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Avoid unnecessary toSeq conversions in Seq methods #8374

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merged 1 commit into from Aug 27, 2019
Merged

Avoid unnecessary toSeq conversions in Seq methods #8374

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21 changes: 13 additions & 8 deletions src/library/scala/collection/Seq.scala
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Expand Up @@ -416,6 +416,11 @@ trait SeqOps[+A, +CC[_], +C] extends Any
@deprecatedOverriding("Override lastIndexWhere(p, end) instead - lastIndexWhere(p) calls lastIndexWhere(p, Int.MaxValue)", "2.13.0")
def lastIndexWhere(p: A => Boolean): Int = lastIndexWhere(p, Int.MaxValue)

@inline private[this] def toGenericSeq: scala.collection.Seq[A] = this match {
case s: scala.collection.Seq[A] => s
case _ => toSeq
}

/** Finds first index after or at a start index where this $coll contains a given sequence as a slice.
* $mayNotTerminateInf
* @param that the sequence to test
Expand All @@ -434,11 +439,11 @@ trait SeqOps[+A, +CC[_], +C] extends Any
if (from > l) -1
else if (tl < 1) clippedFrom
else if (l < tl) -1
else SeqOps.kmpSearch(toSeq, clippedFrom, l, that, 0, tl, forward = true)
else SeqOps.kmpSearch(toGenericSeq, clippedFrom, l, that, 0, tl, forward = true)
}
else {
var i = from
var s: Seq[A] = toSeq drop i
var s: scala.collection.Seq[A] = toGenericSeq.drop(i)
while (!s.isEmpty) {
if (s startsWith that)
return i
Expand Down Expand Up @@ -476,7 +481,7 @@ trait SeqOps[+A, +CC[_], +C] extends Any
if (end < 0) -1
else if (tl < 1) clippedL
else if (l < tl) -1
else SeqOps.kmpSearch(toSeq, 0, clippedL+tl, that, 0, tl, forward = false)
else SeqOps.kmpSearch(toGenericSeq, 0, clippedL+tl, that, 0, tl, forward = false)
}

/** Finds last index where this $coll contains a given sequence as a slice.
Expand Down Expand Up @@ -600,7 +605,7 @@ trait SeqOps[+A, +CC[_], +C] extends Any

private[this] def init() = {
val m = mutable.HashMap[A, Int]()
val (es, is) = (self.toSeq map (e => (e, m.getOrElseUpdate(e, m.size))) sortBy (_._2)).unzip
val (es, is) = (self.toGenericSeq map (e => (e, m.getOrElseUpdate(e, m.size))) sortBy (_._2)).unzip

(es.to(mutable.ArrayBuffer), is.toArray)
}
Expand Down Expand Up @@ -661,7 +666,7 @@ trait SeqOps[+A, +CC[_], +C] extends Any
val m = mutable.HashMap[A, Int]()

// e => (e, weight(e))
val (es, is) = (self.toSeq map (e => (e, m.getOrElseUpdate(e, m.size))) sortBy (_._2)).unzip
val (es, is) = (self.toGenericSeq map (e => (e, m.getOrElseUpdate(e, m.size))) sortBy (_._2)).unzip
val cs = new Array[Int](m.size)
is foreach (i => cs(i) += 1)
val ns = new Array[Int](cs.length)
Expand Down Expand Up @@ -1000,7 +1005,7 @@ object SeqOps {
* @param forward Direction of search (from beginning==true, from end==false)
* @return Index of start of sequence if found, -1 if not (relative to beginning of S, not m0).
*/
private def kmpSearch[B](S: Seq[B], m0: Int, m1: Int, W: Seq[B], n0: Int, n1: Int, forward: Boolean): Int = {
private def kmpSearch[B](S: scala.collection.Seq[B], m0: Int, m1: Int, W: scala.collection.Seq[B], n0: Int, n1: Int, forward: Boolean): Int = {
// Check for redundant case when target has single valid element
def clipR(x: Int, y: Int) = if (x < y) x else -1
def clipL(x: Int, y: Int) = if (x > y) x else -1
Expand All @@ -1020,7 +1025,7 @@ object SeqOps {
}
// Now we know we actually need KMP search, so do it
else S match {
case xs: IndexedSeq[_] =>
case xs: scala.collection.IndexedSeq[_] =>
// We can index into S directly; it should be adequately fast
val Wopt = kmpOptimizeWord(W, n0, n1, forward)
val T = kmpJumpTable(Wopt, n1-n0)
Expand Down Expand Up @@ -1083,7 +1088,7 @@ object SeqOps {
* @param n1 The far end of the target sequence that we should use (exclusive)
* @return Target packed in an IndexedSeq (taken from iterator unless W already is an IndexedSeq)
*/
private def kmpOptimizeWord[B](W: Seq[B], n0: Int, n1: Int, forward: Boolean): IndexedSeqView[B] = W match {
private def kmpOptimizeWord[B](W: scala.collection.Seq[B], n0: Int, n1: Int, forward: Boolean): IndexedSeqView[B] = W match {
case iso: IndexedSeq[B] =>
// Already optimized for indexing--use original (or custom view of original)
if (forward && n0==0 && n1==W.length) iso.view
Expand Down