37 lines
933 B
Haskell
37 lines
933 B
Haskell
{-# LANGUAGE RankNTypes #-}
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module Dodge.Graph
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( pairsToSCC
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, incidenceToFunction
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, pairsToIncidence
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, graphToEdges
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) where
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-- this deserves tests
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import Data.List.Extra
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--import Data.Bifunctor (first)
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import Data.Graph
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import Data.Maybe
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import qualified Data.Graph.Inductive.Graph as F
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import qualified Data.Graph.Inductive.PatriciaTree as F
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import Data.Bifunctor
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pairsToIncidence :: Ord a => [(a,a)] -> [(a,[a])]
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pairsToIncidence
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= map (first head . unzip)
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. groupOn fst
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. sort
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incidenceToFunction :: Eq a => [(a,[a])] -> a -> [a]
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incidenceToFunction xs a = fromMaybe [] $ lookup a xs
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mkNode :: (a,[a]) -> (a,a,[a])
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mkNode (x,xs) = (x,x,xs)
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pairsToSCC :: Ord a => [(a,a)] -> [SCC a]
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pairsToSCC = stronglyConnComp . map mkNode . pairsToIncidence
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graphToEdges :: forall a b . F.Gr a b -> [(a,a)]
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graphToEdges g = map (bimap f f) $ F.edges g
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where
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f n = fromJust . lookup n $ F.labNodes g
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