half-edge.groovy

def map(v, args) {
    def u = g.v(v.id)
    def l = []
    u.inE.filter({!it.outV.outE.retain([it]).hasNext()}).id.fill(l)
    u.outE.filter({!it.inV.inE.retain([it]).hasNext()}).id.fill(l)
    def x = l.inject(" "){acc,val->acc = acc + "\t" + val}
    return x.substring(1).trim()
}