Let's say I have a specialized class and an associated companion object:
trait Slice[@specialized +T] {
...
override def equals(that :Any) = that match {
case s :Slice[_] => ???
case _ => false
}
}
object Slice {
def newInstance[@specialized T] = ???
}
Is there any way to check
without resorting to ClassTags or passing Class[_] manually? It seems like that information should be available, but the only way I can think of involves checking names of the classes.
Use case 2) is particularly important, as I could resort to faster algorithms if I knew I'm comparing apples with apples. It probably could be accomplished by reflection, but it would be quite tricky when you take into account that we have to handle non-synthetic subclasses of Slice, too; if we have also
trait ArraySlice[@specialized T] extends Slice[T] { ... }
that should be considered 'compatible' with Slice[T] instances as long as they are both specialized (or both erased)?
Ok, I figured out a cleaner way:
final val AllButUnit = new Specializable.Group((Byte, Short, Int, Long, Char, Float, Double, Boolean, AnyRef))
def specializationFor[@specialized(AllButUnit) E] :ResolvedSpecialization[E] =
Specializations(new SpecializedKey[E]).asInstanceOf[ResolvedSpecialization[E]]
private val Specializations = Seq(
resolve[Byte],
resolve[Short],
resolve[Int],
resolve[Long],
resolve[Char],
resolve[Float],
resolve[Double],
resolve[Boolean],
resolve[Unit],
resolve[AnyRef]
).map(
spec => spec.key -> spec :(SpecializedKey[_], ResolvedSpecialization[_])
).toMap.withDefaultValue(resolve[AnyRef])
private def resolve[@specialized(AllButUnit) E :ClassTag] :ResolvedSpecialization[E] =
new ResolvedSpecialization[E](new SpecializedKey[E], new Array[E](0))
class ResolvedSpecialization[@specialized(AllButUnit) E] private[SpecializedCompanion]
(val array :Array[E], val elementType :Class[E], val classTag :ClassTag[E], private[SpecializedCompanion] val key :SpecializedKey[E])
{
private[SpecializedCompanion] def this(key :SpecializedKey[E], array :Array[E]) =
this(array, array.getClass.getComponentType.asInstanceOf[Class[E]], ClassTag(array.getClass.getComponentType.asInstanceOf[Class[E]]), key)
override def toString = s"@specialized($elementType)"
override def equals(that :Any) = that match {
case r :ResolvedSpecialization[_] => r.elementType==elementType
case _ => false
}
override def hashCode = elementType.hashCode
}
private class SpecializedKey[@specialized(AllButUnit) E] {
override def equals(that :Any) = that.getClass==getClass
override def hashCode = getClass.hashCode
def className = getClass.getName
override def toString = className.substring(className.indexOf("$")+1)
}
Now specializationFor[E].elementType
returns class corresponding to specialization parameter of E.