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1. mapMaybe :: forall s a b . (a -> Maybe b) -> IntMap s a -> SomeIntMapWith (SupersetProof 'Int s) b

   refined-containers	Data.IntMap.Strict.Refined

   Apply a function to all values in a map and collect only the Just results, returning a potentially smaller map.

2. mapMaybeWithKey :: (Key s -> a -> Maybe b) -> IntMap s a -> SomeIntMapWith (SupersetProof 'Int s) b

   refined-containers	Data.IntMap.Strict.Refined

   Apply a function to all values in a map, together with their corresponding keys, and collect only the Just results, returning a potentially smaller map.

3. mapMaybe :: forall s k a b . (a -> Maybe b) -> Map s k a -> SomeMapWith (SupersetProof 'Regular s) k b

   refined-containers	Data.Map.Refined

   Apply a function to all values in a map and collect only the Just results, returning a potentially smaller map.

4. mapMaybeWithKey :: (Key s k -> a -> Maybe b) -> Map s k a -> SomeMapWith (SupersetProof 'Regular s) k b

   refined-containers	Data.Map.Refined

   Apply a function to all values in a map, together with their corresponding keys, and collect only the Just results, returning a potentially smaller map.

5. mapMaybe :: forall s k a b . (a -> Maybe b) -> Map s k a -> SomeMapWith (SupersetProof 'Regular s) k b

   refined-containers	Data.Map.Strict.Refined

   Apply a function to all values in a map and collect only the Just results, returning a potentially smaller map.

6. mapMaybeWithKey :: (Key s k -> a -> Maybe b) -> Map s k a -> SomeMapWith (SupersetProof 'Regular s) k b

   refined-containers	Data.Map.Strict.Refined

   Apply a function to all values in a map, together with their corresponding keys, and collect only the Just results, returning a potentially smaller map.

7. flattenMaybe :: ProjectableMaybe p => p (Maybe (Maybe a)) -> p (Maybe a)

   relational-record	Database.Relational.Documentation

   Compose nested Maybe phantom type on record.

8. fromMaybe :: (OperatorContext c, HasColumnConstraint NotNull r) => Record c r -> Record c (Maybe r) -> Record c r

   relational-record	Database.Relational.Documentation

   Operator from maybe type using record extended isNull.

9. negateMaybe :: (OperatorContext c, Num a) => Record c (Maybe a) -> Record c (Maybe a)

   relational-record	Database.Relational.Documentation

   Number negate uni-operator corresponding SQL -.

10. queryMaybe :: (MonadQualify ConfigureQuery m, MonadQuery m) => Relation () r -> m (Record Flat (Maybe r))

    relational-record	Database.Relational.Documentation

    Join sub-query. Query result is Maybe. The combinations of query and queryMaybe express inner joins, left outer joins, right outer joins, and full outer joins. Here is an example of a right outer join:

    outerJoin = relation $ do
    e <- queryMaybe employee
    d <- query department
    on $ e ?! E.deptId' .=. just (d ! D.deptId')
    return $ (,) |$| e |*| d
    

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