cc.factorie.variable.ChainVariable.scala Maven / Gradle / Ivy

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/* Copyright (C) 2008-2014 University of Massachusetts Amherst.
   This file is part of "FACTORIE" (Factor graphs, Imperative, Extensible)
   http://factorie.cs.umass.edu, http://github.com/factorie
   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. */

package cc.factorie.variable

import scala.annotation.unchecked.uncheckedVariance

/** A simple superclass of ChainLink that has a self-type argument, but (unlike ChainLink) not the type of the Chain.
    Used by app.chain.Observation and app.chain.Lexicon.LexiconToken.
    @author Andrew McCallum */
trait AbstractChainLink[+This<:AbstractChainLink[This]] {
  this: This =>
  def hasNext: Boolean
  def hasPrev: Boolean
  def next: This
  def prev: This
  def position: Int
  def next(offset:Int): This = {
    if (offset < 0) return prev(-offset)
    var i = offset
    var result = this
    while (i > 0 && hasNext) {
      result = next
      i -= 1
    }
    if (i == 0) result
    else null.asInstanceOf[This]
  }
  def prev(offset:Int): This = {
    if (offset < 0) return next(-offset)
    var i = offset
    var result = this
    while (i > 0 && hasPrev) {
      result = prev
      i -= 1
    }
    if (i == 0) result
    else null.asInstanceOf[This]
  }
  def chainHead: This = { var result = this; while (result.hasPrev) result = prev; result }
  def chainLast: This = { var result = this; while (result.hasPrev) result = prev; result }
}

/** An element or "link" of a Chain sequence.  ChainLink provides methods such as "next" and "prev". 
    @author Andrew McCallum */
trait ChainLink[This<:ChainLink[This,C],C<:Chain[C,This]] extends AbstractChainLink[This] with ThisType[This] {
  this: This =>
  private var _position: Int = -1
  private var _chain: C = null.asInstanceOf[C]
  /** This method should never be called outside Chain.+= or Chain.insert or Chain.remove */
  def _setChainPosition(c:C, p:Int): Unit = {
    //require(_chain eq null)
    require(p >= 0)
    _chain = c
    _position = p
  }
  def chain: C = _chain
  def position: Int = _position
  
  def hasNext = if (_position == -1) throw new IllegalStateException("ChainLink position not yet set") else _chain != null && _position + 1 < _chain.length
  def hasNext(n:Int) = if (_position == -1) throw new IllegalStateException("ChainLink position not yet set") else _chain != null && _position + n < _chain.length
  def next: This = if (_position == -1) throw new IllegalStateException("ChainLink position not yet set") else if (_position + 1 < _chain.length) chain(_position + 1) else null.asInstanceOf[This]
  def hasPrev = if (_position == -1) throw new IllegalStateException("ChainLink position not yet set") else _chain != null && _position > 0
  def hasPrev(n:Int) = if (_position == -1) throw new IllegalStateException("ChainLink position not yet set") else _chain != null && _position - n >= 0
  def prev: This = if (_position == -1) throw new IllegalStateException("ChainLink position not yet set") else if (_position > 0) chain(_position - 1) else null.asInstanceOf[This]
  def getPrev: Option[This] = { val p = prev; if (p eq null) None else Some(p) }
  def getNext: Option[This] = { val n = next; if (n eq null) None else Some(n) }
  /** Return the ChainLink "n" positions ahead.  If this goes past the end of the Chain, return null. */
  override def next(n:Int): This = { 
    if (_position == -1) throw new IllegalStateException("ChainLink position not yet set")
    val i = _position + n
    if (i >= 0 && i < _chain.length) chain(i) else null.asInstanceOf[This]
  }
  /** Return the ChainLink "n" positions behind.  If this goes past the beginning of the Chain, return null. */
  override def prev(n:Int): This = {
    if (_position == -1) throw new IllegalStateException("ChainLink position not yet set") 
    val i = _position - n
    if (i >= 0 && i < _chain.length) chain(i) else null.asInstanceOf[This]
  }
  def chainAfter: IndexedSeq[This] = _chain.links.drop(_position+1)
  def chainBefore: IndexedSeq[This] = _chain.links.take(_position)
  def prevWindow(n:Int): Seq[This] = {
    var i = math.max(_position-n,  0)
    val res = new collection.mutable.ListBuffer[This]
    while (i <= math.max(_position-1, 0)) {res.append(chain(i)) ;i += 1}
    res
  }
  def nextWindow(n:Int): Seq[This] = {
    var i = math.min(_position+1,  _chain.length-1)
    val res = new collection.mutable.ListBuffer[This]
    while (i <= math.min(_position+n, _chain.length-1)) {res.append(chain(i)) ;i += 1}
    res
  }
  // TODO currently the size of the window is actually 2*n; perhaps this should be changed! -akm
  def window(n:Int): Seq[This] = {
    for (i <- math.max(_position-n,0) to math.min(_position+n, _chain.length-1)) yield chain(i)
  }
  // TODO currently the size of the window is actually 2*n; perhaps this should be changed! -akm
  def windowWithoutSelf(n:Int): Seq[This] = {
    for (i <- math.max(_position-n,0) to math.min(_position+n, _chain.length-1); if i != _position) yield chain(i)
  }
  def between(other:This): Seq[This] = {
    require(other.chain == chain)
    if (other.position > _position)
      for (i <- _position until other.position) yield chain(i)
    else
      for (i <- other.position until _position) yield chain(i)
  } 
  def firstInSeq = chain(0)
  /*class InSubChain[+This2<:InSubChain[This,C2],+C2<:Chain[C2,This2]](val subchain:C) extends InChain[This2,C2] {
    this: This2 =>
    def elt: This = InChain.this
  }*/
}

/**
 * A convenience trait for a class which needs to have its own type as a type parameter
 * @tparam This the type of concrete instances.
 */
trait ThisType[+This<:AnyRef] {
  this: This =>
  type ThisType = (This @uncheckedVariance)
}

/** A chain of elements, each of which has methods "next", "prev", etc.
    @author Andrew McCallum */
trait Chain[This<:Chain[This,E],E<:ChainLink[E,This]] extends ThisType[This] with IndexedSeqSimilar[E] {
  this: This =>
  type Value = scala.collection.IndexedSeq[E]
  private val _chainseq = new scala.collection.mutable.ArrayBuffer[E]
  private var _frozen = false
  def value: Value = _chainseq
  override def apply(i:Int): E = _chainseq(i)
  override def length = _chainseq.length
  @inline final def links: IndexedSeq[E] = _chainseq // TODO Remove this?
  def +=(e:E): this.type = {
    if (_frozen) throw new Error("Cannot append to frozen chain "+getClass)
    e._setChainPosition(this, _chainseq.length)
    _chainseq += e
    this
  }
  def ++=(es:Iterable[E]): this.type = { es.foreach(+=(_)); this }
  /** Use with caution, since this would invalidate indices stored elsewhere */
  def insert(i:Int, e:E): this.type = {
    if (_frozen) throw new Error("Cannot insert into a frozen chain "+getClass)
    e._setChainPosition(this, i)
    for (x <- _chainseq.drop(i)) x._setChainPosition(this, x.position+1)
    _chainseq.insert(i, e)
    this
  }
  /** Use with caution, since this would invalidate indices stored elsewhere */
  def remove(i:Int): this.type = {
    if (_frozen) throw new Error("Cannot remove from a frozen chain "+getClass)
    for (x <- _chainseq.drop(i+1)) x._setChainPosition(this, x.position-1)
    _chainseq.remove(i)
    this
  }
  def asSeq: IndexedSeq[E] = _chainseq
  def chainFrozen: Boolean = _frozen
  def chainFreeze(): Unit = _frozen = true
}

/** An abstract variable that is a Chain, with value IndexedSeq[ElementType].
    @author Andrew McCallum */
trait ChainVar[This<:ChainVar[This,E],E<:ChainLink[E,This]] extends Chain[This,E] with IndexedSeqVar[E] {
  this: This =>
  //def value: IndexedSeq[E] = links // TODO But this isn't actually immutable. :-(  Inefficient to copy whole seq though. 
}

/** A variable that is a Chain, with value IndexedSeq[ElementType].
    @author Andrew McCallum */
class ChainVariable[This<:ChainVariable[This,E],E<:ChainLink[E,This]] extends ChainVar[This,E] {
  this: This =>
  def this(elements:Iterable[E]) = { this(); elements.foreach(+=(_)) }
}

/** A Chain which itself is also an element of an outer Chain.
    @author Andrew McCallum */
trait ChainInChain[This<:ChainInChain[This,E,S],E<:ChainLink[E,This],S<:Chain[S,This]] extends ChainLink[This,S] with Chain[This,E] {
  this: This =>
}