Scala 2.8 TreeMap and custom Ordering
- by Dave
I'm switching from scala 2.7 and ordered to scala 2.8 and using ordering. It looks quite straight forward but I was wondering could I make it a little less verbose. For example:
scala> case class A(i: Int)
defined class A
scala> object A extends Ordering[A] { def compare(o1: A, o2: A) = o1.i - o2.i}
defined module A
If I then try to create a TreeMap I get an error
scala> new collection.immutable.TreeMap[A, String]()
<console>:10: error: could not find implicit value for parameter ordering: Ordering[A]
new collection.immutable.TreeMap[A, String]()
^
However if I explicitly specify the object A as the ordering it works fine.
scala> new collection.immutable.TreeMap[A, String]()(A)
res34: scala.collection.immutable.TreeMap[A,String] = Map()
Do I always have to explicitly specify the ordering or is there a shorter format?
Thanks
