Generics in Scala: implementing an interface/trait twice?

On Fri, Oct 28, 2011 at 6:50 PM, Andrei Pozolotin
wrote:
> but I am curious, what is the underlying reason prevents scala from
> doing this?
>
> compiler has access to type information, why not generate overloaded
> methods?

Try writing those overloaded methods yourself. You can't:

scala> def f(xs: List[Int]) = 1 ; def f(xs: List[String]) = 2
:7: error: double definition:
method f:(xs: List[String])Int and
method f:(xs: List[Int])Int at line 7
have same type after erasure: (xs: List)Int
def f(xs: List[Int]) = 1 ; def f(xs: List[String]) = 2
^

You can't inherit the same interface with different type arguments
because of erasure. The methods would not be distinguishable. Java
won't let you do it either. I'm not sure whether the JVM prohibits
it, but it probably doesn't need to because reality will take care of
discouraging anyone who attempts it.

import java.util.*;

public abstract class J extends Object implements
List,List> { }

J.java:3: java.util.List cannot be inherited with different arguments:
and >
public abstract class J extends Object implements
List,List> {
^
1 error

> is it feasible this feature will become available soon?

It will be a long time coming.

On Oct 28, 11:29 pm, Paul Phillips wrote:

> > is it feasible this feature will become available soon?
>
> It will be a long time coming.

thanks for getting back; actually, it has already came :-)

http://groups.google.com/group/scala-user/browse_thread/thread/d82d7b7a1...

now I am looking for a working example; anyone?

thank you;

Andrei.