scala.collection.TraversableView.scala Maven / Gradle / Ivy
/*
* Scala (https://www.scala-lang.org)
*
* Copyright EPFL and Lightbend, Inc.
*
* Licensed under Apache License 2.0
* (http://www.apache.org/licenses/LICENSE-2.0).
*
* See the NOTICE file distributed with this work for
* additional information regarding copyright ownership.
*/
package scala
package collection
import generic._
import mutable.Builder
/** A base trait for non-strict views of traversable collections.
* $traversableViewInfo
*/
trait TraversableView[+A, +Coll] extends TraversableViewLike[A, Coll, TraversableView[A, Coll]] { }
/** An object containing the necessary implicit definitions to make
* `TraversableView`s work. Its definitions are generally not accessed directly by clients.
*/
object TraversableView {
class NoBuilder[A] extends Builder[A, Nothing] {
def +=(elem: A): this.type = this
def iterator: Iterator[A] = Iterator.empty
def result() = throw new UnsupportedOperationException("TraversableView.Builder.result")
def clear() {}
}
type Coll = TraversableView[_, C] forSome {type C <: Traversable[_]}
implicit def canBuildFrom[A]: CanBuildFrom[Coll, A, TraversableView[A, Traversable[_]]] =
new CanBuildFrom[Coll, A, TraversableView[A, Traversable[_]]] {
def apply(from: Coll) = new NoBuilder
def apply() = new NoBuilder
}
}