breeze.collection.mutable.Beam.scala Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of breeze_2.10 Show documentation
breeze
There is a newer version: 0.9
package breeze.collection.mutable

/*
 Copyright 2009 David Hall, Daniel Ramage
 
 Licensed under the Apache License, Version 2.0 (the "License")
 you may not use this file except in compliance with the License.
 You may obtain a copy of the License at 
 
 http://www.apache.org/licenses/LICENSE-2.0
 
 Unless required by applicable law or agreed to in writing, software
 distributed under the License is distributed on an "AS IS" BASIS,
 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License. 
*/




import scala.collection._
import mutable.{GrowingBuilder, PriorityQueue}
import scala.collection.generic._

/**
 * Represents a beam, which is essentially a priority queue
 * with a maximum size.
 * 
 * @author dlwh
 */
class Beam[T](val maxSize:Int, xs:T*)(implicit o : Ordering[T]) extends Iterable[T] 
    with IterableLike[T,Beam[T]]  with Growable[T] { outer =>
  assert(maxSize >= 0)
  protected val queue = new PriorityQueue[T]()(o.reverse)
  xs foreach (cat(queue,_))

  override def size = queue.size

  def min = queue.head

  def best = queue.reduceOption(o.max(_, _))

  def +(x:T) = {this += x; this}
  def +=(x:T) = { cat(queue,x); this }

  private def trim() {
    while(queue.size > maxSize) {
      queue.dequeue()
    }
  }

  private def cat(h : PriorityQueue[T], x : T) {
    if(h.size < maxSize) h += x
    else if (o.compare(h.head,x) < 0) {h.dequeue(); h += x;}
  }

  def iterator = queue.iterator
  override def toString() = iterator.mkString("Beam(",",",")")
  def clear = queue.clear

  override protected def newBuilder = new GrowingBuilder(new Beam[T](maxSize))

  override def equals(other: Any): Boolean = other match {
    case b: Beam[T @unchecked] => (maxSize == b.maxSize) && (iterator sameElements b.iterator)
  }
}

object Beam {
  def apply[T:Ordering](maxSize:Int)(xs:T*): Beam[T] = new Beam[T](maxSize, xs:_*)

  @deprecated("Use Beam(maxSize)(xs) instead", "0.12")
  def apply[T](maxSize:Int, xs:T*)(implicit ordering: Ordering[T], dummyImplicit: DummyImplicit): Beam[T] = new Beam[T](maxSize, xs:_*)

  implicit def canBuildFrom[T: Ordering]:CanBuildFrom[Beam[T], T, Beam[T]] = new CanBuildFrom[Beam[T],T,Beam[T]] {
    def apply() = sys.error("Sorry, need a max size")

    def apply(from: Beam[T]) = from.newBuilder
  }
}