Incompatible Class Change Error on Set Difference

Hi,

I tried List("a", "b").toSet &~ List("b", "c").toSet but couldn't verify your problem on 2.10.0.r25789-b20111005020219.

Could you assemble a small code example?

Thanks,


Simon

Sounds like you're executing against old libraries on the classpath.  The following breaks with something like this:
java -classpath ".;O:/scala-2.8.1/lib/scala-library.jar;O:/scala-2.9.1.final/lib/scala-library.jar" Sets

WFM on 2.9.1, with 3 elements;

object Sets {

  def main(args: Array[String]) {
    val one = List(1,2,3)
    val two = List(2,3,4)

    val result = one.toSet &~ two.toSet
    println(result.toString)

    val three = List("one","two","three")
    val four = List("two","three","four")

    val another = three.toSet &~ four.toSet
    println(another.toString)
  }
}


On Fri, Oct 7, 2011 at 9:52 AM, jhonig <joho@xs4all.nl> wrote:

Hi All,

It's been some time ago, but I have encountered a new problem that I
didn't find a solution for.

I have 2 Set[String] instances and try to take the difference with
&~.  The code compiles fine
(with 2.9.1).  When I run it, I get:

java.lang.IncompatibleClassChangeError: Class
scala.collection.immutable.Set$Set3 does not implement the requested
interface scala.collection.GenSetLike

The sets have been created by calling toSet on some List.

So I tried to use immutable HashSets instead, but when adding the
contents of my lists to
empty HashSets I get this exception:

java.lang.NoSuchMethodError: scala.collection.immutable.HashSet
$.apply(Lscala/collection/Seq;)Lscala/collection/GenTraversable;

Again, the code compiled fine.

Guess I ran into a 2.9.1 bug.  Is there a workaround?  I haven't found
it yet :-(

Job Honig

> Sounds like you're executing against old libraries on the classpath. The
> following breaks with something like this:
> java -classpath
> ".;O:/scala-2.8.1/lib/scala-library.jar;O:/scala-2.9.1.final/lib/scala-libr
> ary.jar" Sets
>

I have heard this before. I'm compiling from Maven and ALL my version
numbers in the POM point to 2.9.1, I'm 100% sure of that.

Job

Hi Simon,

> I tried List("a", "b").toSet &~ List("b", "c").toSet but couldn't verify
> your problem on 2.10.0.r25789-b20111005020219.
>
> Could you assemble a small code example?

I will try later tonight.

Job Honig

Hi All,

> I tried List("a", "b").toSet &~ List("b", "c").toSet but couldn't verify
> your problem on 2.10.0.r25789-b20111005020219.
>
> Could you assemble a small code example?

I now have this:

package org.jhonig.psdevs.lang.parser;
object Test
{
private def test ()
{
val theRelationVars : Set[String] = List ("a", "b", "c").toSet;
val theVariableVars : Set[String] = List ("a", "b", "c").toSet;

System.err.println ("Vars 1 = " + theRelationVars.mkString (", "));
System.err.println ("Vars 2 = " + theVariableVars.mkString (", "));

val theExcessRelationVars : Set[String]
= theRelationVars &~ theVariableVars;

System.err.println ("Difference 1 = " + theExcessRelationVars.mkString
(", "));

val theExcessVariableVars : Set[String]
= theVariableVars &~ theRelationVars;

System.err.println ("Difference 2 = " + theExcessVariableVars.mkString
(", "));
System.err.println ("Finished test");
}

def main (args : Array[String])
{
test ();
}

}

Running it gives:

Vars 1 = a, b, c
Vars 2 = a, b, c
java.lang.IncompatibleClassChangeError: Class
scala.collection.immutable.Set$Set3 does not implement the requested interface
scala.collection.GenSetLike
at org.jhonig.psdevs.lang.parser.Test$.test(Test.scala:19)
at org.jhonig.psdevs.lang.parser.Test$.main(Test.scala:29)
at org.jhonig.psdevs.lang.parser.Test.main(Test.scala)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at
scala.tools.nsc.util.ScalaClassLoader$$anonfun$run$1.apply(ScalaClassLoader.scala:81)
at
scala.tools.nsc.util.ScalaClassLoader$class.asContext(ScalaClassLoader.scala:24)
at
scala.tools.nsc.util.ScalaClassLoader$URLClassLoader.asContext(ScalaClassLoader.scala:86)
at
scala.tools.nsc.util.ScalaClassLoader$class.run(ScalaClassLoader.scala:81)
at
scala.tools.nsc.util.ScalaClassLoader$URLClassLoader.run(ScalaClassLoader.scala:86)
at scala.tools.nsc.MainGenericRunner$.main(MainGenericRunner.scala:83)
at scala.tools.nsc.MainGenericRunner.main(MainGenericRunner.scala)

I run with:

scala -cp "target/classes:/home/joho/.m2/repository/org/scala-lang/scala-
library/2.9.1/scala-library-2.9.1.jar" org.jhonig.psdevs.lang.parser.Test

So there's a problem with the library-2.9.1.jar???

Job H.

Hi All,

Sorry to follow up on my own post. I compiled the same code with
scalac and it runs okay.
When compiled with mvn scala:compile I get the error... I removed ALL
NON-2.9.1 jars
from my local .m2/repository before trying that....

Job

Hi Job,
Would you mind dumping your code that does this into a github project? That way we can check it out, build with scalac vs maven and see if we get the same errors.
Thanks,
Matthew

On 7 October 2011 20:01, jhonig <joho@xs4all.nl> wrote:

Hi All,

Sorry to follow up on my own post.  I compiled the same code with
scalac and it runs okay.
When compiled with mvn scala:compile I get the error...  I removed ALL
NON-2.9.1 jars
from my local .m2/repository before trying that....

Job

--
Dr Matthew PocockIntegrative Bioinformatics Group, School of Computing Science, Newcastle Universitymailto: turingatemyhamster@gmail.com gchat: turingatemyhamster@gmail.commsn: matthew_pocock@yahoo.co.uk irc.freenode.net: drdozertel: (0191) 2566550mob: +447535664143

Hi Matthew,

Thanks to Paul Phillips, I found out that there was indeed another
version of
Scala on my system. So when compiling with Maven, I got another
version
than when running the compiled program. That solved the problem.

Thanks all for responding!

Job Honig

On Oct 7, 11:51 pm, Matthew Pocock
wrote:
> Hi Job,
>
> Would you mind dumping your code that does this into a github project? That
> way we can check it out, build with scalac vs maven and see if we get the
> same errors.
>
> Thanks,
>
> Matthew
>
> On 7 October 2011 20:01, jhonig wrote:
>
> > Hi All,
>
> > Sorry to follow up on my own post.  I compiled the same code with
> > scalac and it runs okay.
> > When compiled with mvn scala:compile I get the error...  I removed ALL
> > NON-2.9.1 jars
> > from my local .m2/repository before trying that....
>
> > Job
>
> --
> Dr Matthew Pocock
> Integrative Bioinformatics Group, School of Computing Science, Newcastle
> University
> mailto: turingatemyhams...@gmail.com
> gchat: turingatemyhams...@gmail.com
> msn: matthew_poc...@yahoo.co.uk
> irc.freenode.net: drdozer
> tel: (0191) 2566550
> mob: +447535664143