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/*
* Scala (https://www.scala-lang.org)
*
* Copyright EPFL and Lightbend, Inc.
*
* Licensed under Apache License 2.0
* (http://www.apache.org/licenses/LICENSE-2.0).
*
* See the NOTICE file distributed with this work for
* additional information regarding copyright ownership.
*/
package scala.collection
import scala.collection.immutable.Range
import scala.util.hashing.MurmurHash3
import Searching.{Found, InsertionPoint, SearchResult}
import scala.annotation.nowarn
/** Base trait for sequence collections
*
* @tparam A the element type of the collection
*/
trait Seq[+A]
extends Iterable[A]
with PartialFunction[Int, A]
with SeqOps[A, Seq, Seq[A]]
with IterableFactoryDefaults[A, Seq]
with Equals {
override def iterableFactory: SeqFactory[Seq] = Seq
def canEqual(that: Any): Boolean = true
override def equals(o: Any): Boolean =
(this eq o.asInstanceOf[AnyRef]) || (o match {
case seq: Seq[A] if seq.canEqual(this) => sameElements(seq)
case _ => false
})
override def hashCode(): Int = MurmurHash3.seqHash(toIterable)
override def toString(): String = super[Iterable].toString()
@nowarn("""cat=deprecation&origin=scala\.collection\.Iterable\.stringPrefix""")
override protected[this] def stringPrefix: String = "Seq"
}
/**
* $factoryInfo
* @define coll sequence
* @define Coll `Seq`
*/
@SerialVersionUID(3L)
object Seq extends SeqFactory.Delegate[Seq](immutable.Seq)
/** Base trait for Seq operations
*
* @tparam A the element type of the collection
* @tparam CC type constructor of the collection (e.g. `List`, `Set`). Operations returning a collection
* with a different type of element `B` (e.g. `map`) return a `CC[B]`.
* @tparam C type of the collection (e.g. `List[Int]`, `String`, `BitSet`). Operations returning a collection
* with the same type of element (e.g. `drop`, `filter`) return a `C`.
* @define orderDependent
* @define orderDependentFold
* @define mayNotTerminateInf
*
* Note: may not terminate for infinite-sized collections.
*
* @define willNotTerminateInf
*
* Note: will not terminate for infinite-sized collections.
*
* @define coll sequence
* @define Coll `Seq`
*/
trait SeqOps[+A, +CC[_], +C] extends Any
with IterableOps[A, CC, C] { self =>
override def view: SeqView[A] = new SeqView.Id[A](this)
/** Get the element at the specified index. This operation is provided for convenience in `Seq`. It should
* not be assumed to be efficient unless you have an `IndexedSeq`. */
@throws[IndexOutOfBoundsException]
def apply(i: Int): A
/** The length (number of elements) of the $coll. `size` is an alias for `length` in `Seq` collections. */
def length: Int
/** A copy of the $coll with an element prepended.
*
* Also, the original $coll is not modified, so you will want to capture the result.
*
* Example:
* {{{
* scala> val x = List(1)
* x: List[Int] = List(1)
*
* scala> val y = 2 +: x
* y: List[Int] = List(2, 1)
*
* scala> println(x)
* List(1)
* }}}
*
* @param elem the prepended element
* @tparam B the element type of the returned $coll.
*
* @return a new $coll consisting of `value` followed
* by all elements of this $coll.
*/
def prepended[B >: A](elem: B): CC[B] = iterableFactory.from(new View.Prepended(elem, this))
/** Alias for `prepended`.
*
* Note that :-ending operators are right associative (see example).
* A mnemonic for `+:` vs. `:+` is: the COLon goes on the COLlection side.
*/
@`inline` final def +: [B >: A](elem: B): CC[B] = prepended(elem)
/** A copy of this $coll with an element appended.
*
* $willNotTerminateInf
*
* Example:
* {{{
* scala> val a = List(1)
* a: List[Int] = List(1)
*
* scala> val b = a :+ 2
* b: List[Int] = List(1, 2)
*
* scala> println(a)
* List(1)
* }}}
*
* @param elem the appended element
* @tparam B the element type of the returned $coll.
* @return a new $coll consisting of
* all elements of this $coll followed by `value`.
*/
def appended[B >: A](elem: B): CC[B] = iterableFactory.from(new View.Appended(this, elem))
/** Alias for `appended`
*
* Note that :-ending operators are right associative (see example).
* A mnemonic for `+:` vs. `:+` is: the COLon goes on the COLlection side.
*/
@`inline` final def :+ [B >: A](elem: B): CC[B] = appended(elem)
/** As with `:++`, returns a new collection containing the elements from the left operand followed by the
* elements from the right operand.
*
* It differs from `:++` in that the right operand determines the type of
* the resulting collection rather than the left one.
* Mnemonic: the COLon is on the side of the new COLlection type.
*
* @param prefix the iterable to prepend.
* @tparam B the element type of the returned collection.
* @return a new $coll which contains all elements of `prefix` followed
* by all the elements of this $coll.
*/
def prependedAll[B >: A](prefix: IterableOnce[B]): CC[B] = iterableFactory.from(prefix match {
case prefix: Iterable[B] => new View.Concat(prefix, this)
case _ => prefix.iterator ++ iterator
})
/** Alias for `prependedAll` */
@`inline` override final def ++: [B >: A](prefix: IterableOnce[B]): CC[B] = prependedAll(prefix)
/** Returns a new $coll containing the elements from the left hand operand followed by the elements from the
* right hand operand. The element type of the $coll is the most specific superclass encompassing
* the element types of the two operands.
*
* @param suffix the iterable to append.
* @tparam B the element type of the returned collection.
* @return a new collection of type `CC[B]` which contains all elements
* of this $coll followed by all elements of `suffix`.
*/
def appendedAll[B >: A](suffix: IterableOnce[B]): CC[B] = super.concat(suffix)
/** Alias for `appendedAll` */
@`inline` final def :++ [B >: A](suffix: IterableOnce[B]): CC[B] = appendedAll(suffix)
// Make `concat` an alias for `appendedAll` so that it benefits from performance
// overrides of this method
@`inline` final override def concat[B >: A](suffix: IterableOnce[B]): CC[B] = appendedAll(suffix)
/** Produces a new sequence which contains all elements of this $coll and also all elements of
* a given sequence. `xs union ys` is equivalent to `xs ++ ys`.
*
* @param that the sequence to add.
* @tparam B the element type of the returned $coll.
* @return a new collection which contains all elements of this $coll
* followed by all elements of `that`.
*/
@deprecated("Use `concat` instead", "2.13.0")
@inline final def union[B >: A](that: Seq[B]): CC[B] = concat(that)
final override def size: Int = length
/** Selects all the elements of this $coll ignoring the duplicates.
*
* @return a new $coll consisting of all the elements of this $coll without duplicates.
*/
def distinct: C = distinctBy(identity)
/** Selects all the elements of this $coll ignoring the duplicates as determined by `==` after applying
* the transforming function `f`.
*
* @param f The transforming function whose result is used to determine the uniqueness of each element
* @tparam B the type of the elements after being transformed by `f`
* @return a new $coll consisting of all the elements of this $coll without duplicates.
*/
def distinctBy[B](f: A => B): C = fromSpecific(new View.DistinctBy(this, f))
/** Returns new $coll with elements in reversed order.
*
* $willNotTerminateInf
* $willForceEvaluation
*
* @return A new $coll with all elements of this $coll in reversed order.
*/
def reverse: C = fromSpecific(reversed)
/** An iterator yielding elements in reversed order.
*
* $willNotTerminateInf
*
* Note: `xs.reverseIterator` is the same as `xs.reverse.iterator` but might be more efficient.
*
* @return an iterator yielding the elements of this $coll in reversed order
*/
def reverseIterator: Iterator[A] = reversed.iterator
/** Tests whether this $coll contains the given sequence at a given index.
*
* '''Note''': If the both the receiver object `this` and the argument
* `that` are infinite sequences this method may not terminate.
*
* @param that the sequence to test
* @param offset the index where the sequence is searched.
* @return `true` if the sequence `that` is contained in this $coll at
* index `offset`, otherwise `false`.
*/
def startsWith[B >: A](that: IterableOnce[B], offset: Int = 0): Boolean = {
val i = iterator drop offset
val j = that.iterator
while (j.hasNext && i.hasNext)
if (i.next() != j.next())
return false
!j.hasNext
}
/** Tests whether this $coll ends with the given sequence.
* $willNotTerminateInf
* @param that the sequence to test
* @return `true` if this $coll has `that` as a suffix, `false` otherwise.
*/
def endsWith[B >: A](that: Iterable[B]): Boolean = {
if (that.isEmpty) true
else {
val i = iterator.drop(length - that.size)
val j = that.iterator
while (i.hasNext && j.hasNext)
if (i.next() != j.next())
return false
!j.hasNext
}
}
/** Tests whether this $coll contains given index.
*
* The implementations of methods `apply` and `isDefinedAt` turn a `Seq[A]` into
* a `PartialFunction[Int, A]`.
*
* @param idx the index to test
* @return `true` if this $coll contains an element at position `idx`, `false` otherwise.
*/
def isDefinedAt(idx: Int): Boolean = idx >= 0 && lengthIs > idx
/** A copy of this $coll with an element value appended until a given target length is reached.
*
* @param len the target length
* @param elem the padding value
* @tparam B the element type of the returned $coll.
* @return a new $coll consisting of
* all elements of this $coll followed by the minimal number of occurrences of `elem` so
* that the resulting collection has a length of at least `len`.
*/
def padTo[B >: A](len: Int, elem: B): CC[B] = iterableFactory.from(new View.PadTo(this, len, elem))
/** Computes the length of the longest segment that starts from the first element
* and whose elements all satisfy some predicate.
*
* $mayNotTerminateInf
*
* @param p the predicate used to test elements.
* @return the length of the longest segment of this $coll that starts from the first element
* such that every element of the segment satisfies the predicate `p`.
*/
final def segmentLength(p: A => Boolean): Int = segmentLength(p, 0)
/** Computes the length of the longest segment that starts from some index
* and whose elements all satisfy some predicate.
*
* $mayNotTerminateInf
*
* @param p the predicate used to test elements.
* @param from the index where the search starts.
* @return the length of the longest segment of this $coll starting from index `from`
* such that every element of the segment satisfies the predicate `p`.
*/
def segmentLength(p: A => Boolean, from: Int): Int = {
var i = 0
val it = iterator.drop(from)
while (it.hasNext && p(it.next()))
i += 1
i
}
/** Returns the length of the longest prefix whose elements all satisfy some predicate.
*
* $mayNotTerminateInf
*
* @param p the predicate used to test elements.
* @return the length of the longest prefix of this $coll
* such that every element of the segment satisfies the predicate `p`.
*/
@deprecated("Use segmentLength instead of prefixLength", "2.13.0")
@`inline` final def prefixLength(p: A => Boolean): Int = segmentLength(p, 0)
/** Finds index of the first element satisfying some predicate after or at some start index.
*
* $mayNotTerminateInf
*
* @param p the predicate used to test elements.
* @param from the start index
* @return the index `>= from` of the first element of this $coll that satisfies the predicate `p`,
* or `-1`, if none exists.
*/
def indexWhere(p: A => Boolean, from: Int): Int = iterator.indexWhere(p, from)
/** Finds index of the first element satisfying some predicate.
*
* $mayNotTerminateInf
*
* @param p the predicate used to test elements.
* @return the index `>= 0` of the first element of this $coll that satisfies the predicate `p`,
* or `-1`, if none exists.
*/
@deprecatedOverriding("Override indexWhere(p, from) instead - indexWhere(p) calls indexWhere(p, 0)", "2.13.0")
def indexWhere(p: A => Boolean): Int = indexWhere(p, 0)
/** Finds index of first occurrence of some value in this $coll after or at some start index.
*
* @param elem the element value to search for.
* @tparam B the type of the element `elem`.
* @param from the start index
* @return the index `>= from` of the first element of this $coll that is equal (as determined by `==`)
* to `elem`, or `-1`, if none exists.
*/
def indexOf[B >: A](elem: B, from: Int): Int = indexWhere(elem == _, from)
/** Finds index of first occurrence of some value in this $coll.
*
* @param elem the element value to search for.
* @tparam B the type of the element `elem`.
* @return the index `>= 0` of the first element of this $coll that is equal (as determined by `==`)
* to `elem`, or `-1`, if none exists.
*/
@deprecatedOverriding("Override indexOf(elem, from) instead - indexOf(elem) calls indexOf(elem, 0)", "2.13.0")
def indexOf[B >: A](elem: B): Int = indexOf(elem, 0)
/** Finds index of last occurrence of some value in this $coll before or at a given end index.
*
* $willNotTerminateInf
*
* @param elem the element value to search for.
* @param end the end index.
* @tparam B the type of the element `elem`.
* @return the index `<= end` of the last element of this $coll that is equal (as determined by `==`)
* to `elem`, or `-1`, if none exists.
*/
def lastIndexOf[B >: A](elem: B, end: Int = length - 1): Int = lastIndexWhere(elem == _, end)
/** Finds index of last element satisfying some predicate before or at given end index.
*
* $willNotTerminateInf
*
* @param p the predicate used to test elements.
* @return the index `<= end` of the last element of this $coll that satisfies the predicate `p`,
* or `-1`, if none exists.
*/
def lastIndexWhere(p: A => Boolean, end: Int): Int = {
var i = length - 1
val it = reverseIterator
while (it.hasNext && { val elem = it.next(); (i > end || !p(elem)) }) i -= 1
i
}
/** Finds index of last element satisfying some predicate.
*
* $willNotTerminateInf
*
* @param p the predicate used to test elements.
* @return the index of the last element of this $coll that satisfies the predicate `p`,
* or `-1`, if none exists.
*/
@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
* @param from the start index
* @return the first index `>= from` such that the elements of this $coll starting at this index
* match the elements of sequence `that`, or `-1` of no such subsequence exists.
*/
// TODO Should be implemented in a way that preserves laziness
def indexOfSlice[B >: A](that: Seq[B], from: Int): Int =
if (that.isEmpty && from == 0) 0
else {
val l = knownSize
val tl = that.knownSize
if (l >= 0 && tl >= 0) {
val clippedFrom = math.max(0, from)
if (from > l) -1
else if (tl < 1) clippedFrom
else if (l < tl) -1
else SeqOps.kmpSearch(toGenericSeq, clippedFrom, l, that, 0, tl, forward = true)
}
else {
var i = from
var s: scala.collection.Seq[A] = toGenericSeq.drop(i)
while (!s.isEmpty) {
if (s startsWith that)
return i
i += 1
s = s.tail
}
-1
}
}
/** Finds first index where this $coll contains a given sequence as a slice.
* $mayNotTerminateInf
* @param that the sequence to test
* @return the first index `>= 0` such that the elements of this $coll starting at this index
* match the elements of sequence `that`, or `-1` of no such subsequence exists.
*/
@deprecatedOverriding("Override indexOfSlice(that, from) instead - indexOfSlice(that) calls indexOfSlice(that, 0)", "2.13.0")
def indexOfSlice[B >: A](that: Seq[B]): Int = indexOfSlice(that, 0)
/** Finds last index before or at a given end index where this $coll contains a given sequence as a slice.
*
* $willNotTerminateInf
*
* @param that the sequence to test
* @param end the end index
* @return the last index `<= end` such that the elements of this $coll starting at this index
* match the elements of sequence `that`, or `-1` of no such subsequence exists.
*/
def lastIndexOfSlice[B >: A](that: Seq[B], end: Int): Int = {
val l = length
val tl = that.length
val clippedL = math.min(l-tl, end)
if (end < 0) -1
else if (tl < 1) clippedL
else if (l < tl) -1
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.
*
* $willNotTerminateInf
*
* @param that the sequence to test
* @return the last index such that the elements of this $coll starting at this index
* match the elements of sequence `that`, or `-1` of no such subsequence exists.
*/
@deprecatedOverriding("Override lastIndexOfSlice(that, end) instead - lastIndexOfSlice(that) calls lastIndexOfSlice(that, Int.MaxValue)", "2.13.0")
def lastIndexOfSlice[B >: A](that: Seq[B]): Int = lastIndexOfSlice(that, Int.MaxValue)
/** Finds the last element of the $coll satisfying a predicate, if any.
*
* $willNotTerminateInf
*
* @param p the predicate used to test elements.
* @return an option value containing the last element in the $coll
* that satisfies `p`, or `None` if none exists.
*/
def findLast(p: A => Boolean): Option[A] = {
val it = reverseIterator
while (it.hasNext) {
val elem = it.next()
if (p(elem)) return Some(elem)
}
None
}
/** Tests whether this $coll contains a given sequence as a slice.
* $mayNotTerminateInf
* @param that the sequence to test
* @return `true` if this $coll contains a slice with the same elements
* as `that`, otherwise `false`.
*/
def containsSlice[B](that: Seq[B]): Boolean = indexOfSlice(that) != -1
/** Tests whether this $coll contains a given value as an element.
* $mayNotTerminateInf
*
* @param elem the element to test.
* @return `true` if this $coll has an element that is equal (as
* determined by `==`) to `elem`, `false` otherwise.
*/
def contains[A1 >: A](elem: A1): Boolean = exists (_ == elem)
@deprecated("Use .reverseIterator.map(f).to(...) instead of .reverseMap(f)", "2.13.0")
def reverseMap[B](f: A => B): CC[B] = iterableFactory.from(new View.Map(View.fromIteratorProvider(() => reverseIterator), f))
/** Iterates over distinct permutations.
*
* $willForceEvaluation
*
* @return An Iterator which traverses the distinct permutations of this $coll.
* @example `"abb".permutations = Iterator(abb, bab, bba)`
*/
def permutations: Iterator[C] =
if (isEmpty) Iterator.single(coll)
else new PermutationsItr
/** Iterates over combinations. A _combination_ of length `n` is a subsequence of
* the original sequence, with the elements taken in order. Thus, `"xy"` and `"yy"`
* are both length-2 combinations of `"xyy"`, but `"yx"` is not. If there is
* more than one way to generate the same subsequence, only one will be returned.
*
* For example, `"xyyy"` has three different ways to generate `"xy"` depending on
* whether the first, second, or third `"y"` is selected. However, since all are
* identical, only one will be chosen. Which of the three will be taken is an
* implementation detail that is not defined.
*
* $willForceEvaluation
*
* @return An Iterator which traverses the possible n-element combinations of this $coll.
* @example `"abbbc".combinations(2) = Iterator(ab, ac, bb, bc)`
*/
def combinations(n: Int): Iterator[C] =
if (n < 0 || n > size) Iterator.empty
else new CombinationsItr(n)
private class PermutationsItr extends AbstractIterator[C] {
private[this] val (elms, idxs) = init()
private[this] var _hasNext = true
def hasNext = _hasNext
@throws[NoSuchElementException]
def next(): C = {
if (!hasNext)
Iterator.empty.next()
val forcedElms = new mutable.ArrayBuffer[A](elms.size) ++= elms
val result = (newSpecificBuilder ++= forcedElms).result()
var i = idxs.length - 2
while(i >= 0 && idxs(i) >= idxs(i+1))
i -= 1
if (i < 0)
_hasNext = false
else {
var j = idxs.length - 1
while(idxs(j) <= idxs(i)) j -= 1
swap(i,j)
val len = (idxs.length - i) / 2
var k = 1
while (k <= len) {
swap(i+k, idxs.length - k)
k += 1
}
}
result
}
private def swap(i: Int, j: Int): Unit = {
val tmpI = idxs(i)
idxs(i) = idxs(j)
idxs(j) = tmpI
val tmpE = elms(i)
elms(i) = elms(j)
elms(j) = tmpE
}
private[this] def init() = {
val m = mutable.HashMap[A, Int]()
val (es, is) = (self.toGenericSeq map (e => (e, m.getOrElseUpdate(e, m.size))) sortBy (_._2)).unzip
(es.to(mutable.ArrayBuffer), is.toArray)
}
}
private class CombinationsItr(n: Int) extends AbstractIterator[C] {
// generating all nums such that:
// (1) nums(0) + .. + nums(length-1) = n
// (2) 0 <= nums(i) <= cnts(i), where 0 <= i <= cnts.length-1
private[this] val (elms, cnts, nums) = init()
private[this] val offs = cnts.scanLeft(0)(_ + _)
private[this] var _hasNext = true
def hasNext = _hasNext
def next(): C = {
if (!hasNext)
Iterator.empty.next()
/* Calculate this result. */
val buf = newSpecificBuilder
for(k <- 0 until nums.length; j <- 0 until nums(k))
buf += elms(offs(k)+j)
val res = buf.result()
/* Prepare for the next call to next. */
var idx = nums.length - 1
while (idx >= 0 && nums(idx) == cnts(idx))
idx -= 1
idx = nums.lastIndexWhere(_ > 0, idx - 1)
if (idx < 0)
_hasNext = false
else {
// OPT: hand rolled version of `sum = nums.view(idx + 1, nums.length).sum + 1`
var sum = 1
var i = idx + 1
while (i < nums.length) {
sum += nums(i)
i += 1
}
nums(idx) -= 1
for (k <- (idx+1) until nums.length) {
nums(k) = sum min cnts(k)
sum -= nums(k)
}
}
res
}
/** Rearrange seq to newSeq a0a0..a0a1..a1...ak..ak such that
* seq.count(_ == aj) == cnts(j)
*
* @return (newSeq,cnts,nums)
*/
private def init(): (IndexedSeq[A], Array[Int], Array[Int]) = {
val m = mutable.HashMap[A, Int]()
// e => (e, weight(e))
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)
var r = n
0 until ns.length foreach { k =>
ns(k) = r min cs(k)
r -= ns(k)
}
(es.to(IndexedSeq), cs, ns)
}
}
/** Sorts this $coll according to an Ordering.
*
* The sort is stable. That is, elements that are equal (as determined by
* `ord.compare`) appear in the same order in the sorted sequence as in the original.
*
* @see [[scala.math.Ordering]]
*
* $willForceEvaluation
*
* @param ord the ordering to be used to compare elements.
* @return a $coll consisting of the elements of this $coll
* sorted according to the ordering `ord`.
*/
def sorted[B >: A](implicit ord: Ordering[B]): C = {
val len = this.length
val b = newSpecificBuilder
if (len == 1) b += head
else if (len > 1) {
b.sizeHint(len)
val arr = new Array[Any](len)
copyToArray(arr)
java.util.Arrays.sort(arr.asInstanceOf[Array[AnyRef]], ord.asInstanceOf[Ordering[AnyRef]])
var i = 0
while (i < len) {
b += arr(i).asInstanceOf[A]
i += 1
}
}
b.result()
}
/** Sorts this $coll according to a comparison function.
* $willNotTerminateInf
* $willForceEvaluation
*
* The sort is stable. That is, elements that are equal (as determined by
* `lt`) appear in the same order in the sorted sequence as in the original.
*
* @param lt the comparison function which tests whether
* its first argument precedes its second argument in
* the desired ordering.
* @return a $coll consisting of the elements of this $coll
* sorted according to the comparison function `lt`.
* @example {{{
* List("Steve", "Tom", "John", "Bob").sortWith(_.compareTo(_) < 0) =
* List("Bob", "John", "Steve", "Tom")
* }}}
*/
def sortWith(lt: (A, A) => Boolean): C = sorted(Ordering.fromLessThan(lt))
/** Sorts this $coll according to the Ordering which results from transforming
* an implicitly given Ordering with a transformation function.
* $willNotTerminateInf
* $willForceEvaluation
*
* The sort is stable. That is, elements that are equal (as determined by
* `ord.compare`) appear in the same order in the sorted sequence as in the original.
*
* @see [[scala.math.Ordering]]
* @param f the transformation function mapping elements
* to some other domain `B`.
* @param ord the ordering assumed on domain `B`.
* @tparam B the target type of the transformation `f`, and the type where
* the ordering `ord` is defined.
* @return a $coll consisting of the elements of this $coll
* sorted according to the ordering where `x < y` if
* `ord.lt(f(x), f(y))`.
*
* @example {{{
* val words = "The quick brown fox jumped over the lazy dog".split(' ')
* // this works because scala.Ordering will implicitly provide an Ordering[Tuple2[Int, Char]]
* words.sortBy(x => (x.length, x.head))
* res0: Array[String] = Array(The, dog, fox, the, lazy, over, brown, quick, jumped)
* }}}
*/
def sortBy[B](f: A => B)(implicit ord: Ordering[B]): C = sorted(ord on f)
/** Produces the range of all indices of this sequence.
* $willForceEvaluation
*
* @return a `Range` value from `0` to one less than the length of this $coll.
*/
def indices: Range = Range(0, length)
override final def sizeCompare(otherSize: Int): Int = lengthCompare(otherSize)
/** Compares the length of this $coll to a test value.
*
* @param len the test value that gets compared with the length.
* @return A value `x` where
* {{{
* x < 0 if this.length < len
* x == 0 if this.length == len
* x > 0 if this.length > len
* }}}
* The method as implemented here does not call `length` directly; its running time
* is `O(length min len)` instead of `O(length)`. The method should be overridden
* if computing `length` is cheap and `knownSize` returns `-1`.
*
* @see [[lengthIs]]
*/
def lengthCompare(len: Int): Int = super.sizeCompare(len)
override final def sizeCompare(that: Iterable[_]): Int = lengthCompare(that)
/** Compares the length of this $coll to the size of another `Iterable`.
*
* @param that the `Iterable` whose size is compared with this $coll's length.
* @return A value `x` where
* {{{
* x < 0 if this.length < that.size
* x == 0 if this.length == that.size
* x > 0 if this.length > that.size
* }}}
* The method as implemented here does not call `length` or `size` directly; its running time
* is `O(this.length min that.size)` instead of `O(this.length + that.size)`.
* The method should be overridden if computing `size` is cheap and `knownSize` returns `-1`.
*/
def lengthCompare(that: Iterable[_]): Int = super.sizeCompare(that)
/** Returns a value class containing operations for comparing the length of this $coll to a test value.
*
* These operations are implemented in terms of [[lengthCompare(Int) `lengthCompare(Int)`]], and
* allow the following more readable usages:
*
* {{{
* this.lengthIs < len // this.lengthCompare(len) < 0
* this.lengthIs <= len // this.lengthCompare(len) <= 0
* this.lengthIs == len // this.lengthCompare(len) == 0
* this.lengthIs != len // this.lengthCompare(len) != 0
* this.lengthIs >= len // this.lengthCompare(len) >= 0
* this.lengthIs > len // this.lengthCompare(len) > 0
* }}}
*/
@inline final def lengthIs: IterableOps.SizeCompareOps = new IterableOps.SizeCompareOps(this)
override def isEmpty: Boolean = lengthCompare(0) == 0
/** Are the elements of this collection the same (and in the same order)
* as those of `that`?
*/
def sameElements[B >: A](that: IterableOnce[B]): Boolean = {
val thisKnownSize = knownSize
val knownSizeDifference = thisKnownSize != -1 && {
val thatKnownSize = that.knownSize
thatKnownSize != -1 && thisKnownSize != thatKnownSize
}
!knownSizeDifference && iterator.sameElements(that)
}
/** Tests whether every element of this $coll relates to the
* corresponding element of another sequence by satisfying a test predicate.
*
* @param that the other sequence
* @param p the test predicate, which relates elements from both sequences
* @tparam B the type of the elements of `that`
* @return `true` if both sequences have the same length and
* `p(x, y)` is `true` for all corresponding elements `x` of this $coll
* and `y` of `that`, otherwise `false`.
*/
def corresponds[B](that: Seq[B])(p: (A, B) => Boolean): Boolean = {
val i = iterator
val j = that.iterator
while (i.hasNext && j.hasNext)
if (!p(i.next(), j.next()))
return false
!i.hasNext && !j.hasNext
}
/** Computes the multiset difference between this $coll and another sequence.
*
* @param that the sequence of elements to remove
* @return a new $coll which contains all elements of this $coll
* except some of occurrences of elements that also appear in `that`.
* If an element value `x` appears
* ''n'' times in `that`, then the first ''n'' occurrences of `x` will not form
* part of the result, but any following occurrences will.
*/
def diff[B >: A](that: Seq[B]): C = {
val occ = occCounts(that)
fromSpecific(iterator.filter { x =>
val ox = occ(x) // Avoid multiple map lookups
if (ox == 0) true
else {
occ(x) = ox - 1
false
}
})
}
/** Computes the multiset intersection between this $coll and another sequence.
*
* @param that the sequence of elements to intersect with.
* @return a new $coll which contains all elements of this $coll
* which also appear in `that`.
* If an element value `x` appears
* ''n'' times in `that`, then the first ''n'' occurrences of `x` will be retained
* in the result, but any following occurrences will be omitted.
*/
def intersect[B >: A](that: Seq[B]): C = {
val occ = occCounts(that)
fromSpecific(iterator.filter { x =>
val ox = occ(x) // Avoid multiple map lookups
if (ox > 0) {
occ(x) = ox - 1
true
} else false
})
}
/** Produces a new $coll where a slice of elements in this $coll is replaced by another sequence.
*
* Patching at negative indices is the same as patching starting at 0.
* Patching at indices at or larger than the length of the original $coll appends the patch to the end.
* If more values are replaced than actually exist, the excess is ignored.
*
* @param from the index of the first replaced element
* @param other the replacement sequence
* @param replaced the number of elements to drop in the original $coll
* @tparam B the element type of the returned $coll.
* @return a new $coll consisting of all elements of this $coll
* except that `replaced` elements starting from `from` are replaced
* by all the elements of `other`.
*/
def patch[B >: A](from: Int, other: IterableOnce[B], replaced: Int): CC[B] =
iterableFactory.from(new View.Patched(this, from, other, replaced))
/** A copy of this $coll with one single replaced element.
* @param index the position of the replacement
* @param elem the replacing element
* @tparam B the element type of the returned $coll.
* @return a new $coll which is a copy of this $coll with the element at position `index` replaced by `elem`.
* @throws IndexOutOfBoundsException if `index` does not satisfy `0 <= index < length`. In case of a
* lazy collection this exception may be thrown at a later time or not at
* all (if the end of the collection is never evaluated).
*/
def updated[B >: A](index: Int, elem: B): CC[B] = {
if(index < 0) throw new IndexOutOfBoundsException(index.toString)
val k = knownSize
if(k >= 0 && index >= k) throw new IndexOutOfBoundsException(index.toString)
iterableFactory.from(new View.Updated(this, index, elem))
}
protected[collection] def occCounts[B](sq: Seq[B]): mutable.Map[B, Int] = {
val occ = new mutable.HashMap[B, Int]().withDefaultValue(0)
for (y <- sq) occ(y) += 1
occ
}
/** Search this sorted sequence for a specific element. If the sequence is an
* `IndexedSeq`, a binary search is used. Otherwise, a linear search is used.
*
* The sequence should be sorted with the same `Ordering` before calling; otherwise,
* the results are undefined.
*
* @see [[scala.collection.IndexedSeq]]
* @see [[scala.math.Ordering]]
* @see [[scala.collection.SeqOps]], method `sorted`
*
* @param elem the element to find.
* @param ord the ordering to be used to compare elements.
*
* @return a `Found` value containing the index corresponding to the element in the
* sequence, or the `InsertionPoint` where the element would be inserted if
* the element is not in the sequence.
*/
def search[B >: A](elem: B)(implicit ord: Ordering[B]): SearchResult =
linearSearch(view, elem, 0)(ord)
/** Search within an interval in this sorted sequence for a specific element. If this
* sequence is an `IndexedSeq`, a binary search is used. Otherwise, a linear search
* is used.
*
* The sequence should be sorted with the same `Ordering` before calling; otherwise,
* the results are undefined.
*
* @see [[scala.collection.IndexedSeq]]
* @see [[scala.math.Ordering]]
* @see [[scala.collection.SeqOps]], method `sorted`
*
* @param elem the element to find.
* @param from the index where the search starts.
* @param to the index following where the search ends.
* @param ord the ordering to be used to compare elements.
*
* @return a `Found` value containing the index corresponding to the element in the
* sequence, or the `InsertionPoint` where the element would be inserted if
* the element is not in the sequence.
*
* @note if `to <= from`, the search space is empty, and an `InsertionPoint` at `from`
* is returned
*/
def search[B >: A](elem: B, from: Int, to: Int) (implicit ord: Ordering[B]): SearchResult =
linearSearch(view.slice(from, to), elem, math.max(0, from))(ord)
private[this] def linearSearch[B >: A](c: View[A], elem: B, offset: Int)
(implicit ord: Ordering[B]): SearchResult = {
var idx = offset
val it = c.iterator
while (it.hasNext) {
val cur = it.next()
if (ord.equiv(elem, cur)) return Found(idx)
else if (ord.lt(elem, cur)) return InsertionPoint(idx)
idx += 1
}
InsertionPoint(idx)
}
}
object SeqOps {
// KMP search utilities
/** A KMP implementation, based on the undoubtedly reliable wikipedia entry.
* Note: I made this private to keep it from entering the API. That can be reviewed.
*
* @param S Sequence that may contain target
* @param m0 First index of S to consider
* @param m1 Last index of S to consider (exclusive)
* @param W Target sequence
* @param n0 First index of W to match
* @param n1 Last index of W to match (exclusive)
* @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: 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
if (n1 == n0+1) {
if (forward)
clipR(S.indexOf(W(n0), m0), m1)
else
clipL(S.lastIndexOf(W(n0), m1-1), m0-1)
}
// Check for redundant case when both sequences are same size
else if (m1-m0 == n1-n0) {
// Accepting a little slowness for the uncommon case.
if (S.iterator.slice(m0, m1).sameElements(W.iterator.slice(n0, n1))) m0
else -1
}
// Now we know we actually need KMP search, so do it
else S match {
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)
var i, m = 0
val zero = if (forward) m0 else m1-1
val delta = if (forward) 1 else -1
while (i+m < m1-m0) {
if (Wopt(i) == S(zero+delta*(i+m))) {
i += 1
if (i == n1-n0) return (if (forward) m+m0 else m1-m-i)
}
else {
val ti = T(i)
m += i - ti
if (i > 0) i = ti
}
}
-1
case _ =>
// We had better not index into S directly!
val iter = S.iterator.drop(m0)
val Wopt = kmpOptimizeWord(W, n0, n1, forward = true)
val T = kmpJumpTable(Wopt, n1-n0)
val cache = new Array[AnyRef](n1-n0) // Ring buffer--need a quick way to do a look-behind
var largest = 0
var i, m = 0
var answer = -1
while (m+m0+n1-n0 <= m1) {
while (i+m >= largest) {
cache(largest%(n1-n0)) = iter.next().asInstanceOf[AnyRef]
largest += 1
}
if (Wopt(i) == cache((i+m)%(n1-n0)).asInstanceOf[B]) {
i += 1
if (i == n1-n0) {
if (forward) return m+m0
else {
i -= 1
answer = m+m0
val ti = T(i)
m += i - ti
if (i > 0) i = ti
}
}
}
else {
val ti = T(i)
m += i - ti
if (i > 0) i = ti
}
}
answer
}
}
/** Make sure a target sequence has fast, correctly-ordered indexing for KMP.
*
* @param W The target sequence
* @param n0 The first element in the target sequence that we should use
* @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: 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
else if (forward) new AbstractIndexedSeqView[B] {
val length = n1 - n0
def apply(x: Int) = iso(n0 + x)
}
else new AbstractIndexedSeqView[B] {
def length = n1 - n0
def apply(x: Int) = iso(n1 - 1 - x)
}
case _ =>
// W is probably bad at indexing. Pack in array (in correct orientation)
// Would be marginally faster to special-case each direction
new AbstractIndexedSeqView[B] {
private[this] val Warr = new Array[AnyRef](n1-n0)
private[this] val delta = if (forward) 1 else -1
private[this] val done = if (forward) n1-n0 else -1
val wit = W.iterator.drop(n0)
var i = if (forward) 0 else (n1-n0-1)
while (i != done) {
Warr(i) = wit.next().asInstanceOf[AnyRef]
i += delta
}
val length = n1 - n0
def apply(x: Int) = Warr(x).asInstanceOf[B]
}
}
/** Make a jump table for KMP search.
*
* @param Wopt The target sequence
* @param wlen Just in case we're only IndexedSeq and not IndexedSeqOptimized
* @return KMP jump table for target sequence
*/
private def kmpJumpTable[B](Wopt: IndexedSeqView[B], wlen: Int) = {
val arr = new Array[Int](wlen)
var pos = 2
var cnd = 0
arr(0) = -1
arr(1) = 0
while (pos < wlen) {
if (Wopt(pos-1) == Wopt(cnd)) {
arr(pos) = cnd + 1
pos += 1
cnd += 1
}
else if (cnd > 0) {
cnd = arr(cnd)
}
else {
arr(pos) = 0
pos += 1
}
}
arr
}
}
/** Explicit instantiation of the `Seq` trait to reduce class file size in subclasses. */
abstract class AbstractSeq[+A] extends AbstractIterable[A] with Seq[A]
