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import scala.language.implicitConversions
import scala.collection.generic.CanBuildFrom
import scala.math.Ordering
import collection.{TraversableLike, SeqLike}
import collection.immutable.BitSet
class QuickSort[Coll](a: Coll) {
//should be able to sort only something with defined order (someting like a Seq)
def quickSort[T](implicit ev0: Coll => SeqLike[T, Coll],
cbf: CanBuildFrom[Coll, T, Coll],
n: Ordering[T]): Coll = {
quickSortAnything(ev0, cbf, n)
}
//we can even sort a Set, if we really want to
def quickSortAnything[T](implicit ev0: Coll => TraversableLike[T, Coll],
cbf: CanBuildFrom[Coll, T, Coll],
n: Ordering[T]): Coll = {
import n._
if (a.size < 2) {
a
} else {
// We pick the first value for the pivot.
val pivot = a.head
val (lower, tmp) = a.partition(_ < pivot)
val (upper, same) = tmp.partition(_ > pivot)
val b = cbf()
b.sizeHint(a.size)
b ++= new QuickSort(lower).quickSortAnything
b ++= same
b ++= new QuickSort(upper).quickSortAnything
b.result
}
}
}
class FilterMap[Repr](a: Repr) {
def filterMap[A, B, That](f: A => Option[B])(implicit ev0: Repr => TraversableLike[A, Repr],
cbf: CanBuildFrom[Repr, B, That]): That = {
a.flatMap(e => f(e).toSeq)
}
}
class FilterMapFixed[A, Repr <% TraversableLike[A, Repr]](a: Repr) {
def filterMap2[B, That](f: A => Option[B])(implicit cbf: CanBuildFrom[Repr, B, That]): That = {
a.flatMap(e => f(e).toSeq)
}
}
object MyEnhancements {
implicit def toQS[Coll](a: Coll) = new QuickSort(a)
implicit def toFM[Coll](a: Coll) = new FilterMap(a)
implicit def toFM2[A, Repr <% TraversableLike[A, Repr]](a: Repr) = new FilterMapFixed(a)
}
object Test extends App {
import MyEnhancements._
println("qwe".quickSort)
println(Array(2, 0).quickSort.toList)
println(Seq(2, 0).quickSort)
//not very useful to sort a set, but just as a demonstration
println(BitSet(2, 0).quickSortAnything)
//need to hint type inferencer,
//probably will be able to overcome after https://issues.scala-lang.org/browse/SI-4699 and
// related issues are fixed (by moving ev0 parameter from filterMap to toFM), see toFM2
println("qwe".filterMap((c: Char) => Some(c.toInt)))
println("qwe".filterMap((c: Char) => Some(c)))
println(Array(2, 0).filterMap((c: Int) => Some(c.toInt)).toList)
println(Seq(2, 0).filterMap((c: Int) => if (c < 2) Some(c + "!") else None))
def test(i:Int) = Option(i)
println(BitSet(2,0).filterMap(test))
println(toFM2("qwe").filterMap2(c => Some(c)))
println(toFM2(Array(2, 0)).filterMap2(c => Some(c.toInt)).toList)
//No implicit view available from java.lang.String => scala.collection.TraversableLike[A,java.lang.String]. :(
//Not anymore :)
println("qwe".filterMap2(c => Some(c)))
}
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