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|
/* __ *\
** ________ ___ / / ___ Scala API **
** / __/ __// _ | / / / _ | (c) 2003-2010, LAMP/EPFL **
** __\ \/ /__/ __ |/ /__/ __ | http://scala-lang.org/ **
** /____/\___/_/ |_/____/_/ | | **
** |/ **
\* */
// $Id$
package scala.collection
import mutable.{ListBuffer, HashMap, GenericArray}
import immutable.{List, Range}
import generic._
/** The companion object for trait `SeqLike`.
*/
object SeqLike {
/** A KMP implementation, based on the undoubtedly reliable wikipedia entry.
* @author paulp
* @since 2.8
*/
private def KMP[B](S: Seq[B], W: Seq[B]): Option[Int] = {
// trivial cases
if (W.isEmpty) return Some(0)
else if (W drop 1 isEmpty) return (S indexOf W(0)) match {
case -1 => None
case x => Some(x)
}
val T: Array[Int] = {
val arr = new Array[Int](W.length)
var pos = 2
var cnd = 0
arr(0) = -1
arr(1) = 0
while (pos < W.length) {
if (W(pos - 1) == W(cnd)) {
arr(pos) = cnd + 1
pos += 1
cnd += 1
}
else if (cnd > 0) {
cnd = arr(cnd)
}
else {
arr(pos) = 0
pos += 1
}
}
arr
}
var m, i = 0
def mi = m + i
while (mi < S.length) {
if (W(i) == S(mi)) {
i += 1
if (i == W.length)
return Some(m)
}
else {
m = mi - T(i)
if (i > 0)
i = T(i)
}
}
None
}
/** Waiting for a doc comment from Paul
*/
def indexOf[B](
source: Seq[B], sourceOffset: Int, sourceCount: Int,
target: Seq[B], targetOffset: Int, targetCount: Int,
fromIndex: Int): Int =
KMP(source.slice(sourceOffset, sourceCount) drop fromIndex, target.slice(targetOffset, targetCount)) match {
case None => -1
case Some(x) => x + fromIndex
}
/** Waiting for a doc comment from Paul
*/
def lastIndexOf[B](
source: Seq[B], sourceOffset: Int, sourceCount: Int,
target: Seq[B], targetOffset: Int, targetCount: Int,
fromIndex: Int): Int = {
val src = (source.slice(sourceOffset, sourceCount) take fromIndex).reverse
val tgt = target.slice(targetOffset, targetCount).reverse
KMP(src, tgt) match {
case None => -1
case Some(x) => (src.length - tgt.length - x) + sourceOffset
}
}
}
/** A template trait for sequences of type `Seq[A]`, representing
* sequences of elements of type <code>A</code>.
*
* Sequences are special cases of iterable collections of class `Iterable`.
* Unlike iterables, sequences always have a defined order of elements.
* Sequences provide a method `apply` for indexing. Indices range from `0` up the the `length` of
* a sequence. Sequences support a number to find occurrences of elements or subsequences, including
* `segmentLength`, `prefixLength`, `indexWhere`, `indexOf`, `lastIndexWhere`, `lastIndexOf`,
* `startsWith`, `endsWith`, `indexOfSlice`.
*
* Another way to see a sequence is as a `PartialFunction` from `Int` values
* to the element type of the sequence. The `isDefinedAt` method of a sequence
* returns `true` for the interval from `0` until `length`.
*
* Sequences can be accessed in reverse order of their elements, using methods
* `reverse` and `reverseIterator`.
*
* Sequences have two principle subtraits, `IndexedSeq` and `LinearSeq`, which give different guarantees for performance.
* An `IndexedSeq` provides fast random-access of elements and a fast `length` operation.
* A `LinearSeq` provides fast access only to the first element via `head`, but also
* has a fast `tail` operation.
*
* @author Martin Odersky
* @author Matthias Zenger
* @version 1.0, 16/07/2003
* @since 2.8
*
* @tparam A the element type of the collection
* @tparam Repr the type of the actual collection containing the elements.
*
* @define Coll Seq
* @define coll sequence
* @define thatinfo the class of the returned collection. Where possible, `That` is
* the same class as the current collection class `Repr`, but this
* depends on the element type `B` being admissible for that class,
* which means that an implicit instance of type `CanBuildFrom[Repr, B, That]`
* is found.
* @define bfinfo an implicit value of class `CanBuildFrom` which determines the
* result class `That` from the current representation type `Repr`
* and the new element type `B`.
* @define orderDependent
* @define orderDependentFold
* @define mayNotTerminateInf
*
* Note: may not terminate for infinite-sized collections.
* @define willNotTerminateInf
*
* Note: will not terminate for infinite-sized collections.
*/
trait SeqLike[+A, +Repr] extends IterableLike[A, Repr] { self =>
override protected[this] def thisCollection: Seq[A] = this.asInstanceOf[Seq[A]]
override protected[this] def toCollection(repr: Repr): Seq[A] = repr.asInstanceOf[Seq[A]]
/** The length of the $coll.
*
* $willNotTerminateInf
*
* Note: `xs.length` and `xs.size` yield the same result.
*
* @return the number of elements in this $coll.
*/
def length: Int
/** Selects an element by its index in the $coll
*
* @param idx The index to select
* @return the element of tyh
*/
def apply(idx: Int): A
/** 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 overwritten
* if computing `length` is cheap.
*/
def lengthCompare(len: Int): Int = {
var i = 0
val it = iterator
while (it.hasNext && i <= len) {
it.next()
i += 1
}
i - len
}
/** The size of this $coll, equivalent to `length`.
*
* $willNotTerminateInf
*
* @return the number of elements in this $coll.
*/
override def size = length
/** 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) && (idx < length)
/** Computes length of longest segment whose elements all satisfy some preficate.
*
* $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
var 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 preficate.
*
* $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`.
*/
def prefixLength(p: A => Boolean) = segmentLength(p, 0)
/** Finds index of first element satisfying some predicate.
*
* $mayNotTerminateInf
*
* @param p the predicate used to test elements.
* @return the index of the first element of this $coll that satisfies the predicate `p`,
* or `-1`, if none exists.
*/
def indexWhere(p: A => Boolean): Int = indexWhere(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 = {
var i = from
var it = iterator.drop(from)
while (it.hasNext && !p(it.next()))
i += 1
if (it.hasNext) i else -1
}
/** Returns index of the first element satisying a predicate, or `-1`.
* @deprecated "Use `indexWhere` instead"
*/
def findIndexOf(p: A => Boolean): Int = indexWhere(p)
/** Finds index of first occurrence of some value in this $coll.
*
* $mayNotTerminateInf
*
* @param elem the element value to search for.
* @tparam B the type of the element `elem`.
* @return the index of the first element of this $coll that is equal (wrt `==`)
* tp `elem`, or `-1`, if none exists.
*
* @usecase def indexOf(elem: A): Int
*
* @param elem the element value to search for.
* @return the index of the first element of this $coll that is equal (wrt `==`)
* to `elem`, or `-1`, if none exists.
*/
def indexOf[B >: A](elem: B): Int = indexOf(elem, 0)
/** Finds index of first occurrence of some value in this $coll after or at some start index.
*
* $mayNotTerminateInf
*
* @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 (wrt `==`)
* tp `elem`, or `-1`, if none exists.
*
* @usecase def indexOf(elem: A): Int
*
* @param elem the element value to search for.
* @param from the start index
* @return the index `>= from` of the first element of this $coll that is equal (wrt `==`)
* to `elem`, or `-1`, if none exists.
*/
def indexOf[B >: A](elem: B, from: Int): Int = indexWhere(elem ==, from)
/** Finds index of last occurrence of some value in this $coll.
*
* $willNotTerminateInf
*
* @param elem the element value to search for.
* @tparam B the type of the element `elem`.
* @return the index of the last element of this $coll that is equal (wrt `==`)
* to `elem`, or `-1`, if none exists.
*
* @usecase def lastIndexOf(elem: A): Int
*
* @param elem the element value to search for.
* @return the index of the last element of this $coll that is equal (wrt `==`)
* to `elem`, or `-1`, if none exists.
*/
def lastIndexOf[B >: A](elem: B): Int = lastIndexWhere(elem ==)
/** Finds index of last occurrence of some value in this $coll before or at a given end index.
*
* @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 (wrt `==`)
* to `elem`, or `-1`, if none exists.
*
* @usecase def lastIndexOf(elem: A): Int
*
* @param elem the element value to search for.
* @return the index `<= end` of the last element of this $coll that is equal (wrt `==`)
* to `elem`, or `-1`, if none exists.
*/
def lastIndexOf[B >: A](elem: B, end: Int): Int = lastIndexWhere(elem ==, end)
/** 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.
*/
def lastIndexWhere(p: A => Boolean): Int = lastIndexWhere(p, length - 1)
/** Finds index of last element satisfying some predicate before or at given end index.
*
* @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
}
/** Returns new $coll wih elements in reversed order.
*
* $willNotTerminateInf
*
* @return A new $coll with all elements of this $coll in reversed order.
*/
def reverse: Repr = {
var xs: List[A] = List()
for (x <- this)
xs = x :: xs
val b = newBuilder
for (x <- xs)
b += x
b.result
}
/**
* Builds a new collection by applying a function to all elements of this $coll and
* collecting the results in reversed order.
*
* $willNotTerminateInf
*
* Note: `xs.reverseMap(f)` is the same as `xs.reverse.map(f)` but might be more efficient.
*
* @param f the function to apply to each element.
* @tparam B the element type of the returned collection.
* @tparam That $thatinfo
* @param bf $bfinfo
* @return a new collection of type `That` resulting from applying the given function
* `f` to each element of this $coll and collecting the results in reversed order.
*
* @usecase def reverseMap[B](f: A => B): $Coll[B]
*
* Note: `xs.reverseMap(f)` is the same as `xs.reverse.map(f)` but might be more efficient.
*
* @param f the function to apply to each element.
* @tparam B the element type of the returned collection.
* @return a new $coll resulting from applying the given function
* `f` to each element of this $coll and collecting the results in reversed order.
*/
def reverseMap[B, That](f: A => B)(implicit bf: CanBuildFrom[Repr, B, That]): That = {
var xs: List[A] = List()
for (x <- this)
xs = x :: xs
val b = bf(repr)
for (x <- xs)
b += f(x)
b.result
}
/** 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] = toCollection(reverse).iterator
/** @deprecated use `reverseIterator` instead */
@deprecated("use `reverseIterator' instead")
def reversedElements = reverseIterator
/** Checks whether this $coll contains the given sequence at a given index.
*
* If the both the receiver object, <code>this</code> and
* the argument, <code>that</code> are infinite sequences
* this method may not terminate.
*
* @param that the candidate sequence
* @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](that: Seq[B], offset: Int): Boolean = {
val i = this.iterator drop offset
val j = that.iterator
while (j.hasNext && i.hasNext)
if (i.next != j.next)
return false
!j.hasNext
}
/** Checks whether this $coll starts with the given sequence.
*
* @param that the candidate sequence
* @return `true` if this collection has `that` as a prefix, `false` otherwise.
* otherwise false
*/
def startsWith[B](that: Seq[B]): Boolean = startsWith(that, 0)
/** @return true if this sequence end with that sequence
* @see String.endsWith
*/
def endsWith[B](that: Seq[B]): Boolean = {
val i = this.iterator.drop(length - that.length)
val j = that.iterator
while (i.hasNext && j.hasNext)
if (i.next != j.next)
return false
!j.hasNext
}
/** @return -1 if <code>that</code> not contained in this, otherwise the
* first index where <code>that</code> is contained.
*/
def indexOfSlice[B >: A](that: Seq[B]): Int = indexOfSlice(that, 0)
def indexOfSlice[B >: A](that: Seq[B], fromIndex: Int): Int =
if (this.hasDefiniteSize && that.hasDefiniteSize)
SeqLike.indexOf(thisCollection, 0, length, that, 0, that.length, fromIndex)
else {
var i = fromIndex
var s: Seq[A] = thisCollection drop i
while (!s.isEmpty) {
if (s startsWith that)
return i
i += 1
s = s.tail
}
-1
}
/** @return -1 if <code>that</code> not contained in this, otherwise the
* last index where <code>that</code> is contained.
* @note may not terminate for infinite-sized collections.
*/
def lastIndexOfSlice[B >: A](that: Seq[B]): Int = lastIndexOfSlice(that, that.length)
// since there's no way to find the last index in an infinite sequence,
// we just document it may not terminate and assume it will.
def lastIndexOfSlice[B >: A](that: Seq[B], fromIndex: Int): Int =
SeqLike.lastIndexOf(thisCollection, 0, length, that, 0, that.length, fromIndex)
/** Tests if the given value <code>elem</code> is a member of this
* sequence.
*
* @param elem element whose membership has to be tested.
* @return <code>true</code> iff there is an element of this sequence
* which is equal (w.r.t. <code>==</code>) to <code>elem</code>.
*/
def contains(elem: Any): Boolean = exists (_ == elem)
/** <p>
* Computes the multiset union of this sequence and the given sequence
* <code>that</code>. For example:
* </p><pre>
* <b>val</b> xs = List(1, 1, 2)
* <b>val</b> ys = List(1, 2, 2, 3)
* println(xs union ys) // prints "List(1, 1, 2, 1, 2, 2, 3)"
* println(ys union xs) // prints "List(1, 2, 2, 3, 1, 1, 2)"
* </pre>
*
* @param that the sequence of elements to add to the sequence.
* @return a sequence containing the elements of this
* sequence and those of the given sequence <code>that</code>.
*/
def union[B >: A, That](that: Seq[B])(implicit bf: CanBuildFrom[Repr, B, That]): That =
this ++ that
/** <p>
* Computes the multiset difference between this sequence and the
* given sequence <code>that</code>. If an element appears more
* than once in both sequences, the difference contains <i>m</i> copies
* of that element, where <i>m</i> is the difference between the
* number of times the element appears in this sequence and the number
* of times it appears in <code>that</code>. For example:
* </p><pre>
* <b>val</b> xs = List(1, 1, 2)
* <b>val</b> ys = List(1, 2, 2, 3)
* println(xs diff ys) // prints "List(1)"
* println(xs -- ys) // prints "List()"
* </pre>
*
* @param that the sequence of elements to remove from this sequence.
* @return the sequence of elements contained only in this sequence plus
* <i>m</i> copies of each element present in both sequences,
* where <i>m</i> is defined as above.
*/
def diff[B >: A, That](that: Seq[B]): Repr = {
val occ = occCounts(that)
val b = newBuilder
for (x <- this)
if (occ(x) == 0) b += x
else occ(x) -= 1
b.result
}
/** <p>
* Computes the multiset intersection between this sequence and the
* given sequence <code>that</code>; the intersection contains <i>m</i>
* copies of an element contained in both sequences, where <i>m</i> is
* the smaller of the number of times the element appears in this
* sequence or in <code>that</code>. For example:
* </p><pre>
* <b>val</b> xs = List(1, 1, 2)
* <b>val</b> ys = List(3, 2, 2, 1)
* println(xs intersect ys) // prints "List(1, 2)"
* println(ys intersect xs) // prints "List(2, 1)"
* </pre>
*
* @param that the sequence to intersect.
* @return the sequence of elements contained both in this sequence and
* in the given sequence <code>that</code>.
*/
def intersect[B >: A, That](that: Seq[B]): Repr = {
val occ = occCounts(that)
val b = newBuilder
for (x <- this)
if (occ(x) > 0) {
b += x
occ(x) -= 1
}
b.result
}
private def occCounts[B](seq: Seq[B]): mutable.Map[B, Int] = {
val occ = new mutable.HashMap[B, Int] { override def default(k: B) = 0 }
for (y <- seq) occ(y) += 1
occ
}
/** Builds a new sequence from this sequence in which any duplicates (wrt to ==) removed.
* Among duplicate elements, only the first one is retained in the result sequence
*/
def removeDuplicates: Repr = {
val b = newBuilder
var seen = Set[A]() //TR: should use mutable.HashSet?
for (x <- this) {
if (!(seen contains x)) {
b += x
seen = (seen + x)
}
}
b.result
}
/** A new sequence, consisting of all elements of current sequence
* except that `replaced` elements starting from `from` are replaced
* by `patch`.
*/
def patch[B >: A, That](from: Int, patch: Seq[B], replaced: Int)(implicit bf: CanBuildFrom[Repr, B, That]): That = {
val b = bf(repr)
val (prefix, rest) = this.splitAt(from)
b ++= toCollection(prefix)
b ++= patch
b ++= toCollection(rest).view drop replaced
b.result
}
/** Returns a copy of this sequence with the element at position `index` replaced by `elem`.
*/
def updated[B >: A, That](index: Int, elem: B)(implicit bf: CanBuildFrom[Repr, B, That]): That = {
val b = bf(repr)
val (prefix, rest) = this.splitAt(index)
b ++= toCollection(prefix)
b += elem
b ++= toCollection(rest).view.tail
b.result
}
/** Returns a new sequence consisting of `elem` followed by the elements of this sequence.
*/
def +:[B >: A, That](elem: B)(implicit bf: CanBuildFrom[Repr, B, That]): That = {
val b = bf(repr)
b += elem
b ++= thisCollection
b.result
}
/** Returns a new sequence consisting of the elements of this sequence followed by `elem`.
*/
def :+[B >: A, That](elem: B)(implicit bf: CanBuildFrom[Repr, B, That]): That = {
val b = bf(repr)
b ++= thisCollection
b += elem
b.result
}
/** Returns a new sequence of given length containing the elements of this sequence followed by zero
* or more occurrences of given elements.
*/
def padTo[B >: A, That](len: Int, elem: B)(implicit bf: CanBuildFrom[Repr, B, That]): That = {
val b = bf(repr)
b.sizeHint(length max len)
var diff = len - length
b ++= thisCollection
while (diff > 0) {
b += elem
diff -=1
}
b.result
}
/** Sort the sequence according to the comparison function
* <code>lt(e1: a, e2: a) => Boolean</code>,
* which should be true iff <code>e1</code> precedes
* <code>e2</code> in the desired ordering.
* The sort is stable. That is elements that are equal wrt `lt` appear in the
* same order in the sorted sequence as in the original.
*
* @param lt the comparison function
* @return a sequence sorted according to the comparison function
* <code>lt(e1: a, e2: a) => Boolean</code>.
* @ex <pre>
* List("Steve", "Tom", "John", "Bob")
* .sortWith((e1, e2) => (e1 compareTo e2) < 0) =
* List("Bob", "John", "Steve", "Tom")</pre>
*/
def sortWith(lt: (A, A) => Boolean): Repr = sortWith(Ordering fromLessThan lt)
def sortWith[B >: A](ord: Ordering[B]): Repr = {
val arr = new GenericArray[A](this.length)
var i = 0
for (x <- this) {
arr(i) = x
i += 1
}
java.util.Arrays.sort(
arr.array, ord.asInstanceOf[Ordering[Object]])
val b = newBuilder
for (x <- arr) b += x
b.result
}
/** Sort the sequence according to the Ordering which results from transforming
* the implicitly given Ordering[B] to an Ordering[A]. For example:
*
* <code>
* 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)
* </code>
*
* @param f the transformation function A => B
* @param ord the Ordering[B]
* @return the sorted representation
*/
def sortBy[B](f: A => B)(implicit ord: Ordering[B]): Repr = sortWith(ord on f)
/**
* Overridden for efficiency.
*
* @return the sequence itself
*/
override def toSeq: Seq[A] = thisCollection
/** The range of all indices of this sequence.
*/
def indices: Range = 0 until length
override def view = new SeqView[A, Repr] {
protected lazy val underlying = self.repr
override def iterator = self.iterator
override def length = self.length
override def apply(idx: Int) = self.apply(idx)
}
override def view(from: Int, until: Int) = view.slice(from, until)
override def hashCode() = (Seq.hashSeed /: this)(_ * 41 + _.hashCode)
override def equals(that: Any): Boolean = that match {
case that: Seq[_] => (that canEqual this) && (this sameElements that)
case _ => false
}
/** Need to override string, so that it's not the Function1's string that gets mixed in.
*/
override def toString = super[IterableLike].toString
/** Returns index of the last element satisying a predicate, or -1. */
@deprecated("use `lastIndexWhere' instead")
def findLastIndexOf(p: A => Boolean): Int = lastIndexWhere(p)
@deprecated("Should be replaced by <code>(s1, s2) forall { case (x, y) => f(x, y) }</code>")
def equalsWith[B](that: Seq[B])(f: (A,B) => Boolean): Boolean = {
val i = this.iterator
val j = that.iterator
while (i.hasNext && j.hasNext)
if (!f(i.next, j.next))
return false
!i.hasNext && !j.hasNext
}
/** Is <code>that</code> a slice in this? */
def containsSlice[B](that: Seq[B]): Boolean = indexOfSlice(that) != -1
/**
* returns a projection that can be used to call non-strict <code>filter</code>,
* <code>map</code>, and <code>flatMap</code> methods that build projections
* of the collection.
*/
@deprecated("use `view' instead")
override def projection = view
}
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