Scala Graph Cycle Detection Algo 'return' needed?

Question

I have implemented a small cycle detection algorithm for a DAG in Scala. The \'return\' bothers me - I\'d like to have a version without the return...possible?

Answer 1

Yes, by using '.find' instead of 'foreach' + 'return':

http://www.scala-lang.org/api/current/index.html#scala.collection.immutable.Seq

def isCyclic() : Boolean = {
  def visit(node: MyNode): Boolean = {
      node.marker = 3

      val nodeId = node.id
      val children = vertexMap.getChildren(nodeId).toList.map(nodeId => id2nodeMap(nodeId))
      val found = children.exists(child => (3 == child.marker || (1 == child.marker && visit(child))))

      node.marker = 2

      found
  }

  lock.readLock().lock()
  try {
    nodes.foreach(node => node.marker = 1)
    nodes.exists(node => node.marker && visit(node))
  } finally {
    lock.readLock().unlock()
  }
}