graph

type BiGraph interface {
	Graph

	// In returns the nodes which point to node i.
	In(i int) []int
}

type Edge struct {
	Node int // Node ID
	Edge int // Edge index
}

type Graph interface {
	// NumNodes returns the number of nodes in this graph.
	NumNodes() int

	// Out returns the nodes to which node i points.
	Out(i int) []int
}

type IntGraph [][]int

type Subgraph interface {
	Graph

	// Underlying returns the underlying graph that this is a
	// subgraph of.
	Underlying() Graph

	// NodeMap transduces a node property map on the underlying
	// graph into a node property map on this graph.
	NodeMap(underlyingMap func(node int) interface{}) func(node int) interface{}

	// EdgeMap transduces an edge property map on the underlying
	// graph into an edge property map on this graph.
	EdgeMap(underlyingMap func(node, edge int) interface{}) func(node, edge int) interface{}
}

type Weighted interface {
	Graph

	// OutWeight returns the weight of the e'th edge out from node
	// i. e must be in the range [0, len(Out(i))).
	OutWeight(i, e int) float64
}

type WeightedUnit struct {
	Graph
}