Unclear Scala manifest syntax

Question

I saw a piece of Scala code with manifest syntax as follows. I do not know what WireFormat means here. What constraint does it add to the Manifest A? Does it mean the type A must extends the trait WireFormat?

I could not find any document about such syntax.

trait WireFormat[A] {
  def toWire(x: A, out: DataOutput)
  def fromWire(in: DataInput): A
}

class DList[A : Manifest : WireFormat]

Read it as _takes an `A` such that there's a `Manifest` and a `WireFormat` context for `A`_. — Daniel C. Sobral, Apr 01 '12 at 16:43

score 4 · Accepted Answer · edited May 23 '17 at 12:20

4

It is a context bound. With two types separated by colons it just means there are two implicit parameters.

In other words it's the same as:

class DList[A](implicit x: Manifest[A], y: WireFormat[A])

edited May 23 '17 at 12:20

Community

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answered Apr 01 '12 at 02:41

Luigi Plinge

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On [context bounds and view bounds](http://stackoverflow.com/questions/4465948/what-are-scala-context-and-view-bounds) is also very handy. – Matt Roberts May 30 '13 at 21:28

Unclear Scala manifest syntax

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