Exposing Future.toBoxed and related machinery

[Paolo G. Giarrusso]

Future.mapTo[S] casts a value of type S to a value at type T with Class.cast, but needs to take boxing into account. The code for that is generally useful and IMHO should become part of the reflection API.

From Future:

 private[concurrent] val toBoxed = Map[Class[_], Class[_]](

    classOf[Boolean] -> classOf[java.lang.Boolean],

    classOf[Byte]    -> classOf[java.lang.Byte],

    classOf[Char]    -> classOf[java.lang.Character],

    classOf[Short]   -> classOf[java.lang.Short],

    classOf[Int]     -> classOf[java.lang.Integer],

    classOf[Long]    -> classOf[java.lang.Long],

    classOf[Float]   -> classOf[java.lang.Float],

    classOf[Double]  -> classOf[java.lang.Double],

    classOf[Unit]    -> classOf[scala.runtime.BoxedUnit]

  )

    def boxedType(c: Class[_]): Class[_] = {

      if (c.isPrimitive) Future.toBoxed(c) else c

    }

def mapTo[S](implicit tag: ClassTag[S]) = {

   boxedType(tag.runtimeClass).cast(t).asInstanceOf[S]

}

I believe this is generally useful because I've also written some very similar code, although apparently I didn't get it as correct or elegant (why is Unit not boxed to java.lang.Void?):

https://github.com/ps-mr/LinqOnSteroids/blob/master/src/main/scala/ivm/expressiontree/Util.scala#L10

https://github.com/ps-mr/LinqOnSteroids/blob/master/src/main/scala/ivm/expressiontree/Util.scala#L67

Best regards

Paolo

[Paul Phillips]

On Fri, Oct 19, 2012 at 1:32 PM, Paolo G. Giarrusso <p.gia...@gmail.com> wrote:

I believe this is generally useful because I've also written some very similar code, although apparently I didn't get it as correct or elegant (why is Unit not boxed to java.lang.Void?):

Have you an instance of java.lang.Void squirreled away somewhere?

[√iktor Ҡlang]

val v = new Void // Put the lime in the coconut and shake it all up

[Paolo Giarrusso]

Still, what about the main idea?

I see your point. OK, I'll check my side remarks next time, and have
more unit tests for my code.

But what about the main idea of exposing the code from Future.toBoxed
code in the Scala (reflection) library?
--
Paolo G. Giarrusso - Ph.D. Student, Philipps-University Marburg
http://www.informatik.uni-marburg.de/~pgiarrusso/

[Paul Phillips]

On Fri, Oct 19, 2012 at 2:51 PM, Paolo Giarrusso <pgiar...@mathematik.uni-marburg.de> wrote:

But what about the main idea of exposing the code from Future.toBoxed
code in the Scala (reflection) library?

My only reservation is that it doesn't go far enough, but yes, some convenient way to jump between these things and lots of variations on them would be wonderful.  I've written that method so many times I no longer see the method - it's just blonde, brunette.

[√iktor Ҡlang]

BoxesRuntime or something like that?

Cheers,
V