Text.Show.Text.Generic

Generic versions of Show class functions, as an alternative to Text.Show.Text.TH, which uses Template Haskell. This module is only available if the compiler supports generics (on GHC, 7.2 or above).

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 Text.Show.Text
import Text.Show.Generic (genericShowbPrec)

data D a = Nullary
         | Unary Int
         | Product String Char a
         | Record { testOne   :: Double
                  , testTwo   :: Bool
                  , testThree :: D a
                  }

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

D now has a Show instance analogous to what would be generated by a deriving Show clause.

Understanding a compiler error

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

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

instance Show 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 (GShow (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.

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

Converts a Generic instance to a strict Text.

Since: 0.6

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

Converts a Generic instance to a lazy Text.

Since: 0.6

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

Converts a Generic instance to a strict Text with the given precedence.

Since: 0.6

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

Converts a Generic instance to a lazy Text with the given precedence.

Since: 0.6

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

Converts a list of Generic instances to a strict Text.

Since: 0.6

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

Converts a list of Generic instances to a lazy Text.

Since: 0.6

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

Converts a Generic instance to a Builder with the given precedence.

Since: 0.6

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

Converts a Generic instance to a Builder with the given precedence.

Since: 0.6

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

Converts a list of Generic instances to a Builder.

Since: 0.6

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

Writes a Generic instance's strict Text representation to the standard output, followed by a newline.

Since: 0.6

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

Writes a Generic instance's lazy Text representation to the standard output, followed by a newline.

Since: 0.6

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

Writes a Generic instance's strict Text representation to the given file handle, followed by a newline.

Since: 0.6

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

Writes a Generic instance's lazy Text representation to the given file handle, followed by a newline.

Since: 0.6

The GShow class

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

isNullary :: f a -> Bool

Instances

GShow U1

Show c => GShow (K1 i c)

(GShow a, GShow b) => GShow ((:+:) a b)

(GShow a, GShow b) => GShow ((:*:) a b)

GShow a => GShow (M1 D d a)

(Constructor c, GShow a) => GShow (M1 C c a)

(Selector s, GShow a) => GShow (M1 S s a)

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 Builder

Instances

Eq ConType

Ord ConType

Show ConType

Generic ConType

Show ConType

type Rep ConType