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768 lines
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<!doctype html>
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<title>CodeMirror: Scala mode</title>
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<li><a class=active href="#">Scala</a>
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<article>
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<h2>Scala mode</h2>
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<form>
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<textarea id="code" name="code">
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/* __ *\
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** ________ ___ / / ___ Scala API **
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** / __/ __// _ | / / / _ | (c) 2003-2011, LAMP/EPFL **
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** __\ \/ /__/ __ |/ /__/ __ | http://scala-lang.org/ **
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** /____/\___/_/ |_/____/_/ | | **
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** |/ **
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\* */
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package scala.collection
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import generic._
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import mutable.{ Builder, ListBuffer }
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import annotation.{tailrec, migration, bridge}
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import annotation.unchecked.{ uncheckedVariance => uV }
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import parallel.ParIterable
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/** A template trait for traversable collections of type `Traversable[A]`.
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*
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* $traversableInfo
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* @define mutability
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* @define traversableInfo
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* This is a base trait of all kinds of $mutability Scala collections. It
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* implements the behavior common to all collections, in terms of a method
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* `foreach` with signature:
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* {{{
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* def foreach[U](f: Elem => U): Unit
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* }}}
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* Collection classes mixing in this trait provide a concrete
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* `foreach` method which traverses all the
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* elements contained in the collection, applying a given function to each.
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* They also need to provide a method `newBuilder`
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* which creates a builder for collections of the same kind.
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*
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* A traversable class might or might not have two properties: strictness
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* and orderedness. Neither is represented as a type.
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*
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* The instances of a strict collection class have all their elements
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* computed before they can be used as values. By contrast, instances of
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* a non-strict collection class may defer computation of some of their
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* elements until after the instance is available as a value.
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* A typical example of a non-strict collection class is a
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* <a href="../immutable/Stream.html" target="ContentFrame">
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* `scala.collection.immutable.Stream`</a>.
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* A more general class of examples are `TraversableViews`.
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*
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* If a collection is an instance of an ordered collection class, traversing
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* its elements with `foreach` will always visit elements in the
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* same order, even for different runs of the program. If the class is not
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* ordered, `foreach` can visit elements in different orders for
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* different runs (but it will keep the same order in the same run).'
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*
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* A typical example of a collection class which is not ordered is a
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* `HashMap` of objects. The traversal order for hash maps will
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* depend on the hash codes of its elements, and these hash codes might
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* differ from one run to the next. By contrast, a `LinkedHashMap`
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* is ordered because it's `foreach` method visits elements in the
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* order they were inserted into the `HashMap`.
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*
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* @author Martin Odersky
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* @version 2.8
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* @since 2.8
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* @tparam A the element type of the collection
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* @tparam Repr the type of the actual collection containing the elements.
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*
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* @define Coll Traversable
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* @define coll traversable collection
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*/
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trait TraversableLike[+A, +Repr] extends HasNewBuilder[A, Repr]
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with FilterMonadic[A, Repr]
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with TraversableOnce[A]
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with GenTraversableLike[A, Repr]
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with Parallelizable[A, ParIterable[A]]
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{
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self =>
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import Traversable.breaks._
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/** The type implementing this traversable */
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protected type Self = Repr
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/** The collection of type $coll underlying this `TraversableLike` object.
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* By default this is implemented as the `TraversableLike` object itself,
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* but this can be overridden.
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*/
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def repr: Repr = this.asInstanceOf[Repr]
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/** The underlying collection seen as an instance of `$Coll`.
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* By default this is implemented as the current collection object itself,
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* but this can be overridden.
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*/
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protected[this] def thisCollection: Traversable[A] = this.asInstanceOf[Traversable[A]]
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/** A conversion from collections of type `Repr` to `$Coll` objects.
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* By default this is implemented as just a cast, but this can be overridden.
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*/
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protected[this] def toCollection(repr: Repr): Traversable[A] = repr.asInstanceOf[Traversable[A]]
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/** Creates a new builder for this collection type.
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*/
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protected[this] def newBuilder: Builder[A, Repr]
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protected[this] def parCombiner = ParIterable.newCombiner[A]
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/** Applies a function `f` to all elements of this $coll.
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*
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* Note: this method underlies the implementation of most other bulk operations.
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* It's important to implement this method in an efficient way.
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*
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*
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* @param f the function that is applied for its side-effect to every element.
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* The result of function `f` is discarded.
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*
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* @tparam U the type parameter describing the result of function `f`.
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* This result will always be ignored. Typically `U` is `Unit`,
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* but this is not necessary.
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*
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* @usecase def foreach(f: A => Unit): Unit
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*/
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def foreach[U](f: A => U): Unit
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/** Tests whether this $coll is empty.
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*
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* @return `true` if the $coll contain no elements, `false` otherwise.
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*/
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def isEmpty: Boolean = {
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var result = true
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breakable {
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for (x <- this) {
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result = false
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break
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}
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}
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result
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}
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/** Tests whether this $coll is known to have a finite size.
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* All strict collections are known to have finite size. For a non-strict collection
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* such as `Stream`, the predicate returns `true` if all elements have been computed.
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* It returns `false` if the stream is not yet evaluated to the end.
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*
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* Note: many collection methods will not work on collections of infinite sizes.
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*
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* @return `true` if this collection is known to have finite size, `false` otherwise.
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*/
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def hasDefiniteSize = true
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def ++[B >: A, That](that: GenTraversableOnce[B])(implicit bf: CanBuildFrom[Repr, B, That]): That = {
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val b = bf(repr)
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if (that.isInstanceOf[IndexedSeqLike[_, _]]) b.sizeHint(this, that.seq.size)
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b ++= thisCollection
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b ++= that.seq
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b.result
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}
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@bridge
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def ++[B >: A, That](that: TraversableOnce[B])(implicit bf: CanBuildFrom[Repr, B, That]): That =
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++(that: GenTraversableOnce[B])(bf)
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/** Concatenates this $coll with the elements of a traversable collection.
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* It differs from ++ in that the right operand determines the type of the
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* resulting collection rather than the left one.
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*
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* @param that the traversable to append.
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* @tparam B the element type of the returned collection.
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* @tparam That $thatinfo
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* @param bf $bfinfo
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* @return a new collection of type `That` which contains all elements
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* of this $coll followed by all elements of `that`.
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*
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* @usecase def ++:[B](that: TraversableOnce[B]): $Coll[B]
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*
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* @return a new $coll which contains all elements of this $coll
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* followed by all elements of `that`.
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*/
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def ++:[B >: A, That](that: TraversableOnce[B])(implicit bf: CanBuildFrom[Repr, B, That]): That = {
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val b = bf(repr)
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if (that.isInstanceOf[IndexedSeqLike[_, _]]) b.sizeHint(this, that.size)
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b ++= that
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b ++= thisCollection
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b.result
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}
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/** This overload exists because: for the implementation of ++: we should reuse
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* that of ++ because many collections override it with more efficient versions.
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* Since TraversableOnce has no '++' method, we have to implement that directly,
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* but Traversable and down can use the overload.
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*/
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def ++:[B >: A, That](that: Traversable[B])(implicit bf: CanBuildFrom[Repr, B, That]): That =
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(that ++ seq)(breakOut)
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def map[B, That](f: A => B)(implicit bf: CanBuildFrom[Repr, B, That]): That = {
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val b = bf(repr)
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b.sizeHint(this)
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for (x <- this) b += f(x)
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b.result
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}
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def flatMap[B, That](f: A => GenTraversableOnce[B])(implicit bf: CanBuildFrom[Repr, B, That]): That = {
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val b = bf(repr)
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for (x <- this) b ++= f(x).seq
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b.result
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}
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/** Selects all elements of this $coll which satisfy a predicate.
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*
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* @param p the predicate used to test elements.
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* @return a new $coll consisting of all elements of this $coll that satisfy the given
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* predicate `p`. The order of the elements is preserved.
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*/
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def filter(p: A => Boolean): Repr = {
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val b = newBuilder
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for (x <- this)
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if (p(x)) b += x
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b.result
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}
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/** Selects all elements of this $coll which do not satisfy a predicate.
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*
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* @param p the predicate used to test elements.
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* @return a new $coll consisting of all elements of this $coll that do not satisfy the given
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* predicate `p`. The order of the elements is preserved.
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*/
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def filterNot(p: A => Boolean): Repr = filter(!p(_))
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def collect[B, That](pf: PartialFunction[A, B])(implicit bf: CanBuildFrom[Repr, B, That]): That = {
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val b = bf(repr)
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for (x <- this) if (pf.isDefinedAt(x)) b += pf(x)
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b.result
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}
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/** Builds a new collection by applying an option-valued function to all
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* elements of this $coll on which the function is defined.
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*
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* @param f the option-valued function which filters and maps the $coll.
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* @tparam B the element type of the returned collection.
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* @tparam That $thatinfo
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* @param bf $bfinfo
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* @return a new collection of type `That` resulting from applying the option-valued function
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* `f` to each element and collecting all defined results.
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* The order of the elements is preserved.
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*
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* @usecase def filterMap[B](f: A => Option[B]): $Coll[B]
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*
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* @param pf the partial function which filters and maps the $coll.
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* @return a new $coll resulting from applying the given option-valued function
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* `f` to each element and collecting all defined results.
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* The order of the elements is preserved.
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def filterMap[B, That](f: A => Option[B])(implicit bf: CanBuildFrom[Repr, B, That]): That = {
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val b = bf(repr)
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for (x <- this)
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f(x) match {
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case Some(y) => b += y
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case _ =>
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}
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b.result
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}
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*/
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/** Partitions this $coll in two ${coll}s according to a predicate.
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*
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* @param p the predicate on which to partition.
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* @return a pair of ${coll}s: the first $coll consists of all elements that
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* satisfy the predicate `p` and the second $coll consists of all elements
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* that don't. The relative order of the elements in the resulting ${coll}s
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* is the same as in the original $coll.
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*/
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def partition(p: A => Boolean): (Repr, Repr) = {
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val l, r = newBuilder
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for (x <- this) (if (p(x)) l else r) += x
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(l.result, r.result)
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}
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def groupBy[K](f: A => K): immutable.Map[K, Repr] = {
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val m = mutable.Map.empty[K, Builder[A, Repr]]
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for (elem <- this) {
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val key = f(elem)
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val bldr = m.getOrElseUpdate(key, newBuilder)
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bldr += elem
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}
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val b = immutable.Map.newBuilder[K, Repr]
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for ((k, v) <- m)
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b += ((k, v.result))
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b.result
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}
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/** Tests whether a predicate holds for all elements of this $coll.
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*
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* $mayNotTerminateInf
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*
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* @param p the predicate used to test elements.
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* @return `true` if the given predicate `p` holds for all elements
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* of this $coll, otherwise `false`.
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*/
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def forall(p: A => Boolean): Boolean = {
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var result = true
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breakable {
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for (x <- this)
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if (!p(x)) { result = false; break }
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}
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result
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}
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/** Tests whether a predicate holds for some of the elements of this $coll.
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*
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* $mayNotTerminateInf
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*
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* @param p the predicate used to test elements.
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* @return `true` if the given predicate `p` holds for some of the
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* elements of this $coll, otherwise `false`.
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*/
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def exists(p: A => Boolean): Boolean = {
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var result = false
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breakable {
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for (x <- this)
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if (p(x)) { result = true; break }
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}
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result
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}
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/** Finds the first element of the $coll satisfying a predicate, if any.
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*
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* $mayNotTerminateInf
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* $orderDependent
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*
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|
|
* @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>
|
||
|
|
</article>
|