transformers-compat-0.7.1: A small compatibility shim for the transformers library
Copyright(C) 2015-2016 Edward Kmett Ryan Scott
LicenseBSD-style (see the file LICENSE)
MaintainerRyan Scott
StabilityProvisional
PortabilityGHC
Safe HaskellNone
LanguageHaskell2010

Data.Functor.Classes.Generic

Description

Functions to generically derive Eq1, Ord1, Read1, and Show1 instances from Data.Functor.Classes.

Synopsis

Options

newtype Options Source #

Options that further configure how the functions in Data.Functor.Classes.Generic should behave.

Constructors

Options 

Fields

defaultOptions :: Options Source #

Options that match the behavior of the installed version of GHC.

latestGHCOptions :: Options Source #

Options that match the behavior of the most recent GHC release.

Eq1

liftEqDefault :: (GEq1 NonV4 (Rep1 f), Generic1 f) => (a -> b -> Bool) -> f a -> f b -> Bool Source #

A sensible default liftEq implementation for Generic1 instances.

liftEqOptions :: (GEq1 NonV4 (Rep1 f), Generic1 f) => Options -> (a -> b -> Bool) -> f a -> f b -> Bool Source #

Like liftEqDefault, but with configurable Options. Currently, the Options have no effect (but this may change in the future).

Ord1

liftCompareDefault :: (GOrd1 NonV4 (Rep1 f), Generic1 f) => (a -> b -> Ordering) -> f a -> f b -> Ordering Source #

A sensible default liftCompare implementation for Generic1 instances.

liftCompareOptions :: (GOrd1 NonV4 (Rep1 f), Generic1 f) => Options -> (a -> b -> Ordering) -> f a -> f b -> Ordering Source #

Like liftCompareDefault, but with configurable Options. Currently, the Options have no effect (but this may change in the future).

Read1

liftReadsPrecDefault :: (GRead1 NonV4 (Rep1 f), Generic1 f) => (Int -> ReadS a) -> ReadS [a] -> Int -> ReadS (f a) Source #

A sensible default liftReadsPrec implementation for Generic1 instances.

liftReadsPrecOptions :: (GRead1 NonV4 (Rep1 f), Generic1 f) => Options -> (Int -> ReadS a) -> ReadS [a] -> Int -> ReadS (f a) Source #

Like liftReadsPrecDefault, but with configurable Options. Currently, the Options have no effect (but this may change in the future).

Show1

liftShowsPrecDefault :: (GShow1 NonV4 (Rep1 f), Generic1 f) => (Int -> a -> ShowS) -> ([a] -> ShowS) -> Int -> f a -> ShowS Source #

A sensible default liftShowsPrec implementation for Generic1 instances.

liftShowsPrecOptions :: (GShow1 NonV4 (Rep1 f), Generic1 f) => Options -> (Int -> a -> ShowS) -> ([a] -> ShowS) -> Int -> f a -> ShowS Source #

Like liftShowsPrecDefault, but with configurable Options.

GenericFunctorClasses

newtype FunctorClassesDefault f a Source #

An adapter newtype, suitable for DerivingVia. Its Eq1, Ord1, Read1, and Show1 instances leverage Generic1-based defaults.

Example

The most straightforward way to use the defaults in this module is to use DerivingVia on GHC 8.6 or later. For example:

{-# LANGUAGE DeriveGeneric, DerivingVia #-}

import Data.Functor.Classes
import Data.Functor.Classes.Generic
import GHC.Generics

data Pair a = Pair a a
  deriving stock Generic1
  deriving (Eq1, Ord1, Read1, Show1)
           via FunctorClassesDefault Pair

If using an older version of GHC, then one can also define instances manually. This is slightly trickier to accomplish since this module exports different functions depending on which version of transformers this library is built against. Here is an example of how to define instances manually:

{-# LANGUAGE CPP, DeriveGeneric #-}

import Data.Functor.Classes
import Data.Functor.Classes.Generic
import GHC.Generics

data Pair a = Pair a a deriving Generic1

instance Eq1 Pair where
#if MIN_VERSION_transformers(0,4,0) && !(MIN_VERSION_transformers(0,5,0))
    eq1 = eq1Default
#else
    liftEq = liftEqDefault
#endif

instance Ord1 Pair where
#if MIN_VERSION_transformers(0,4,0) && !(MIN_VERSION_transformers(0,5,0))
    compare1 = compare1Default
#else
    liftCompare = liftCompareDefault
#endif

instance Read1 Pair where
#if MIN_VERSION_transformers(0,4,0) && !(MIN_VERSION_transformers(0,5,0))
    readsPrec1 = readsPrec1Default
#else
    liftReadsPrec = liftReadsPrecDefault
#endif

instance Show1 Pair where
#if MIN_VERSION_transformers(0,4,0) && !(MIN_VERSION_transformers(0,5,0))
    showsPrec1 = showsPrec1Default
#else
    liftShowsPrec = liftShowsPrecDefault
#endif