Safe Haskell	Safe-Inferred
Language	GHC2021

Label

Contents

Labels
Named Tuples
Named Sums/Enums

Synopsis

data Label (label :: Symbol) value
label :: forall label value. value -> Label label value
label' :: forall label value. Proxy label -> value -> Label label value
getLabel :: forall label record a. HasField label record a => record -> Label label a
mapLabel :: forall label a b. (a -> b) -> Label label a -> Label label b
traverseLabel :: forall label f a b. Functor f => (a -> f b) -> Label label a -> f (Label label b)
data T2 (l1 :: Symbol) t1 (l2 :: Symbol) t2 = T2 (Label l1 t1) (Label l2 t2)
focusOnField :: forall field rec subrec t. HasField field subrec t => (rec -> subrec) -> rec -> T2 field t "dat" rec
monoMapT2 :: (t -> t') -> T2 l1 t l2 t -> T2 l1 t' l2 t'
tupleToT2 :: forall l1 l2 t1 t2. (t1, t2) -> T2 l1 t1 l2 t2
data T3 (l1 :: Symbol) t1 (l2 :: Symbol) t2 (l3 :: Symbol) t3 = T3 (Label l1 t1) (Label l2 t2) (Label l3 t3)
monoMapT3 :: (t -> t') -> T3 l1 t l2 t l3 t -> T3 l1 t' l2 t' l3 t'
tupleToT3 :: forall l1 l2 l3 t1 t2 t3. (t1, t2, t3) -> T3 l1 t1 l2 t2 l3 t3
data E2 (l1 :: Symbol) t1 (l2 :: Symbol) t2
- = E21 (Label l1 t1)
- | E22 (Label l2 t2)
mapE2 :: forall l1 t1 t1' l2 t2 t2'. (Label l1 t1 -> t1') -> (Label l2 t2 -> t2') -> E2 l1 t1 l2 t2 -> E2 l1 t1' l2 t2'
monoMapE2 :: (t -> t') -> E2 l1 t l2 t -> E2 l1 t' l2 t'
monoFoldE2 :: E2 l1 t l2 t -> t
monoTraverseE2 :: Functor f => (t -> f t') -> E2 l1 t l2 t -> f (E2 l1 t' l2 t')
partitionE2 :: forall l1 t1 l2 t2. [E2 l1 t1 l2 t2] -> T2 l1 [t1] l2 [t2]
isE21 :: forall l1 t1 l2 t2. E2 l1 t1 l2 t2 -> Bool
isE22 :: forall l2 t2 l1 t1. E2 l1 t1 l2 t2 -> Bool
getE21 :: forall l1 t1 l2 t2. E2 l1 t1 l2 t2 -> Maybe t1
getE22 :: forall l2 t2 l1 t1. E2 l1 t1 l2 t2 -> Maybe t2
data E3 (l1 :: Symbol) t1 (l2 :: Symbol) t2 (l3 :: Symbol) t3
- = E31 (Label l1 t1)
- | E32 (Label l2 t2)
- | E33 (Label l3 t3)
mapE3 :: forall l1 t1 t1' l2 t2 t2' l3 t3 t3'. (Label l1 t1 -> t1') -> (Label l2 t2 -> t2') -> (Label l3 t3 -> t3') -> E3 l1 t1 l2 t2 l3 t3 -> E3 l1 t1' l2 t2' l3 t3'

Labels

data Label (label :: Symbol) value Source #

A labelled value.

Use label/label' to construct, then use dot-syntax to get the inner value.

Instances

Instances details

HasField (label :: Symbol) (Label label value) value Source #	Fetches the labelled value.
Instance details Defined in Label Methods getField :: Label label value -> value #
Monoid value => Monoid (Label label value) Source #
Instance details Defined in Label Methods mempty :: Label label value # mappend :: Label label value -> Label label value -> Label label value # mconcat :: [Label label value] -> Label label value #
Semigroup value => Semigroup (Label label value) Source #
Instance details Defined in Label Methods (<>) :: Label label value -> Label label value -> Label label value # sconcat :: NonEmpty (Label label value) -> Label label value # stimes :: Integral b => b -> Label label value -> Label label value #
(KnownSymbol label, Show value) => Show (Label label value) Source #
Instance details Defined in Label Methods showsPrec :: Int -> Label label value -> ShowS # show :: Label label value -> String # showList :: [Label label value] -> ShowS #
Eq value => Eq (Label label value) Source #
Instance details Defined in Label Methods (==) :: Label label value -> Label label value -> Bool # (/=) :: Label label value -> Label label value -> Bool #
Ord value => Ord (Label label value) Source #
Instance details Defined in Label Methods compare :: Label label value -> Label label value -> Ordering # (<) :: Label label value -> Label label value -> Bool # (<=) :: Label label value -> Label label value -> Bool # (>) :: Label label value -> Label label value -> Bool # (>=) :: Label label value -> Label label value -> Bool # max :: Label label value -> Label label value -> Label label value # min :: Label label value -> Label label value -> Label label value #

label :: forall label value. value -> Label label value Source #

Attach a label to a value; should be used with a type application to name the label.

let f = label @"foo" f :: Label "foo" Char
in f.foo :: Char

Use dot-syntax to get the labelled value.

label' :: forall label value. Proxy label -> value -> Label label value Source #

Attach a label to a value; Pass it a proxy with the label name in the argument type. This is intended for passing through the label value; you can also use label.

let f = label' (Proxy @"foo") f :: Label "foo" Char
in f.foo :: Char

Use dot-syntax to get the labelled value.

getLabel :: forall label record a. HasField label record a => record -> Label label a Source #

Fetch a value from a record, like getField, but also keep it wrapped by its label.

mapLabel :: forall label a b. (a -> b) -> Label label a -> Label label b Source #

fmap over the contents of the labbelled value. Helper.

traverseLabel :: forall label f a b. Functor f => (a -> f b) -> Label label a -> f (Label label b) Source #

traverse over the contents of the labbelled value. Helper.

Named Tuples

data T2 (l1 :: Symbol) t1 (l2 :: Symbol) t2 Source #

A named 2-element tuple. Since the elements are named, you can access them with ..

let t2 = T2 (label "myfield" c) (label "otherfield" True) :: T2 "myfield" Char "otherfield" Bool
in (
  t2.myfield :: Char,
  t2.otherfield :: Bool
)

Constructors

T2 (Label l1 t1) (Label l2 t2)

Instances

Instances details

HasField (l1 :: Symbol) (T2 l1 t1 l2 t2) t1 Source #	Access the first field by label
Instance details Defined in Label Methods getField :: T2 l1 t1 l2 t2 -> t1 #
HasField (l2 :: Symbol) (T2 l1 t1 l2 t2) t2 Source #	Access the second field by label
Instance details Defined in Label Methods getField :: T2 l1 t1 l2 t2 -> t2 #
(Monoid t1, Monoid t2) => Monoid (T2 l1 t1 l2 t2) Source #
Instance details Defined in Label Methods mempty :: T2 l1 t1 l2 t2 # mappend :: T2 l1 t1 l2 t2 -> T2 l1 t1 l2 t2 -> T2 l1 t1 l2 t2 # mconcat :: [T2 l1 t1 l2 t2] -> T2 l1 t1 l2 t2 #
(Semigroup t1, Semigroup t2) => Semigroup (T2 l1 t1 l2 t2) Source #
Instance details Defined in Label Methods (<>) :: T2 l1 t1 l2 t2 -> T2 l1 t1 l2 t2 -> T2 l1 t1 l2 t2 # sconcat :: NonEmpty (T2 l1 t1 l2 t2) -> T2 l1 t1 l2 t2 # stimes :: Integral b => b -> T2 l1 t1 l2 t2 -> T2 l1 t1 l2 t2 #
(KnownSymbol l1, KnownSymbol l2, Show t1, Show t2) => Show (T2 l1 t1 l2 t2) Source #
Instance details Defined in Label Methods showsPrec :: Int -> T2 l1 t1 l2 t2 -> ShowS # show :: T2 l1 t1 l2 t2 -> String # showList :: [T2 l1 t1 l2 t2] -> ShowS #
(Eq t1, Eq t2) => Eq (T2 l1 t1 l2 t2) Source #
Instance details Defined in Label Methods (==) :: T2 l1 t1 l2 t2 -> T2 l1 t1 l2 t2 -> Bool # (/=) :: T2 l1 t1 l2 t2 -> T2 l1 t1 l2 t2 -> Bool #
(Ord t1, Ord t2) => Ord (T2 l1 t1 l2 t2) Source #
Instance details Defined in Label Methods compare :: T2 l1 t1 l2 t2 -> T2 l1 t1 l2 t2 -> Ordering # (<) :: T2 l1 t1 l2 t2 -> T2 l1 t1 l2 t2 -> Bool # (<=) :: T2 l1 t1 l2 t2 -> T2 l1 t1 l2 t2 -> Bool # (>) :: T2 l1 t1 l2 t2 -> T2 l1 t1 l2 t2 -> Bool # (>=) :: T2 l1 t1 l2 t2 -> T2 l1 t1 l2 t2 -> Bool # max :: T2 l1 t1 l2 t2 -> T2 l1 t1 l2 t2 -> T2 l1 t1 l2 t2 # min :: T2 l1 t1 l2 t2 -> T2 l1 t1 l2 t2 -> T2 l1 t1 l2 t2 #

focusOnField :: forall field rec subrec t. HasField field subrec t => (rec -> subrec) -> rec -> T2 field t "dat" rec Source #

Given a record with some field, “focus” on that field by pulling it into the first part of the T2, and put the original record into the second part of the T2.

This can be useful when you have a function that requires something with a field, but the field itself is nested somewhere in the record.

Example:

data Foo = Foo
  { nested :: Label "myId" Text
  }

foo = Foo {nested = "hi"}

fn :: HasField "myId" rec Text => rec -> Text
fn rec = rec.myId <> "!"

x = fn (focusOnField @"myId" (.nested) foo) == "hi!"

Note that you will have to give focusOnField a type annotation of which label to use, otherwise it cannot infer it.

monoMapT2 :: (t -> t') -> T2 l1 t l2 t -> T2 l1 t' l2 t' Source #

Map a function over all fields in the tuple. All fields have to have the same type.

tupleToT2 :: forall l1 l2 t1 t2. (t1, t2) -> T2 l1 t1 l2 t2 Source #

Convert a tuple to a T2 by giving its elements names.

tupleToT2 "left" "right" (c, True) :: T2 "left" Char "right" Bool

data T3 (l1 :: Symbol) t1 (l2 :: Symbol) t2 (l3 :: Symbol) t3 Source #

A named 3-element tuple. Since the elements are named, you can access them with .. See T2 for an example.

Constructors

T3 (Label l1 t1) (Label l2 t2) (Label l3 t3)

Instances

Instances details

HasField (l1 :: Symbol) (T3 l1 t1 l2 t2 l3 t3) t1 Source #	Access the first field by label
Instance details Defined in Label Methods getField :: T3 l1 t1 l2 t2 l3 t3 -> t1 #
HasField (l2 :: Symbol) (T3 l1 t1 l2 t2 l3 t3) t2 Source #	Access the second field by label
Instance details Defined in Label Methods getField :: T3 l1 t1 l2 t2 l3 t3 -> t2 #
HasField (l3 :: Symbol) (T3 l1 t1 l2 t2 l3 t3) t3 Source #	Access the third field by label
Instance details Defined in Label Methods getField :: T3 l1 t1 l2 t2 l3 t3 -> t3 #
(Monoid t1, Monoid t2, Monoid t3) => Monoid (T3 l1 t1 l2 t2 l3 t3) Source #
Instance details Defined in Label Methods mempty :: T3 l1 t1 l2 t2 l3 t3 # mappend :: T3 l1 t1 l2 t2 l3 t3 -> T3 l1 t1 l2 t2 l3 t3 -> T3 l1 t1 l2 t2 l3 t3 # mconcat :: [T3 l1 t1 l2 t2 l3 t3] -> T3 l1 t1 l2 t2 l3 t3 #
(Semigroup t1, Semigroup t2, Semigroup t3) => Semigroup (T3 l1 t1 l2 t2 l3 t3) Source #
Instance details Defined in Label Methods (<>) :: T3 l1 t1 l2 t2 l3 t3 -> T3 l1 t1 l2 t2 l3 t3 -> T3 l1 t1 l2 t2 l3 t3 # sconcat :: NonEmpty (T3 l1 t1 l2 t2 l3 t3) -> T3 l1 t1 l2 t2 l3 t3 # stimes :: Integral b => b -> T3 l1 t1 l2 t2 l3 t3 -> T3 l1 t1 l2 t2 l3 t3 #
(KnownSymbol l1, KnownSymbol l2, KnownSymbol l3, Show t1, Show t2, Show t3) => Show (T3 l1 t1 l2 t2 l3 t3) Source #
Instance details Defined in Label Methods showsPrec :: Int -> T3 l1 t1 l2 t2 l3 t3 -> ShowS # show :: T3 l1 t1 l2 t2 l3 t3 -> String # showList :: [T3 l1 t1 l2 t2 l3 t3] -> ShowS #
(Eq t1, Eq t2, Eq t3) => Eq (T3 l1 t1 l2 t2 l3 t3) Source #
Instance details Defined in Label Methods (==) :: T3 l1 t1 l2 t2 l3 t3 -> T3 l1 t1 l2 t2 l3 t3 -> Bool # (/=) :: T3 l1 t1 l2 t2 l3 t3 -> T3 l1 t1 l2 t2 l3 t3 -> Bool #
(Ord t1, Ord t2, Ord t3) => Ord (T3 l1 t1 l2 t2 l3 t3) Source #
Instance details Defined in Label Methods compare :: T3 l1 t1 l2 t2 l3 t3 -> T3 l1 t1 l2 t2 l3 t3 -> Ordering # (<) :: T3 l1 t1 l2 t2 l3 t3 -> T3 l1 t1 l2 t2 l3 t3 -> Bool # (<=) :: T3 l1 t1 l2 t2 l3 t3 -> T3 l1 t1 l2 t2 l3 t3 -> Bool # (>) :: T3 l1 t1 l2 t2 l3 t3 -> T3 l1 t1 l2 t2 l3 t3 -> Bool # (>=) :: T3 l1 t1 l2 t2 l3 t3 -> T3 l1 t1 l2 t2 l3 t3 -> Bool # max :: T3 l1 t1 l2 t2 l3 t3 -> T3 l1 t1 l2 t2 l3 t3 -> T3 l1 t1 l2 t2 l3 t3 # min :: T3 l1 t1 l2 t2 l3 t3 -> T3 l1 t1 l2 t2 l3 t3 -> T3 l1 t1 l2 t2 l3 t3 #

monoMapT3 :: (t -> t') -> T3 l1 t l2 t l3 t -> T3 l1 t' l2 t' l3 t' Source #

Map a function over all fields in the tuple. All fields have to have the same type.

tupleToT3 :: forall l1 l2 l3 t1 t2 t3. (t1, t2, t3) -> T3 l1 t1 l2 t2 l3 t3 Source #

Convert a tuple to a T3 by giving its elements names.

tupleToT3 "left" "right" "grip" (c, True, Maybe x) :: T3 "left" Char "right" Bool "grip" (Maybe Char)@

Named Sums/Enums

data E2 (l1 :: Symbol) t1 (l2 :: Symbol) t2 Source #

A named 2-alternative sum (“Either with labels”).

Constructors

E21 (Label l1 t1)
E22 (Label l2 t2)

Instances

Instances details

(Bounded t1, Bounded t2) => Bounded (E2 l1 t1 l2 t2) Source #
Instance details Defined in Label Methods minBound :: E2 l1 t1 l2 t2 # maxBound :: E2 l1 t1 l2 t2 #
Enum (E2 l1 () l2 ()) Source #
Instance details Defined in Label Methods succ :: E2 l1 () l2 () -> E2 l1 () l2 () # pred :: E2 l1 () l2 () -> E2 l1 () l2 () # toEnum :: Int -> E2 l1 () l2 () # fromEnum :: E2 l1 () l2 () -> Int # enumFrom :: E2 l1 () l2 () -> [E2 l1 () l2 ()] # enumFromThen :: E2 l1 () l2 () -> E2 l1 () l2 () -> [E2 l1 () l2 ()] # enumFromTo :: E2 l1 () l2 () -> E2 l1 () l2 () -> [E2 l1 () l2 ()] # enumFromThenTo :: E2 l1 () l2 () -> E2 l1 () l2 () -> E2 l1 () l2 () -> [E2 l1 () l2 ()] #
(KnownSymbol l1, KnownSymbol l2, Show t1, Show t2) => Show (E2 l1 t1 l2 t2) Source #
Instance details Defined in Label Methods showsPrec :: Int -> E2 l1 t1 l2 t2 -> ShowS # show :: E2 l1 t1 l2 t2 -> String # showList :: [E2 l1 t1 l2 t2] -> ShowS #
(Eq t1, Eq t2) => Eq (E2 l1 t1 l2 t2) Source #
Instance details Defined in Label Methods (==) :: E2 l1 t1 l2 t2 -> E2 l1 t1 l2 t2 -> Bool # (/=) :: E2 l1 t1 l2 t2 -> E2 l1 t1 l2 t2 -> Bool #

mapE2 :: forall l1 t1 t1' l2 t2 t2'. (Label l1 t1 -> t1') -> (Label l2 t2 -> t2') -> E2 l1 t1 l2 t2 -> E2 l1 t1' l2 t2' Source #

Map a separate function over every possibility in this enum. The label names stay the same.

Each function has access to its label, this is intentional so that you have to mention the label once (e.g. by using dot-notation), to prevent confusing the cases.

monoMapE2 :: (t -> t') -> E2 l1 t l2 t -> E2 l1 t' l2 t' Source #

Map a single function over every possiblity in this enum. All fields have to have the same type.

monoFoldE2 :: E2 l1 t l2 t -> t Source #

If ever branch of this enum has the same type, fold the enum into its contents. This loses the distinction between cases.

monoTraverseE2 :: Functor f => (t -> f t') -> E2 l1 t l2 t -> f (E2 l1 t' l2 t') Source #

Map a monadic (actually just a functor-ic) function over each possibility in this enum. All fields have to have the same type.

partitionE2 :: forall l1 t1 l2 t2. [E2 l1 t1 l2 t2] -> T2 l1 [t1] l2 [t2] Source #

Partition a list of E2 into two lists that each keep their respective label. Like partitionEithers, but with labels.

isE21 :: forall l1 t1 l2 t2. E2 l1 t1 l2 t2 -> Bool Source #

Check the E21 case. Use TypeApplications to make sure you are checking the right case.

>>> isE21 @"foo" (E21 (label @"foo" 'c') :: E2 "foo" Char "bar" Int)
True

isE22 :: forall l2 t2 l1 t1. E2 l1 t1 l2 t2 -> Bool Source #

Check the E22 case. Use TypeApplications to make sure you are checking the right case.

>>> isE22 @"bar" (E21 (label @"foo" 'c') :: E2 "foo" Char "bar" Int)
False

getE21 :: forall l1 t1 l2 t2. E2 l1 t1 l2 t2 -> Maybe t1 Source #

getE22 :: forall l2 t2 l1 t1. E2 l1 t1 l2 t2 -> Maybe t2 Source #

data E3 (l1 :: Symbol) t1 (l2 :: Symbol) t2 (l3 :: Symbol) t3 Source #

A named 3-alternative sum (“Either with labels”).

Constructors

E31 (Label l1 t1)
E32 (Label l2 t2)
E33 (Label l3 t3)

Instances

Instances details

(Bounded t1, Bounded t3) => Bounded (E3 l1 t1 l2 t2 l3 t3) Source #
Instance details Defined in Label Methods minBound :: E3 l1 t1 l2 t2 l3 t3 # maxBound :: E3 l1 t1 l2 t2 l3 t3 #
Enum (E3 l1 () l2 () l3 ()) Source #
Instance details Defined in Label Methods succ :: E3 l1 () l2 () l3 () -> E3 l1 () l2 () l3 () # pred :: E3 l1 () l2 () l3 () -> E3 l1 () l2 () l3 () # toEnum :: Int -> E3 l1 () l2 () l3 () # fromEnum :: E3 l1 () l2 () l3 () -> Int # enumFrom :: E3 l1 () l2 () l3 () -> [E3 l1 () l2 () l3 ()] # enumFromThen :: E3 l1 () l2 () l3 () -> E3 l1 () l2 () l3 () -> [E3 l1 () l2 () l3 ()] # enumFromTo :: E3 l1 () l2 () l3 () -> E3 l1 () l2 () l3 () -> [E3 l1 () l2 () l3 ()] # enumFromThenTo :: E3 l1 () l2 () l3 () -> E3 l1 () l2 () l3 () -> E3 l1 () l2 () l3 () -> [E3 l1 () l2 () l3 ()] #
(KnownSymbol l1, KnownSymbol l2, KnownSymbol l3, Show t1, Show t2, Show t3) => Show (E3 l1 t1 l2 t2 l3 t3) Source #
Instance details Defined in Label Methods showsPrec :: Int -> E3 l1 t1 l2 t2 l3 t3 -> ShowS # show :: E3 l1 t1 l2 t2 l3 t3 -> String # showList :: [E3 l1 t1 l2 t2 l3 t3] -> ShowS #
(Eq t1, Eq t2, Eq t3) => Eq (E3 l1 t1 l2 t2 l3 t3) Source #
Instance details Defined in Label Methods (==) :: E3 l1 t1 l2 t2 l3 t3 -> E3 l1 t1 l2 t2 l3 t3 -> Bool # (/=) :: E3 l1 t1 l2 t2 l3 t3 -> E3 l1 t1 l2 t2 l3 t3 -> Bool #

mapE3 :: forall l1 t1 t1' l2 t2 t2' l3 t3 t3'. (Label l1 t1 -> t1') -> (Label l2 t2 -> t2') -> (Label l3 t3 -> t3') -> E3 l1 t1 l2 t2 l3 t3 -> E3 l1 t1' l2 t2' l3 t3' Source #

Map a function over every element in this enum. The label names stay the same.