First commit

README.md

@@ -1,2 +1,5 @@
-# path-finding
+# Path finding
+
 Experimenting with path-finding algorithms in Haskell
+
+Build with `stack build` and run the example with `stack exec bfs`.

examples/bfs.hs

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+import Data.Array
+import Tuura.BFS
+
+box :: Graph
+box = array (1, 4) [ (1, [2, 3])
+                   , (2, [1, 4])
+                   , (3, [1, 4])
+                   , (4, [2, 3]) ]
+
+tree :: Graph
+tree = array (1, 7) [ (1, [2, 3])
+                    , (2, [4, 5])
+                    , (3, [6, 7])
+                    , (4, [])
+                    , (5, [])
+                    , (6, [])
+                    , (7, []) ]
+
+main :: IO ()
+main = do
+    print (bfs box 1)
+    print (bfs tree 1)

path-finding.cabal

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+name:          path-finding
+version:       0.0.1
+synopsis:      Path-finding algorithms in Haskell
+license:       MIT
+license-file:  LICENSE
+author:        Andrey Mokhov <[email protected]>, github: @snowleopard
+maintainer:    Andrey Mokhov <[email protected]>, github: @snowleopard
+copyright:     2017 Tuura, https://github.com/tuura
+homepage:      https://github.com/tuura/path-finding.git
+category:      Algorithms
+build-type:    Simple
+cabal-version: >=1.10
+
+source-repository head
+    type:     git
+    location: https://github.com/tuura/path-finding.git
+
+library
+    hs-source-dirs:   src
+    exposed-modules:  Tuura.BFS
+    build-depends:    array == 0.5.*,
+                      base >= 4.7 && < 5,
+                      containers == 0.5.*
+    default-language: Haskell2010
+    GHC-options:      -Wall -fno-warn-name-shadowing -fwarn-tabs -O2
+
+executable bfs
+    hs-source-dirs:   examples
+    main-is:          bfs.hs
+    build-depends:    array == 0.5.*,
+                      base >= 4.7 && < 5,
+                      containers == 0.5.*,
+                      path-finding
+    default-language: Haskell2010
+    GHC-options:      -Wall -fno-warn-name-shadowing -fwarn-tabs -O2

src/Tuura/BFS.hs

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+module Tuura.BFS (Graph, Vertex, bfs) where
+
+import Data.Array
+import Data.Sequence (Seq, ViewL (..), (><))
+import Data.IntSet   (IntSet)
+
+import qualified Data.Sequence as Seq
+import qualified Data.IntSet as Set
+
+type Vertex = Int
+type Graph  = Array Vertex [Vertex]
+
+bfs :: Graph -> Vertex -> [Vertex]
+bfs graph vertex = visit Set.empty (Seq.singleton vertex)
+  where
+    visit :: IntSet -> Seq Vertex -> [Vertex]
+    visit visited queue = case Seq.viewl queue of
+        EmptyL  -> []
+        v :< vs -> if Set.member v visited
+                   then visit visited vs
+                   else v : (visit newVisited newQueue)
+          where
+            toVisit    = filter (\u -> Set.notMember u visited) (graph ! v)
+            newVisited = Set.insert v visited
+            newQueue   = vs >< Seq.fromList toVisit

stack.yaml

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+resolver: lts-9.11
+packages:
+- .
+extra-deps: []
+flags: {}
+extra-package-dbs: []