- fold:procedure
graph cycles iterator; every cycle is reprensented as a list of edges. Adjacent edges are adjacent in the list; the cycles are folded together using the user-supplied function F, which is of the form LAMBDA CYCLE STATE
graph cycles iterator; every cycle is reprensented as a list of edges. Adjacent edges are adjacent in the list; the cycles are folded together using the user-supplied function F, which is of the form LAMBDA CYCLE STATE