The reason why Scala doesn't have them right know is that no one has
worked out reasonable semantics for them yet: order of evaluation, what
happens in the case of diamond inheritance and so on.
We are currently working on adding them though.
Ingo
Sebastien Braun wrote:
> Hello, List.
>
> I know that traits can not have constructor parameters, however I have not
> been able to find out much about the rationale behind this restriction; my
> google-fu fails me and the SLS is quiet on it (or, maybe, I just don't know
> where to look for it).
>
> For this scala code
>
>> trait A {
>> System.out.println("Hello, World!")
>> }
>>
>> class AImpl extends A
>
> scalac will generate (something closely resembling) the following pseudo-Java:
>
>> public interface A {}
>>
>> public class A$class {
>> public static void $init$(A $this) {
>> System.out.println("Hello, World!");
>> }
>> }
>>
>> public class AImpl implements A {
>> public A() {
>> A$class.$init$(this);
>> }
>> }
>
> So, intuitively (and perhaps naïvely...), it seems to me that the compiler
> should also be able to accept constructor parameters for traits:
>
>> trait A(message: String) {
>> System.out.println(message)
>> }
>
> and just tack on the arguments to the $init$ method of the trait's
> implementation class:
>
>> public interface A {}
>>
>> public class A$class {
>> public static void $init$(A $this, String message) {
>> System.out.println(message);
>> }
>> }
>
> Is this a bad idea?
>
> Cheers,
>
> Sébastien
