What is ClassManifest in Scala?

Question

I am new to Scala and I was learning "context bound" from posts. But I found many of those are explaining "context bound" using ClassManifest as example. For instance,

def tabulate[T](len: Int, f: Int => T)(implicit m: ClassManifest[T]) = {
    val xs = new Array[T](len)
    for (i <- 0 until len) xs(i) = f(i)
    xs
}

I find it weird that the implicit parameter m is required but never used in the function body. Thus I would like to know what ClassManifest is and what its relationship is with context bound. Thanks!

EDIT:

I have seen What is a Manifest in Scala and when do you need it? before, but it's asking for Manifest not ClassManifest, and there is no explanation regarding ClassManifest in that post, thus I ask this similar (but, IMO, not duplicate) question.

Possible duplicate of [What is a Manifest in Scala and when do you need it?](http://stackoverflow.com/questions/3213510/what-is-a-manifest-in-scala-and-when-do-you-need-it) — manojlds, Sep 14 '16 at 09:18
@manojlds Sorry I am new to Scala, but is `Manifest` the same thing as `ClassManifest`? Thanks — Lifu Huang, Sep 14 '16 at 09:27

score 3 · Answer 1 · edited May 23 '17 at 12:32

You can find explanation about ClassManifest for old scala versions (before 2.10) here. Please, read all answers, some of them explain not only Manifest but ClassManifest too:

There exists also a weaker form named ClassManifest which can be constructed from knowing just the top-level class of a type, without necessarily knowing all its argument types.

In Scala 2.11.8, 2.12-M4 ClassManifest is deprecated and became an alias to ClassTag :

type  ClassManifest[T] = ClassTag[T]

It's deprecated since 2.10.0.

P.S. Actually this post from scala documentation that you probably read is completely outdated, even the view bounds (<%) described there are deprecated too (for a quite long time) so you should avoid them as well (using this simple trick if you really need them, but implicit views are not recommended in any form)

What is ClassManifest in Scala?

1 Answers1