Safe Haskell	Safe
Language	Haskell2010

Capability.Constraints

Description

This module defines helper types and type families for working with sets of capabilities.

Synopsis

type family All (xs :: [k -> Constraint]) a :: Constraint where ...
type Capability = (* -> *) -> Constraint
data Constraint
data Dict a where
- Dict :: forall a. a => Dict a

Documentation

type family All (xs :: [k -> Constraint]) a :: Constraint where ... Source #

Type family used used to express a conjunction of constraints over a single type.

Examples:

All '[Num, Eq] Int
  -- Equivalent to: (Num Int, Eq Int)

All '[HasReader "foo" Int, HasSink "bar" Float] m
  -- Equivalent to: (HasReader "foo" Int m, HasSink "bar" Float m)

Equations

All '[] a = ()
All (x ': xs) a = (x a, All xs a)

type Capability = (* -> *) -> Constraint Source #

A Capability takes a type constructor * -> * (e.g., a monad) and returns a Constraint. Examples of capabilities includ: HasReader "foo" Int, MonadIO, …

data Constraint #

The kind of constraints, like Show a

data Dict a where #

Values of type Dict p capture a dictionary for a constraint of type p.

e.g.

Dict :: Dict (Eq Int)

captures a dictionary that proves we have an:

instance Eq 'Int

Pattern matching on the Dict constructor will bring this instance into scope.

Constructors

Dict :: forall a. a => Dict a

Instances

a :=> (Read (Dict a))
Instance details Defined in Data.Constraint Methods ins :: a :- Read (Dict a) #
a :=> (Monoid (Dict a))
Instance details Defined in Data.Constraint Methods ins :: a :- Monoid (Dict a) #
a :=> (Enum (Dict a))
Instance details Defined in Data.Constraint Methods ins :: a :- Enum (Dict a) #
a :=> (Bounded (Dict a))
Instance details Defined in Data.Constraint Methods ins :: a :- Bounded (Dict a) #
() :=> (Eq (Dict a))
Instance details Defined in Data.Constraint Methods ins :: () :- Eq (Dict a) #
() :=> (Ord (Dict a))
Instance details Defined in Data.Constraint Methods ins :: () :- Ord (Dict a) #
() :=> (Show (Dict a))
Instance details Defined in Data.Constraint Methods ins :: () :- Show (Dict a) #
() :=> (Semigroup (Dict a))
Instance details Defined in Data.Constraint Methods ins :: () :- Semigroup (Dict a) #
a => Bounded (Dict a)
Instance details Defined in Data.Constraint Methods minBound :: Dict a # maxBound :: Dict a #
a => Enum (Dict a)
Instance details Defined in Data.Constraint Methods succ :: Dict a -> Dict a # pred :: Dict a -> Dict a # toEnum :: Int -> Dict a # fromEnum :: Dict a -> Int # enumFrom :: Dict a -> [Dict a] # enumFromThen :: Dict a -> Dict a -> [Dict a] # enumFromTo :: Dict a -> Dict a -> [Dict a] # enumFromThenTo :: Dict a -> Dict a -> Dict a -> [Dict a] #
Eq (Dict a)
Instance details Defined in Data.Constraint Methods (==) :: Dict a -> Dict a -> Bool # (/=) :: Dict a -> Dict a -> Bool #
(Typeable p, p) => Data (Dict p)
Instance details Defined in Data.Constraint Methods gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> Dict p -> c (Dict p) # gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (Dict p) # toConstr :: Dict p -> Constr # dataTypeOf :: Dict p -> DataType # dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c (Dict p)) # dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c (Dict p)) # gmapT :: (forall b. Data b => b -> b) -> Dict p -> Dict p # gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Dict p -> r # gmapQr :: (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Dict p -> r # gmapQ :: (forall d. Data d => d -> u) -> Dict p -> [u] # gmapQi :: Int -> (forall d. Data d => d -> u) -> Dict p -> u # gmapM :: Monad m => (forall d. Data d => d -> m d) -> Dict p -> m (Dict p) # gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Dict p -> m (Dict p) # gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Dict p -> m (Dict p) #
Ord (Dict a)
Instance details Defined in Data.Constraint Methods compare :: Dict a -> Dict a -> Ordering # (<) :: Dict a -> Dict a -> Bool # (<=) :: Dict a -> Dict a -> Bool # (>) :: Dict a -> Dict a -> Bool # (>=) :: Dict a -> Dict a -> Bool # max :: Dict a -> Dict a -> Dict a # min :: Dict a -> Dict a -> Dict a #
a => Read (Dict a)
Instance details Defined in Data.Constraint Methods readsPrec :: Int -> ReadS (Dict a) # readList :: ReadS [Dict a] # readPrec :: ReadPrec (Dict a) # readListPrec :: ReadPrec [Dict a] #
Show (Dict a)
Instance details Defined in Data.Constraint Methods showsPrec :: Int -> Dict a -> ShowS # show :: Dict a -> String # showList :: [Dict a] -> ShowS #
Semigroup (Dict a)
Instance details Defined in Data.Constraint Methods (<>) :: Dict a -> Dict a -> Dict a # sconcat :: NonEmpty (Dict a) -> Dict a # stimes :: Integral b => b -> Dict a -> Dict a #
a => Monoid (Dict a)
Instance details Defined in Data.Constraint Methods mempty :: Dict a # mappend :: Dict a -> Dict a -> Dict a # mconcat :: [Dict a] -> Dict a #
NFData (Dict c)
Instance details Defined in Data.Constraint Methods rnf :: Dict c -> () #