-- A module for creating and handling directed graphs

module Digraph (AdjList, Digraph, Edge,
                insertVertex, insertEdge, makeDigraph, getAdj, 
                empty, vertexInGraph  
               ) where

-- In these type declarations, v is the vertex type 
-- and e is the edge label type

type AdjList v e = [(v, e)]
type Digraph v e = [(v, AdjList v e)]
type Edge v e    = (v, v, e)

empty            :: Digraph v e

insertVertex     :: (Eq v) => v -> Digraph v e -> Digraph v e 

insertEdge       :: (Eq v) => Edge v e -> Digraph v e -> Digraph v e
   
makeDigraph      :: (Eq v) => [v] -> [Edge v e] -> Digraph v e

getAdj           :: (Eq v) => v -> Digraph v e -> AdjList v e

vertexInGraph    :: (Eq v) => v -> Digraph v e -> Bool