diff options
author | Miles Sabin <miles@milessabin.com> | 2012-04-29 14:23:38 +0100 |
---|---|---|
committer | Miles Sabin <miles@milessabin.com> | 2012-05-17 16:19:41 +0100 |
commit | 73f7001d963a80950751b4e13b95b05d2526edc8 (patch) | |
tree | 4aaacf85d904087d9d9ef49e663eaafc156c0f87 /src | |
parent | ce896d6531122410659492c07926a0a293b94afa (diff) | |
download | scala-73f7001d963a80950751b4e13b95b05d2526edc8.tar.gz scala-73f7001d963a80950751b4e13b95b05d2526edc8.tar.bz2 scala-73f7001d963a80950751b4e13b95b05d2526edc8.zip |
Added infrastructure to enable easy enrichment of GenTraversables.
Diffstat (limited to 'src')
-rw-r--r-- | src/library/scala/collection/GenTraversableLike.scala | 9 | ||||
-rw-r--r-- | src/library/scala/collection/generic/FromRepr.scala | 56 | ||||
-rw-r--r-- | src/library/scala/collection/generic/package.scala | 6 |
3 files changed, 71 insertions, 0 deletions
diff --git a/src/library/scala/collection/GenTraversableLike.scala b/src/library/scala/collection/GenTraversableLike.scala index 0d51230623..eaec7a2a76 100644 --- a/src/library/scala/collection/GenTraversableLike.scala +++ b/src/library/scala/collection/GenTraversableLike.scala @@ -411,3 +411,12 @@ trait GenTraversableLike[+A, +Repr] extends Any with GenTraversableOnce[A] with def stringPrefix: String } + +object GenTraversableLike { + /** Manufacture a conversion from collection representation type `Repr` to + * its corresponding `GenTraversableLike` given an implicitly available + * instance of `FromRepr[Repr]`. + * @see [[scala.collection.generic.FromRepr]] + */ + implicit def fromRepr[Repr](implicit fr : FromRepr[Repr]) = fr.hasElem +} diff --git a/src/library/scala/collection/generic/FromRepr.scala b/src/library/scala/collection/generic/FromRepr.scala new file mode 100644 index 0000000000..c08761332c --- /dev/null +++ b/src/library/scala/collection/generic/FromRepr.scala @@ -0,0 +1,56 @@ +/* __ *\ +** ________ ___ / / ___ 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, + * {{{ + * import scala.collection.generic.{ CanBuildFrom, FromRepr, HasElem } + * + * class FilterMapImpl[A, Repr](val r : Repr)(implicit hasElem : HasElem[Repr, A]) { + * def filterMap[B, That](f : A => Option[B]) + * (implicit cbf : CanBuildFrom[Repr, B, That]) : That = r.flatMap(f(_).toSeq) + * } + * + * implicit def filterMap[Repr : FromRepr](r : Repr) = new FilterMapImpl(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 + * @since 2.10 + */ +trait FromRepr[Repr] { + type A + val hasElem: HasElem[Repr, A] +} + +object FromRepr { + import language.higherKinds + + implicit val stringFromRepr : FromRepr[String] { type A = Char } = new FromRepr[String] { + type A = Char + val hasElem = implicitly[HasElem[String, Char]] + } + + implicit def genTraversableLikeFromRepr[C[_], A0] + (implicit hasElem0: HasElem[C[A0], A0]) : FromRepr[C[A0]] { type A = A0 } = new FromRepr[C[A0]] { + type A = A0 + val hasElem = hasElem0 + } +} diff --git a/src/library/scala/collection/generic/package.scala b/src/library/scala/collection/generic/package.scala index 32006b4bf0..e0351ebae6 100644 --- a/src/library/scala/collection/generic/package.scala +++ b/src/library/scala/collection/generic/package.scala @@ -4,6 +4,12 @@ import generic.CanBuildFrom package object generic { type CanBuild[-Elem, +To] = CanBuildFrom[Nothing, Elem, To] + /** The type of conversions from a collection representation type + * `Repr` to its corresponding GenTraversableLike. + * @see [[scala.collection.generic.FromRepr]] + */ + type HasElem[Repr, A] = Repr => GenTraversableLike[A, Repr] + @deprecated("use ArrayTagTraversableFactory instead", "2.10.0") type ClassManifestTraversableFactory[CC[X] <: Traversable[X] with GenericClassManifestTraversableTemplate[X, CC]] = ArrayTagTraversableFactory[CC] |