elm-community/graph

Name: graph

Owner: Elm Community

Description: Functional Graph Library in Elm.

Forked from: sgraf812/elm-graph

Created: 2016-06-08 01:11:42.0

Updated: 2018-04-30 17:02:19.0

Pushed: 2018-04-30 17:02:18.0

Homepage: http://package.elm-lang.org/packages/elm-community/graph/latest

Size: 119

Language: Elm

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README

Graph

An neat graph library for Elm.

Got confused about what to wear when putting on shoes? This will help you out:

sUp : Graph String () -- node labels are strings, edge labels are empty
sUp =
t
nodes =
  [ Node 0 "Socks"
  , Node 1 "Undershirt"
  , Node 2 "Pants"
  , Node 3 "Shoes"
  , Node 4 "Watch"
  , Node 5 "Shirt"
  , Node 6 "Belt"
  , Node 7 "Tie"
  , Node 8 "Jacket"
  ]

e from to =
  Edge from to ()

edges =
  [ e 0 3 -- socks before shoes
  , e 1 2 -- undershorts before pants
  , e 1 3 -- undershorts before shoes
  , e 2 3 -- pants before shoes
  , e 2 6 -- pants before belt
  , e 5 6 -- shirt before belt
  , e 5 7 -- shirt before tie
  , e 6 8 -- belt before jacket
  , e 7 8 -- tie before jacket
  ]

Graph.fromNodesAndEdges nodes edges


tToWearShoes: List String
tToWearShoes =
aph.guidedDfs
Graph.alongIncomingEdges            -- which edges to follow
(Graph.onDiscovery (\ctx list ->    -- append node labels on discovery
  ctx.node.label :: list))
[3 {- "Shoes" NodeId -}]            -- start with the node labelled "Shoes"
[]                                  -- accumulate starting with the empty list
dressUp                             -- traverse our dressUp graph from above
|> Tuple.first                      -- ignores the untraversed rest of the graph


tToWearShoes == ["Pants", "Undershorts", "Socks", "Shoes"]

So better wear pants, undershorts, pants and socks with your shoes. (In case you wonder: There is also a topologicalSort function which can compute valid linear orderings)

Credits

I was inspired by Martin Erwig's original idea realized in the functional graph library, but I also tried to keep it as simple as possible, bringing the neatness of Elm to graph libraries.