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# reachables(+Graph, +SourceVertex, ?ReachSet)

Determines the reachables-set of a vertex in a graph.
Graph
A graph.
SourceVertex
A vertex of Graph.
ReachSet
Set of vertices reachable from SourceVertex in Graph.

## Description

Determines the reachables-set of a vertex in a graph.

### Fail Conditions

Fails if Graph is not a graph variable, if SourceVertex does not belong to Graph's vertex-set or if Graph can not be constrained to have the vertices in ReachSet reachable from Vertex.

## Examples

?- reachables(G,V,Reachs).
No.

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

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

?- V`::[]..[1,2,3], E`::[[1,2]]..[[1,2],[2,3],[3,1],[3,2]], dirgraph(G,V,E), reachables(G,3,Reachs).
V = V{cardinal([[1, 2] : 2, [3] : 3], Card{cardinal : _647, fd : [2, 3]}, _539, _540, _541, [], [], ['SUSP-_2484-susp'], ['SUSP-_2108-dead'])}
E = E{cardinal([[[1, 2]] : 1, [[2, 3], [3, 1], [3, 2]] : 4], Card{cardinal : _845, fd : [1 .. 4]}, _737, _738, _739, [], ['SUSP-_3145-susp', 'SUSP-_2494-susp'], ['SUSP-_3133-susp'], ['SUSP-_1802-dead'])}
G = dirgraph(V{cardinal([[1, 2] : 2, [3] : 3], Card{cardinal : _647, fd : [2, 3]}, _539, _540, _541, [], [], ['SUSP-_2484-susp'], ['SUSP-_2108-dead'])}, E{cardinal([[[1, 2]] : 1, [[2, 3], [3, 1], [3, 2]] : 4], Card{cardinal : _845, fd : [1 .. 4]}, _737, _738, _739, [], ['SUSP-_3145-susp', 'SUSP-_2494-susp'], ['SUSP-_3133-susp'], ['SUSP-_1802-dead'])})
Reachs = Reachs{cardinal([[3] : 1, [1, 2] : 3], Card{cardinal : _3086, fd : [1 .. 3]}, _2978, _2979, _2980, [], ['SUSP-_3121-susp'], ['SUSP-_3110-susp'], [])}

?- V`::[]..[1,2,3], E`::[[1,2]]..[[1,2],[2,3],[3,1],[3,2]], dirgraph(G,V,E), reachables(G,3,Reachs), 1 `@ Reachs.
V = [1, 2, 3]
E = E{cardinal([[[1, 2], [3, 1]] : 2, [[2, 3], [3, 2]] : 4], Card{cardinal : _873, fd : [2 .. 4]}, _765, _766, _767, [], ['SUSP-_3173-susp', 'SUSP-_2522-susp'], ['SUSP-_5570-dead', 'SUSP-_3161-susp'], ['SUSP-_5651-dead'])}
G = dirgraph([1, 2, 3], E{cardinal([[[1, 2], [3, 1]] : 2, [[2, 3], [3, 2]] : 4], Card{cardinal : _873, fd : [2 .. 4]}, _765, _766, _767, [], ['SUSP-_3173-susp', 'SUSP-_2522-susp'], ['SUSP-_5570-dead', 'SUSP-_3161-susp'], ['SUSP-_5651-dead'])})
Reachs = [1, 2, 3]

?- V`::[]..[1,2,3], E`::[[1,2]]..[[1,2],[2,3],[3,1],[3,2]], dirgraph(G,V,E), reachables(G,3,Reachs), 1 `-@ Reachs.
V = V{cardinal([[1, 2] : 2, [3] : 3], Card{cardinal : _675, fd : [2, 3]}, _567, _568, _569, [], [], ['SUSP-_2512-susp'], ['SUSP-_2136-dead'])}
E = E{cardinal([[[1, 2]] : 1, [[2, 3], [3, 2]] : 3], Card{cardinal : _873, fd : [1 .. 3]}, _765, _766, _767, [], ['SUSP-_3480-dead', 'SUSP-_3173-susp', 'SUSP-_2522-susp'], ['SUSP-_3161-susp'], ['SUSP-_3665-dead'])}
G = dirgraph(V{cardinal([[1, 2] : 2, [3] : 3], Card{cardinal : _675, fd : [2, 3]}, _567, _568, _569, [], [], ['SUSP-_2512-susp'], ['SUSP-_2136-dead'])}, E{cardinal([[[1, 2]] : 1, [[2, 3], [3, 2]] : 3], Card{cardinal : _873, fd : [1 .. 3]}, _765, _766, _767, [], ['SUSP-_3480-dead', 'SUSP-_3173-susp', 'SUSP-_2522-susp'], ['SUSP-_3161-susp'], ['SUSP-_3665-dead'])})
Reachs = Reachs{cardinal([[3] : 1, [2] : 2], Card{cardinal : _3114, fd : [1, 2]}, _3006, _3007, _3008, [], ['SUSP-_4091-dead', 'SUSP-_3149-susp'], ['SUSP-_3138-susp'], ['SUSP-_4317-dead'])}