Copyright	(c) Carl Howells 2021-2022
License	MIT
Maintainer	chowells79@gmail.com
Safe Haskell	Safe-Inferred
Language	Haskell2010

Witherable.Lens.Withering

Description

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.

Synopsis

newtype Withering f a = Withering {
- runWithering :: f (Maybe a)
}
empty :: Applicative f => Withering f a

Documentation

newtype Withering f a Source #

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

Instances details

Applicative f => Applicative (Withering f) Source #
Instance details 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) Source #
Instance details 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) Source #
Instance details 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) Source #
Instance details 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) Source #
Instance details 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 Source #

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.