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+/* __ *\
+** ________ ___ / / ___ Scala API **
+** / __/ __// _ | / / / _ | (c) 2003-2013, LAMP/EPFL **
+** __\ \/ /__/ __ |/ /__/ __ | http://scala-lang.org/ **
+** /____/\___/_/ |_/____/_/ | | **
+** |/ **
+\* */
+
+package scala.collection
+
+import scala.annotation.tailrec
+import scala.collection.generic.IsSeqLike
+import scala.math.Ordering
+
+/** A collection of wrappers that provide sequence classes with search functionality.
+ *
+ * Example usage:
+ * {{{
+ * import scala.collection.Searching._
+ * val l = List(1, 2, 3, 4, 5)
+ * l.search(3)
+ * // == Found(2)
+ * }}}
+ */
+object Searching {
+ sealed abstract class SearchResult {
+ def insertionPoint: Int
+ }
+
+ case class Found(foundIndex: Int) extends SearchResult {
+ override def insertionPoint = foundIndex
+ }
+ case class InsertionPoint(insertionPoint: Int) extends SearchResult
+
+ class SearchImpl[A, Repr](val coll: SeqLike[A, Repr]) {
+ /** Search the sorted sequence for a specific element. If the sequence is an
+ * `IndexedSeq`, a binary search is used. Otherwise, a linear search is used.
+ *
+ * The sequence should be sorted with the same `Ordering` before calling; otherwise,
+ * the results are undefined.
+ *
+ * @see [[scala.collection.IndexedSeq]]
+ * @see [[scala.math.Ordering]]
+ * @see [[scala.collection.SeqLike]], method `sorted`
+ *
+ * @param elem the element to find.
+ * @param ord the ordering to be used to compare elements.
+ *
+ * @return a `Found` value containing the index corresponding to the element in the
+ * sequence, or the `InsertionPoint` where the element would be inserted if
+ * the element is not in the sequence.
+ */
+ final def search[B >: A](elem: B)(implicit ord: Ordering[B]): SearchResult =
+ coll match {
+ case _: IndexedSeq[A] => binarySearch(elem, -1, coll.length)(ord)
+ case _ => linearSearch(coll.view, elem, 0)(ord)
+ }
+
+ /** Search within an interval in the sorted sequence for a specific element. If the
+ * sequence is an IndexedSeq, a binary search is used. Otherwise, a linear search
+ * is used.
+ *
+ * The sequence should be sorted with the same `Ordering` before calling; otherwise,
+ * the results are undefined.
+ *
+ * @see [[scala.collection.IndexedSeq]]
+ * @see [[scala.math.Ordering]]
+ * @see [[scala.collection.SeqLike]], method `sorted`
+ *
+ * @param elem the element to find.
+ * @param from the index where the search starts.
+ * @param to the index following where the search ends.
+ * @param ord the ordering to be used to compare elements.
+ *
+ * @return a `Found` value containing the index corresponding to the element in the
+ * sequence, or the `InsertionPoint` where the element would be inserted if
+ * the element is not in the sequence.
+ */
+ final def search[B >: A](elem: B, from: Int, to: Int)
+ (implicit ord: Ordering[B]): SearchResult =
+ coll match {
+ case _: IndexedSeq[A] => binarySearch(elem, from-1, to)(ord)
+ case _ => linearSearch(coll.view(from, to), elem, from)(ord)
+ }
+
+ @tailrec
+ private def binarySearch[B >: A](elem: B, from: Int, to: Int)
+ (implicit ord: Ordering[B]): SearchResult = {
+ if ((to-from) == 1) InsertionPoint(from) else {
+ val idx = from+(to-from)/2
+ math.signum(ord.compare(elem, coll(idx))) match {
+ case -1 => binarySearch(elem, from, idx)(ord)
+ case 1 => binarySearch(elem, idx, to)(ord)
+ case _ => Found(idx)
+ }
+ }
+ }
+
+ private def linearSearch[B >: A](c: SeqView[A, Repr], elem: B, offset: Int)
+ (implicit ord: Ordering[B]): SearchResult = {
+ var idx = offset
+ val it = c.iterator
+ while (it.hasNext) {
+ val cur = it.next()
+ if (ord.equiv(elem, cur)) return Found(idx)
+ else if (ord.lt(elem, cur)) return InsertionPoint(idx-1)
+ idx += 1
+ }
+ InsertionPoint(idx)
+ }
+
+ }
+
+ implicit def search[Repr, A](coll: Repr)
+ (implicit fr: IsSeqLike[Repr]): SearchImpl[fr.A, Repr] = new SearchImpl(fr.conversion(coll))
+}