Implicit parameter to partial functions?

On Thu, Jan 29, 2009 at 09:33:25PM -0200, Thomas Sant Ana wrote:
> Is there a way to specify implicit parameter to a partial Function?

I'm not all that optimistic this will accomplish what you want, but here's what I came up with:

scala> case class PF(implicit prefix: String) extends PartialFunction[String,Int] {
| def isDefinedAt(x: String): Boolean = x startsWith prefix
| def apply(x: String) = if (isDefinedAt(x)) x.length else throw new MatchError(x)
| }
defined class PF

scala> implicit val starter = "a"
starter: java.lang.String = a

scala> val startsWithA = PF()
startsWithA: PF =

scala> startsWithA.isDefinedAt("abc")
res0: Boolean = true

scala> startsWithA("abc")
res1: Int = 3

scala> startsWithA.isDefinedAt("cba")
res2: Boolean = false

scala> startsWithA("cba")
scala.MatchError: cba
at PF.apply(:6)
at .(:9)
at .()