navigate digraph

[Luc Taesch]

are there any functions to navigate digraph ? ( ideally, some HoF).

i realise that the schema i was implemeinting was in fact a graph, so i
may use digraph, but i havent found navigation around that.
( ive done already something, but i realise some thinking should have
been put into that, already)

( e.g, the classical nav for tree, is deep first, of breadth first).

or any papers ?