An neat graph library for Elm.
Got confused about what to wear when putting on shoes? This will help you out:
dressUp : Graph String () -- node labels are strings, edge labels are empty
dressUp =
let
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
]
in
Graph.fromNodesAndEdges nodes edges
iWantToWearShoes: List String
iWantToWearShoes =
Graph.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
iWantToWearShoes == ["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)
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.