Groovy traits implementation of http://stackoverflow.com/questions/16115757/groovy-equivalent-to-scala-trait-stackable-modifications

gistfile1.groovy

// Tried to provide a Groovy translation of this Scala code:
// See http://stackoverflow.com/questions/16115757/groovy-equivalent-to-scala-trait-stackable-modifications

import groovy.transform.ForceOverride

interface IntQueue {
    Integer get()
    void put(Integer x)
}
trait Incrementing implements IntQueue {
    @ForceOverride
    void put(Integer x) {put(x+1) }
}  
trait Filtering implements IntQueue{
    @ForceOverride
    void put(Integer x) { if(x >=0) put(x) }
}

class BasicIntQueue implements IntQueue{
    private buf = new ArrayList<Integer>()
    Integer get() { buf.remove(0) }
    void put(Integer x) { buf << x}
    String toString() { buf.toString() }
}

def queue = new BasicIntQueue().withTraits Incrementing, Filtering
queue.put(-1)
queue.put(0)
queue.put(1)
queue.get()

/*
java.lang.StackOverflowError
	at Incrementing$Trait$Helper.put(ConsoleScript26:9)
	at Incrementing$Trait$Helper$put$1.call(Unknown Source)
	at Incrementing$TraitAdapter.put(Incrementing$TraitAdapterwrapper)
	at Incrementing$put.call(Unknown Source)
	at Incrementing$Trait$Helper.put(ConsoleScript26:9)
	at Incrementing$Trait$Helper$put$1.call(Unknown Source)
	at Incrementing$TraitAdapter.put(Incrementing$TraitAdapterwrapper)
	at Incrementing$put.call(Unknown Source)
	at Incrementing$Trait$Helper.put(ConsoleScript26:9)
*/