
weight(+Graph, +WeightHash, ?Weight)

   Calculates the Weight of Graph given a WeightHash.

Arguments
   Graph               A graph.
   WeightHash          An hashtable an hashtable matching some elements (vertex or edge) of Graph to a positive weight. An unweighed element will be considered to have weight 0.
   Weight              The sum of the graph's vertices' and edges' weights.

Type
   library(grasper)

Description
Calculates the Weight of Graph given a WeightHash.

Fail Conditions
   Fails
			 if Graph is not a graph variable,
			 if Weight is not an hash variable (lib(hash)) with positive integer weights or
			 if Graph can not be constrained to have a weight delimited by Weight.
			

Examples
   
?- weight(G,WH,W).
No.
 
?- V`::[]..[1,2,3], E`::[]..[[1,2],[2,3],[3,1]], dirgraph(G,V,E), weight(G,WH,W).
instantiation fault in term_hash(1, -1, Size, _2486)
Abort
 
?- V`::[]..[1,2,3], E`::[[1,2]]..[[1,2],[2,3],[3,1]], dirgraph(G,V,E), hash_create(WH), hash_add(WH,1,1), hash_add(WH,2,1), hash_add(WH,3,1), hash_add(WH,[1,2],1), hash_add(WH,[2,3],1), hash_add(WH,[3,1],1), weight(G,WH,0).
No.
 
?- V`::[]..[1,2,3], E`::[[1,2]]..[[1,2],[2,3],[3,1]], dirgraph(G,V,E), hash_create(WH), hash_add(WH,1,1), hash_add(WH,2,1), hash_add(WH,3,1), hash_add(WH,[1,2],1), hash_add(WH,[2,3],1), hash_add(WH,[3,1],1), weight(G,WH,7).
No.
 
?- V`::[]..[1,2,3], E`::[[1,2]]..[[1,2],[2,3],[3,1]], dirgraph(G,V,E), hash_create(WH), hash_add(WH,1,1), hash_add(WH,2,1), hash_add(WH,3,1), hash_add(WH,[1,2],1), hash_add(WH,[2,3],1), hash_add(WH,[3,1],1), weight(G,WH,W).
V = V{cardinal([[1, 2] : 2, [3] : 3], Card{cardinal : _941, fd : [2, 3]}, _833, _834, _835, [], ['SUSP-_3104-susp'], ['SUSP-_3130-susp', 'SUSP-_2731-susp'], ['SUSP-_2355-dead'])}
E = E{cardinal([[[1, 2]] : 1, [[2, 3], [3, 1]] : 3], Card{cardinal : _1131, fd : [1 .. 3]}, _1023, _1024, _1025, [], ['SUSP-_3117-susp', 'SUSP-_2741-susp'], ['SUSP-_3143-susp'], ['SUSP-_2049-dead'])}
G = dirgraph(V{cardinal([[1, 2] : 2, [3] : 3], Card{cardinal : _941, fd : [2, 3]}, _833, _834, _835, [], ['SUSP-_3104-susp'], ['SUSP-_3130-susp', 'SUSP-_2731-susp'], ['SUSP-_2355-dead'])}, E{cardinal([[[1, 2]] : 1, [[2, 3], [3, 1]] : 3], Card{cardinal : _1131, fd : [1 .. 3]}, _1023, _1024, _1025, [], ['SUSP-_3117-susp', 'SUSP-_2741-susp'], ['SUSP-_3143-susp'], ['SUSP-_2049-dead'])})
WH = hash(4, 6, [[3, 1] -> 1, [2, 3] -> 1, 1 -> 1, 2 -> 1, [1, 2] -> 1, 3 -> 1])
W = W{cardinal : _3033, fd : [3 .. 6]}
 
?- V`::[]..[1,2,3], E`::[[1,2]]..[[1,2],[2,3],[3,1]], dirgraph(G,V,E), hash_create(WH), hash_add(WH,1,1), hash_add(WH,2,1), hash_add(WH,3,1), hash_add(WH,[1,2],1), hash_add(WH,[2,3],1), hash_add(WH,[3,1],1), weight(G,WH,3).
V = [1, 2]
E = [[1, 2]]
G = dirgraph([1, 2], [[1, 2]])
WH = hash(4, 6, [[3, 1] -> 1, [2, 3] -> 1, 1 -> 1, 2 -> 1, [1, 2] -> 1, 3 -> 1])
 
?- V`::[]..[1,2,3], E`::[[1,2]]..[[1,2],[2,3],[3,1]], dirgraph(G,V,E), hash_create(WH), hash_add(WH,1,1), hash_add(WH,2,1), hash_add(WH,3,1), hash_add(WH,[1,2],1), hash_add(WH,[2,3],1), hash_add(WH,[3,1],1), weight(G,WH,6).
V = [1, 2, 3]
E = [[1, 2], [2, 3], [3, 1]]
G = dirgraph([1, 2, 3], [[1, 2], [2, 3], [3, 1]])
WH = hash(4, 6, [[3, 1] -> 1, [2, 3] -> 1, 1 -> 1, 2 -> 1, [1, 2] -> 1, 3 -> 1])
			


