Text.Show.Text.Generic

Generic versions of Show and Show1 class functions, as an alternative to Text.Show.Text.TH, which uses Template Haskell. Because there is no Generic2 class, Show2 cannot be implemented generically.

This implementation is based off of the Generics.Deriving.Show module from the generic-deriving library.

Since: 0.6

Generic show functions

Show instances can be easily defined for data types that are Generic instances. The easiest way to do this is to use the DeriveGeneric extension.

{-# LANGUAGE DeriveGeneric #-}
import GHC.Generics
import Text.Show.Text
import Text.Show.Generic

data D a = D a
  deriving (Generic, Generic1)

instance Show a => Show (D a) where
    showbPrec = genericShowbPrec

instance Show1 D where
    showbPrecWith = genericShowbPrecWith

Understanding a compiler error

Suppose you intend to use genericShowbPrec to define a Show instance.

data Oops1 = Oops1
    -- forgot to add "deriving Generic" here!

instance Show Oops1 where
    showbPrec = genericShowbPrec

If you forget to add a deriving Generic clause to your data type, at compile-time, you will get an error message that begins roughly as follows:

No instance for (GShow (Rep Oops1))

This error can be confusing, but don't let it intimidate you. The correct fix is simply to add the missing "deriving Generic" clause.

Similarly, if the compiler complains about not having an instance for (GShow1 (Rep1 Oops2)), add a "deriving Generic1" clause.

genericShow :: (Generic a, GShow (Rep a)) => a -> Text

A Generic implementation of show.

Since: 0.6

genericShowLazy :: (Generic a, GShow (Rep a)) => a -> Text

A Generic implementation of showLazy.

Since: 0.6

genericShowPrec :: (Generic a, GShow (Rep a)) => Int -> a -> Text

A Generic implementation of showPrec.

Since: 0.6

genericShowPrecLazy :: (Generic a, GShow (Rep a)) => Int -> a -> Text

A Generic implementation of showPrecLazy.

Since: 0.6

genericShowList :: (Generic a, GShow (Rep a)) => [a] -> Text

A Generic implementation of showList.

Since: 0.6

genericShowListLazy :: (Generic a, GShow (Rep a)) => [a] -> Text

A Generic implementation of showListLazy.

Since: 0.6

genericShowb :: (Generic a, GShow (Rep a)) => a -> Builder

A Generic implementation of showb.

Since: 0.6

genericShowbPrec :: (Generic a, GShow (Rep a)) => Int -> a -> Builder

A Generic implementation of showbPrec.

Since: 0.6

genericShowbList :: (Generic a, GShow (Rep a)) => [a] -> Builder

A Generic implementation of showbList.

Since: 0.6

genericPrint :: (Generic a, GShow (Rep a)) => a -> IO ()

A Generic implementation of print.

Since: 0.6

genericPrintLazy :: (Generic a, GShow (Rep a)) => a -> IO ()

A Generic implementation of printLazy.

Since: 0.6

genericHPrint :: (Generic a, GShow (Rep a)) => Handle -> a -> IO ()

A Generic implementation of hPrint.

Since: 0.6

genericHPrintLazy :: (Generic a, GShow (Rep a)) => Handle -> a -> IO ()

A Generic implementation of hPrintLazy.

Since: 0.6

genericShowbPrecWith :: (Generic1 f, GShow1 (Rep1 f)) => (Int -> a -> Builder) -> Int -> f a -> Builder

A Generic1 implementation of showbPrecWith.

Since: 1

genericShowbPrec1 :: (Generic a, Generic1 f, GShow (Rep a), GShow1 (Rep1 f)) => Int -> f a -> Builder

A 'Generic'/'Generic1' implementation of showbPrec1.

Since: 1

The GShow and GShow1 classes

class GShow f where

Class of generic representation types (Rep) that can be converted to a Builder.

Since: 0.6

Minimal complete definition

gShowbPrec

Methods

gShowbPrec :: ConType -> Int -> f a -> Builder

This is used as the default generic implementation of showbPrec.

isNullary :: f a -> Bool

Whether a representation type has any constructors.

Instances

GShow * U1

Show c => GShow * (K1 i c)

(GShow * f, GShow * g) => GShow * ((:+:) f g)

(GShow * f, GShow * g) => GShow * ((:*:) f g)

GShow * f => GShow * (D1 d f)

(Constructor c, GShow * f) => GShow * (C1 c f)

(Selector s, GShow * f) => GShow * (S1 s f)

Typeable ((k -> *) -> Constraint) (GShow k)

class GShow1 f where

Class of generic representation types (Rep1) that can be converted to a Builder by lifting through a unary type constructor.

Since: 1

Minimal complete definition

gShowbPrecWith

Methods

gShowbPrecWith :: ConType -> (Int -> a -> Builder) -> Int -> f a -> Builder

This is used as the default generic implementation of showbPrecWith.

isNullary1 :: f a -> Bool

Whether a representation type has any constructors.

Instances

GShow1 U1

GShow1 Par1

Show1 f => GShow1 (Rec1 f)

Show c => GShow1 (K1 i c)

(GShow1 f, GShow1 g) => GShow1 ((:+:) f g)

(GShow1 f, GShow1 g) => GShow1 ((:*:) f g)

(Show1 f, GShow1 g) => GShow1 ((:.:) f g)

GShow1 f => GShow1 (D1 d f)

(Constructor c, GShow1 f) => GShow1 (C1 c f)

(Selector s, GShow1 f) => GShow1 (S1 s f)

Typeable ((* -> *) -> Constraint) GShow1

data ConType

Whether a constructor is a record (Rec), a tuple (Tup), is prefix (Pref), or infix (Inf).

Since: 0.6

Constructors

Rec

Tup

Pref

Inf String

Instances

Eq ConType

Ord ConType

Read ConType

Show ConType

Generic ConType

Show ConType

Typeable * ConType

type Rep ConType