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| /* __ *\ | |
| ** ________ ___ / / ___ 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) | |
| } | |
| } | |
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