Witherable.Lens.Withering

This module contains a replacement for MaybeT intended for use in lens-like contexts. The important difference from MaybeT is that Withering drops the short-circuiting behavior that requires Monad constraints.

Documentation

newtype Withering f a

A replacement for MaybeT with no short-circuiting behavior. This allows its Applicative instance to not require f to be an instance of Monad.

Constructors

Withering

Fields

• runWithering :: f (Maybe a)

Instances

Applicative f => Applicative (Withering f)

Defined in Witherable.Lens.Withering

Methods

pure :: a -> Withering f a

(<*>) :: Withering f (a -> b) -> Withering f a -> Withering f b

liftA2 :: (a -> b -> c) -> Withering f a -> Withering f b -> Withering f c

(*>) :: Withering f a -> Withering f b -> Withering f b

(<*) :: Withering f a -> Withering f b -> Withering f a

Functor f => Functor (Withering f)

Defined in Witherable.Lens.Withering

Methods

fmap :: (a -> b) -> Withering f a -> Withering f b

(<$) :: a -> Withering f b -> Withering f a

Show (f (Maybe a)) => Show (Withering f a)

Defined in Witherable.Lens.Withering

Methods

showsPrec :: Int -> Withering f a -> ShowS

show :: Withering f a -> String

showList :: [Withering f a] -> ShowS

Eq (f (Maybe a)) => Eq (Withering f a)

Defined in Witherable.Lens.Withering

Methods

(==) :: Withering f a -> Withering f a -> Bool

(/=) :: Withering f a -> Withering f a -> Bool

Ord (f (Maybe a)) => Ord (Withering f a)

Defined in Witherable.Lens.Withering

Methods

compare :: Withering f a -> Withering f a -> Ordering

(<) :: Withering f a -> Withering f a -> Bool

(<=) :: Withering f a -> Withering f a -> Bool

(>) :: Withering f a -> Withering f a -> Bool

(>=) :: Withering f a -> Withering f a -> Bool

max :: Withering f a -> Withering f a -> Withering f a

min :: Withering f a -> Withering f a -> Withering f a

empty :: Applicative f => Withering f a

A Withering value wrapping Nothing. This cannot be part of an Alternative instance for Withering because it needs to be available with only an Applicative constraint on f, and any lawful Alternative instance would require more structure than that.