TextShow.Generic

Generic versions of TextShow and TextShow1 class functions, as an alternative to TextShow.TH, which uses Template Haskell. Because there is no Generic2 class, TextShow2 cannot be implemented generically.

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

Since: 2

Generic show functions

TextShow 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 TextShow
import TextShow.Generic

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

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

instance TextShow1 D where
    showbPrecWith = genericShowbPrecWith

Understanding a compiler error

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

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

instance TextShow Oops 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 (GTextShow (Rep Oops))

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 (GTextShow1 (Rep1 Oops1)), add a "deriving Generic1" clause.

genericShowt :: (Generic a, GTextShow (Rep a)) => a -> Text

A Generic implementation of showt.

Since: 2

genericShowtl :: (Generic a, GTextShow (Rep a)) => a -> Text

A Generic implementation of showtl.

Since: 2

genericShowtPrec :: (Generic a, GTextShow (Rep a)) => Int -> a -> Text

A Generic implementation of showPrect.

Since: 2

genericShowtlPrec :: (Generic a, GTextShow (Rep a)) => Int -> a -> Text

A Generic implementation of showtlPrec.

Since: 2

genericShowtList :: (Generic a, GTextShow (Rep a)) => [a] -> Text

A Generic implementation of showtList.

Since: 2

genericShowtlList :: (Generic a, GTextShow (Rep a)) => [a] -> Text

A Generic implementation of showtlList.

Since: 2

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

A Generic implementation of showb.

Since: 2

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

A Generic implementation of showbPrec.

Since: 2

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

A Generic implementation of showbList.

Since: 2

genericPrintT :: (Generic a, GTextShow (Rep a)) => a -> IO ()

A Generic implementation of printT.

Since: 2

genericPrintTL :: (Generic a, GTextShow (Rep a)) => a -> IO ()

A Generic implementation of printTL.

Since: 2

genericHPrintT :: (Generic a, GTextShow (Rep a)) => Handle -> a -> IO ()

A Generic implementation of hPrintT.

Since: 2

genericHPrintTL :: (Generic a, GTextShow (Rep a)) => Handle -> a -> IO ()

A Generic implementation of hPrintTL.

Since: 2

genericShowbPrecWith :: (Generic1 f, GTextShow1 (Rep1 f)) => (Int -> a -> Builder) -> Int -> f a -> Builder

A Generic1 implementation of showbPrecWith.

Since: 2

genericShowbPrec1 :: (Generic a, Generic1 f, GTextShow (Rep a), GTextShow1 (Rep1 f)) => Int -> f a -> Builder

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

Since: 2

The GTextShow and GTextShow1 classes

class GTextShow f where

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

Since: 2

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

GTextShow * U1

TextShow c => GTextShow * (K1 i c)

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

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

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

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

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

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

class GTextShow1 f where

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

Since: 2

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

GTextShow1 U1

GTextShow1 Par1

TextShow1 f => GTextShow1 (Rec1 f)

TextShow c => GTextShow1 (K1 i c)

(GTextShow1 f, GTextShow1 g) => GTextShow1 ((:+:) f g)

(GTextShow1 f, GTextShow1 g) => GTextShow1 ((:*:) f g)

(TextShow1 f, GTextShow1 g) => GTextShow1 ((:.:) f g)

GTextShow1 f => GTextShow1 (D1 d f)

(Constructor c, GTextShow1 f) => GTextShow1 (C1 c f)

(Selector s, GTextShow1 f) => GTextShow1 (S1 s f)

Typeable ((* -> *) -> Constraint) GTextShow1

data ConType

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

Since: 2

Constructors

Rec

Tup

Pref

Inf String

Instances

Eq ConType

Ord ConType

Read ConType

Show ConType

Generic ConType

TextShow ConType

Typeable * ConType

type Rep ConType