suzanne.soy/tock-mirror
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

Added a new function to Utils, and made one of the existing functions simpler and more efficient

Browse Source
This commit is contained in:
Neil Brown 2009-04-14 12:07:12 +00:00
parent 1a3df54ee7
commit d2260e1736
1 changed files with 9 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
common/Utils.hs
View File

@ -359,14 +359,19 @@ mapMapM f m = mapMapWithKeyM (const f) m
-- A version of mapM that acts on the values in maps. -- A version of mapM that acts on the values in maps.
mapMapWithKeyM :: (Ord a, Monad m) => (a -> b -> m c) -> Map.Map a b -> m (Map.Map a c) mapMapWithKeyM :: (Ord a, Monad m) => (a -> b -> m c) -> Map.Map a b -> m (Map.Map a c)
mapMapWithKeyM f m = liftM Map.fromAscList $ mapM f' $ Map.toAscList m mapMapWithKeyM f = T.mapM (uncurry f) . Map.mapWithKey (,)
where
f' (x,y) = do y' <- f x y
return (x, y')
filterMapByKey :: Ord k => (k -> Bool) -> Map.Map k v -> Map.Map k v filterMapByKey :: Ord k => (k -> Bool) -> Map.Map k v -> Map.Map k v
filterMapByKey f = Map.filterWithKey (\k _ -> f k) filterMapByKey f = Map.filterWithKey (\k _ -> f k)
filterMapByKeyM :: (Ord k, Monad m) => (k -> m Bool) -> Map.Map k v -> m (Map.Map k v)
-- There are several ways we could implement this, but this seems okay:
filterMapByKeyM f m = do mDecision <- mapMapWithKeyM addDecision m
return $ Map.map snd $ Map.filter fst mDecision
where
addDecision k v = do d <- f k
return (d, v)
-- | Transforms an Either into a Maybe. If it's a Left value, it is transformed -- | Transforms an Either into a Maybe. If it's a Left value, it is transformed
-- into Nothing. If it is a Right value, it is transformed into Just. -- into Nothing. If it is a Right value, it is transformed into Just.
eitherToMaybe :: Either a b -> Maybe b eitherToMaybe :: Either a b -> Maybe b