From 8e92e6e11d2b3b0bfb5ac9d68f347219493e6380 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Kier=C3=A1n=20Meinhardt?= Date: Wed, 23 Sep 2020 17:44:40 +0200 Subject: split into library + executables --- src/Much/MappedSets.hs | 28 ++++++++++++++++++++++++++++ 1 file changed, 28 insertions(+) create mode 100644 src/Much/MappedSets.hs (limited to 'src/Much/MappedSets.hs') diff --git a/src/Much/MappedSets.hs b/src/Much/MappedSets.hs new file mode 100644 index 0000000..ec0ae73 --- /dev/null +++ b/src/Much/MappedSets.hs @@ -0,0 +1,28 @@ +module Much.MappedSets (invert, mk) where + +import Control.Arrow +import Data.Map.Strict (Map) +import qualified Data.Map.Strict as Map +import Data.Maybe +import Data.Set (Set) +import qualified Data.Set as Set + + +mk :: (Ord a, Ord b) => [(a, [b])] -> Map a (Set b) +mk = + Map.fromList . map (second Set.fromList) + + +invert :: (Ord a, Ord b) => Map a (Set b) -> Map b (Set a) +invert = + Map.foldrWithKey invert1 Map.empty + + +invert1 :: (Ord a, Ord b) => a -> Set b -> Map b (Set a) -> Map b (Set a) +invert1 k v a = + Set.foldr (upsert k) a v + + +upsert :: (Ord a, Ord b) => a -> b -> Map b (Set a) -> Map b (Set a) +upsert k = + Map.alter (Just . Set.insert k . fromMaybe Set.empty) -- cgit v1.2.3