Data.Tuple

Copyright	(c) The University of Glasgow 2001
License	BSD-style (see the file libraries/base/LICENSE)
Maintainer	libraries@haskell.org
Stability	stable
Portability	portable
Safe Haskell	Safe
Language	Haskell2010

Description

Functions associated with the tuple data types.

data Solo a Source

Solo is the canonical lifted 1-tuple, just like (,) is the canonical lifted 2-tuple (pair) and (,,) is the canonical lifted 3-tuple (triple).

The most important feature of Solo is that it is possible to force its "outside" (usually by pattern matching) without forcing its "inside", because it is defined as a datatype rather than a newtype. One situation where this can be useful is when writing a function to extract a value from a data structure. Suppose you write an implementation of arrays and offer only this function to index into them:

index :: Array a -> Int -> a

Now imagine that someone wants to extract a value from an array and store it in a lazy-valued finite map/dictionary:

insert "hello" (arr index 12) m

This can actually lead to a space leak. The value is not actually extracted from the array until that value (now buried in a map) is forced. That means the entire array may be kept live by just that value! Often, the solution is to use a strict map, or to force the value before storing it, but for some purposes that's undesirable.

One common solution is to include an indexing function that can produce its result in an arbitrary Applicative context:

indexA :: Applicative f => Array a -> Int -> f a

When using indexA in a pure context, Solo serves as a handy Applicative functor to hold the result. You could write a non-leaky version of the above example thus:

case arr indexA 12 of
  Solo a -> insert "hello" a m

While such simple extraction functions are the most common uses for unary tuples, they can also be useful for fine-grained control of strict-spined data structure traversals, and for unifying the implementations of lazy and strict mapping functions.

Constructors

MkSolo a

Bundled Patterns

pattern Solo :: a -> Solo a

Deprecated: The Solo constructor has been renamed to MkSolo to avoid punning.

Instances

Instances details

Foldable1 Solo Source

Since: base-4.18.0.0

Instance details

Defined in Data.Foldable1

Methods

fold1 :: Semigroup m => Solo m -> m Source

foldMap1 :: Semigroup m => (a -> m) -> Solo a -> m Source

foldMap1' :: Semigroup m => (a -> m) -> Solo a -> m Source

toNonEmpty :: Solo a -> NonEmpty a Source

maximum :: Ord a => Solo a -> a Source

minimum :: Ord a => Solo a -> a Source

head :: Solo a -> a Source

last :: Solo a -> a Source

foldrMap1 :: (a -> b) -> (a -> b -> b) -> Solo a -> b Source

foldlMap1' :: (a -> b) -> (b -> a -> b) -> Solo a -> b Source

foldlMap1 :: (a -> b) -> (b -> a -> b) -> Solo a -> b Source

foldrMap1' :: (a -> b) -> (a -> b -> b) -> Solo a -> b Source

Eq1 Solo Source

Since: base-4.15

Instance details

Defined in Data.Functor.Classes

Methods

liftEq :: (a -> b -> Bool) -> Solo a -> Solo b -> Bool Source

Ord1 Solo Source

Since: base-4.15

Instance details

Defined in Data.Functor.Classes

Methods

liftCompare :: (a -> b -> Ordering) -> Solo a -> Solo b -> Ordering Source

Read1 Solo Source

Since: base-4.15

Instance details

Defined in Data.Functor.Classes

Methods

liftReadsPrec :: (Int -> ReadS a) -> ReadS [a] -> Int -> ReadS (Solo a) Source

liftReadList :: (Int -> ReadS a) -> ReadS [a] -> ReadS [Solo a] Source

liftReadPrec :: ReadPrec a -> ReadPrec [a] -> ReadPrec (Solo a) Source

liftReadListPrec :: ReadPrec a -> ReadPrec [a] -> ReadPrec [Solo a] Source

Show1 Solo Source

Since: base-4.15

Instance details

Defined in Data.Functor.Classes

Methods

liftShowsPrec :: (Int -> a -> ShowS) -> ([a] -> ShowS) -> Int -> Solo a -> ShowS Source

liftShowList :: (Int -> a -> ShowS) -> ([a] -> ShowS) -> [Solo a] -> ShowS Source

Applicative Solo Source

Since: base-4.15

Instance details

Defined in GHC.Internal.Base

Methods

pure :: a -> Solo a Source

(<*>) :: Solo (a -> b) -> Solo a -> Solo b Source

liftA2 :: (a -> b -> c) -> Solo a -> Solo b -> Solo c Source

(*>) :: Solo a -> Solo b -> Solo b Source

(<*) :: Solo a -> Solo b -> Solo a Source

Functor Solo Source

Since: base-4.15

Instance details

Defined in GHC.Internal.Base

Methods

fmap :: (a -> b) -> Solo a -> Solo b Source

(<$) :: a -> Solo b -> Solo a Source

Monad Solo Source

Since: base-4.15

Instance details

Defined in GHC.Internal.Base

Methods

(>>=) :: Solo a -> (a -> Solo b) -> Solo b Source

(>>) :: Solo a -> Solo b -> Solo b Source

return :: a -> Solo a Source

MonadFix Solo Source

Since: base-4.15

Instance details

Defined in GHC.Internal.Control.Monad.Fix

Methods

mfix :: (a -> Solo a) -> Solo a Source

MonadZip Solo Source

Since: ghc-internal-4.15.0.0

Instance details

Defined in GHC.Internal.Control.Monad.Zip

Methods

mzip :: Solo a -> Solo b -> Solo (a, b) Source

mzipWith :: (a -> b -> c) -> Solo a -> Solo b -> Solo c Source

munzip :: Solo (a, b) -> (Solo a, Solo b) Source

Foldable Solo Source

Since: base-4.15

Instance details

Defined in GHC.Internal.Data.Foldable

Methods

fold :: Monoid m => Solo m -> m Source

foldMap :: Monoid m => (a -> m) -> Solo a -> m Source

foldMap' :: Monoid m => (a -> m) -> Solo a -> m Source

foldr :: (a -> b -> b) -> b -> Solo a -> b Source

foldr' :: (a -> b -> b) -> b -> Solo a -> b Source

foldl :: (b -> a -> b) -> b -> Solo a -> b Source

foldl' :: (b -> a -> b) -> b -> Solo a -> b Source

foldr1 :: (a -> a -> a) -> Solo a -> a Source

foldl1 :: (a -> a -> a) -> Solo a -> a Source

toList :: Solo a -> [a] Source

null :: Solo a -> Bool Source

length :: Solo a -> Int Source

elem :: Eq a => a -> Solo a -> Bool Source

maximum :: Ord a => Solo a -> a Source

minimum :: Ord a => Solo a -> a Source

sum :: Num a => Solo a -> a Source

product :: Num a => Solo a -> a Source

Traversable Solo Source

Since: base-4.15

Instance details

Defined in GHC.Internal.Data.Traversable

Methods

traverse :: Applicative f => (a -> f b) -> Solo a -> f (Solo b) Source

sequenceA :: Applicative f => Solo (f a) -> f (Solo a) Source

mapM :: Monad m => (a -> m b) -> Solo a -> m (Solo b) Source

sequence :: Monad m => Solo (m a) -> m (Solo a) Source

Generic1 Solo Source

Instance details

Defined in GHC.Internal.Generics

Associated Types

type Rep1 Solo	Since: base-4.15
Instance details Defined in GHC.Internal.Generics type Rep1 Solo = D1 ('MetaData "Solo" "GHC.Tuple" "ghc-prim" 'False) (C1 ('MetaCons "MkSolo" 'PrefixI 'False) (S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) Par1))

Methods

from1 :: Solo a -> Rep1 Solo a Source

to1 :: Rep1 Solo a -> Solo a Source

Monoid a => Monoid (Solo a) Source

Since: base-4.15

Instance details

Defined in GHC.Internal.Base

Methods

mempty :: Solo a Source

mappend :: Solo a -> Solo a -> Solo a Source

mconcat :: [Solo a] -> Solo a Source

Semigroup a => Semigroup (Solo a) Source

Since: base-4.15

Instance details

Defined in GHC.Internal.Base

Methods

(<>) :: Solo a -> Solo a -> Solo a Source

sconcat :: NonEmpty (Solo a) -> Solo a Source

stimes :: Integral b => b -> Solo a -> Solo a Source

Data a => Data (Solo a) Source

Since: base-4.15

Instance details

Defined in GHC.Internal.Data.Data

Methods

gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> Solo a -> c (Solo a) Source

gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (Solo a) Source

toConstr :: Solo a -> Constr Source

dataTypeOf :: Solo a -> DataType Source

dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c (Solo a)) Source

dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c (Solo a)) Source

gmapT :: (forall b. Data b => b -> b) -> Solo a -> Solo a Source

gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Solo a -> r Source

gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Solo a -> r Source

gmapQ :: (forall d. Data d => d -> u) -> Solo a -> [u] Source

gmapQi :: Int -> (forall d. Data d => d -> u) -> Solo a -> u Source

gmapM :: Monad m => (forall d. Data d => d -> m d) -> Solo a -> m (Solo a) Source

gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Solo a -> m (Solo a) Source

gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Solo a -> m (Solo a) Source

Bounded a => Bounded (Solo a) Source

Instance details

Defined in GHC.Internal.Enum

Methods

minBound :: Solo a Source

maxBound :: Solo a Source

Enum a => Enum (Solo a) Source

Instance details

Defined in GHC.Internal.Enum

Methods

succ :: Solo a -> Solo a Source

pred :: Solo a -> Solo a Source

toEnum :: Int -> Solo a Source

fromEnum :: Solo a -> Int Source

enumFrom :: Solo a -> [Solo a] Source

enumFromThen :: Solo a -> Solo a -> [Solo a] Source

enumFromTo :: Solo a -> Solo a -> [Solo a] Source

enumFromThenTo :: Solo a -> Solo a -> Solo a -> [Solo a] Source

Generic (Solo a) Source

Instance details

Defined in GHC.Internal.Generics

Associated Types

type Rep (Solo a)	Since: base-4.15
Instance details Defined in GHC.Internal.Generics type Rep (Solo a) = D1 ('MetaData "Solo" "GHC.Tuple" "ghc-prim" 'False) (C1 ('MetaCons "MkSolo" 'PrefixI 'False) (S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 a)))

Methods

from :: Solo a -> Rep (Solo a) x Source

to :: Rep (Solo a) x -> Solo a Source

Ix a => Ix (Solo a) Source

Instance details

Defined in GHC.Internal.Ix

Methods

range :: (Solo a, Solo a) -> [Solo a] Source

index :: (Solo a, Solo a) -> Solo a -> Int Source

unsafeIndex :: (Solo a, Solo a) -> Solo a -> Int Source

inRange :: (Solo a, Solo a) -> Solo a -> Bool Source

rangeSize :: (Solo a, Solo a) -> Int Source

unsafeRangeSize :: (Solo a, Solo a) -> Int Source

Read a => Read (Solo a) Source

Since: base-4.15

Instance details

Defined in GHC.Internal.Read

Methods

readsPrec :: Int -> ReadS (Solo a) Source

readList :: ReadS [Solo a] Source

readPrec :: ReadPrec (Solo a) Source

readListPrec :: ReadPrec [Solo a] Source

Show a => Show (Solo a) Source

Since: base-4.15

Instance details

Defined in GHC.Internal.Show

Methods

showsPrec :: Int -> Solo a -> ShowS Source

show :: Solo a -> String Source

showList :: [Solo a] -> ShowS Source

Eq a => Eq (Solo a) Source

Instance details

Defined in GHC.Classes

Methods

(==) :: Solo a -> Solo a -> Bool Source

(/=) :: Solo a -> Solo a -> Bool Source

Ord a => Ord (Solo a) Source

Instance details

Defined in GHC.Classes

Methods

compare :: Solo a -> Solo a -> Ordering Source

(<) :: Solo a -> Solo a -> Bool Source

(<=) :: Solo a -> Solo a -> Bool Source

(>) :: Solo a -> Solo a -> Bool Source

(>=) :: Solo a -> Solo a -> Bool Source

max :: Solo a -> Solo a -> Solo a Source

min :: Solo a -> Solo a -> Solo a Source

type Rep1 Solo Source

Since: base-4.15

Instance details

Defined in GHC.Internal.Generics

type Rep1 Solo = D1 ('MetaData "Solo" "GHC.Tuple" "ghc-prim" 'False) (C1 ('MetaCons "MkSolo" 'PrefixI 'False) (S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) Par1))

type Rep (Solo a) Source

Since: base-4.15

Instance details

Defined in GHC.Internal.Generics

type Rep (Solo a) = D1 ('MetaData "Solo" "GHC.Tuple" "ghc-prim" 'False) (C1 ('MetaCons "MkSolo" 'PrefixI 'False) (S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 a)))

getSolo :: Solo a -> a Source

Extract the value from a Solo. Very often, values should be extracted directly using pattern matching, to control just what gets evaluated when. getSolo is for convenience in situations where that is not the case:

When the result is passed to a strict function, it makes no difference whether the pattern matching is done on the "outside" or on the "inside":

Data.Set.insert (getSolo sol) set === case sol of Solo v -> Data.Set.insert v set

A traversal may be performed in Solo in order to control evaluation internally, while using getSolo to extract the final result. A strict mapping function, for example, could be defined

map' :: Traversable t => (a -> b) -> t a -> t b
map' f = getSolo . traverse ((Solo $!) . f)

fst :: (a, b) -> a Source

Extract the first component of a pair.

snd :: (a, b) -> b Source

Extract the second component of a pair.

curry :: ((a, b) -> c) -> a -> b -> c Source

Convert an uncurried function to a curried function.

Examples

Expand

>>> curry fst 1 2
1

uncurry :: (a -> b -> c) -> (a, b) -> c Source

uncurry converts a curried function to a function on pairs.

Examples

Expand

>>> uncurry (+) (1,2)
3

>>> uncurry ($) (show, 1)
"1"

>>> map (uncurry max) [(1,2), (3,4), (6,8)]
[2,4,8]

swap :: (a, b) -> (b, a) Source

Swap the components of a pair.

© The University of Glasgow and others
Licensed under a BSD-style license (see top of the page).
https://downloads.haskell.org/~ghc/9.12.1/docs/libraries/base-4.21.0.0-8e62/Data-Tuple.html