Bidirectional implicit conversion in Scala - scala

Question

Consider the follwing generic function:
def compare[I:Ordering,T:Ordering](i:I,t:T):Int
It should compare a value of type I with a value of type T with both of them assumed to have Ordering defined. The comparison should work if there is either a way to implicitly convert I to T, or T to I. Obviously, if one uses types I and T that do not have any of the two conversions, the compiler should complain.
I am tempted to write something like this:
def compare[I:Ordering,T:Ordering](i:I,t:T)(implicit c1:I=>T, c2:T=>I):Int
But this actually asks for both conversions to exist, not at least one.
Any ideas?
EDIT: Given the comments I want to make the question complete. If both implicit conversions exist, I would like to assume a priority among the types. Then use the higher priority implicit conversion for the comparison.

Answer 1

Wrong Answer which I wrote initially:
Of course it will ask because you are trying to compare two different ordering. T:Ordering means that there should be an Ordering[T] available in the scope. Ordering[T] is different from Ordering[I]. It is like comparing numbers and strings where both can be ordered differently but ordering together does not makes sense.
PS: Both numbers and strings can be ordered together but that means numbers & strings will represent the same datatype here and there will be only one instance of Ordering for that data type.
Better answer:
Use a wrapper class to define the converters
object Main extends App {
def compare[I: Ordering, T: Ordering](i: I, t: T)(implicit wrapper: Wrapper[I, T]): Int = {
val converter: Either[(I) => T, (T) => I] = wrapper.getConverterBasedOnPriority
val convertedValue = if(converter.isLeft){
converter.left.map(c => c(i))
} else{
converter.right.map(c => c(t))
}
// do what ever you want
1
}
val iToT: (Int => String) = i => i.toString
val tToI: (String => Int) = s => s.toInt
// implicit def iToTWrapper = new Wrapper[Int , String ](iToT, null)
implicit def tToIWrapper = new Wrapper[Int , String ](null, tToI)
compare(1, "a")
}
class Wrapper[I, T](iToT: I => T, tToI : T => I) {
def getConverterBasedOnPriority:Either[I => T, T => I] = {
// return ordering based on priority check.
// returning iToT for example sake. Do the priority check and return accordingly
Left(iToT)
}
}
If you uncomment both implicits, it will throw and error. If you comment both implicits, it will throw and error.