That isn't a complete program (there's no definition for the type Rational), so I wouldn't expect it to be compilable or runnable as it stands.

Nevertheless, I think you have a different problem ... the stacktrace implies that you're missing the reference to the Scala library in your project .classpath file. How did you create this project? Can you show us the contents of your .project and .classpath files. Thanks.

Hi Miles,

thanks for your response.

The class Rational exists in the same project and I simply wanted to publish things which are obviously related to the problem ... from my point of view.

I'm using Win XP pro and have set the enviroment variables as follows:

JAVA_HOME = C:\Program Files\Java\jdk1.6.0_20
SCALA_HOME = E:\Java\Scala\scala-2.8.0.final
CLASSPATH = E:\Java\workspace;%JAVA_HOME%
Path = %JAVA_HOME%\bin;%SCALA_HOME%\bin; ...{all the other pathes}...

Here is the class :

package RationalPack
/**
 * Implements Rational numbers. Calculates the Greatest Common Denominator and 
 * stores the values in shortened form. Written in Scala
 * @param n	numerator (int)
 * @param d	denominator (int)
 * @return a rational object
 * @throws nothing 
 * @version 1.0
 */
class Rational(n:Int, d:Int) extends Ordered[Rational] {	
	require(d!=0)
	
	private val g=gcd(n.abs, d.abs)
	
	val numer = n / g
	val denom = d / g
	
	def this(n:Int)= this(n,1)
	
	def + (that:Rational):Rational=
		new Rational(
				numer*that.denom+that.numer*denom,
				denom*that.denom)
	def + (i:Int):Rational =
		new Rational(numer + i *denom,denom)
	
	def - (that:Rational):Rational =
		new Rational(
				numer*that.denom - that.numer*denom,
				denom*that.denom)
	def - (i:Int):Rational =
		new Rational(numer-i*denom,denom)
	
	def * (that:Rational):Rational =
		new Rational(numer*that.numer,denom*that.denom)
	
	def * (i:Int):Rational =
		new Rational(numer*i,denom)
	
	def / (that:Rational):Rational=
		new Rational(numer*that.denom, denom*that.numer )
	
	def / (i:Int):Rational =
		new Rational(numer,denom*i)
	
	def compare(that:Rational)=(this.numer*that.denom)-(that.numer*this.denom )
	
	override def toString=numer +"/"+ denom
	
	implicit def intToRational(x:Int)=new Rational(x)
	
	private def gcd(a:Int, b:Int):Int =
		if(b==0) a else gcd(b, a%b)
	
}

Here comes the *.classpath* file in the project subdir:

<?xml version="1.0" encoding="UTF-8"?>
<classpath>
	<classpathentry kind="src" path="src"/>
	<classpathentry kind="con" path="ch.epfl.lamp.sdt.launching.SCALA_CONTAINER"/>
	<classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/JavaSE-1.6"/>
	<classpathentry kind="output" path="bin"/>
</classpath>

...and last but not least ... *.project*

<?xml version="1.0" encoding="UTF-8"?>
<projectDescription>
	<name>RationalNumbers</name>
	<comment></comment>
	<projects>
	</projects>
	<buildSpec>
		<buildCommand>
			<name>ch.epfl.lamp.sdt.core.scalabuilder</name>
			<arguments>
			</arguments>
		</buildCommand>
	</buildSpec>
	<natures>
		<nature>ch.epfl.lamp.sdt.core.scalanature</nature>
		<nature>org.eclipse.jdt.core.javanature</nature>
	</natures>
</projectDescription>

In your .classpath file, could you change the line,

<classpathentry kind="con" path="ch.epfl.lamp.sdt.launching.SCALA_CONTAINER"/>

to read,

<classpathentry kind="con" path="org.scala-ide.sdt.launching.SCALA_CONTAINER"/>

Hi Miles,


Bingooooo ! You found it ! Though I don't understand the logic behind it ...

Thanks a lot and have a nice weekend !

Joe Herrmann

Neither do I at the moment ... the old id is supposed to still be working. Presumably you created the project a little while ago and then it stopped working recently when you upgraded the Scala IDE?

Yes, that's absolutly right.

I learn Scala/Eclipse when I have some free time and so it can happen that a project is already several IDE-updates "old"

So, what is the fix, then? Do we expect people who upgrade to manually go and edit all their project files? I fear that many will not be so persistent to even find out what the problem is, and will turn their backs in frustration, instead. With some justification.

I wasted a number of hours myself, on this problem.

Joe-eoJ was a bit too quick off the mark closing this. I've just now committed a fix in revision:446d97343779294157b69bff067e6a30b38f02f7 ... projects using the old ids will now behave sensibly in recent builds of the SDT. The change will show up in tomorrow's nightly build.