úÎ å [NoneThe state employed by visiting visited nodes to be visited nodes threaded accumulator ~Abstract graph visit, over arbitrary structures, using state holding visited nodes (also acting als start) and an accumulator thr.  All is done in strict StateT. *Abstract graph visit, running graphVisitM  5fun: visit node, get new thr and nodes to visit next graph over which we visit 5fun: visit node, get new thr and nodes to visit next root/start graph over which we visit #the accumulator, threaded as state yield accum and visited     graph-visit-0.1Data.Graph.GraphVisit graphVisitM graphVisitGraphVisitState _gvsVisited_gvsYetToVisit _gvsAccum gvsVisited gvsYetToVisitgvsAccum