
dirgraph(-Graph, +VertexSet, +EdgeSet)

   Directed graph constructor.

Arguments
   Graph               A directed graph.
   VertexSet           The vertex-set that constitutes Graph.
   EdgeSet             The edge-set that constitutes Graph.

Type
   library(grasper)

Description
Creates Graph as a directed graph variable composed by the vertexes in VertexSet and the edges in EdgeSet.

Fail Conditions
   Fails 
			 if VertexSet is not a set variable,
			 if EdgeSet is not a set variable or
			 if EdgeSet cannot be contained in (VertexSet x VertexSet).
			

Examples
   
?- E`::[]..[[1,2],[2,3],[3,1]], dirgraph(G,V,E).
No.

?- V`::[]..[1,2,3], dirgraph(G,V,E).
No.

?- V`::[]..[1,2,3], E`::[[4,5]]..[[1,2],[2,3],[3,1],[4,5]], dirgraph(G,V,E).
No.

?- V`::[]..[1,2,3], E`::[]..[[1,2],[2,3],[3,1]], dirgraph(G,V,E).
V = V{cardinal([[]:0, [1, 2, 3]:3], Card{cardinal : _543, fd:[0..3]}, _435, _436, _437, [], [], ['SUSP-_2315-susp'], ['SUSP-_1925-dead'])}
E = E{cardinal([[]:0, [[1, 2], [2, 3], [3, 1]]:3], Card{cardinal : _728, fd:[0..3]}, _620, _621, _622, [], ['SUSP-_2325-susp'], [], ['SUSP-_1641-dead'])}
G = dirgraph(V{cardinal([[]:0, [1, 2, 3]:3], Card{cardinal : _543, fd:[0..3]}, _435, _436, _437, [], [], ['SUSP-_2315-susp'], ['SUSP-_1925-dead'])}, E{cardinal([[]:0, [[1, 2], [2, 3], [3, 1]]:3], Card{cardinal : _728, fd:[0..3]}, _620, _621, _622, [], ['SUSP-_2325-susp'], [], ['SUSP-_1641-dead'])})

?- V`::[]..[1,2,3], E`::[]..[[1,2],[2,3],[3,1],[4,5]], dirgraph(G,V,E).
V = V{cardinal([[]:0, [1, 2, 3]:3], Card{cardinal : _573, fd:[0..3]}, _465, _466, _467, [], [], ['SUSP-_2391-susp'], ['SUSP-_2001-dead'])}
E = E{cardinal([[]:0, [[1, 2], [2, 3], [3, 1]]:3], Card{cardinal : _766, fd:[0..3]}, _658, _659, _660, [], ['SUSP-_2401-susp'], [], ['SUSP-_1717-dead'])}
G = dirgraph(V{cardinal([[]:0, [1, 2, 3]:3], Card{cardinal : _573, fd:[0..3]}, _465, _466, _467, [], [], ['SUSP-_2391-susp'], ['SUSP-_2001-dead'])}, E{cardinal([[]:0, [[1, 2], [2, 3], [3, 1]]:3], Card{cardinal : _766, fd:[0..3]}, _658, _659, _660, [], ['SUSP-_2401-susp'], [], ['SUSP-_1717-dead'])})

?- V`::[]..[1,2,3], E`::[[1,2]]..[[1,2],[2,3],[3,1]], dirgraph(G,V,E).
V = V{cardinal([[1, 2]:2, [3]:3], Card{cardinal : _573, fd:[2, 3]}, _465, _466, _467, [], [], ['SUSP-_2363-susp'], ['SUSP-_1987-dead'])}
E = E{cardinal([[[1, 2]]:1, [[2, 3], [3, 1]]:3], Card{cardinal : _763, fd:[1..3]}, _655, _656, _657, [], ['SUSP-_2373-susp'], [], ['SUSP-_1681-dead'])}
G = dirgraph(V{cardinal([[1, 2]:2, [3]:3], Card{cardinal : _573, fd:[2, 3]}, _465, _466, _467, [], [], ['SUSP-_2363-susp'], ['SUSP-_1987-dead'])}, E{cardinal([[[1, 2]]:1, [[2, 3], [3, 1]]:3], Card{cardinal : _763, fd:[1..3]}, _655, _656, _657, [], ['SUSP-_2373-susp'], [], ['SUSP-_1681-dead'])})
			


