
else {
b.sizeHintBounded(n, this)
var i = 0
val it = iterator
while (i < n && it.hasNext) {
b += it.next
i += 1
}
b.result
}
}
override /*TraversableLike*/ def drop(n: Int): Repr = {
val b = newBuilder
val lo = math.max(0, n)
b.sizeHint(this, -lo)
var i = 0
val it = iterator
while (i < n && it.hasNext) {
it.next
i += 1
}
(b ++= it).result
}
override /*TraversableLike*/ def takeWhile(p: A => Boolean): Repr = {
val b = newBuilder
val it = iterator
while (it.hasNext) {
val x = it.next
if (!p(x)) return b.result
b += x
}
b.result
}
/** Partitions elements in fixed size ${coll}s.
* @see [[scala.collection.Iterator]], method `grouped`
*
* @param size the number of elements per group
* @return An iterator producing ${coll}s of size `size`, except the
* last will be truncated if the elements don't divide evenly.
*/
def grouped(size: Int): Iterator[Repr] =
for (xs <- iterator grouped size) yield {
val b = newBuilder
b ++= xs
b.result
}
/** Groups elements in fixed size blocks by passing a "sliding window"
* over them (as opposed to partitioning them, as is done in grouped.)
* @see [[scala.collection.Iterator]], method `sliding`
*
* @param size the number of elements per group
* @return An iterator producing ${coll}s of size `size`, except the
* last and the only element will be truncated if there are
* fewer elements than size.
*/
def sliding(size: Int): Iterator[Repr] = sliding(size, 1)
/** Groups elements in fixed size blocks by passing a "sliding window"
* over them (as opposed to partitioning them, as is done in grouped.)
* @see [[scala.collection.Iterator]], method `sliding`
*
* @param size the number of elements per group
* @param step the distance between the first elements of successive
* groups (defaults to 1)
* @return An iterator producing ${coll}s of size `size`, except the
* last and the only element will be truncated if there are
* fewer elements than size.
*/
def sliding(size: Int, step: Int): Iterator[Repr] =
for (xs <- iterator.sliding(size, step)) yield {
val b = newBuilder
b ++= xs
b.result
}
/** Selects last ''n'' elements.
* $orderDependent
*
* @param n the number of elements to take
* @return a $coll consisting only of the last `n` elements of this $coll, or else the
* whole $coll, if it has less than `n` elements.
*/
def takeRight(n: Int): Repr = {
val b = newBuilder
b.sizeHintBounded(n, this)
val lead = this.iterator drop n
var go = false
for (x <- this.seq) {
if (lead.hasNext) lead.next
else go = true
if (go) b += x
}
b.result
}
/** Selects all elements except last ''n'' ones.
* $orderDependent
*
* @param n The number of elements to take
* @return a $coll consisting of all elements of this $coll except the last `n` ones, or else the
* empty $coll, if this $coll has less than `n` elements.
*/
def dropRight(n: Int): Repr = {
val b = newBuilder
if (n >= 0) b.sizeHint(this, -n)
val lead = iterator drop n
val it = iterator
while (lead.hasNext) {
b += it.next
lead.next
}
b.result
}
override /*TraversableLike*/ def copyToArray[B >: A](xs: Array[B], start: Int, len: Int) {
var i = start
val end = (start + len) min xs.length
val it = iterator
while (i < end && it.hasNext) {
xs(i) = it.next
i += 1
}
}
def zip[A1 >: A, B, That](that: GenIterable[B])(implicit bf: CanBuildFrom[Repr, (A1, B), That]): That = {
val b = bf(repr)
val these = this.iterator
val those = that.iterator
while (these.hasNext && those.hasNext)
b += ((these.next, those.next))
b.result
}
def zipAll[B, A1 >: A, That](that: GenIterable[B], thisElem: A1, thatElem: B)(implicit bf: CanBuildFrom[Repr, (A1, B), That]): That = {
val b = bf(repr)
val these = this.iterator
val those = that.iterator
while (these.hasNext && those.hasNext)
b += ((these.next, those.next))
while (these.hasNext)
b += ((these.next, thatElem))
while (those.hasNext)
b += ((thisElem, those.next))
b.result
}
def zipWithIndex[A1 >: A, That](implicit bf: CanBuildFrom[Repr, (A1, Int), That]): That = {
val b = bf(repr)
var i = 0
for (x <- this) {
b += ((x, i))
i +=1
}
b.result
}
def sameElements[B >: A](that: GenIterable[B]): Boolean = {
val these = this.iterator
val those = that.iterator
while (these.hasNext && those.hasNext)
if (these.next != those.next)
return false
!these.hasNext && !those.hasNext
}
override /*TraversableLike*/ def toStream: Stream[A] = iterator.toStream
/** Method called from equality methods, so that user-defined subclasses can
* refuse to be equal to other collections of the same kind.
* @param that The object with which this $coll should be compared
* @return `true`, if this $coll can possibly equal `that`, `false` otherwise. The test
* takes into consideration only the run-time types of objects but ignores their elements.
*/
override /*TraversableLike*/ def canEqual(that: Any) = true
override /*TraversableLike*/ def view = new IterableView[A, Repr] {
protected lazy val underlying = self.repr
override def isEmpty = self.isEmpty
override def iterator = self.iterator
}
override /*TraversableLike*/ def view(from: Int, until: Int) = view.slice(from, until)
}
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