It's not pretty, but this can be done with IsTraversableLike
,
import scala.language.implicitConversions
import scala.collection.generic.{ CanBuildFrom, IsTraversableLike }
import scala.collection.GenTraversableLike
class SelfCrossMappable[A, Repr](xs: GenTraversableLike[A, Repr]) {
def crossMap[B, That](f: (A, A) => B)
(implicit
cbf: CanBuildFrom[Repr, B, That],
itl: IsTraversableLike[That] { type A = B }
) = xs.flatMap { a => itl.conversion(xs.map(f(a, _)))
}
}
implicit def toSelfCrossMappable[Repr](xs: Repr)
(implicit traversable: IsTraversableLike[Repr]) =
new SelfCrossMappable(traversable.conversion(xs))
Sample REPL session,
scala> List("foo", "foo", "bar").crossMap(_ == _)
res0: List[Boolean] = List(true, true, false, true, true, false, false, false, true)