module Graph (Graph(..), IncidenceGraph(..), 
	      BidirectionalGraph(..), AdjacencyGraph(..),
	      VertexListGraph(..), EdgeListGraph(..)) where

  class Graph g e v | g -> e, g -> v where
    src :: e -> g -> v
    tgt :: e -> g -> v
    
  class Graph g e v => IncidenceGraph g e v where
    out_edges :: v -> g -> [e]
    out_degree :: v -> g  -> Int
		
  class (IncidenceGraph g e v) => BidirectionalGraph g e v where
    in_edges :: v -> g -> [e]
    in_degree :: v -> g -> Int
    degree :: v -> g -> Int
		   
  class AdjacencyGraph g v | g -> v where
    adjacent_vertices :: v -> g -> [v]

  class VertexListGraph g v | g -> v where
    vertices :: g -> [v]
    num_vertices :: g -> Int
		      
  class Graph g e v => EdgeListGraph g e v where
    edges :: g -> [e]
    num_edges :: g -> Int