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Convince ghc that diffAt is exhaustive.

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This commit is contained in:
Rob Rix 2016-06-06 08:31:53 -04:00
parent 9b698b023b
commit 1327c115f2
1 changed files with 3 additions and 3 deletions
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6
src/SES.hs
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@ -18,9 +18,6 @@ ses diffTerms cost as bs = fst <$> evalState diffState Map.empty where
-- | Find the shortest edit script between two terms at a given vertex in the edit graph.
diffAt :: Applicative edit => Compare term (edit (Patch term)) -> Cost (edit (Patch term)) -> (Integer, Integer) -> [term] -> [term] -> State (Map.Map (Integer, Integer) [(edit (Patch term), Integer)]) [(edit (Patch term), Integer)]
diffAt diffTerms cost (i, j) as bs
| null as, null bs = pure []
| null as = pure $ foldr insert [] bs
| null bs = pure $ foldr delete [] as
| (a : as) <- as, (b : bs) <- bs = do
cachedDiffs <- get
case Map.lookup (i, j) cachedDiffs of
@ -36,6 +33,9 @@ diffAt diffTerms cost (i, j) as bs
cachedDiffs' <- get
put $ Map.insert (i, j) nomination cachedDiffs'
pure nomination
| null as = pure $ foldr insert [] bs
| null bs = pure $ foldr delete [] as
| otherwise = pure []
where
delete = consWithCost cost . pure . Delete
insert = consWithCost cost . pure . Insert