astar (empty) → 0.0

raw patch · 4 files changed

+109/−0 lines, 4 filesdep +PSQueuedep +basedep +containerssetup-changed

Dependencies added: PSQueue, base, containers

Files

• Data/Graph/AStar.hs +83/−0
• LICENSE +10/−0
• Setup.lhs +3/−0
• astar.cabal +13/−0

@@ -0,0 +1,83 @@+module Data.Graph.AStar (aStar) where++import qualified Data.Set as Set+import Data.Set (Set, (\\))+import qualified Data.Map as Map+import Data.Map (Map, (!))+import qualified Data.PSQueue as PSQ+import Data.PSQueue (PSQ, Binding(..), minView)+import Data.List (foldl')++data AStar a c = AStar { visited  :: !(Set a),+                         waiting  :: !(PSQ a c),+                         score    :: !(Map a c),+                         memoHeur :: !(Map a c),+                         cameFrom :: !(Map a a),+                         end      :: !(Maybe a) }+    deriving Show+    +aStarInit start = AStar { visited  = Set.empty,+                          waiting  = PSQ.singleton start 0,+                          score    = Map.singleton start 0,+                          memoHeur = Map.empty,+                          cameFrom = Map.empty,+                          end      = Nothing }++runAStar :: (Ord a, Ord c, Num c) =>+         (a -> Set a)     -- adjacencies in graph+         -> (a -> a -> c) -- distance function+         -> (a -> c)      -- heuristic distance to goal+         -> (a -> Bool)   -- goal+         -> a             -- starting vertex+         -> AStar a c     -- final state++runAStar graph dist heur goal start = aStar' (aStarInit start)+  where aStar' s+          = case minView (waiting s) of+              Nothing            -> s+              Just (x :-> _, w') ->+                if goal x+                  then s { end = Just x }+                  else aStar' $ foldl' (expand x)+                                       (s { waiting = w',+                                            visited = Set.insert x (visited s)})+                                       (Set.toList (graph x \\ visited s))+        expand x s y+          = let v = score s ! x + dist x y+            in case PSQ.lookup y (waiting s) of+                 Nothing -> link x y v+                              (s { memoHeur+                                     = Map.insert y (heur y) (memoHeur s) })+                 Just _  -> if v < score s ! y+                              then link x y v s+                              else s+        link x y v s+           = s { cameFrom = Map.insert y x (cameFrom s),+                 score    = Map.insert y v (score s),+                 waiting  = PSQ.insert y (v + memoHeur s ! y) (waiting s) }++-- | This function computes an optimal (minimal distance) path through a graph in a best-first fashion,+-- starting from a given starting point.+aStar :: (Ord a, Ord c, Num c) =>+         (a -> Set a)     -- ^ The graph we are searching through, given as a function from vertices+                          -- to their neighbours.+         -> (a -> a -> c) -- ^ Distance function between neighbouring vertices of the graph. This will+                          -- never be applied to vertices that are not neighbours, so may be undefined+                          -- on pairs that are not neighbours in the graph.+         -> (a -> c)      -- ^ Heuristic distance to the (nearest) goal.+         -> (a -> Bool)   -- ^ The goal, specified as a boolean predicate on vertices.+         -> a             -- ^ The vertex to start searching from.+         -> Maybe [a]     -- ^ An optimal path, if any path exists.+aStar graph dist heur goal start+    = let s = runAStar graph dist heur goal start+      in case end s of+            Nothing -> Nothing+            Just e  -> Just (reverse . takeWhile (not . (== start)) . iterate (cameFrom s !) $ e)++plane :: (Integer, Integer) -> Set (Integer, Integer)+plane (x,y) = Set.fromList [(x-1,y),(x+1,y),(x,y-1),(x,y+1),(x-1,y-1),(x+1,y+1),(x-1,y+1),(x+1,y-1)]++planeDist :: (Integer, Integer) -> (Integer, Integer) -> Double+planeDist (x1,y1) (x2,y2) = sqrt ((x1'-x2')^2 + (y1'-y2')^2)+    where [x1',y1',x2',y2'] = map fromInteger [x1,y1,x2,y2]+

@@ -0,0 +1,10 @@+Copyright (c) 2008, Cale Gibbard+All rights reserved.++Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:++    * Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.+    * Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.+    * Neither the name of Cale Gibbard nor the names of any contributors to this software may be used to endorse or promote products derived from this software without specific prior written permission.++THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

@@ -0,0 +1,3 @@+#!/usr/bin/env runhaskell+> import Distribution.Simple+> main = defaultMain

@@ -0,0 +1,13 @@+name:                astar+version:             0.0+synopsis:            General A* search algorithm.+description:         This is a data-structure independent implementation of A* search.+category:            Data+license:             BSD3+license-file:        LICENSE+author:              Cale Gibbard+maintainer:          cgibbard@gmail.com+build-Depends:       base,containers,PSQueue+build-type:          Simple+exposed-modules:     Data.Graph.AStar+ghc-options:         -O2