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1 <!doctype html> | |
2 | |
3 <title>CodeMirror: Scala mode</title> | |
4 <meta charset="utf-8"/> | |
5 <link rel=stylesheet href="../../doc/docs.css"> | |
6 | |
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11 <script src="clike.js"></script> | |
12 <div id=nav> | |
13 <a href="https://codemirror.net/5"><h1>CodeMirror</h1><img id=logo src="../../doc/logo.png" alt=""></a> | |
14 | |
15 <ul> | |
16 <li><a href="../../index.html">Home</a> | |
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21 <li><a href="../index.html">Language modes</a> | |
22 <li><a class=active href="#">Scala</a> | |
23 </ul> | |
24 </div> | |
25 | |
26 <article> | |
27 <h2>Scala mode</h2> | |
28 <form> | |
29 <textarea id="code" name="code"> | |
30 | |
31 /* __ *\ | |
32 ** ________ ___ / / ___ Scala API ** | |
33 ** / __/ __// _ | / / / _ | (c) 2003-2011, LAMP/EPFL ** | |
34 ** __\ \/ /__/ __ |/ /__/ __ | http://scala-lang.org/ ** | |
35 ** /____/\___/_/ |_/____/_/ | | ** | |
36 ** |/ ** | |
37 \* */ | |
38 | |
39 package scala.collection | |
40 | |
41 import generic._ | |
42 import mutable.{ Builder, ListBuffer } | |
43 import annotation.{tailrec, migration, bridge} | |
44 import annotation.unchecked.{ uncheckedVariance => uV } | |
45 import parallel.ParIterable | |
46 | |
47 /** A template trait for traversable collections of type `Traversable[A]`. | |
48 * | |
49 * $traversableInfo | |
50 * @define mutability | |
51 * @define traversableInfo | |
52 * This is a base trait of all kinds of $mutability Scala collections. It | |
53 * implements the behavior common to all collections, in terms of a method | |
54 * `foreach` with signature: | |
55 * {{{ | |
56 * def foreach[U](f: Elem => U): Unit | |
57 * }}} | |
58 * Collection classes mixing in this trait provide a concrete | |
59 * `foreach` method which traverses all the | |
60 * elements contained in the collection, applying a given function to each. | |
61 * They also need to provide a method `newBuilder` | |
62 * which creates a builder for collections of the same kind. | |
63 * | |
64 * A traversable class might or might not have two properties: strictness | |
65 * and orderedness. Neither is represented as a type. | |
66 * | |
67 * The instances of a strict collection class have all their elements | |
68 * computed before they can be used as values. By contrast, instances of | |
69 * a non-strict collection class may defer computation of some of their | |
70 * elements until after the instance is available as a value. | |
71 * A typical example of a non-strict collection class is a | |
72 * <a href="../immutable/Stream.html" target="ContentFrame"> | |
73 * `scala.collection.immutable.Stream`</a>. | |
74 * A more general class of examples are `TraversableViews`. | |
75 * | |
76 * If a collection is an instance of an ordered collection class, traversing | |
77 * its elements with `foreach` will always visit elements in the | |
78 * same order, even for different runs of the program. If the class is not | |
79 * ordered, `foreach` can visit elements in different orders for | |
80 * different runs (but it will keep the same order in the same run).' | |
81 * | |
82 * A typical example of a collection class which is not ordered is a | |
83 * `HashMap` of objects. The traversal order for hash maps will | |
84 * depend on the hash codes of its elements, and these hash codes might | |
85 * differ from one run to the next. By contrast, a `LinkedHashMap` | |
86 * is ordered because it's `foreach` method visits elements in the | |
87 * order they were inserted into the `HashMap`. | |
88 * | |
89 * @author Martin Odersky | |
90 * @version 2.8 | |
91 * @since 2.8 | |
92 * @tparam A the element type of the collection | |
93 * @tparam Repr the type of the actual collection containing the elements. | |
94 * | |
95 * @define Coll Traversable | |
96 * @define coll traversable collection | |
97 */ | |
98 trait TraversableLike[+A, +Repr] extends HasNewBuilder[A, Repr] | |
99 with FilterMonadic[A, Repr] | |
100 with TraversableOnce[A] | |
101 with GenTraversableLike[A, Repr] | |
102 with Parallelizable[A, ParIterable[A]] | |
103 { | |
104 self => | |
105 | |
106 import Traversable.breaks._ | |
107 | |
108 /** The type implementing this traversable */ | |
109 protected type Self = Repr | |
110 | |
111 /** The collection of type $coll underlying this `TraversableLike` object. | |
112 * By default this is implemented as the `TraversableLike` object itself, | |
113 * but this can be overridden. | |
114 */ | |
115 def repr: Repr = this.asInstanceOf[Repr] | |
116 | |
117 /** The underlying collection seen as an instance of `$Coll`. | |
118 * By default this is implemented as the current collection object itself, | |
119 * but this can be overridden. | |
120 */ | |
121 protected[this] def thisCollection: Traversable[A] = this.asInstanceOf[Traversable[A]] | |
122 | |
123 /** A conversion from collections of type `Repr` to `$Coll` objects. | |
124 * By default this is implemented as just a cast, but this can be overridden. | |
125 */ | |
126 protected[this] def toCollection(repr: Repr): Traversable[A] = repr.asInstanceOf[Traversable[A]] | |
127 | |
128 /** Creates a new builder for this collection type. | |
129 */ | |
130 protected[this] def newBuilder: Builder[A, Repr] | |
131 | |
132 protected[this] def parCombiner = ParIterable.newCombiner[A] | |
133 | |
134 /** Applies a function `f` to all elements of this $coll. | |
135 * | |
136 * Note: this method underlies the implementation of most other bulk operations. | |
137 * It's important to implement this method in an efficient way. | |
138 * | |
139 * | |
140 * @param f the function that is applied for its side-effect to every element. | |
141 * The result of function `f` is discarded. | |
142 * | |
143 * @tparam U the type parameter describing the result of function `f`. | |
144 * This result will always be ignored. Typically `U` is `Unit`, | |
145 * but this is not necessary. | |
146 * | |
147 * @usecase def foreach(f: A => Unit): Unit | |
148 */ | |
149 def foreach[U](f: A => U): Unit | |
150 | |
151 /** Tests whether this $coll is empty. | |
152 * | |
153 * @return `true` if the $coll contain no elements, `false` otherwise. | |
154 */ | |
155 def isEmpty: Boolean = { | |
156 var result = true | |
157 breakable { | |
158 for (x <- this) { | |
159 result = false | |
160 break | |
161 } | |
162 } | |
163 result | |
164 } | |
165 | |
166 /** Tests whether this $coll is known to have a finite size. | |
167 * All strict collections are known to have finite size. For a non-strict collection | |
168 * such as `Stream`, the predicate returns `true` if all elements have been computed. | |
169 * It returns `false` if the stream is not yet evaluated to the end. | |
170 * | |
171 * Note: many collection methods will not work on collections of infinite sizes. | |
172 * | |
173 * @return `true` if this collection is known to have finite size, `false` otherwise. | |
174 */ | |
175 def hasDefiniteSize = true | |
176 | |
177 def ++[B >: A, That](that: GenTraversableOnce[B])(implicit bf: CanBuildFrom[Repr, B, That]): That = { | |
178 val b = bf(repr) | |
179 if (that.isInstanceOf[IndexedSeqLike[_, _]]) b.sizeHint(this, that.seq.size) | |
180 b ++= thisCollection | |
181 b ++= that.seq | |
182 b.result | |
183 } | |
184 | |
185 @bridge | |
186 def ++[B >: A, That](that: TraversableOnce[B])(implicit bf: CanBuildFrom[Repr, B, That]): That = | |
187 ++(that: GenTraversableOnce[B])(bf) | |
188 | |
189 /** Concatenates this $coll with the elements of a traversable collection. | |
190 * It differs from ++ in that the right operand determines the type of the | |
191 * resulting collection rather than the left one. | |
192 * | |
193 * @param that the traversable to append. | |
194 * @tparam B the element type of the returned collection. | |
195 * @tparam That $thatinfo | |
196 * @param bf $bfinfo | |
197 * @return a new collection of type `That` which contains all elements | |
198 * of this $coll followed by all elements of `that`. | |
199 * | |
200 * @usecase def ++:[B](that: TraversableOnce[B]): $Coll[B] | |
201 * | |
202 * @return a new $coll which contains all elements of this $coll | |
203 * followed by all elements of `that`. | |
204 */ | |
205 def ++:[B >: A, That](that: TraversableOnce[B])(implicit bf: CanBuildFrom[Repr, B, That]): That = { | |
206 val b = bf(repr) | |
207 if (that.isInstanceOf[IndexedSeqLike[_, _]]) b.sizeHint(this, that.size) | |
208 b ++= that | |
209 b ++= thisCollection | |
210 b.result | |
211 } | |
212 | |
213 /** This overload exists because: for the implementation of ++: we should reuse | |
214 * that of ++ because many collections override it with more efficient versions. | |
215 * Since TraversableOnce has no '++' method, we have to implement that directly, | |
216 * but Traversable and down can use the overload. | |
217 */ | |
218 def ++:[B >: A, That](that: Traversable[B])(implicit bf: CanBuildFrom[Repr, B, That]): That = | |
219 (that ++ seq)(breakOut) | |
220 | |
221 def map[B, That](f: A => B)(implicit bf: CanBuildFrom[Repr, B, That]): That = { | |
222 val b = bf(repr) | |
223 b.sizeHint(this) | |
224 for (x <- this) b += f(x) | |
225 b.result | |
226 } | |
227 | |
228 def flatMap[B, That](f: A => GenTraversableOnce[B])(implicit bf: CanBuildFrom[Repr, B, That]): That = { | |
229 val b = bf(repr) | |
230 for (x <- this) b ++= f(x).seq | |
231 b.result | |
232 } | |
233 | |
234 /** Selects all elements of this $coll which satisfy a predicate. | |
235 * | |
236 * @param p the predicate used to test elements. | |
237 * @return a new $coll consisting of all elements of this $coll that satisfy the given | |
238 * predicate `p`. The order of the elements is preserved. | |
239 */ | |
240 def filter(p: A => Boolean): Repr = { | |
241 val b = newBuilder | |
242 for (x <- this) | |
243 if (p(x)) b += x | |
244 b.result | |
245 } | |
246 | |
247 /** Selects all elements of this $coll which do not satisfy a predicate. | |
248 * | |
249 * @param p the predicate used to test elements. | |
250 * @return a new $coll consisting of all elements of this $coll that do not satisfy the given | |
251 * predicate `p`. The order of the elements is preserved. | |
252 */ | |
253 def filterNot(p: A => Boolean): Repr = filter(!p(_)) | |
254 | |
255 def collect[B, That](pf: PartialFunction[A, B])(implicit bf: CanBuildFrom[Repr, B, That]): That = { | |
256 val b = bf(repr) | |
257 for (x <- this) if (pf.isDefinedAt(x)) b += pf(x) | |
258 b.result | |
259 } | |
260 | |
261 /** Builds a new collection by applying an option-valued function to all | |
262 * elements of this $coll on which the function is defined. | |
263 * | |
264 * @param f the option-valued function which filters and maps the $coll. | |
265 * @tparam B the element type of the returned collection. | |
266 * @tparam That $thatinfo | |
267 * @param bf $bfinfo | |
268 * @return a new collection of type `That` resulting from applying the option-valued function | |
269 * `f` to each element and collecting all defined results. | |
270 * The order of the elements is preserved. | |
271 * | |
272 * @usecase def filterMap[B](f: A => Option[B]): $Coll[B] | |
273 * | |
274 * @param pf the partial function which filters and maps the $coll. | |
275 * @return a new $coll resulting from applying the given option-valued function | |
276 * `f` to each element and collecting all defined results. | |
277 * The order of the elements is preserved. | |
278 def filterMap[B, That](f: A => Option[B])(implicit bf: CanBuildFrom[Repr, B, That]): That = { | |
279 val b = bf(repr) | |
280 for (x <- this) | |
281 f(x) match { | |
282 case Some(y) => b += y | |
283 case _ => | |
284 } | |
285 b.result | |
286 } | |
287 */ | |
288 | |
289 /** Partitions this $coll in two ${coll}s according to a predicate. | |
290 * | |
291 * @param p the predicate on which to partition. | |
292 * @return a pair of ${coll}s: the first $coll consists of all elements that | |
293 * satisfy the predicate `p` and the second $coll consists of all elements | |
294 * that don't. The relative order of the elements in the resulting ${coll}s | |
295 * is the same as in the original $coll. | |
296 */ | |
297 def partition(p: A => Boolean): (Repr, Repr) = { | |
298 val l, r = newBuilder | |
299 for (x <- this) (if (p(x)) l else r) += x | |
300 (l.result, r.result) | |
301 } | |
302 | |
303 def groupBy[K](f: A => K): immutable.Map[K, Repr] = { | |
304 val m = mutable.Map.empty[K, Builder[A, Repr]] | |
305 for (elem <- this) { | |
306 val key = f(elem) | |
307 val bldr = m.getOrElseUpdate(key, newBuilder) | |
308 bldr += elem | |
309 } | |
310 val b = immutable.Map.newBuilder[K, Repr] | |
311 for ((k, v) <- m) | |
312 b += ((k, v.result)) | |
313 | |
314 b.result | |
315 } | |
316 | |
317 /** Tests whether a predicate holds for all elements of this $coll. | |
318 * | |
319 * $mayNotTerminateInf | |
320 * | |
321 * @param p the predicate used to test elements. | |
322 * @return `true` if the given predicate `p` holds for all elements | |
323 * of this $coll, otherwise `false`. | |
324 */ | |
325 def forall(p: A => Boolean): Boolean = { | |
326 var result = true | |
327 breakable { | |
328 for (x <- this) | |
329 if (!p(x)) { result = false; break } | |
330 } | |
331 result | |
332 } | |
333 | |
334 /** Tests whether a predicate holds for some of the elements of this $coll. | |
335 * | |
336 * $mayNotTerminateInf | |
337 * | |
338 * @param p the predicate used to test elements. | |
339 * @return `true` if the given predicate `p` holds for some of the | |
340 * elements of this $coll, otherwise `false`. | |
341 */ | |
342 def exists(p: A => Boolean): Boolean = { | |
343 var result = false | |
344 breakable { | |
345 for (x <- this) | |
346 if (p(x)) { result = true; break } | |
347 } | |
348 result | |
349 } | |
350 | |
351 /** Finds the first element of the $coll satisfying a predicate, if any. | |
352 * | |
353 * $mayNotTerminateInf | |
354 * $orderDependent | |
355 * | |
356 * @param p the predicate used to test elements. | |
357 * @return an option value containing the first element in the $coll | |
358 * that satisfies `p`, or `None` if none exists. | |
359 */ | |
360 def find(p: A => Boolean): Option[A] = { | |
361 var result: Option[A] = None | |
362 breakable { | |
363 for (x <- this) | |
364 if (p(x)) { result = Some(x); break } | |
365 } | |
366 result | |
367 } | |
368 | |
369 def scan[B >: A, That](z: B)(op: (B, B) => B)(implicit cbf: CanBuildFrom[Repr, B, That]): That = scanLeft(z)(op) | |
370 | |
371 def scanLeft[B, That](z: B)(op: (B, A) => B)(implicit bf: CanBuildFrom[Repr, B, That]): That = { | |
372 val b = bf(repr) | |
373 b.sizeHint(this, 1) | |
374 var acc = z | |
375 b += acc | |
376 for (x <- this) { acc = op(acc, x); b += acc } | |
377 b.result | |
378 } | |
379 | |
380 @migration(2, 9, | |
381 "This scanRight definition has changed in 2.9.\n" + | |
382 "The previous behavior can be reproduced with scanRight.reverse." | |
383 ) | |
384 def scanRight[B, That](z: B)(op: (A, B) => B)(implicit bf: CanBuildFrom[Repr, B, That]): That = { | |
385 var scanned = List(z) | |
386 var acc = z | |
387 for (x <- reversed) { | |
388 acc = op(x, acc) | |
389 scanned ::= acc | |
390 } | |
391 val b = bf(repr) | |
392 for (elem <- scanned) b += elem | |
393 b.result | |
394 } | |
395 | |
396 /** Selects the first element of this $coll. | |
397 * $orderDependent | |
398 * @return the first element of this $coll. | |
399 * @throws `NoSuchElementException` if the $coll is empty. | |
400 */ | |
401 def head: A = { | |
402 var result: () => A = () => throw new NoSuchElementException | |
403 breakable { | |
404 for (x <- this) { | |
405 result = () => x | |
406 break | |
407 } | |
408 } | |
409 result() | |
410 } | |
411 | |
412 /** Optionally selects the first element. | |
413 * $orderDependent | |
414 * @return the first element of this $coll if it is nonempty, `None` if it is empty. | |
415 */ | |
416 def headOption: Option[A] = if (isEmpty) None else Some(head) | |
417 | |
418 /** Selects all elements except the first. | |
419 * $orderDependent | |
420 * @return a $coll consisting of all elements of this $coll | |
421 * except the first one. | |
422 * @throws `UnsupportedOperationException` if the $coll is empty. | |
423 */ | |
424 override def tail: Repr = { | |
425 if (isEmpty) throw new UnsupportedOperationException("empty.tail") | |
426 drop(1) | |
427 } | |
428 | |
429 /** Selects the last element. | |
430 * $orderDependent | |
431 * @return The last element of this $coll. | |
432 * @throws NoSuchElementException If the $coll is empty. | |
433 */ | |
434 def last: A = { | |
435 var lst = head | |
436 for (x <- this) | |
437 lst = x | |
438 lst | |
439 } | |
440 | |
441 /** Optionally selects the last element. | |
442 * $orderDependent | |
443 * @return the last element of this $coll$ if it is nonempty, `None` if it is empty. | |
444 */ | |
445 def lastOption: Option[A] = if (isEmpty) None else Some(last) | |
446 | |
447 /** Selects all elements except the last. | |
448 * $orderDependent | |
449 * @return a $coll consisting of all elements of this $coll | |
450 * except the last one. | |
451 * @throws `UnsupportedOperationException` if the $coll is empty. | |
452 */ | |
453 def init: Repr = { | |
454 if (isEmpty) throw new UnsupportedOperationException("empty.init") | |
455 var lst = head | |
456 var follow = false | |
457 val b = newBuilder | |
458 b.sizeHint(this, -1) | |
459 for (x <- this.seq) { | |
460 if (follow) b += lst | |
461 else follow = true | |
462 lst = x | |
463 } | |
464 b.result | |
465 } | |
466 | |
467 def take(n: Int): Repr = slice(0, n) | |
468 | |
469 def drop(n: Int): Repr = | |
470 if (n <= 0) { | |
471 val b = newBuilder | |
472 b.sizeHint(this) | |
473 b ++= thisCollection result | |
474 } | |
475 else sliceWithKnownDelta(n, Int.MaxValue, -n) | |
476 | |
477 def slice(from: Int, until: Int): Repr = sliceWithKnownBound(math.max(from, 0), until) | |
478 | |
479 // Precondition: from >= 0, until > 0, builder already configured for building. | |
480 private[this] def sliceInternal(from: Int, until: Int, b: Builder[A, Repr]): Repr = { | |
481 var i = 0 | |
482 breakable { | |
483 for (x <- this.seq) { | |
484 if (i >= from) b += x | |
485 i += 1 | |
486 if (i >= until) break | |
487 } | |
488 } | |
489 b.result | |
490 } | |
491 // Precondition: from >= 0 | |
492 private[scala] def sliceWithKnownDelta(from: Int, until: Int, delta: Int): Repr = { | |
493 val b = newBuilder | |
494 if (until <= from) b.result | |
495 else { | |
496 b.sizeHint(this, delta) | |
497 sliceInternal(from, until, b) | |
498 } | |
499 } | |
500 // Precondition: from >= 0 | |
501 private[scala] def sliceWithKnownBound(from: Int, until: Int): Repr = { | |
502 val b = newBuilder | |
503 if (until <= from) b.result | |
504 else { | |
505 b.sizeHintBounded(until - from, this) | |
506 sliceInternal(from, until, b) | |
507 } | |
508 } | |
509 | |
510 def takeWhile(p: A => Boolean): Repr = { | |
511 val b = newBuilder | |
512 breakable { | |
513 for (x <- this) { | |
514 if (!p(x)) break | |
515 b += x | |
516 } | |
517 } | |
518 b.result | |
519 } | |
520 | |
521 def dropWhile(p: A => Boolean): Repr = { | |
522 val b = newBuilder | |
523 var go = false | |
524 for (x <- this) { | |
525 if (!p(x)) go = true | |
526 if (go) b += x | |
527 } | |
528 b.result | |
529 } | |
530 | |
531 def span(p: A => Boolean): (Repr, Repr) = { | |
532 val l, r = newBuilder | |
533 var toLeft = true | |
534 for (x <- this) { | |
535 toLeft = toLeft && p(x) | |
536 (if (toLeft) l else r) += x | |
537 } | |
538 (l.result, r.result) | |
539 } | |
540 | |
541 def splitAt(n: Int): (Repr, Repr) = { | |
542 val l, r = newBuilder | |
543 l.sizeHintBounded(n, this) | |
544 if (n >= 0) r.sizeHint(this, -n) | |
545 var i = 0 | |
546 for (x <- this) { | |
547 (if (i < n) l else r) += x | |
548 i += 1 | |
549 } | |
550 (l.result, r.result) | |
551 } | |
552 | |
553 /** Iterates over the tails of this $coll. The first value will be this | |
554 * $coll and the final one will be an empty $coll, with the intervening | |
555 * values the results of successive applications of `tail`. | |
556 * | |
557 * @return an iterator over all the tails of this $coll | |
558 * @example `List(1,2,3).tails = Iterator(List(1,2,3), List(2,3), List(3), Nil)` | |
559 */ | |
560 def tails: Iterator[Repr] = iterateUntilEmpty(_.tail) | |
561 | |
562 /** Iterates over the inits of this $coll. The first value will be this | |
563 * $coll and the final one will be an empty $coll, with the intervening | |
564 * values the results of successive applications of `init`. | |
565 * | |
566 * @return an iterator over all the inits of this $coll | |
567 * @example `List(1,2,3).inits = Iterator(List(1,2,3), List(1,2), List(1), Nil)` | |
568 */ | |
569 def inits: Iterator[Repr] = iterateUntilEmpty(_.init) | |
570 | |
571 /** Copies elements of this $coll to an array. | |
572 * Fills the given array `xs` with at most `len` elements of | |
573 * this $coll, starting at position `start`. | |
574 * Copying will stop once either the end of the current $coll is reached, | |
575 * or the end of the array is reached, or `len` elements have been copied. | |
576 * | |
577 * $willNotTerminateInf | |
578 * | |
579 * @param xs the array to fill. | |
580 * @param start the starting index. | |
581 * @param len the maximal number of elements to copy. | |
582 * @tparam B the type of the elements of the array. | |
583 * | |
584 * | |
585 * @usecase def copyToArray(xs: Array[A], start: Int, len: Int): Unit | |
586 */ | |
587 def copyToArray[B >: A](xs: Array[B], start: Int, len: Int) { | |
588 var i = start | |
589 val end = (start + len) min xs.length | |
590 breakable { | |
591 for (x <- this) { | |
592 if (i >= end) break | |
593 xs(i) = x | |
594 i += 1 | |
595 } | |
596 } | |
597 } | |
598 | |
599 def toTraversable: Traversable[A] = thisCollection | |
600 def toIterator: Iterator[A] = toStream.iterator | |
601 def toStream: Stream[A] = toBuffer.toStream | |
602 | |
603 /** Converts this $coll to a string. | |
604 * | |
605 * @return a string representation of this collection. By default this | |
606 * string consists of the `stringPrefix` of this $coll, | |
607 * followed by all elements separated by commas and enclosed in parentheses. | |
608 */ | |
609 override def toString = mkString(stringPrefix + "(", ", ", ")") | |
610 | |
611 /** Defines the prefix of this object's `toString` representation. | |
612 * | |
613 * @return a string representation which starts the result of `toString` | |
614 * applied to this $coll. By default the string prefix is the | |
615 * simple name of the collection class $coll. | |
616 */ | |
617 def stringPrefix : String = { | |
618 var string = repr.asInstanceOf[AnyRef].getClass.getName | |
619 val idx1 = string.lastIndexOf('.' : Int) | |
620 if (idx1 != -1) string = string.substring(idx1 + 1) | |
621 val idx2 = string.indexOf('$') | |
622 if (idx2 != -1) string = string.substring(0, idx2) | |
623 string | |
624 } | |
625 | |
626 /** Creates a non-strict view of this $coll. | |
627 * | |
628 * @return a non-strict view of this $coll. | |
629 */ | |
630 def view = new TraversableView[A, Repr] { | |
631 protected lazy val underlying = self.repr | |
632 override def foreach[U](f: A => U) = self foreach f | |
633 } | |
634 | |
635 /** Creates a non-strict view of a slice of this $coll. | |
636 * | |
637 * Note: the difference between `view` and `slice` is that `view` produces | |
638 * a view of the current $coll, whereas `slice` produces a new $coll. | |
639 * | |
640 * Note: `view(from, to)` is equivalent to `view.slice(from, to)` | |
641 * $orderDependent | |
642 * | |
643 * @param from the index of the first element of the view | |
644 * @param until the index of the element following the view | |
645 * @return a non-strict view of a slice of this $coll, starting at index `from` | |
646 * and extending up to (but not including) index `until`. | |
647 */ | |
648 def view(from: Int, until: Int): TraversableView[A, Repr] = view.slice(from, until) | |
649 | |
650 /** Creates a non-strict filter of this $coll. | |
651 * | |
652 * Note: the difference between `c filter p` and `c withFilter p` is that | |
653 * the former creates a new collection, whereas the latter only | |
654 * restricts the domain of subsequent `map`, `flatMap`, `foreach`, | |
655 * and `withFilter` operations. | |
656 * $orderDependent | |
657 * | |
658 * @param p the predicate used to test elements. | |
659 * @return an object of class `WithFilter`, which supports | |
660 * `map`, `flatMap`, `foreach`, and `withFilter` operations. | |
661 * All these operations apply to those elements of this $coll which | |
662 * satisfy the predicate `p`. | |
663 */ | |
664 def withFilter(p: A => Boolean): FilterMonadic[A, Repr] = new WithFilter(p) | |
665 | |
666 /** A class supporting filtered operations. Instances of this class are | |
667 * returned by method `withFilter`. | |
668 */ | |
669 class WithFilter(p: A => Boolean) extends FilterMonadic[A, Repr] { | |
670 | |
671 /** Builds a new collection by applying a function to all elements of the | |
672 * outer $coll containing this `WithFilter` instance that satisfy predicate `p`. | |
673 * | |
674 * @param f the function to apply to each element. | |
675 * @tparam B the element type of the returned collection. | |
676 * @tparam That $thatinfo | |
677 * @param bf $bfinfo | |
678 * @return a new collection of type `That` resulting from applying | |
679 * the given function `f` to each element of the outer $coll | |
680 * that satisfies predicate `p` and collecting the results. | |
681 * | |
682 * @usecase def map[B](f: A => B): $Coll[B] | |
683 * | |
684 * @return a new $coll resulting from applying the given function | |
685 * `f` to each element of the outer $coll that satisfies | |
686 * predicate `p` and collecting the results. | |
687 */ | |
688 def map[B, That](f: A => B)(implicit bf: CanBuildFrom[Repr, B, That]): That = { | |
689 val b = bf(repr) | |
690 for (x <- self) | |
691 if (p(x)) b += f(x) | |
692 b.result | |
693 } | |
694 | |
695 /** Builds a new collection by applying a function to all elements of the | |
696 * outer $coll containing this `WithFilter` instance that satisfy | |
697 * predicate `p` and concatenating the results. | |
698 * | |
699 * @param f the function to apply to each element. | |
700 * @tparam B the element type of the returned collection. | |
701 * @tparam That $thatinfo | |
702 * @param bf $bfinfo | |
703 * @return a new collection of type `That` resulting from applying | |
704 * the given collection-valued function `f` to each element | |
705 * of the outer $coll that satisfies predicate `p` and | |
706 * concatenating the results. | |
707 * | |
708 * @usecase def flatMap[B](f: A => TraversableOnce[B]): $Coll[B] | |
709 * | |
710 * @return a new $coll resulting from applying the given collection-valued function | |
711 * `f` to each element of the outer $coll that satisfies predicate `p` and concatenating the results. | |
712 */ | |
713 def flatMap[B, That](f: A => GenTraversableOnce[B])(implicit bf: CanBuildFrom[Repr, B, That]): That = { | |
714 val b = bf(repr) | |
715 for (x <- self) | |
716 if (p(x)) b ++= f(x).seq | |
717 b.result | |
718 } | |
719 | |
720 /** Applies a function `f` to all elements of the outer $coll containing | |
721 * this `WithFilter` instance that satisfy predicate `p`. | |
722 * | |
723 * @param f the function that is applied for its side-effect to every element. | |
724 * The result of function `f` is discarded. | |
725 * | |
726 * @tparam U the type parameter describing the result of function `f`. | |
727 * This result will always be ignored. Typically `U` is `Unit`, | |
728 * but this is not necessary. | |
729 * | |
730 * @usecase def foreach(f: A => Unit): Unit | |
731 */ | |
732 def foreach[U](f: A => U): Unit = | |
733 for (x <- self) | |
734 if (p(x)) f(x) | |
735 | |
736 /** Further refines the filter for this $coll. | |
737 * | |
738 * @param q the predicate used to test elements. | |
739 * @return an object of class `WithFilter`, which supports | |
740 * `map`, `flatMap`, `foreach`, and `withFilter` operations. | |
741 * All these operations apply to those elements of this $coll which | |
742 * satisfy the predicate `q` in addition to the predicate `p`. | |
743 */ | |
744 def withFilter(q: A => Boolean): WithFilter = | |
745 new WithFilter(x => p(x) && q(x)) | |
746 } | |
747 | |
748 // A helper for tails and inits. | |
749 private def iterateUntilEmpty(f: Traversable[A @uV] => Traversable[A @uV]): Iterator[Repr] = { | |
750 val it = Iterator.iterate(thisCollection)(f) takeWhile (x => !x.isEmpty) | |
751 it ++ Iterator(Nil) map (newBuilder ++= _ result) | |
752 } | |
753 } | |
754 | |
755 | |
756 </textarea> | |
757 </form> | |
758 | |
759 <script> | |
760 var editor = CodeMirror.fromTextArea(document.getElementById("code"), { | |
761 lineNumbers: true, | |
762 matchBrackets: true, | |
763 theme: "ambiance", | |
764 mode: "text/x-scala" | |
765 }); | |
766 </script> | |
767 </article> |