<:< operator in scala

Question

Can anybody provide some details on <:< operator in scala. I think:

if(apple <:< fruit)  //checks if apple is a subclass of fruit.         


        

Answer 1

To better understand the implementation.

sealed abstract class <:<[-From, +To] extends (From => To)
implicit def conforms[A]: A <:< A = new (A <:< A) {def apply(x: A) = x}

I tried to devise a simpler implementation. The following did not work.

sealed class <:<[-From <: To, +To]
implicit def conforms[A <: B, B]: A <:< B = new (A <:< B)

At least because it won't type check in all valid use cases.

case class L[+A]( elem: A )
{
   def contains[B](x: B)(implicit ev: A <:< B) = elem == x
}

error: type arguments [A,B] do not conform to class <:<'s
       type parameter bounds [-From <: To,+To]
def contains[B](x: B)(implicit ev: A <:< B) = elem == x
                                     ^