Data.Tuple.Compat.Repl

base-compat-0.14.1: A compatibility layer for base

Safe Haskell | Safe-Inferred
Language | Haskell2010

Data.Tuple.Compat.Repl

Description

Reexports Data.Tuple.Compat from a globally unique namespace.

Synopsis

- data Solo a where
  - pattern Solo :: a -> Solo a
- getSolo :: Solo a -> a
- fst :: (a, b) -> a
- snd :: (a, b) -> b
- curry :: ((a, b) -> c) -> a -> b -> c
- uncurry :: (a -> b -> c) -> (a, b) -> c
- swap :: (a, b) -> (b, a)

# Documentation

data Solo a where #

`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.

Bundled Patterns

pattern Solo :: a -> Solo a |

#### Instances

Instances details

MonadZip Solo | Since: base-4.15.0.0
Instance details Defined in Control.Monad.Zip Methods mzip :: Solo a -> Solo b -> Solo (a, b) # mzipWith :: (a -> b -> c) -> Solo a -> Solo b -> Solo c # munzip :: Solo (a, b) -> (Solo a, Solo b) #
Foldable1 Solo | Since: base-4.18.0.0
Instance details Defined in Data.Foldable1 Methods fold1 :: Semigroup m => Solo m -> m # foldMap1 :: Semigroup m => (a -> m) -> Solo a -> m # foldMap1' :: Semigroup m => (a -> m) -> Solo a -> m # toNonEmpty :: Solo a -> NonEmpty a # maximum :: Ord a => Solo a -> a # minimum :: Ord a => Solo a -> a # head :: Solo a -> a # last :: Solo a -> a # foldrMap1 :: (a -> b) -> (a -> b -> b) -> Solo a -> b # foldlMap1' :: (a -> b) -> (b -> a -> b) -> Solo a -> b # foldlMap1 :: (a -> b) -> (b -> a -> b) -> Solo a -> b # foldrMap1' :: (a -> b) -> (a -> b -> b) -> Solo a -> b #
Eq1 Solo | Since: base-4.15
Instance details Defined in Data.Functor.Classes Methods liftEq :: (a -> b -> Bool) -> Solo a -> Solo b -> Bool #
Ord1 Solo | Since: base-4.15
Instance details Defined in Data.Functor.Classes Methods liftCompare :: (a -> b -> Ordering) -> Solo a -> Solo b -> Ordering #
Read1 Solo | Since: base-4.15
Instance details Defined in Data.Functor.Classes Methods liftReadsPrec :: (Int -> ReadS a) -> ReadS [a] -> Int -> ReadS (Solo a) # liftReadList :: (Int -> ReadS a) -> ReadS [a] -> ReadS [Solo a] # liftReadPrec :: ReadPrec a -> ReadPrec [a] -> ReadPrec (Solo a) # liftReadListPrec :: ReadPrec a -> ReadPrec [a] -> ReadPrec [Solo a] #
Show1 Solo | Since: base-4.15
Instance details Defined in Data.Functor.Classes Methods liftShowsPrec :: (Int -> a -> ShowS) -> ([a] -> ShowS) -> Int -> Solo a -> ShowS # liftShowList :: (Int -> a -> ShowS) -> ([a] -> ShowS) -> [Solo a] -> ShowS #
Applicative Solo | @since base-4.15
Instance details Defined in GHC.Internal.Base Methods pure :: a -> Solo a # (<*>) :: Solo (a -> b) -> Solo a -> Solo b # liftA2 :: (a -> b -> c) -> Solo a -> Solo b -> Solo c # (*>) :: Solo a -> Solo b -> Solo b # (<*) :: Solo a -> Solo b -> Solo a #
Functor Solo | @since base-4.15
Instance details Defined in GHC.Internal.Base Methods fmap :: (a -> b) -> Solo a -> Solo b # (<$) :: a -> Solo b -> Solo a #
Monad Solo | @since base-4.15
Instance details Defined in GHC.Internal.Base Methods (>>=) :: Solo a -> (a -> Solo b) -> Solo b # (>>) :: Solo a -> Solo b -> Solo b # return :: a -> Solo a #
Foldable Solo | @since base-4.15
Instance details Defined in GHC.Internal.Data.Foldable Methods fold :: Monoid m => Solo m -> m # foldMap :: Monoid m => (a -> m) -> Solo a -> m # foldMap' :: Monoid m => (a -> m) -> Solo a -> m # foldr :: (a -> b -> b) -> b -> Solo a -> b # foldr' :: (a -> b -> b) -> b -> Solo a -> b # foldl :: (b -> a -> b) -> b -> Solo a -> b # foldl' :: (b -> a -> b) -> b -> Solo a -> b # foldr1 :: (a -> a -> a) -> Solo a -> a # foldl1 :: (a -> a -> a) -> Solo a -> a # toList :: Solo a -> [a] # null :: Solo a -> Bool # length :: Solo a -> Int # elem :: Eq a => a -> Solo a -> Bool # maximum :: Ord a => Solo a -> a # minimum :: Ord a => Solo a -> a # sum :: Num a => Solo a -> a # product :: Num a => Solo a -> a #
Traversable Solo | @since base-4.15
Instance details Defined in GHC.Internal.Data.Traversable Methods traverse :: Applicative f => (a -> f b) -> Solo a -> f (Solo b) # sequenceA :: Applicative f => Solo (f a) -> f (Solo a) # mapM :: Monad m => (a -> m b) -> Solo a -> m (Solo b) # sequence :: Monad m => Solo (m a) -> m (Solo a) #
Generic1 Solo |
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 # to1 :: Rep1 Solo a -> Solo a #
Monoid a => Monoid (Solo a) | @since base-4.15
Instance details Defined in GHC.Internal.Base Methods mempty :: Solo a # mappend :: Solo a -> Solo a -> Solo a # mconcat :: [Solo a] -> Solo a #
Semigroup a => Semigroup (Solo a) | @since base-4.15
Instance details Defined in GHC.Internal.Base Methods (<>) :: Solo a -> Solo a -> Solo a # sconcat :: NonEmpty (Solo a) -> Solo a # stimes :: Integral b => b -> Solo a -> Solo a #
Bounded a => Bounded (Solo a) |
Instance details Defined in GHC.Internal.Enum Methods minBound :: Solo a # maxBound :: Solo a #
Enum a => Enum (Solo a) |
Instance details Defined in GHC.Internal.Enum Methods succ :: Solo a -> Solo a # pred :: Solo a -> Solo a # toEnum :: Int -> Solo a # fromEnum :: Solo a -> Int # enumFrom :: Solo a -> [Solo a] # enumFromThen :: Solo a -> Solo a -> [Solo a] # enumFromTo :: Solo a -> Solo a -> [Solo a] # enumFromThenTo :: Solo a -> Solo a -> Solo a -> [Solo a] #
Generic (Solo a) |
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 # to :: Rep (Solo a) x -> Solo a #
Read a => Read (Solo a) | @since base-4.15
Instance details Defined in GHC.Internal.Read Methods readsPrec :: Int -> ReadS (Solo a) # readList :: ReadS [Solo a] # readPrec :: ReadPrec (Solo a) # readListPrec :: ReadPrec [Solo a] #
Show a => Show (Solo a) | @since base-4.15
Instance details Defined in GHC.Internal.Show Methods showsPrec :: Int -> Solo a -> ShowS # show :: Solo a -> String # showList :: [Solo a] -> ShowS #
Eq a => Eq (Solo a) |
Instance details Defined in GHC.Classes Methods (==) :: Solo a -> Solo a -> Bool # (/=) :: Solo a -> Solo a -> Bool #
Ord a => Ord (Solo a) |
Instance details Defined in GHC.Classes Methods compare :: Solo a -> Solo a -> Ordering # (<) :: Solo a -> Solo a -> Bool # (<=) :: Solo a -> Solo a -> Bool # (>) :: Solo a -> Solo a -> Bool # (>=) :: Solo a -> Solo a -> Bool # max :: Solo a -> Solo a -> Solo a # min :: Solo a -> Solo a -> Solo a #
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))
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)))

getSolo :: Solo a -> a #

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 #

Extract the first component of a pair.

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

Extract the second component of a pair.

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

Convert an uncurried function to a curried function.

#### Examples

Expand

    >>> curry fst 1 2
    1

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

`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) #

Swap the components of a pair.