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/* __ *\
** ________ ___ / / ___ Scala API **
** / __/ __// _ | / / / _ | (c) 2003-2012, LAMP/EPFL **
** __\ \/ /__/ __ |/ /__/ __ | http://scala-lang.org/ **
** /____/\___/_/ |_/____/_/ | | **
** |/ **
\* */
package scala.collection
package generic
/** Type class witnessing that a collection representation type `Repr` has
* elements of type `A` and has a conversion to `GenTraversableLike[A, Repr]`.
*
* This type enables simple enrichment of `GenTraversable`s with extension
* methods which can make full use of the mechanics of the Scala collections
* framework in their implementation.
*
* Example usage,
* {{{
* class FilterMapImpl[A, Repr](val r: GenTraversableLike[A, Repr]) {
* final def filterMap[B, That](f: A => Option[B])(implicit cbf: CanBuildFrom[Repr, B, That]): That =
* r.flatMap(f(_).toSeq)
* }
* implicit def filterMap[Repr, A](r: Repr)(implicit fr: IsTraversableOnce[Repr]): FilterMapImpl[fr.A,Repr] =
* new FilterMapImpl(fr.conversion(r))
*
* val l = List(1, 2, 3, 4, 5)
* List(1, 2, 3, 4, 5) filterMap (i => if(i % 2 == 0) Some(i) else None)
* // == List(2, 4)
* }}}
*
* @author Miles Sabin
* @author J. Suereth
* @since 2.10
*/
trait IsTraversableLike[Repr] {
/** The type of elements we can traverse over. */
type A
/** A conversion from the representation type `Repr` to a `GenTraversableLike[A,Repr]`. */
val conversion: Repr => GenTraversableLike[A, Repr]
}
object IsTraversableLike {
import scala.language.higherKinds
implicit val stringRepr: IsTraversableLike[String] { type A = Char } =
new IsTraversableLike[String] {
type A = Char
val conversion = implicitly[String => GenTraversableLike[Char, String]]
}
implicit def genTraversableLikeRepr[C[_], A0](implicit conv: C[A0] => GenTraversableLike[A0,C[A0]]): IsTraversableLike[C[A0]] { type A = A0 } =
new IsTraversableLike[C[A0]] {
type A = A0
val conversion = conv
}
}
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