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Decrement size of graph when removing vertices #6

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Decrement size of graph when removing vertices #6

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6 changes: 2 additions & 4 deletions src/Data/Graph/DGraph.hs
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Expand Up @@ -136,10 +136,8 @@ instance Graph DGraph where
| otherwise = graph
where v1Links' = HM.delete v2 $ getLinks v1 g


removeVertex v g@(DGraph s _) = DGraph s
$ (\(DGraph _ g') -> HM.delete v g')
$ foldl' (flip removeArc) g $ incidentArcs g v
removeVertex v g = DGraph s $ HM.delete v g'
where (DGraph s g') = foldl' (flip removeArc) g $ incidentArcs g v

isSimple g = foldl' go True $ vertices g
where go bool v = bool && not (HM.member v $ getLinks v $ unDGraph g)
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5 changes: 2 additions & 3 deletions src/Data/Graph/UGraph.hs
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Expand Up @@ -116,9 +116,8 @@ instance Graph UGraph where
v2Links = HM.delete v1 $ getLinks v2 g
update = HM.adjust . const

removeVertex v g@(UGraph s _) = UGraph s
$ (\(UGraph _ g') -> HM.delete v g')
$ foldl' (flip removeEdge) g $ incidentEdges g v
removeVertex v g = UGraph s $ HM.delete v g'
where (UGraph s g') = foldl' (flip removeEdge) g $ incidentEdges g v

isSimple g = foldl' go True $ vertices g
where go bool v = bool && not (HM.member v $ getLinks v $ unUGraph g)
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3 changes: 3 additions & 0 deletions test/Data/Graph/DGraphSpec.hs
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Expand Up @@ -78,3 +78,6 @@ spec = do
edgeTriples g2 `shouldBe` [(1, 2, 'a'), (2, 1, 'b')]
length (arcs g2) `shouldBe` 2

it "Decrements its size when vertices incident to an arc are removed" $ property $
\g v -> (g `containsVertex` v) && (vertexDegree g v > 0) && (size g > 0)
==> let g1 = removeVertex v (g :: DGraph Int ()) in size g1 == length (arcs g1)
4 changes: 4 additions & 0 deletions test/Data/Graph/UGraphSpec.hs
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Expand Up @@ -85,3 +85,7 @@ spec = do
let g = insertEdge (Edge 3 4 'b') $ insertEdge (Edge 1 2 'a') empty :: UGraph Int Char
edgeTriples g `shouldBe` [(1, 2, 'a'), (3, 4, 'b')]
length (edges g) `shouldBe` 2

it "Decrements its size when vertices incident to an edge are removed" $ property $
\g v -> (g `containsVertex` v) && (vertexDegree g v > 0) && (size g > 0)
==> let g1 = removeVertex v (g :: UGraph Int ()) in size g1 == length (edges g1)