{-# LANGUAGE Trustworthy #-}{-# LANGUAGE DeriveGeneric #-}{-# LANGUAGE GeneralizedNewtypeDeriving #-}{-# LANGUAGE NoImplicitPrelude #-}{-# LANGUAGE KindSignatures #-}{-# LANGUAGE StandaloneDeriving #-}{-# LANGUAGE DeriveDataTypeable #-}------------------------------------------------------------------------------- |-- Module : Control.Applicative-- Copyright : Conor McBride and Ross Paterson 2005-- License : BSD-style (see the LICENSE file in the distribution)---- Maintainer : libraries@haskell.org-- Stability : stable-- Portability : portable---- This module describes a structure intermediate between a functor and-- a monad (technically, a strong lax monoidal functor). Compared with-- monads, this interface lacks the full power of the binding operation-- '>>=', but---- * it has more instances.---- * it is sufficient for many uses, e.g. context-free parsing, or the-- 'Data.Traversable.Traversable' class.---- * instances can perform analysis of computations before they are-- executed, and thus produce shared optimizations.---- This interface was introduced for parsers by Niklas R&#xF6;jemo, because-- it admits more sharing than the monadic interface. The names here are-- mostly based on parsing work by Doaitse Swierstra.---- For more details, see-- <http://www.soi.city.ac.uk/~ross/papers/Applicative.html Applicative Programming with Effects>,-- by Conor McBride and Ross Paterson.moduleControl.Applicative (-- * Applicative functorsApplicative (..),-- * AlternativesAlternative (..),-- * InstancesConst (..),WrappedMonad (..),WrappedArrow (..),ZipList (..),-- * Utility functions(<$>) ,(<$) ,(<**>) ,liftA ,liftA3 ,optional ,asum ,)whereimportGHC.Internal.Control.Category hiding((.) ,id )importGHC.Internal.Control.Arrow importGHC.Internal.Data.Maybe importGHC.Internal.Data.Tuple importGHC.Internal.Data.Foldable (asum )importGHC.Internal.Data.Functor ((<$>) )importGHC.Internal.Data.Functor.Const (Const (..))importGHC.Internal.Data.Typeable (Typeable )importGHC.Internal.Data.Data (Data )importGHC.Internal.Base importGHC.Internal.Functor.ZipList (ZipList (..))importGHC.Generics -- $setup-- >>> import PreludenewtypeWrappedMonad m a =WrapMonad {forall (m :: * -> *) a. WrappedMonad m a -> m a
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v )-- | @since 4.14.0.0derivinginstance(Typeable (a ::Type ->Type ->Type ),Typeable b ,Typeable c ,Data (a b c ))=>Data (WrappedArrow a b c )-- extra functions-- | One or none.---- It is useful for modelling any computation that is allowed to fail.---- ==== __Examples__---- Using the 'Alternative' instance of "Control.Monad.Except", the following functions:---- >>> import Control.Monad.Except---- >>> canFail = throwError "it failed" :: Except String Int-- >>> final = return 42 :: Except String Int---- Can be combined by allowing the first function to fail:---- >>> runExcept $ canFail *> final-- Left "it failed"---- >>> runExcept $ optional canFail *> final-- Right 42optional ::Alternative f =>f a ->f (Maybe a )optional :: forall (f :: * -> *) a. Alternative f => f a -> f (Maybe a)
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