Function differential_dataflow::algorithms::graphs::bfs::bfs

pub fn bfs<G, N>(
    edges: &Collection<G, (N, N)>, 
    roots: &Collection<G, N>
) -> Collection<G, (N, u32)> where
    G: Scope,
    G::Timestamp: Lattice + Ord,
    N: ExchangeData + Hash, 

Returns pairs (node, dist) indicating distance of each node from a root.