Hi,
Am 09.02.2011 um 15:44 schrieb Yoav Zibin:
> It's a spec thing, and the compiler is doing the right thing:
> The normal casting takes precedence over user-defined casting.
>
> Bard, please update the spec and specify priorities for casting:
> - if a regular (java-like) casting can be done, we do that.
> - otherwise we try user-defined casts
thanks for the information.
> for example:
>
> public class Hello
> {
> public static def main(Array[String])
> {
> val b1:B = new B();
> Console.OUT.println("b1 as C: " + b1 as C); // Must use the
> user-defined casting, so we get: b1 as C: C@a32b
> val b2:Base = b1;
> Console.OUT.println("b2 as C: " + b2 as C); // Can use the regular
> casting, so we get: x10.lang.ClassCastException: C
> }
> }
>
> protected class Base
> {
> public static operator (base: Base) as C = new C();
> }
> protected class B extends Base {}
> protected class C extends Base {}
Ok, but that is not the original intent of my sample.
There each class knows how it can be cast to type 'C'
which is specified in the polymorphic 'asC()' method.
The 'asC()' method is then called in the static cast operator.
I am only using the approach with the polymorphic method
because non-static cast operators which can be overridden
in subclasses didn't work for me.
So the problem I am having is that I don't understand why the cast should fail
when I specified that it is possible and how to do it.
> PS
> Your examples always gives me the same output:
> $ x10 Hello
> b: 15
> b as C: 42
> c: 51
> c as C: 51
>
> b2: 15
> b2 as C: 42
> c2: 51
> c2 as C: 51
>
> b3: 15
> x10.lang.ClassCastException: C
> at x10.rtt.Types.cast(Types.java:338)
> at Hello.main(Hello.java:117)
> at Hello$$Main.runtimeCallback(Hello.java:26)
> at x10.runtime.impl.java.Runtime$3.$apply(Runtime.java:109)
> at x10.lang.Runtime$$Closure$144.$apply(Runtime.java:4138)
> at x10.lang.Activity.run(Activity.java:594)
> at x10.lang.Runtime$Worker$$Closure$137.$apply(Runtime.java:1347)
> at x10.lang.Runtime.runAtLocal(Runtime.java:215)
> at x10.lang.Runtime$Worker.loop(Runtime.java:1055)
> at x10.lang.Runtime$Worker.$apply(Runtime.java:988)
> at x10.lang.Runtime$Pool.$apply(Runtime.java:1659)
> at x10.lang.Runtime.start(Runtime.java:2368)
> at x10.runtime.impl.java.Runtime.$apply(Runtime.java:87)
> at x10.runtime.impl.java.Thread.run(Thread.java:48)
Yes, it always gives the output shown above.
But instead of the ClassCastException I would expect the output of the last
section to look like this:
b3: 15
b3 as C: 42
c3: 51
c3 as C: 51
Thanks for your time and best regards,
Manfred
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