This probably is an error in the documentation (and the book), but I thought I'd just check to make sure: The documentation for the EventVisitor concept states: <quote> For example, the BFSVisitor of breadth_first_search() has a cycle_edge() member function. The corresponding tag is on_cycle_edge. </quote> As far as I can see BFSVisitor has no cycle_edge() function, and there is no on_cycle_edge tag in the code. The same function is also mentioned in chapter 12.3.1 of the book in the documentation of gray_target(e,g) and black_target(e,g) where it says that "A call to this function is always preceded by a call to the cycle_edge() function.". Kind of strange as the cycle_edge() function is not documented in the same chapter :) Regards, Tarjei