Lib.rs

rust_bounded_graph

A thin newtype wrapper for petgraph to assist in the creation of graphs with restrictions on their edges

This crate is a simple wrapper around petgraph's Graph type. It exists to make it simpler to enforce restrictions at the time of edge creation, to ensure that the graph is never in a state with an "invalid" edge between two nodes.

In order to do so, your Node type should implement the following trait:

pub trait BoundedNode<Ix: IndexType = DefaultIx> {
    fn can_add_edge(&self, dir: Direction, existing_edge_count: usize, other_node: &Self) -> bool;
}

Alternatively, for the common and simple situation of a Node with an associated limit on incoming and outgoing edges, one can alternatively implement the following trait:

pub trait EdgeNumberBoundedNode<Ix: IndexType = DefaultIx> {
    fn max_incoming_edges(&self) -> Ix;
    fn max_outgoing_edges(&self) -> Ix;
}

This will provide a function

has_edge_space(&self, dir: Direction, existing_edge_count: usize) -> bool

If you have no other requirements for your node type, implement the marker trait SimpleEdgeNumberBoundedNode to automatically use has_edge_space as can_add_edge

Most methods and traits of Graph have been added directly to the BoundedGraph struct provided by this crate, although updating and adding edges is now a failable operation. You may obtain a Graph from a bounded Graph by calling as_graph().

Currently, the following methods are known to be unimplemented:

• update_edge on the Build trait can panic if the edge is new, and invalid.
• raw_nodes(), raw_edges(), first_edge() and next_edge() are not implemented on BoundedGraph, as they are low level functions and I currently do not need them. Please file an issue if this is a problem for you.
• reverse() is skipped for the first version as its especially likely to break constraits... and I don't need it yet.
• Arbitrary trait is unlikely to be implemented at this time.

Please let me know if anything else is missing or incorrect!