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package scala
object RandomAccessSeq {
trait Projection[+A] extends Seq.Projection[A] with RandomAccessSeq[A] {
override def projection = this
protected class MapProjection[B](f : A => B) extends super.MapProjection(f) with Projection[B]
override def map[B](f: A => B) : Projection[B] = new MapProjection[B](f)
}
/** A random access sequence that supports update (e.g., an array) */
trait Mutable[A] extends RandomAccessSeq[A] {
def update(idx : Int, what : A) : Unit
override def projection : MutableProjection[A] = new MutableProjection[A] {
def update(idx : Int, what : A) : Unit = Mutable.this.update(idx, what)
def length = Mutable.this.length
def apply(idx : Int) = Mutable.this.apply(idx)
}
def readOnly : RandomAccessSeq[A] = new RandomAccessSeq[A] {
def length = Mutable.this.length
def apply(idx : Int) = Mutable.this.apply(idx)
override def stringPrefix = Mutable.this.stringPrefix + "RO"
}
}
trait MutableProjection[A] extends Projection[A] with Mutable[A] {
override def projection : MutableProjection[A] = this
override def reverse : MutableProjection[A] = new MutableProjection[A] {
def update(idx : Int, what : A) : Unit = MutableProjection.this.update(length - idx - 1, what)
def length = MutableProjection.this.length
def apply(idx : Int) = MutableProjection.this.apply(length - idx - 1)
override def stringPrefix = MutableProjection.this.stringPrefix + "R"
override def reverse : MutableProjection[A] = MutableProjection.this
}
}
}
/** Sequences that support O(1) element access
* @author Sean McDirmid
*/
trait RandomAccessSeq[+A] extends Seq[A] {
override def projection : RandomAccessSeq.Projection[A] = new RandomAccessSeq.Projection[A] {
def length = RandomAccessSeq.this.length
def apply(idx : Int) = RandomAccessSeq.this.apply(idx)
override def elements = RandomAccessSeq.this.elements
override def stringPrefix = RandomAccessSeq.this.stringPrefix + "P"
}
override def elements : Iterator[A] = new BufferedIterator.Advanced[A] {
var idx = 0
override def peekList(sz : Int) = new RandomAccessSeq[A] {
override def length = RandomAccessSeq.this.length - idx
override def apply(jdx : Int) = RandomAccessSeq.this.apply(jdx + idx)
}
override def hasNext = idx < RandomAccessSeq.this.length
def next = {
if (!hasNext) throw new Predef.NoSuchElementException
val ret = RandomAccessSeq.this.apply(idx)
idx = idx + 1
ret
}
}
/** Appends two random access sequences in a non-strict way */
def +++[B >: A](that: RandomAccessSeq[B]): RandomAccessSeq.Projection[B] = new RandomAccessSeq.Projection[B] {
def length = RandomAccessSeq.this.length + that.length
def apply(idx : Int) =
if (idx < RandomAccessSeq.this.length) RandomAccessSeq.this(idx)
else that(idx - RandomAccessSeq.this.length)
}
override def drop( from: Int): RandomAccessSeq[A] = slice(from, length)
override def take(until: Int): RandomAccessSeq[A] = slice(0, until)
override def slice(from : Int, until : Int) : RandomAccessSeq[A] = {
if (from == 0 && until >= length) return projection
else if (from >= until) new RandomAccessSeq.Projection[A] {
def length = 0
def apply(idx : Int) = throw new Predef.IndexOutOfBoundsException
} else new RandomAccessSeq.Projection[A] {
def length = until - from
def apply(idx : Int) = if (idx < 0 || idx >= length) throw new Predef.IndexOutOfBoundsException
else RandomAccessSeq.this.apply(from + idx)
}
}
override def reverse : Seq[A] = new RandomAccessSeq.Projection[A] {
def length = RandomAccessSeq.this.length
def apply(idx : Int) = RandomAccessSeq.this.apply(length - idx - 1)
override def stringPrefix = RandomAccessSeq.this.stringPrefix + "R"
override def reverse : RandomAccessSeq.Projection[A] = RandomAccessSeq.this.projection
}
/** will return false if index is out of bounds */
final def safeIs(idx : Int, a : Any) = if (idx >= 0 && idx < length) this(idx) == a else false
}
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