unwanted implicit argument resolution in higher order function map - scala

Question

I'm having issues trying to map some methods defined with implicit arguments over an Option type.
Let's say I define a custom class and a trait with the aforementioned methods operating on said class
class MyClass
trait Processor {
def stringy(implicit arg: MyClass) = arg.toString
def lengthy(implicit arg: MyClass) = arg.toString.length
def inty(implicit arg: MyClass) = arg.toString.map(_.toInt).sum
}
Then I create an implementation with some tests
object TestProcessing extends Processor {
//Here everything works fine, the argument is passed explicitly
def test() {
val my = new MyClass
val res = List(stringy(my), lengthy(my), inty(my))
println(res.mkString("\n"))
}
//Still everything ok, the argument is passed implicitly
def testImplicit() {
implicit val my = new MyClass
val res = List(stringy, lengthy, inty)
println(res.mkString("\n"))
}
object Mapper {
//class wrapped in an Option
val optional = Some(new MyClass)
//trying to factor out common code
def optionally[T](processFunction: MyClass => T): Option[T] = optional map processFunction
//now the specific processing methods that should work on the optional value
def s: Option[String] = optionally(stringy)
def l: Option[Int] = optionally(lengthy)
def i: Option[Int] = optionally(inty)
/*
* Here the compiler complains that
*
*<console>:40: error: could not find implicit value for parameter arg: MyClass
* def s: Option[String] = optionally(stringy)
* ^
*<console>:41: error: could not find implicit value for parameter arg: MyClass
* def l: Option[Int] = optionally(lengthy)
* ^
*<console>:42: error: could not find implicit value for parameter arg: MyClass
* def i: Option[Int] = optionally(inty)
* ^
*/
}
}
While optionally is conceived to explicitly pass the optional value explicitly to its argument function, the compiler demands an implicit definition when I use it on the actual functions.
I have two possible solutions, neither of which is satisfactiory:
passing an implicit argument to optionally as in
optionally(implicit my => stringy)
avoid defining the argument to the specific functions as implicit, as in
def stringy(arg: MyClass)
Each solution defies the goal of achieving both readability and usability.
Is there a third way to go?

Answer 1

If I understand correctly, the problem is that the compiler doesn't seem recognize that you want to partially apply / lift the method to a function here (instead it "thinks" you want to leave out the implicit parameter), so doing that explicitly seems to work:
def s: Option[String] = optionally(stringy(_))
def l: Option[Int] = optionally(lengthy(_))
def i: Option[Int] = optionally(inty(_))