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
|
<!doctype html>
<html>
<head>
<title>CodeMirror: C-like mode</title>
<link rel="stylesheet" href="../../lib/codemirror.css">
<link rel="stylesheet" href="../../theme/ambiance.css">
<script src="../../lib/codemirror.js"></script>
<script src="clike.js"></script>
<link rel="stylesheet" href="../../doc/docs.css">
<style>
body
{
margin: 0;
padding: 0;
max-width:inherit;
height: 100%;
}
html, form, .CodeMirror, .CodeMirror-scroll
{
height: 100%;
}
</style>
</head>
<body>
<form>
<textarea id="code" name="code">
/* __ *\
** ________ ___ / / ___ Scala API **
** / __/ __// _ | / / / _ | (c) 2003-2011, LAMP/EPFL **
** __\ \/ /__/ __ |/ /__/ __ | http://scala-lang.org/ **
** /____/\___/_/ |_/____/_/ | | **
** |/ **
\* */
package scala.collection
import generic._
import mutable.{ Builder, ListBuffer }
import annotation.{tailrec, migration, bridge}
import annotation.unchecked.{ uncheckedVariance => uV }
import parallel.ParIterable
/** 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
* <a href="../immutable/Stream.html" target="ContentFrame">
* `scala.collection.immutable.Stream`</a>.
* 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 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 type Self = Repr
/** The collection of type $coll underlying this `TraversableLike` object.
* By default this is implemented as the `TraversableLike` object itself,
* but this can be overridden.
*/
def repr: Repr = this.asInstanceOf[Repr]
/** The underlying collection seen as an instance of `$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.
*
* Note: this method underlies the implementation of most other bulk operations.
* It's important to implement this method in an efficient way.
*
*
* @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
*/
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
}
@bridge
def ++[B >: A, That](that: TraversableOnce[B])(implicit bf: CanBuildFrom[Repr, B, That]): That =
++(that: GenTraversableOnce[B])(bf)
/** Concatenates this $coll with the elements of a traversable collection.
* It differs from ++ in that the right operand determines the type of the
* resulting collection rather than the left one.
*
* @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]
*
* @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
}
/** 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.
*/
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 = {
val b = bf(repr)
b.sizeHint(this)
for (x <- this) b += f(x)
b.result
}
def flatMap[B, That](f: A => GenTraversableOnce[B])(implicit bf: CanBuildFrom[Repr, B, That]): That = {
val b = bf(repr)
for (x <- this) b ++= f(x).seq
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 = {
val b = newBuilder
for (x <- this)
if (p(x)) b += x
b.result
}
/** 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 = filter(!p(_))
def collect[B, That](pf: PartialFunction[A, B])(implicit bf: CanBuildFrom[Repr, B, That]): That = {
val b = bf(repr)
for (x <- this) if (pf.isDefinedAt(x)) b += pf(x)
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]
*
* @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(2, 9,
"This scanRight definition has changed in 2.9.\n" +
"The previous behavior can be reproduced with scanRight.reverse."
)
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.seq) {
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(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.seq) {
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 (!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.
*
* $willNotTerminateInf
*
* @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
*/
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
}
}
}
def toTraversable: Traversable[A] = thisCollection
def toIterator: Iterator[A] = toStream.iterator
def toStream: Stream[A] = toBuffer.toStream
/** 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 $coll.
*/
def stringPrefix : String = {
var string = repr.asInstanceOf[AnyRef].getClass.getName
val idx1 = string.lastIndexOf('.' : Int)
if (idx1 != -1) string = string.substring(idx1 + 1)
val idx2 = string.indexOf('$')
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]
*
* @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]
*
* @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
*/
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 (newBuilder ++= _ result)
}
}
</textarea>
</form>
<script>
var editor = CodeMirror.fromTextArea(document.getElementById("code"), {
lineNumbers: true,
matchBrackets: true,
theme: "ambiance",
mode: "text/x-scala"
});
</script>
</body>
</html>
|
