Copyright | (C) 2014-2015 Ryan Scott |
---|---|
License | BSD-style (see the file LICENSE) |
Maintainer | Ryan Scott |
Stability | Provisional |
Portability | GHC |
Safe Haskell | None |
Language | Haskell2010 |
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
- genericShow :: (Generic a, GShow (Rep a)) => a -> Text
- genericShowLazy :: (Generic a, GShow (Rep a)) => a -> Text
- genericShowPrec :: (Generic a, GShow (Rep a)) => Int -> a -> Text
- genericShowPrecLazy :: (Generic a, GShow (Rep a)) => Int -> a -> Text
- genericShowList :: (Generic a, GShow (Rep a)) => [a] -> Text
- genericShowListLazy :: (Generic a, GShow (Rep a)) => [a] -> Text
- genericShowb :: (Generic a, GShow (Rep a)) => a -> Builder
- genericShowbPrec :: (Generic a, GShow (Rep a)) => Int -> a -> Builder
- genericShowbList :: (Generic a, GShow (Rep a)) => [a] -> Builder
- genericPrint :: (Generic a, GShow (Rep a)) => a -> IO ()
- genericPrintLazy :: (Generic a, GShow (Rep a)) => a -> IO ()
- genericHPrint :: (Generic a, GShow (Rep a)) => Handle -> a -> IO ()
- genericHPrintLazy :: (Generic a, GShow (Rep a)) => Handle -> a -> IO ()
- genericShowbPrecWith :: (Generic1 f, GShow1 (Rep1 f)) => (Int -> a -> Builder) -> Int -> f a -> Builder
- genericShowbPrec1 :: (Generic a, Generic1 f, GShow (Rep a), GShow1 (Rep1 f)) => Int -> f a -> Builder
- class GShow f where
- class GShow1 f where
- gShowbPrecWith :: ConType -> (Int -> a -> Builder) -> Int -> f a -> Builder
- isNullary1 :: f a -> Bool
- data ConType
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
clause to your data type, at
compile-time, you will get an error message that begins roughly as follows:Generic
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
" clause.Generic
Similarly, if the compiler complains about not having an instance for (
, add a "GShow1
(Rep1 Oops2))deriving
" clause.Generic1
genericShowPrecLazy :: (Generic a, GShow (Rep a)) => Int -> a -> Text Source
A Generic
implementation of showPrecLazy
.
Since: 0.6
genericShowListLazy :: (Generic a, GShow (Rep a)) => [a] -> Text Source
A Generic
implementation of showListLazy
.
Since: 0.6
genericHPrintLazy :: (Generic a, GShow (Rep a)) => Handle -> a -> IO () Source
A Generic
implementation of hPrintLazy
.
Since: 0.6
genericShowbPrecWith :: (Generic1 f, GShow1 (Rep1 f)) => (Int -> a -> Builder) -> Int -> f a -> Builder Source
A Generic1
implementation of showbPrecWith
.
Since: 1
genericShowbPrec1 :: (Generic a, Generic1 f, GShow (Rep a), GShow1 (Rep1 f)) => Int -> f a -> Builder Source
A 'Generic'/'Generic1' implementation of showbPrec1
.
Since: 1
The GShow
and GShow1
classes
Class of generic representation types (Rep1
) that can be converted to
a Builder
by lifting through a unary type constructor.
Since: 1
gShowbPrecWith :: ConType -> (Int -> a -> Builder) -> Int -> f a -> Builder Source
This is used as the default generic implementation of showbPrecWith
.
isNullary1 :: f a -> Bool Source
Whether a representation type has any constructors.
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 |