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/* __ *\
** ________ ___ / / ___ Scala API **
** / __/ __// _ | / / / _ | (c) 2003-2013, LAMP/EPFL **
** __\ \/ /__/ __ |/ /__/ __ | http://scala-lang.org/ **
** /____/\___/_/ |_/____/_/ | | **
** |/ **
\* */
package scala
package collection
import generic._
import Seq.fill
/** A template trait for non-strict views of sequences.
* $seqViewInfo
*
* @define seqViewInfo
* $viewInfo
* All views for sequences are defined by re-interpreting the `length` and
* `apply` methods.
*
* @author Martin Odersky
* @version 2.8
* @since 2.8
* @tparam A the element type of the view
* @tparam Coll the type of the underlying collection containing the elements.
* @tparam This the type of the view itself
*/
trait SeqViewLike[+A,
+Coll,
+This <: SeqView[A, Coll] with SeqViewLike[A, Coll, This]]
extends Seq[A] with SeqLike[A, This] with IterableView[A, Coll] with IterableViewLike[A, Coll, This]
{ self =>
/** Explicit instantiation of the `Transformed` trait to reduce class file size in subclasses. */
private[collection] abstract class AbstractTransformed[+B] extends Seq[B] with super[IterableViewLike].Transformed[B] with Transformed[B]
trait Transformed[+B] extends SeqView[B, Coll] with super.Transformed[B] {
def length: Int
def apply(idx: Int): B
override def toString = viewToString
}
trait EmptyView extends Transformed[Nothing] with super.EmptyView {
final override def length = 0
final override def apply(n: Int) = Nil(n)
}
trait Forced[B] extends super.Forced[B] with Transformed[B] {
def length = forced.length
def apply(idx: Int) = forced.apply(idx)
}
trait Sliced extends super.Sliced with Transformed[A] {
def length = iterator.size
def apply(idx: Int): A =
if (idx + from < until) self.apply(idx + from)
else throw new IndexOutOfBoundsException(idx.toString)
override def foreach[U](f: A => U) = iterator foreach f
override def iterator: Iterator[A] = self.iterator drop from take endpoints.width
}
trait Mapped[B] extends super.Mapped[B] with Transformed[B] {
def length = self.length
def apply(idx: Int): B = mapping(self(idx))
}
trait FlatMapped[B] extends super.FlatMapped[B] with Transformed[B] {
protected[this] lazy val index = {
val index = new Array[Int](self.length + 1)
index(0) = 0
for (i <- 0 until self.length) // note that if the mapping returns a list, performance is bad, bad
index(i + 1) = index(i) + mapping(self(i)).seq.size
index
}
protected[this] def findRow(idx: Int, lo: Int, hi: Int): Int = {
val mid = (lo + hi) / 2
if (idx < index(mid)) findRow(idx, lo, mid - 1)
else if (idx >= index(mid + 1)) findRow(idx, mid + 1, hi)
else mid
}
def length = index(self.length)
def apply(idx: Int) = {
val row = findRow(idx, 0, self.length - 1)
mapping(self(row)).seq.toSeq(idx - index(row))
}
}
trait Appended[B >: A] extends super.Appended[B] with Transformed[B] {
protected[this] lazy val restSeq = rest.toSeq
def length = self.length + restSeq.length
def apply(idx: Int) =
if (idx < self.length) self(idx) else restSeq(idx - self.length)
}
trait Filtered extends super.Filtered with Transformed[A] {
protected[this] lazy val index = {
var len = 0
val arr = new Array[Int](self.length)
for (i <- 0 until self.length)
if (pred(self(i))) {
arr(len) = i
len += 1
}
arr take len
}
def length = index.length
def apply(idx: Int) = self(index(idx))
}
trait TakenWhile extends super.TakenWhile with Transformed[A] {
protected[this] lazy val len = self prefixLength pred
def length = len
def apply(idx: Int) =
if (idx < len) self(idx)
else throw new IndexOutOfBoundsException(idx.toString)
}
trait DroppedWhile extends super.DroppedWhile with Transformed[A] {
protected[this] lazy val start = self prefixLength pred
def length = self.length - start
def apply(idx: Int) =
if (idx >= 0) self(idx + start)
else throw new IndexOutOfBoundsException(idx.toString)
}
trait Zipped[B] extends super.Zipped[B] with Transformed[(A, B)] {
protected[this] lazy val thatSeq = other.seq.toSeq
/* Have to be careful here - other may be an infinite sequence. */
def length = if ((thatSeq lengthCompare self.length) <= 0) thatSeq.length else self.length
def apply(idx: Int) = (self.apply(idx), thatSeq.apply(idx))
}
trait ZippedAll[A1 >: A, B] extends super.ZippedAll[A1, B] with Transformed[(A1, B)] {
protected[this] lazy val thatSeq = other.seq.toSeq
def length: Int = self.length max thatSeq.length
def apply(idx: Int) =
(if (idx < self.length) self.apply(idx) else thisElem,
if (idx < thatSeq.length) thatSeq.apply(idx) else thatElem)
}
trait Reversed extends Transformed[A] {
override def iterator: Iterator[A] = createReversedIterator
def length: Int = self.length
def apply(idx: Int): A = self.apply(length - 1 - idx)
final override protected[this] def viewIdentifier = "R"
private def createReversedIterator = {
var lst = List[A]()
for (elem <- self) lst ::= elem
lst.iterator
}
}
trait Patched[B >: A] extends Transformed[B] {
protected[this] val from: Int
protected[this] val patch: GenSeq[B]
protected[this] val replaced: Int
private lazy val plen = patch.length
override def iterator: Iterator[B] = self.iterator patch (from, patch.iterator, replaced)
def length: Int = self.length + plen - replaced
def apply(idx: Int): B =
if (idx < from) self.apply(idx)
else if (idx < from + plen) patch.apply(idx - from)
else self.apply(idx - plen + replaced)
final override protected[this] def viewIdentifier = "P"
}
trait Prepended[B >: A] extends Transformed[B] {
protected[this] val fst: B
override def iterator: Iterator[B] = Iterator.single(fst) ++ self.iterator
def length: Int = 1 + self.length
def apply(idx: Int): B =
if (idx == 0) fst
else self.apply(idx - 1)
final override protected[this] def viewIdentifier = "A"
}
/** Boilerplate method, to override in each subclass
* This method could be eliminated if Scala had virtual classes
*/
protected override def newForced[B](xs: => GenSeq[B]): Transformed[B] = new { val forced = xs } with AbstractTransformed[B] with Forced[B]
protected override def newAppended[B >: A](that: GenTraversable[B]): Transformed[B] = new { val rest = that } with AbstractTransformed[B] with Appended[B]
protected override def newMapped[B](f: A => B): Transformed[B] = new { val mapping = f } with AbstractTransformed[B] with Mapped[B]
protected override def newFlatMapped[B](f: A => GenTraversableOnce[B]): Transformed[B] = new { val mapping = f } with AbstractTransformed[B] with FlatMapped[B]
protected override def newFiltered(p: A => Boolean): Transformed[A] = new { val pred = p } with AbstractTransformed[A] with Filtered
protected override def newSliced(_endpoints: SliceInterval): Transformed[A] = new { val endpoints = _endpoints } with AbstractTransformed[A] with Sliced
protected override def newDroppedWhile(p: A => Boolean): Transformed[A] = new { val pred = p } with AbstractTransformed[A] with DroppedWhile
protected override def newTakenWhile(p: A => Boolean): Transformed[A] = new { val pred = p } with AbstractTransformed[A] with TakenWhile
protected override def newZipped[B](that: GenIterable[B]): Transformed[(A, B)] = new { val other = that } with AbstractTransformed[(A, B)] with Zipped[B]
protected override def newZippedAll[A1 >: A, B](that: GenIterable[B], _thisElem: A1, _thatElem: B): Transformed[(A1, B)] = new {
val other = that
val thisElem = _thisElem
val thatElem = _thatElem
} with AbstractTransformed[(A1, B)] with ZippedAll[A1, B]
protected def newReversed: Transformed[A] = new AbstractTransformed[A] with Reversed
protected def newPatched[B >: A](_from: Int, _patch: GenSeq[B], _replaced: Int): Transformed[B] = new {
val from = _from
val patch = _patch
val replaced = _replaced
} with AbstractTransformed[B] with Patched[B]
protected def newPrepended[B >: A](elem: B): Transformed[B] = new { protected[this] val fst = elem } with AbstractTransformed[B] with Prepended[B]
// see comment in IterableViewLike.
protected override def newTaken(n: Int): Transformed[A] = newSliced(SliceInterval(0, n))
protected override def newDropped(n: Int): Transformed[A] = newSliced(SliceInterval(n, Int.MaxValue))
override def reverse: This = newReversed.asInstanceOf[This]
override def patch[B >: A, That](from: Int, patch: GenSeq[B], replaced: Int)(implicit bf: CanBuildFrom[This, B, That]): That = {
newPatched(from, patch, replaced).asInstanceOf[That]
// was: val b = bf(repr)
// if (b.isInstanceOf[NoBuilder[_]]) newPatched(from, patch, replaced).asInstanceOf[That]
// else super.patch[B, That](from, patch, replaced)(bf)
}
override def padTo[B >: A, That](len: Int, elem: B)(implicit bf: CanBuildFrom[This, B, That]): That =
patch(length, fill(len - length)(elem), 0)
override def reverseMap[B, That](f: A => B)(implicit bf: CanBuildFrom[This, B, That]): That =
reverse map f
override def updated[B >: A, That](index: Int, elem: B)(implicit bf: CanBuildFrom[This, B, That]): That = {
require(0 <= index && index < length) // !!! can't call length like this.
patch(index, List(elem), 1)(bf)
}
override def +:[B >: A, That](elem: B)(implicit bf: CanBuildFrom[This, B, That]): That =
newPrepended(elem).asInstanceOf[That]
override def :+[B >: A, That](elem: B)(implicit bf: CanBuildFrom[This, B, That]): That =
++(Iterator.single(elem))(bf)
override def union[B >: A, That](that: GenSeq[B])(implicit bf: CanBuildFrom[This, B, That]): That =
newForced(thisSeq union that).asInstanceOf[That]
override def diff[B >: A](that: GenSeq[B]): This =
newForced(thisSeq diff that).asInstanceOf[This]
override def intersect[B >: A](that: GenSeq[B]): This =
newForced(thisSeq intersect that).asInstanceOf[This]
override def sorted[B >: A](implicit ord: Ordering[B]): This =
newForced(thisSeq sorted ord).asInstanceOf[This]
override def sortWith(lt: (A, A) => Boolean): This =
newForced(thisSeq sortWith lt).asInstanceOf[This]
override def sortBy[B](f: (A) => B)(implicit ord: Ordering[B]): This =
newForced(thisSeq sortBy f).asInstanceOf[This]
override def combinations(n: Int): Iterator[This] =
(thisSeq combinations n).map(as => newForced(as).asInstanceOf[This])
override def permutations: Iterator[This] =
thisSeq.permutations.map(as => newForced(as).asInstanceOf[This])
override def distinct: This =
newForced(thisSeq.distinct).asInstanceOf[This]
override def stringPrefix = "SeqView"
}
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