Scala Standard Library 2.12.6 - scala.collection.generic

trait AtomicIndexFlag extends Signalling

A mixin trait that implements index flag behaviour using atomic integers.

A mixin trait that implements index flag behaviour using atomic integers. The setIndex operation is wait-free, while conditional set operations setIndexIfGreater and setIndexIfLesser are lock-free and support only monotonic changes.

trait BitSetFactory[Coll <: BitSet with BitSetLike[Coll]] extends AnyRef

type CanBuild[-Elem, +To] = CanBuildFrom[Nothing, Elem, To]

trait CanBuildFrom[-From, -Elem, +To] extends AnyRef

A base trait for builder factories.

From: the type of the underlying collection that requests a builder to be created.
Elem: the element type of the collection to be created.
To: the type of the collection to be created.

Annotations: @implicitNotFound( msg = ... )
Since: 2.8
See also: scala.collection.mutable.Builder

trait CanCombineFrom[-From, -Elem, +To] extends CanBuildFrom[From, Elem, To] with Parallel

A base trait for parallel builder factories.

From: the type of the underlying collection that requests a builder to be created.
Elem: the element type of the collection to be created.
To: the type of the collection to be created.

Since: 2.8

abstract class ClassTagTraversableFactory[CC[X] <: Traversable[X] with GenericClassTagTraversableTemplate[X, CC]] extends GenericClassTagCompanion[CC]

A template for companion objects of ClassTagTraversable and subclasses thereof.

trait Clearable extends AnyRef

This trait forms part of collections that can be cleared with a clear() call.

Version: 2.10
Since: 2.10

class DefaultSignalling extends Signalling with VolatileAbort

This signalling implementation returns default values and ignores received signals.

class DelegatedContext extends DelegatedSignalling

Class implementing delegated signalling.

trait DelegatedSignalling extends Signalling

An implementation of the signalling interface using delegates.

trait FilterMonadic[+A, +Repr] extends Any

A template trait that contains just the map, flatMap, foreach and withFilter methods of trait TraversableLike.

abstract class GenMapFactory[CC[A, B] <: GenMap[A, B] with GenMapLike[A, B, CC[A, B]]] extends AnyRef

A template for companion objects of Map and subclasses thereof.

abstract class GenSeqFactory[CC[X] <: GenSeq[X] with GenericTraversableTemplate[X, CC]] extends GenTraversableFactory[CC]

A template for companion objects of Seq and subclasses thereof.

Since: 2.8

abstract class GenSetFactory[CC[X] <: GenSet[X] with GenSetLike[X, CC[X]]] extends GenericCompanion[CC]

A template for companion objects of Set and subclasses thereof.

abstract class GenTraversableFactory[CC[X] <: GenTraversable[X] with GenericTraversableTemplate[X, CC]] extends GenericCompanion[CC]

A template for companion objects of Traversable and subclasses thereof.

A template for companion objects of Traversable and subclasses thereof. This class provides a set of operations to create Traversable objects. It is typically inherited by companion objects of subclasses of Traversable.

Since: 2.8

abstract class GenericClassTagCompanion[+CC[X] <: Traversable[X]] extends AnyRef

This class represents companions of classes which require ClassTags for their element types.

trait GenericClassTagTraversableTemplate[+A, +CC[X] <: Traversable[X]] extends HasNewBuilder[A, CC[A]]

This trait represents collections classes which require class tags for their element types.

Since: 2.8

abstract class GenericCompanion[+CC[X] <: GenTraversable[X]] extends AnyRef

A template class for companion objects of "regular" collection classes represent an unconstrained higher-kinded type.

A template class for companion objects of "regular" collection classes represent an unconstrained higher-kinded type. Typically such classes inherit from trait GenericTraversableTemplate.

CC: The type constructor representing the collection class.

Since: 2.8
See also: scala.collection.generic.GenericTraversableTemplate

abstract class GenericOrderedCompanion[+CC[X] <: Traversable[X]] extends AnyRef

This class represents companions of classes which require the ordered trait for their element types.

Since: 2.8

trait GenericOrderedTraversableTemplate[+A, +CC[X] <: Traversable[X]] extends HasNewBuilder[A, CC[A]]

This trait represents collections classes which require ordered element types.

trait GenericParCompanion[+CC[X] <: ParIterable[X]] extends AnyRef

A template class for companion objects of parallel collection classes.

A template class for companion objects of parallel collection classes. They should be mixed in together with GenericCompanion type.

trait GenericParMapCompanion[+CC[P, Q] <: ParMap[P, Q]] extends AnyRef

trait GenericParMapTemplate[K, +V, +CC[X, Y] <: ParMap[X, Y]] extends GenericParTemplate[(K, V), ParIterable]

trait GenericParTemplate[+A, +CC[X] <: ParIterable[X]] extends GenericTraversableTemplate[A, CC] with HasNewCombiner[A, CC[A]]

A template trait for collections having a companion.

A: the element type of the collection
CC: the type constructor representing the collection class

Since: 2.8

trait GenericSeqCompanion[CC[X] <: Traversable[X]] extends GenericCompanion[CC]

trait GenericSetTemplate[A, +CC[X] <: GenSet[X]] extends GenericTraversableTemplate[A, CC]

Since: 2.8

trait GenericTraversableTemplate[+A, +CC[X] <: GenTraversable[X]] extends HasNewBuilder[A, CC[A]]

A template class for companion objects of regular collection classes that represent an unconstrained higher-kinded type.

A: The type of the collection elements.
CC: The type constructor representing the collection class.

Since: 2.8

trait Growable[-A] extends Clearable

This trait forms part of collections that can be augmented using a += operator and that can be cleared of all elements using a clear method.

Version: 2.8
Since: 2.8

trait HasNewBuilder[+A, +Repr] extends Any

trait HasNewCombiner[+T, +Repr] extends AnyRef

Since: 2.8

abstract class ImmutableMapFactory[CC[A, +B] <: immutable.Map[A, B] with immutable.MapLike[A, B, CC[A, B]]] extends MapFactory[CC]

A template for companion objects of immutable.Map and subclasses thereof.

Version: 2.8
Since: 2.8

abstract class ImmutableSetFactory[CC[X] <: immutable.Set[X] with SetLike[X, CC[X]]] extends SetFactory[CC]

abstract class ImmutableSortedMapFactory[CC[A, B] <: immutable.SortedMap[A, B] with SortedMapLike[A, B, CC[A, B]]] extends SortedMapFactory[CC]

A template for companion objects of SortedMap and subclasses thereof.

Since: 2.8

abstract class ImmutableSortedSetFactory[CC[A] <: immutable.SortedSet[A] with SortedSetLike[A, CC[A]]] extends SortedSetFactory[CC]

A template for companion objects of SortedSet and subclasses thereof.

Since: 2.8

abstract class IndexedSeqFactory[CC[X] <: IndexedSeq[X] with GenericTraversableTemplate[X, CC]] extends SeqFactory[CC]

A template for companion objects of IndexedSeq and subclasses thereof.

Since: 2.11

trait IsSeqLike[Repr] extends AnyRef

Type class witnessing that a collection representation type Repr has elements of type A and has a conversion to SeqLike[A, Repr].

This type enables simple enrichment of Seqs with extension methods which can make full use of the mechanics of the Scala collections framework in their implementation.

Example usage:

class FilterMapImpl[A, Repr](val r: SeqLike[A, Repr]) {
  final def filterMap[B, That](f: A => Option[B])(implicit cbf: CanBuildFrom[Repr, B, That]): That =
    r.flatMap(f(_))
}
implicit def filterMap[Repr, A](r: Repr)(implicit fr: IsSeqLike[Repr]): FilterMapImpl[fr.A,Repr] =
  new FilterMapImpl(fr.conversion(r))

val l = List(1, 2, 3, 4, 5)
List(1, 2, 3, 4, 5) filterMap (i => if(i % 2 == 0) Some(i) else None)
// == List(2, 4)

See also: scala.collection.Seq
scala.collection.generic.IsTraversableLike

trait IsTraversableLike[Repr] extends AnyRef

A trait which can be used to avoid code duplication when defining extension methods that should be applicable both to existing Scala collections (i.e., types extending GenTraversableLike) as well as other (potentially user-defined) types that could be converted to a Scala collection type.

A trait which can be used to avoid code duplication when defining extension methods that should be applicable both to existing Scala collections (i.e., types extending GenTraversableLike) as well as other (potentially user-defined) types that could be converted to a Scala collection type. This trait makes it possible to treat Scala collections and types that can be implicitly converted to a collection type uniformly. For example, one can provide extension methods that work both on collection types and on Strings (Strings do not extend GenTraversableLike, but can be converted to GenTraversableLike)

IsTraversable provides two members:

type member A, which represents the element type of the target GenTraversableLike[A, Repr]
value member conversion, which provides a way to convert between the type we wish to add extension methods to, Repr, and GenTraversableLike[A, Repr].

Usage

One must provide IsTraversableLike as an implicit parameter type of an implicit conversion. Its usage is shown below. Our objective in the following example is to provide a generic extension method mapReduce to any type that extends or can be converted to GenTraversableLike. In our example, this includes String.

  import scala.collection.GenTraversableLike
  import scala.collection.generic.IsTraversableLike

  class ExtensionMethods[A, Repr](coll: GenTraversableLike[A, Repr]) {
    def mapReduce[B](mapper: A => B)(reducer: (B, B) => B): B = {
      val iter = coll.toIterator
      var res = mapper(iter.next())
      while (iter.hasNext)
        res = reducer(res, mapper(iter.next()))
      res
    }
  }

  implicit def withExtensions[Repr](coll: Repr)(implicit traversable: IsTraversableLike[Repr]) =
    new ExtensionMethods(traversable.conversion(coll))

// See it in action!
List(1, 2, 3).mapReduce(_ * 2)(_ + _) // res0: Int = 12
"Yeah, well, you know, that's just, like, your opinion, man.".mapReduce(x => 1)(_ + _) // res1: Int = 59

Here, we begin by creating a class ExtensionMethods which contains our mapReduce extension method. Note that ExtensionMethods takes a constructor argument coll of type GenTraversableLike[A, Repr], where A represents the element type and Repr represents (typically) the collection type. The implementation of mapReduce itself is straightforward.

The interesting bit is the implicit conversion withExtensions, which returns an instance of ExtensionMethods. This implicit conversion can only be applied if there is an implicit value traversable of type IsTraversableLike[Repr] in scope. Since IsTraversableLike provides value member conversion, which gives us a way to convert between whatever type we wish to add an extension method to (in this case, Repr) and GenTraversableLike[A, Repr], we can now convert coll from type Repr to GenTraversableLike[A, Repr]. This allows us to create an instance of the ExtensionMethods class, which we pass our new GenTraversableLike[A, Repr] to.

When the mapReduce method is called on some type of which it is not a member, implicit search is triggered. Because implicit conversion withExtensions is generic, it will be applied as long as an implicit value of type IsTraversableLike[Repr] can be found. Given that IsTraversableLike contains implicit members that return values of type IsTraversableLike, this requirement is typically satisfied, and the chain of interactions described in the previous paragraph is set into action. (See the IsTraversableLike companion object, which contains a precise specification of the available implicits.)

Note: Currently, it's not possible to combine the implicit conversion and the class with the extension methods into an implicit class due to limitations of type inference.

Implementing `IsTraversableLike` for New Types

One must simply provide an implicit value of type IsTraversableLike specific to the new type, or an implicit conversion which returns an instance of IsTraversableLike specific to the new type.

Below is an example of an implementation of the IsTraversableLike trait where the Repr type is String.

implicit val stringRepr: IsTraversableLike[String] { type A = Char } =
  new IsTraversableLike[String] {
    type A = Char
    val conversion = implicitly[String => GenTraversableLike[Char, String]]
  }

Since: 2.10

trait IsTraversableOnce[Repr] extends AnyRef

Type class witnessing that a collection representation type Repr has elements of type A and has a conversion to GenTraversableOnce[A].

This type enables simple enrichment of GenTraversableOnces with extension methods which can make full use of the mechanics of the Scala collections framework in their implementation.

Example usage,

class FilterMapImpl[A, Repr](val r: GenTraversableOnce[A]) {
  final def filterMap[B, That](f: A => Option[B])(implicit cbf: CanBuildFrom[Repr, B, That]): That = {
    val b = cbf()
    for(e <- r.seq) f(e) foreach (b +=)
    b.result
  }
}
implicit def filterMap[Repr, A](r: Repr)(implicit fr: IsTraversableOnce[Repr]): FilterMapImpl[fr.A,Repr] =
  new FilterMapImpl[fr.A, Repr](fr.conversion(r))

val l = List(1, 2, 3, 4, 5)
List(1, 2, 3, 4, 5) filterMap (i => if(i % 2 == 0) Some(i) else None)
// == List(2, 4)

Since: 2.10

abstract class MapFactory[CC[A, B] <: Map[A, B] with MapLike[A, B, CC[A, B]]] extends GenMapFactory[CC]

A template for companion objects of Map and subclasses thereof.

abstract class MutableMapFactory[CC[A, B] <: mutable.Map[A, B] with mutable.MapLike[A, B, CC[A, B]]] extends MapFactory[CC]

A template for companion objects of mutable.Map and subclasses thereof.

Version: 2.8
Since: 2.8

abstract class MutableSetFactory[CC[X] <: mutable.Set[X] with mutable.SetLike[X, CC[X]]] extends SetFactory[CC]

abstract class MutableSortedMapFactory[CC[A, B] <: mutable.SortedMap[A, B] with SortedMapLike[A, B, CC[A, B]]] extends SortedMapFactory[CC]

A template for companion objects of SortedMap and subclasses thereof.

CC: the type of the collection.

Version: 2.12
Since: 2.12

abstract class MutableSortedSetFactory[CC[A] <: mutable.SortedSet[A] with SortedSetLike[A, CC[A]] with mutable.Set[A] with mutable.SetLike[A, CC[A]]] extends SortedSetFactory[CC]

abstract class OrderedTraversableFactory[CC[X] <: Traversable[X] with GenericOrderedTraversableTemplate[X, CC]] extends GenericOrderedCompanion[CC]

abstract class ParFactory[CC[X] <: ParIterable[X] with GenericParTemplate[X, CC]] extends GenTraversableFactory[CC] with GenericParCompanion[CC]

A template class for companion objects of ParIterable and subclasses thereof.

A template class for companion objects of ParIterable and subclasses thereof. This class extends TraversableFactory and provides a set of operations to create ParIterable objects.

abstract class ParMapFactory[CC[X, Y] <: ParMap[X, Y] with ParMapLike[X, Y, CC[X, Y], _]] extends GenMapFactory[CC] with GenericParMapCompanion[CC]

A template class for companion objects of ParMap and subclasses thereof.

A template class for companion objects of ParMap and subclasses thereof. This class extends TraversableFactory and provides a set of operations to create ParMap objects.

abstract class ParSetFactory[CC[X] <: ParSet[X] with ParSetLike[X, CC[X], _] with GenericParTemplate[X, CC]] extends GenSetFactory[CC] with GenericParCompanion[CC]

Since: 2.8

abstract class SeqFactory[CC[X] <: Seq[X] with GenericTraversableTemplate[X, CC]] extends GenSeqFactory[CC] with TraversableFactory[CC]

A template for companion objects of Seq and subclasses thereof.

Since: 2.8

abstract class SetFactory[CC[X] <: Set[X] with SetLike[X, CC[X]]] extends GenSetFactory[CC] with GenericSeqCompanion[CC]

trait Shrinkable[-A] extends AnyRef

This trait forms part of collections that can be reduced using a -= operator.

Version: 2.8
Since: 2.8

trait Signalling extends AnyRef

A message interface serves as a unique interface to the part of the collection capable of receiving messages from a different task.

One example of use of this is the find method, which can use the signalling interface to inform worker threads that an element has been found and no further search is necessary.

trait Sizing extends AnyRef

A trait for objects which have a size.

trait Sorted[K, +This <: Sorted[K, This]] extends AnyRef

Any collection (including maps) whose keys (or elements) are ordered.

Since: 2.8

abstract class SortedMapFactory[CC[A, B] <: SortedMap[A, B] with SortedMapLike[A, B, CC[A, B]]] extends AnyRef

A template for companion objects of mutable.Map and subclasses thereof.

Since: 2.8

abstract class SortedSetFactory[CC[A] <: SortedSet[A] with SortedSetLike[A, CC[A]]] extends AnyRef

A template for companion objects of Set and subclasses thereof.

Since: 2.8

trait Subtractable[A, +Repr <: Subtractable[A, Repr]] extends AnyRef

This trait represents collection-like objects that can be reduced using a '+' operator.

This trait represents collection-like objects that can be reduced using a '+' operator. It defines variants of - and -- as convenience methods in terms of single-element removal -.

A: the type of the elements of the collection.
Repr: the type of the collection itself

Version: 2.8
Since: 2.8

class TaggedDelegatedContext extends DelegatedContext

Class implementing delegated signalling, but having its own distinct tag.

trait TraversableFactory[CC[X] <: Traversable[X] with GenericTraversableTemplate[X, CC]] extends GenTraversableFactory[CC] with GenericSeqCompanion[CC]

A template for companion objects of Traversable and subclasses thereof.

A template for companion objects of Traversable and subclasses thereof. This class provides a set of operations to create Traversable objects. It is typically inherited by companion objects of subclasses of Traversable.

Since: 2.8

trait VolatileAbort extends Signalling

A mixin trait that implements abort flag behaviour using volatile variables.

type ClassManifestTraversableFactory[CC[X] <: Traversable[X] with GenericClassManifestTraversableTemplate[X, CC]] = ClassTagTraversableFactory[CC]

Annotations: @deprecated
Deprecated: (Since version 2.10.0) use ClassTagTraversableFactory instead

type GenericClassManifestCompanion[+CC[X] <: Traversable[X]] = GenericClassTagCompanion[CC]

Annotations: @deprecated
Deprecated: (Since version 2.10.0) use GenericClassTagCompanion instead

type GenericClassManifestTraversableTemplate[+A, +CC[X] <: Traversable[X]] = GenericClassTagTraversableTemplate[A, CC]

Annotations: @deprecated
Deprecated: (Since version 2.10.0) use GenericClassTagTraversableTemplate instead

trait IterableForwarder[+A] extends Iterable[A] with TraversableForwarder[A]

This trait implements a forwarder for iterable objects.

This trait implements a forwarder for iterable objects. It forwards all calls to a different iterable object, except for

toString, hashCode, equals, stringPrefix
newBuilder, view
all calls creating a new iterable object of the same kind

The above methods are forwarded by subclass `IterableProxy`.

Annotations: @deprecated
Deprecated: (Since version 2.11.0) forwarding is inherently unreliable since it is not automated and methods can be forgotten
Version: 2.8
Since: 2.8

trait SeqForwarder[+A] extends Seq[A] with IterableForwarder[A]

This class implements a forwarder for sequences.

This class implements a forwarder for sequences. It forwards all calls to a different sequence object except for

toString, hashCode, equals, stringPrefix
newBuilder, view, toSeq
all calls creating a new sequence of the same kind

The above methods are forwarded by subclass SeqProxy.

Annotations: @deprecated
Deprecated: (Since version 2.11.0) forwarding is inherently unreliable since it is not automated and new methods can be forgotten
Version: 2.8
Since: 2.8

trait TraversableForwarder[+A] extends Traversable[A]

This trait implements a forwarder for traversable objects.

This trait implements a forwarder for traversable objects. It forwards all calls to a different traversable, except for:

toString, hashCode, equals, stringPrefix
newBuilder, view

All calls creating a new traversable of the same kind.

Annotations: @deprecated
Deprecated: (Since version 2.11.0) forwarding is inherently unreliable since it is not automated and new methods can be forgotten
Version: 2.8
Since: 2.8

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generic

package generic

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package generic

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generic

Implementing `IsTraversableLike` for New Types