- maybeZero :: MonadPlus m => Maybe a -> m a
- joinMaybe :: MonadPlus m => m (Maybe a) -> m a
- access :: Monad m => PartialLens a b -> StateT a m (Maybe b)
- accessPlus :: MonadPlus m => PartialLens a b -> StateT a m b
- (~=) :: Monad m => PartialLens a b -> b -> StateT a m (Maybe b)
- (%=) :: Monad m => PartialLens a b -> (b -> b) -> StateT a m (Maybe b)
- (%%=) :: Monad m => PartialLens a b -> (b -> (c, b)) -> StateT a m (Maybe c)
- (+=), (*=), (-=) :: (Monad m, Num b) => PartialLens a b -> b -> StateT a m (Maybe b)
- (//=) :: (Monad m, Fractional b) => PartialLens a b -> b -> StateT a m (Maybe b)
- (&&=), (||=) :: Monad m => PartialLens a Bool -> Bool -> StateT a m (Maybe Bool)

# Documentation

# State actions

access :: Monad m => PartialLens a b -> StateT a m (Maybe b)Source

get the value of a partial lens into state

accessPlus :: MonadPlus m => PartialLens a b -> StateT a m bSource

returns mzero in case of a null reference

(~=) :: Monad m => PartialLens a b -> b -> StateT a m (Maybe b)Source

set a value using a partial lens into state
returns `Nothing`

in case of a null reference

(%=) :: Monad m => PartialLens a b -> (b -> b) -> StateT a m (Maybe b)Source

infix modification a value through a partial lens into state
returns `Nothing`

in case of a null reference

(%%=) :: Monad m => PartialLens a b -> (b -> (c, b)) -> StateT a m (Maybe c)Source

infix modification of a value through a partial lens into state
with a supplemental response.
returns `Nothing`

in case of a null reference

(//=) :: (Monad m, Fractional b) => PartialLens a b -> b -> StateT a m (Maybe b)Source