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

Answer added just to show that the mutable-visited isn't too unreadable either (untested, though!)

def isCyclic() : Boolean =
{
     var visited = HashSet()

     def hasCycle(node:Node) = {
        if (visited.contains(node)) {
           true
        } else {
           visited :+= node
           children(node).exists(hasCycle(_))
        }
    }
    nodes.exists(hasCycle(_))
}

def children(node:Node) = vertexMap.getChildren(node.id).toList.map(nodeId => id2nodeMap(nodeId))