Skip to content
This repository
Fetching contributors…

Octocat-spinner-32-eaf2f5

Cannot retrieve contributors at this time

file 798 lines (733 sloc) 28.498 kb
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797
/* __ *\
** ________ ___ / / ___ Scala API **
** / __/ __// _ | / / / _ | (c) 2003-2013, LAMP/EPFL **
** __\ \/ /__/ __ |/ /__/ __ | http://scala-lang.org/ **
** /____/\___/_/ |_/____/_/ | | **
** |/ **
\* */

package scala
package collection

import generic._
import mutable.{ Builder }
import scala.annotation.{tailrec, migration, bridge}
import scala.annotation.unchecked.{ uncheckedVariance => uV }
import parallel.ParIterable
import scala.language.higherKinds

/** A template trait for traversable collections of type `Traversable[A]`.
*
* $traversableInfo
* @define mutability
* @define traversableInfo
* This is a base trait of all kinds of $mutability Scala collections. It
* implements the behavior common to all collections, in terms of a method
* `foreach` with signature:
* {{{
* def foreach[U](f: Elem => U): Unit
* }}}
* Collection classes mixing in this trait provide a concrete
* `foreach` method which traverses all the
* elements contained in the collection, applying a given function to each.
* They also need to provide a method `newBuilder`
* which creates a builder for collections of the same kind.
*
* A traversable class might or might not have two properties: strictness
* and orderedness. Neither is represented as a type.
*
* The instances of a strict collection class have all their elements
* computed before they can be used as values. By contrast, instances of
* a non-strict collection class may defer computation of some of their
* elements until after the instance is available as a value.
* A typical example of a non-strict collection class is a
* [[scala.collection.immutable.Stream]].
* A more general class of examples are `TraversableViews`.
*
* If a collection is an instance of an ordered collection class, traversing
* its elements with `foreach` will always visit elements in the
* same order, even for different runs of the program. If the class is not
* ordered, `foreach` can visit elements in different orders for
* different runs (but it will keep the same order in the same run).'
*
* A typical example of a collection class which is not ordered is a
* `HashMap` of objects. The traversal order for hash maps will
* depend on the hash codes of its elements, and these hash codes might
* differ from one run to the next. By contrast, a `LinkedHashMap`
* is ordered because it's `foreach` method visits elements in the
* order they were inserted into the `HashMap`.
*
* @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 Traversable
* @define coll traversable collection
*/
trait TraversableLike[+A, +Repr] extends Any
                                    with HasNewBuilder[A, Repr]
                                    with FilterMonadic[A, Repr]
                                    with TraversableOnce[A]
                                    with GenTraversableLike[A, Repr]
                                    with Parallelizable[A, ParIterable[A]]
{
  self =>

  import Traversable.breaks._

  /** The type implementing this traversable */
  protected[this] type Self = Repr

  /** The collection of type $coll underlying this `TraversableLike` object.
* By default this is implemented as the `TraversableLike` object itself,
* but this can be overridden.
*/
  def repr: Repr = this.asInstanceOf[Repr]

  final def isTraversableAgain: Boolean = true

  /** The underlying collection seen as an instance of `$Coll`.
* By default this is implemented as the current collection object itself,
* but this can be overridden.
*/
  protected[this] def thisCollection: Traversable[A] = this.asInstanceOf[Traversable[A]]

  /** A conversion from collections of type `Repr` to `$Coll` objects.
* By default this is implemented as just a cast, but this can be overridden.
*/
  protected[this] def toCollection(repr: Repr): Traversable[A] = repr.asInstanceOf[Traversable[A]]

  /** Creates a new builder for this collection type.
*/
  protected[this] def newBuilder: Builder[A, Repr]

  protected[this] def parCombiner = ParIterable.newCombiner[A]

  /** Applies a function `f` to all elements of this $coll.
*
* @param f the function that is applied for its side-effect to every element.
* The result of function `f` is discarded.
*
* @tparam U the type parameter describing the result of function `f`.
* This result will always be ignored. Typically `U` is `Unit`,
* but this is not necessary.
*
* @usecase def foreach(f: A => Unit): Unit
* @inheritdoc
*
* Note: this method underlies the implementation of most other bulk operations.
* It's important to implement this method in an efficient way.
*
*/
  def foreach[U](f: A => U): Unit

  /** Tests whether this $coll is empty.
*
* @return `true` if the $coll contain no elements, `false` otherwise.
*/
  def isEmpty: Boolean = {
    var result = true
    breakable {
      for (x <- this) {
        result = false
        break
      }
    }
    result
  }

  /** Tests whether this $coll is known to have a finite size.
* All strict collections are known to have finite size. For a non-strict
* collection such as `Stream`, the predicate returns `'''true'''` if all
* elements have been computed. It returns `'''false'''` if the stream is
* not yet evaluated to the end.
*
* Note: many collection methods will not work on collections of infinite sizes.
*
* @return `'''true'''` if this collection is known to have finite size,
* `'''false'''` otherwise.
*/
  def hasDefiniteSize = true

  def ++[B >: A, That](that: GenTraversableOnce[B])(implicit bf: CanBuildFrom[Repr, B, That]): That = {
    val b = bf(repr)
    if (that.isInstanceOf[IndexedSeqLike[_, _]]) b.sizeHint(this, that.seq.size)
    b ++= thisCollection
    b ++= that.seq
    b.result
  }

  /** 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 that the traversable to append.
* @tparam B the element type of the returned collection.
* @tparam That $thatinfo
* @param bf $bfinfo
* @return a new collection of type `That` which contains all elements
* of this $coll followed by all elements of `that`.
*
* @usecase def ++:[B](that: TraversableOnce[B]): $Coll[B]
* @inheritdoc
*
* Example:
* {{{
* scala> val x = List(1)
* x: List[Int] = List(1)
*
* scala> val y = LinkedList(2)
* y: scala.collection.mutable.LinkedList[Int] = LinkedList(2)
*
* scala> val z = x ++: y
* z: scala.collection.mutable.LinkedList[Int] = LinkedList(1, 2)
* }}}
*
* @return a new $coll which contains all elements of this $coll
* followed by all elements of `that`.
*/
  def ++:[B >: A, That](that: TraversableOnce[B])(implicit bf: CanBuildFrom[Repr, B, That]): That = {
    val b = bf(repr)
    if (that.isInstanceOf[IndexedSeqLike[_, _]]) b.sizeHint(this, that.size)
    b ++= that
    b ++= thisCollection
    b.result
  }

  /** 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.
*
* Example:
* {{{
* scala> val x = List(1)
* x: List[Int] = List(1)
*
* scala> val y = LinkedList(2)
* y: scala.collection.mutable.LinkedList[Int] = LinkedList(2)
*
* scala> val z = x ++: y
* z: scala.collection.mutable.LinkedList[Int] = LinkedList(1, 2)
* }}}
*
* This overload exists because: for the implementation of `++:` we should
* reuse that of `++` because many collections override it with more
* efficient versions.
*
* Since `TraversableOnce` has no `++` method, we have to implement that
* directly, but `Traversable` and down can use the overload.
*
* @param that the traversable to append.
* @tparam B the element type of the returned collection.
* @tparam That $thatinfo
* @param bf $bfinfo
* @return a new collection of type `That` which contains all elements
* of this $coll followed by all elements of `that`.
*/
  def ++:[B >: A, That](that: Traversable[B])(implicit bf: CanBuildFrom[Repr, B, That]): That =
    (that ++ seq)(breakOut)

  def map[B, That](f: A => B)(implicit bf: CanBuildFrom[Repr, B, That]): That = {
    def builder = { // extracted to keep method size under 35 bytes, so that it can be JIT-inlined
      val b = bf(repr)
      b.sizeHint(this)
      b
    }
    val b = builder
    for (x <- this) b += f(x)
    b.result
  }

  def flatMap[B, That](f: A => GenTraversableOnce[B])(implicit bf: CanBuildFrom[Repr, B, That]): That = {
    def builder = bf(repr) // extracted to keep method size under 35 bytes, so that it can be JIT-inlined
    val b = builder
    for (x <- this) b ++= f(x).seq
    b.result
  }

  private def filterImpl(p: A => Boolean, isFlipped: Boolean): Repr = {
    val b = newBuilder
    for (x <- this)
      if (p(x) != isFlipped) b += x

    b.result
  }

  /** Selects all elements of this $coll which satisfy a predicate.
*
* @param p the predicate used to test elements.
* @return a new $coll consisting of all elements of this $coll that satisfy the given
* predicate `p`. The order of the elements is preserved.
*/
  def filter(p: A => Boolean): Repr = filterImpl(p, isFlipped = false)

  /** Selects all elements of this $coll which do not satisfy a predicate.
*
* @param p the predicate used to test elements.
* @return a new $coll consisting of all elements of this $coll that do not satisfy the given
* predicate `p`. The order of the elements is preserved.
*/
  def filterNot(p: A => Boolean): Repr = filterImpl(p, isFlipped = true)

  def collect[B, That](pf: PartialFunction[A, B])(implicit bf: CanBuildFrom[Repr, B, That]): That = {
    val b = bf(repr)
    foreach(pf.runWith(b += _))
    b.result
  }

  /** Builds a new collection by applying an option-valued function to all
* elements of this $coll on which the function is defined.
*
* @param f the option-valued function which filters and maps the $coll.
* @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 option-valued function
* `f` to each element and collecting all defined results.
* The order of the elements is preserved.
*
* @usecase def filterMap[B](f: A => Option[B]): $Coll[B]
* @inheritdoc
*
* @param pf the partial function which filters and maps the $coll.
* @return a new $coll resulting from applying the given option-valued function
* `f` to each element and collecting all defined results.
* The order of the elements is preserved.
def filterMap[B, That](f: A => Option[B])(implicit bf: CanBuildFrom[Repr, B, That]): That = {
val b = bf(repr)
for (x <- this)
f(x) match {
case Some(y) => b += y
case _ =>
}
b.result
}
*/

  /** Partitions this $coll in two ${coll}s according to a predicate.
*
* @param p the predicate on which to partition.
* @return a pair of ${coll}s: the first $coll consists of all elements that
* satisfy the predicate `p` and the second $coll consists of all elements
* that don't. The relative order of the elements in the resulting ${coll}s
* is the same as in the original $coll.
*/
  def partition(p: A => Boolean): (Repr, Repr) = {
    val l, r = newBuilder
    for (x <- this) (if (p(x)) l else r) += x
    (l.result, r.result)
  }

  def groupBy[K](f: A => K): immutable.Map[K, Repr] = {
    val m = mutable.Map.empty[K, Builder[A, Repr]]
    for (elem <- this) {
      val key = f(elem)
      val bldr = m.getOrElseUpdate(key, newBuilder)
      bldr += elem
    }
    val b = immutable.Map.newBuilder[K, Repr]
    for ((k, v) <- m)
      b += ((k, v.result))

    b.result
  }

  /** Tests whether a predicate holds for all elements of this $coll.
*
* $mayNotTerminateInf
*
* @param p the predicate used to test elements.
* @return `true` if the given predicate `p` holds for all elements
* of this $coll, otherwise `false`.
*/
  def forall(p: A => Boolean): Boolean = {
    var result = true
    breakable {
      for (x <- this)
        if (!p(x)) { result = false; break }
    }
    result
  }

  /** Tests whether a predicate holds for some of the elements of this $coll.
*
* $mayNotTerminateInf
*
* @param p the predicate used to test elements.
* @return `true` if the given predicate `p` holds for some of the
* elements of this $coll, otherwise `false`.
*/
  def exists(p: A => Boolean): Boolean = {
    var result = false
    breakable {
      for (x <- this)
        if (p(x)) { result = true; break }
    }
    result
  }

  /** Finds the first element of the $coll satisfying a predicate, if any.
*
* $mayNotTerminateInf
* $orderDependent
*
* @param p the predicate used to test elements.
* @return an option value containing the first element in the $coll
* that satisfies `p`, or `None` if none exists.
*/
  def find(p: A => Boolean): Option[A] = {
    var result: Option[A] = None
    breakable {
      for (x <- this)
        if (p(x)) { result = Some(x); break }
    }
    result
  }

  def scan[B >: A, That](z: B)(op: (B, B) => B)(implicit cbf: CanBuildFrom[Repr, B, That]): That = scanLeft(z)(op)

  def scanLeft[B, That](z: B)(op: (B, A) => B)(implicit bf: CanBuildFrom[Repr, B, That]): That = {
    val b = bf(repr)
    b.sizeHint(this, 1)
    var acc = z
    b += acc
    for (x <- this) { acc = op(acc, x); b += acc }
    b.result
  }

  @migration("The behavior of `scanRight` has changed. The previous behavior can be reproduced with scanRight.reverse.", "2.9.0")
  def scanRight[B, That](z: B)(op: (A, B) => B)(implicit bf: CanBuildFrom[Repr, B, That]): That = {
    var scanned = List(z)
    var acc = z
    for (x <- reversed) {
      acc = op(x, acc)
      scanned ::= acc
    }
    val b = bf(repr)
    for (elem <- scanned) b += elem
    b.result
  }

  /** Selects the first element of this $coll.
* $orderDependent
* @return the first element of this $coll.
* @throws `NoSuchElementException` if the $coll is empty.
*/
  def head: A = {
    var result: () => A = () => throw new NoSuchElementException
    breakable {
      for (x <- this) {
        result = () => x
        break
      }
    }
    result()
  }

  /** Optionally selects the first element.
* $orderDependent
* @return the first element of this $coll if it is nonempty,
* `None` if it is empty.
*/
  def headOption: Option[A] = if (isEmpty) None else Some(head)

  /** Selects all elements except the first.
* $orderDependent
* @return a $coll consisting of all elements of this $coll
* except the first one.
* @throws `UnsupportedOperationException` if the $coll is empty.
*/
  override def tail: Repr = {
    if (isEmpty) throw new UnsupportedOperationException("empty.tail")
    drop(1)
  }

  /** Selects the last element.
* $orderDependent
* @return The last element of this $coll.
* @throws NoSuchElementException If the $coll is empty.
*/
  def last: A = {
    var lst = head
    for (x <- this)
      lst = x
    lst
  }

  /** Optionally selects the last element.
* $orderDependent
* @return the last element of this $coll$ if it is nonempty,
* `None` if it is empty.
*/
  def lastOption: Option[A] = if (isEmpty) None else Some(last)

  /** Selects all elements except the last.
* $orderDependent
* @return a $coll consisting of all elements of this $coll
* except the last one.
* @throws `UnsupportedOperationException` if the $coll is empty.
*/
  def init: Repr = {
    if (isEmpty) throw new UnsupportedOperationException("empty.init")
    var lst = head
    var follow = false
    val b = newBuilder
    b.sizeHint(this, -1)
    for (x <- this) {
      if (follow) b += lst
      else follow = true
      lst = x
    }
    b.result
  }

  def take(n: Int): Repr = slice(0, n)

  def drop(n: Int): Repr =
    if (n <= 0) {
      val b = newBuilder
      b.sizeHint(this)
      (b ++= thisCollection).result
    }
    else sliceWithKnownDelta(n, Int.MaxValue, -n)

  def slice(from: Int, until: Int): Repr =
    sliceWithKnownBound(scala.math.max(from, 0), until)

  // Precondition: from >= 0, until > 0, builder already configured for building.
  private[this] def sliceInternal(from: Int, until: Int, b: Builder[A, Repr]): Repr = {
    var i = 0
    breakable {
      for (x <- this) {
        if (i >= from) b += x
        i += 1
        if (i >= until) break
      }
    }
    b.result
  }
  // Precondition: from >= 0
  private[scala] def sliceWithKnownDelta(from: Int, until: Int, delta: Int): Repr = {
    val b = newBuilder
    if (until <= from) b.result
    else {
      b.sizeHint(this, delta)
      sliceInternal(from, until, b)
    }
  }
  // Precondition: from >= 0
  private[scala] def sliceWithKnownBound(from: Int, until: Int): Repr = {
    val b = newBuilder
    if (until <= from) b.result
    else {
      b.sizeHintBounded(until - from, this)
      sliceInternal(from, until, b)
    }
  }

  def takeWhile(p: A => Boolean): Repr = {
    val b = newBuilder
    breakable {
      for (x <- this) {
        if (!p(x)) break
        b += x
      }
    }
    b.result
  }

  def dropWhile(p: A => Boolean): Repr = {
    val b = newBuilder
    var go = false
    for (x <- this) {
      if (!go && !p(x)) go = true
      if (go) b += x
    }
    b.result
  }

  def span(p: A => Boolean): (Repr, Repr) = {
    val l, r = newBuilder
    var toLeft = true
    for (x <- this) {
      toLeft = toLeft && p(x)
      (if (toLeft) l else r) += x
    }
    (l.result, r.result)
  }

  def splitAt(n: Int): (Repr, Repr) = {
    val l, r = newBuilder
    l.sizeHintBounded(n, this)
    if (n >= 0) r.sizeHint(this, -n)
    var i = 0
    for (x <- this) {
      (if (i < n) l else r) += x
      i += 1
    }
    (l.result, r.result)
  }

  /** Iterates over the tails of this $coll. The first value will be this
* $coll and the final one will be an empty $coll, with the intervening
* values the results of successive applications of `tail`.
*
* @return an iterator over all the tails of this $coll
* @example `List(1,2,3).tails = Iterator(List(1,2,3), List(2,3), List(3), Nil)`
*/
  def tails: Iterator[Repr] = iterateUntilEmpty(_.tail)

  /** Iterates over the inits of this $coll. The first value will be this
* $coll and the final one will be an empty $coll, with the intervening
* values the results of successive applications of `init`.
*
* @return an iterator over all the inits of this $coll
* @example `List(1,2,3).inits = Iterator(List(1,2,3), List(1,2), List(1), Nil)`
*/
  def inits: Iterator[Repr] = iterateUntilEmpty(_.init)

  /** Copies elements of this $coll to an array.
* Fills the given array `xs` with at most `len` elements of
* this $coll, starting at position `start`.
* Copying will stop once either the end of the current $coll is reached,
* or the end of the array is reached, or `len` elements have been copied.
*
* @param xs the array to fill.
* @param start the starting index.
* @param len the maximal number of elements to copy.
* @tparam B the type of the elements of the array.
*
*
* @usecase def copyToArray(xs: Array[A], start: Int, len: Int): Unit
* @inheritdoc
*
* $willNotTerminateInf
*/
  def copyToArray[B >: A](xs: Array[B], start: Int, len: Int) {
    var i = start
    val end = (start + len) min xs.length
    breakable {
      for (x <- this) {
        if (i >= end) break
        xs(i) = x
        i += 1
      }
    }
  }

  @deprecatedOverriding("Enforce contract of toTraversable that if it is Traversable it returns itself.", "2.11.0")
  def toTraversable: Traversable[A] = thisCollection
  
  def toIterator: Iterator[A] = toStream.iterator
  def toStream: Stream[A] = toBuffer.toStream
  // Override to provide size hint.
  override def to[Col[_]](implicit cbf: CanBuildFrom[Nothing, A, Col[A @uV]]): Col[A @uV] = {
    val b = cbf()
    b.sizeHint(this)
    b ++= thisCollection
    b.result
  }

  /** Converts this $coll to a string.
*
* @return a string representation of this collection. By default this
* string consists of the `stringPrefix` of this $coll, followed
* by all elements separated by commas and enclosed in parentheses.
*/
  override def toString = mkString(stringPrefix + "(", ", ", ")")

  /** Defines the prefix of this object's `toString` representation.
*
* @return a string representation which starts the result of `toString`
* applied to this $coll. By default the string prefix is the
* simple name of the collection class $coll.
*/
  def stringPrefix : String = {
    var string = repr.getClass.getName
    val idx1 = string.lastIndexOf('.' : Int)
    if (idx1 != -1) string = string.substring(idx1 + 1)
    val idx2 = string.indexOf('$')
    if (idx2 != -1) string = string.substring(0, idx2)
    string
  }

  /** Creates a non-strict view of this $coll.
*
* @return a non-strict view of this $coll.
*/
  def view = new TraversableView[A, Repr] {
    protected lazy val underlying = self.repr
    override def foreach[U](f: A => U) = self foreach f
  }

  /** Creates a non-strict view of a slice of this $coll.
*
* Note: the difference between `view` and `slice` is that `view` produces
* a view of the current $coll, whereas `slice` produces a new $coll.
*
* Note: `view(from, to)` is equivalent to `view.slice(from, to)`
* $orderDependent
*
* @param from the index of the first element of the view
* @param until the index of the element following the view
* @return a non-strict view of a slice of this $coll, starting at index `from`
* and extending up to (but not including) index `until`.
*/
  def view(from: Int, until: Int): TraversableView[A, Repr] = view.slice(from, until)

  /** Creates a non-strict filter of this $coll.
*
* Note: the difference between `c filter p` and `c withFilter p` is that
* the former creates a new collection, whereas the latter only
* restricts the domain of subsequent `map`, `flatMap`, `foreach`,
* and `withFilter` operations.
* $orderDependent
*
* @param p the predicate used to test elements.
* @return an object of class `WithFilter`, which supports
* `map`, `flatMap`, `foreach`, and `withFilter` operations.
* All these operations apply to those elements of this $coll
* which satisfy the predicate `p`.
*/
  def withFilter(p: A => Boolean): FilterMonadic[A, Repr] = new WithFilter(p)

  /** A class supporting filtered operations. Instances of this class are
* returned by method `withFilter`.
*/
  class WithFilter(p: A => Boolean) extends FilterMonadic[A, Repr] {

    /** Builds a new collection by applying a function to all elements of the
* outer $coll containing this `WithFilter` instance that satisfy predicate `p`.
*
* @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 the outer $coll
* that satisfies predicate `p` and collecting the results.
*
* @usecase def map[B](f: A => B): $Coll[B]
* @inheritdoc
*
* @return a new $coll resulting from applying the given function
* `f` to each element of the outer $coll that satisfies
* predicate `p` and collecting the results.
*/
    def map[B, That](f: A => B)(implicit bf: CanBuildFrom[Repr, B, That]): That = {
      val b = bf(repr)
      for (x <- self)
        if (p(x)) b += f(x)
      b.result
    }

    /** Builds a new collection by applying a function to all elements of the
* outer $coll containing this `WithFilter` instance that satisfy
* predicate `p` and concatenating the results.
*
* @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 collection-valued function `f` to each element
* of the outer $coll that satisfies predicate `p` and
* concatenating the results.
*
* @usecase def flatMap[B](f: A => TraversableOnce[B]): $Coll[B]
* @inheritdoc
*
* The type of the resulting collection will be guided by the static type
* of the outer $coll.
*
* @return a new $coll resulting from applying the given
* collection-valued function `f` to each element of the
* outer $coll that satisfies predicate `p` and concatenating
* the results.
*/
    def flatMap[B, That](f: A => GenTraversableOnce[B])(implicit bf: CanBuildFrom[Repr, B, That]): That = {
      val b = bf(repr)
      for (x <- self)
        if (p(x)) b ++= f(x).seq
      b.result
    }

    /** Applies a function `f` to all elements of the outer $coll containing
* this `WithFilter` instance that satisfy predicate `p`.
*
* @param f the function that is applied for its side-effect to every element.
* The result of function `f` is discarded.
*
* @tparam U the type parameter describing the result of function `f`.
* This result will always be ignored. Typically `U` is `Unit`,
* but this is not necessary.
*
* @usecase def foreach(f: A => Unit): Unit
* @inheritdoc
*/
    def foreach[U](f: A => U): Unit =
      for (x <- self)
        if (p(x)) f(x)

    /** Further refines the filter for this $coll.
*
* @param q the predicate used to test elements.
* @return an object of class `WithFilter`, which supports
* `map`, `flatMap`, `foreach`, and `withFilter` operations.
* All these operations apply to those elements of this $coll which
* satisfy the predicate `q` in addition to the predicate `p`.
*/
    def withFilter(q: A => Boolean): WithFilter =
      new WithFilter(x => p(x) && q(x))
  }

  // A helper for tails and inits.
  private def iterateUntilEmpty(f: Traversable[A @uV] => Traversable[A @uV]): Iterator[Repr] = {
    val it = Iterator.iterate(thisCollection)(f) takeWhile (x => !x.isEmpty)
    it ++ Iterator(Nil) map (x => (newBuilder ++= x).result)
  }
}
Something went wrong with that request. Please try again.