instance (Eq1 f) => Eq1 (T f) where ...
instance (Ord1 f) => Ord1 (T f) where ...
instance (Read1 f) => Read1 (T f) where ...
instance (Show1 f) => Show1 (T f) where ...

instance (Eq1 f, Eq a) => Eq (T f a) where (==) = eq1
instance (Ord1 f, Ord a) => Ord (T f a) where compare = compare1
instance (Read1 f, Read a) => Read (T f a) where
  readPrec     = readPrec1
  readListPrec = readListPrecDefault
instance (Show1 f, Show a) => Show (T f a) where showsPrec = showsPrec1

Liftings of Prelude classes

For unary constructors

class Eq1 f where Source

Lifting of the Eq class to unary type constructors.

Since: 4.9.0.0

eq1 :: (Eq1 f, Eq a) => f a -> f a -> Bool Source

Lift the standard (==) function through the type constructor.

Since: 4.9.0.0

class Eq1 f => Ord1 f where Source

Lifting of the Ord class to unary type constructors.

Since: 4.9.0.0

compare1 :: (Ord1 f, Ord a) => f a -> f a -> Ordering Source

Lift the standard compare function through the type constructor.

Since: 4.9.0.0

class Read1 f where Source

Lifting of the Read class to unary type constructors.

Both liftReadsPrec and liftReadPrec exist to match the interface provided in the Read type class, but it is recommended to implement Read1 instances using liftReadPrec as opposed to liftReadsPrec, since the former is more efficient than the latter. For example:

instance Read1 T where
  liftReadPrec     = ...
  liftReadListPrec = liftReadListPrecDefault

For more information, refer to the documentation for the Read class.

Since: 4.9.0.0

readsPrec1 :: (Read1 f, Read a) => Int -> ReadS (f a) Source

Lift the standard readsPrec and readList functions through the type constructor.

Since: 4.9.0.0

readPrec1 :: (Read1 f, Read a) => ReadPrec (f a) Source

Lift the standard readPrec and readListPrec functions through the type constructor.

Since: 4.10.0.0

liftReadListDefault :: Read1 f => (Int -> ReadS a) -> ReadS [a] -> ReadS [f a] Source

A possible replacement definition for the liftReadList method. This is only needed for Read1 instances where liftReadListPrec isn't defined as liftReadListPrecDefault.

Since: 4.10.0.0

liftReadListPrecDefault :: Read1 f => ReadPrec a -> ReadPrec [a] -> ReadPrec [f a] Source

A possible replacement definition for the liftReadListPrec method, defined using liftReadPrec.

Since: 4.10.0.0

class Show1 f where Source

Lifting of the Show class to unary type constructors.

Since: 4.9.0.0

showsPrec1 :: (Show1 f, Show a) => Int -> f a -> ShowS Source

Lift the standard showsPrec and showList functions through the type constructor.

Since: 4.9.0.0

For binary constructors

class Eq2 f where Source

Lifting of the Eq class to binary type constructors.

Since: 4.9.0.0

eq2 :: (Eq2 f, Eq a, Eq b) => f a b -> f a b -> Bool Source

Lift the standard (==) function through the type constructor.

Since: 4.9.0.0

class Eq2 f => Ord2 f where Source

Lifting of the Ord class to binary type constructors.

Since: 4.9.0.0

compare2 :: (Ord2 f, Ord a, Ord b) => f a b -> f a b -> Ordering Source

Lift the standard compare function through the type constructor.

Since: 4.9.0.0

class Read2 f where Source

Lifting of the Read class to binary type constructors.

Both liftReadsPrec2 and liftReadPrec2 exist to match the interface provided in the Read type class, but it is recommended to implement Read2 instances using liftReadPrec2 as opposed to liftReadsPrec2, since the former is more efficient than the latter. For example:

instance Read2 T where
  liftReadPrec2     = ...
  liftReadListPrec2 = liftReadListPrec2Default

For more information, refer to the documentation for the Read class. @since 4.9.0.0

readsPrec2 :: (Read2 f, Read a, Read b) => Int -> ReadS (f a b) Source

Lift the standard readsPrec function through the type constructor.

Since: 4.9.0.0

readPrec2 :: (Read2 f, Read a, Read b) => ReadPrec (f a b) Source

Lift the standard readPrec function through the type constructor.

Since: 4.10.0.0

liftReadList2Default :: Read2 f => (Int -> ReadS a) -> ReadS [a] -> (Int -> ReadS b) -> ReadS [b] -> ReadS [f a b] Source

A possible replacement definition for the liftReadList2 method. This is only needed for Read2 instances where liftReadListPrec2 isn't defined as liftReadListPrec2Default.

Since: 4.10.0.0

liftReadListPrec2Default :: Read2 f => ReadPrec a -> ReadPrec [a] -> ReadPrec b -> ReadPrec [b] -> ReadPrec [f a b] Source

A possible replacement definition for the liftReadListPrec2 method, defined using liftReadPrec2.

Since: 4.10.0.0

class Show2 f where Source

Lifting of the Show class to binary type constructors.

Since: 4.9.0.0

showsPrec2 :: (Show2 f, Show a, Show b) => Int -> f a b -> ShowS Source

Lift the standard showsPrec function through the type constructor.

Since: 4.9.0.0

Helper functions

These functions can be used to assemble Read and Show instances for new algebraic types. For example, given the definition

data T f a = Zero a | One (f a) | Two a (f a)

a standard Read1 instance may be defined as

instance (Read1 f) => Read1 (T f) where
    liftReadPrec rp rl = readData $
        readUnaryWith rp "Zero" Zero <|>
        readUnaryWith (liftReadPrec rp rl) "One" One <|>
        readBinaryWith rp (liftReadPrec rp rl) "Two" Two
    liftReadListPrec = liftReadListPrecDefault

and the corresponding Show1 instance as

instance (Show1 f) => Show1 (T f) where
    liftShowsPrec sp _ d (Zero x) =
        showsUnaryWith sp "Zero" d x
    liftShowsPrec sp sl d (One x) =
        showsUnaryWith (liftShowsPrec sp sl) "One" d x
    liftShowsPrec sp sl d (Two x y) =
        showsBinaryWith sp (liftShowsPrec sp sl) "Two" d x y

readsData :: (String -> ReadS a) -> Int -> ReadS a Source

readsData p d is a parser for datatypes where each alternative begins with a data constructor. It parses the constructor and passes it to p. Parsers for various constructors can be constructed with readsUnary, readsUnary1 and readsBinary1, and combined with mappend from the Monoid class.

Since: 4.9.0.0

readData :: ReadPrec a -> ReadPrec a Source

readData p is a parser for datatypes where each alternative begins with a data constructor. It parses the constructor and passes it to p. Parsers for various constructors can be constructed with readUnaryWith and readBinaryWith, and combined with '(|)' from the Alternative class.

Since: 4.10.0.0

readsUnaryWith :: (Int -> ReadS a) -> String -> (a -> t) -> String -> ReadS t Source

readsUnaryWith rp n c n' matches the name of a unary data constructor and then parses its argument using rp.

Since: 4.9.0.0

readUnaryWith :: ReadPrec a -> String -> (a -> t) -> ReadPrec t Source

readUnaryWith rp n c' matches the name of a unary data constructor and then parses its argument using rp.

Since: 4.10.0.0

readsBinaryWith :: (Int -> ReadS a) -> (Int -> ReadS b) -> String -> (a -> b -> t) -> String -> ReadS t Source

readsBinaryWith rp1 rp2 n c n' matches the name of a binary data constructor and then parses its arguments using rp1 and rp2 respectively.

Since: 4.9.0.0

readBinaryWith :: ReadPrec a -> ReadPrec b -> String -> (a -> b -> t) -> ReadPrec t Source

readBinaryWith rp1 rp2 n c' matches the name of a binary data constructor and then parses its arguments using rp1 and rp2 respectively.

Since: 4.10.0.0

showsUnaryWith :: (Int -> a -> ShowS) -> String -> Int -> a -> ShowS Source

showsUnaryWith sp n d x produces the string representation of a unary data constructor with name n and argument x, in precedence context d.

Since: 4.9.0.0

showsBinaryWith :: (Int -> a -> ShowS) -> (Int -> b -> ShowS) -> String -> Int -> a -> b -> ShowS Source

showsBinaryWith sp1 sp2 n d x y produces the string representation of a binary data constructor with name n and arguments x and y, in precedence context d.

Since: 4.9.0.0

Obsolete helpers

readsUnary :: Read a => String -> (a -> t) -> String -> ReadS t Source

readsUnary n c n' matches the name of a unary data constructor and then parses its argument using readsPrec.

Since: 4.9.0.0

readsUnary1 :: (Read1 f, Read a) => String -> (f a -> t) -> String -> ReadS t Source

readsUnary1 n c n' matches the name of a unary data constructor and then parses its argument using readsPrec1.

Since: 4.9.0.0

readsBinary1 :: (Read1 f, Read1 g, Read a) => String -> (f a -> g a -> t) -> String -> ReadS t Source

readsBinary1 n c n' matches the name of a binary data constructor and then parses its arguments using readsPrec1.

Since: 4.9.0.0

showsUnary :: Show a => String -> Int -> a -> ShowS Source

showsUnary n d x produces the string representation of a unary data constructor with name n and argument x, in precedence context d.

Since: 4.9.0.0

showsUnary1 :: (Show1 f, Show a) => String -> Int -> f a -> ShowS Source

showsUnary1 n d x produces the string representation of a unary data constructor with name n and argument x, in precedence context d.

Since: 4.9.0.0

showsBinary1 :: (Show1 f, Show1 g, Show a) => String -> Int -> f a -> g a -> ShowS Source

showsBinary1 n d x y produces the string representation of a binary data constructor with name n and arguments x and y, in precedence context d.

Since: 4.9.0.0