constraints-0.12: Constraint manipulation

Copyright(C) 2015-2016 Edward Kmett
LicenseBSD-style (see the file LICENSE)
MaintainerEdward Kmett <ekmett@gmail.com>
Stabilityexperimental
Portabilitynon-portable
Safe HaskellNone
LanguageHaskell2010

Data.Constraint.Deferrable

Description

The idea for this trick comes from Dimitrios Vytiniotis.

Synopsis

Documentation

class Deferrable p where Source #

Allow an attempt at resolution of a constraint at a later time

Methods

deferEither :: proxy p -> (p => r) -> Either String r Source #

Resolve a Deferrable constraint with observable failure.

Instances
Deferrable () Source # 
Instance details

Defined in Data.Constraint.Deferrable

Methods

deferEither :: proxy () -> (() -> r) -> Either String r Source #

(Deferrable a, Deferrable b) => Deferrable (a, b) Source # 
Instance details

Defined in Data.Constraint.Deferrable

Methods

deferEither :: proxy (a, b) -> ((a, b) -> r) -> Either String r Source #

(Typeable k, Typeable a, Typeable b) => Deferrable (a ~ b) Source #

Deferrable homogeneous equality constraints.

Note that due to a GHC bug (https:/ghc.haskell.orgtracghcticket/10343), using this instance on GHC 7.10 will only work with *-kinded types.

Instance details

Defined in Data.Constraint.Deferrable

Methods

deferEither :: proxy (a ~ b) -> ((a ~ b) -> r) -> Either String r Source #

(Deferrable a, Deferrable b, Deferrable c) => Deferrable (a, b, c) Source # 
Instance details

Defined in Data.Constraint.Deferrable

Methods

deferEither :: proxy (a, b, c) -> ((a, b, c) -> r) -> Either String r Source #

(Typeable i, Typeable j, Typeable a, Typeable b) => Deferrable (a ~~ b) Source #

Deferrable heterogenous equality constraints.

Only available on GHC 8.0 or later.

Instance details

Defined in Data.Constraint.Deferrable

Methods

deferEither :: proxy (a ~~ b) -> ((a ~~ b) -> r) -> Either String r Source #

defer :: forall p r proxy. Deferrable p => proxy p -> (p => r) -> r Source #

Defer a constraint for later resolution in a context where we want to upgrade failure into an error

deferred :: forall p. Deferrable p :- p Source #

defer_ :: forall p r. Deferrable p => (p => r) -> r Source #

A version of defer that uses visible type application in place of a Proxy.

Only available on GHC 8.0 or later.

deferEither_ :: forall p r. Deferrable p => (p => r) -> Either String r Source #

A version of deferEither that uses visible type application in place of a Proxy.

Only available on GHC 8.0 or later.

data (a :: k1) :~~: (b :: k2) :: forall k1 k2. k1 -> k2 -> Type where infix 4 #

Kind heterogeneous propositional equality. Like :~:, a :~~: b is inhabited by a terminating value if and only if a is the same type as b.

Since: base-4.10.0.0

Constructors

HRefl :: forall k1 k2 (a :: k1) (b :: k2). a :~~: a 
Instances
Category ((:~~:) :: k -> k -> Type)

Since: base-4.10.0.0

Instance details

Defined in Control.Category

Methods

id :: a :~~: a #

(.) :: (b :~~: c) -> (a :~~: b) -> a :~~: c #

TestCoercion ((:~~:) a :: k -> Type)

Since: base-4.10.0.0

Instance details

Defined in Data.Type.Coercion

Methods

testCoercion :: (a :~~: a0) -> (a :~~: b) -> Maybe (Coercion a0 b) #

TestEquality ((:~~:) a :: k -> Type)

Since: base-4.10.0.0

Instance details

Defined in Data.Type.Equality

Methods

testEquality :: (a :~~: a0) -> (a :~~: b) -> Maybe (a0 :~: b) #

NFData2 ((:~~:) :: Type -> Type -> Type)

Since: deepseq-1.4.3.0

Instance details

Defined in Control.DeepSeq

Methods

liftRnf2 :: (a -> ()) -> (b -> ()) -> (a :~~: b) -> () #

NFData1 ((:~~:) a :: Type -> Type)

Since: deepseq-1.4.3.0

Instance details

Defined in Control.DeepSeq

Methods

liftRnf :: (a0 -> ()) -> (a :~~: a0) -> () #

a ~~ b => Bounded (a :~~: b)

Since: base-4.10.0.0

Instance details

Defined in Data.Type.Equality

Methods

minBound :: a :~~: b #

maxBound :: a :~~: b #

a ~~ b => Enum (a :~~: b)

Since: base-4.10.0.0

Instance details

Defined in Data.Type.Equality

Methods

succ :: (a :~~: b) -> a :~~: b #

pred :: (a :~~: b) -> a :~~: b #

toEnum :: Int -> a :~~: b #

fromEnum :: (a :~~: b) -> Int #

enumFrom :: (a :~~: b) -> [a :~~: b] #

enumFromThen :: (a :~~: b) -> (a :~~: b) -> [a :~~: b] #

enumFromTo :: (a :~~: b) -> (a :~~: b) -> [a :~~: b] #

enumFromThenTo :: (a :~~: b) -> (a :~~: b) -> (a :~~: b) -> [a :~~: b] #

Eq (a :~~: b)

Since: base-4.10.0.0

Instance details

Defined in Data.Type.Equality

Methods

(==) :: (a :~~: b) -> (a :~~: b) -> Bool #

(/=) :: (a :~~: b) -> (a :~~: b) -> Bool #

(Typeable i, Typeable j, Typeable a, Typeable b, a ~~ b) => Data (a :~~: b)

Since: base-4.10.0.0

Instance details

Defined in Data.Data

Methods

gfoldl :: (forall d b0. Data d => c (d -> b0) -> d -> c b0) -> (forall g. g -> c g) -> (a :~~: b) -> c (a :~~: b) #

gunfold :: (forall b0 r. Data b0 => c (b0 -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (a :~~: b) #

toConstr :: (a :~~: b) -> Constr #

dataTypeOf :: (a :~~: b) -> DataType #

dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c (a :~~: b)) #

dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c (a :~~: b)) #

gmapT :: (forall b0. Data b0 => b0 -> b0) -> (a :~~: b) -> a :~~: b #

gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> (a :~~: b) -> r #

gmapQr :: (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> (a :~~: b) -> r #

gmapQ :: (forall d. Data d => d -> u) -> (a :~~: b) -> [u] #

gmapQi :: Int -> (forall d. Data d => d -> u) -> (a :~~: b) -> u #

gmapM :: Monad m => (forall d. Data d => d -> m d) -> (a :~~: b) -> m (a :~~: b) #

gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> (a :~~: b) -> m (a :~~: b) #

gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> (a :~~: b) -> m (a :~~: b) #

Ord (a :~~: b)

Since: base-4.10.0.0

Instance details

Defined in Data.Type.Equality

Methods

compare :: (a :~~: b) -> (a :~~: b) -> Ordering #

(<) :: (a :~~: b) -> (a :~~: b) -> Bool #

(<=) :: (a :~~: b) -> (a :~~: b) -> Bool #

(>) :: (a :~~: b) -> (a :~~: b) -> Bool #

(>=) :: (a :~~: b) -> (a :~~: b) -> Bool #

max :: (a :~~: b) -> (a :~~: b) -> a :~~: b #

min :: (a :~~: b) -> (a :~~: b) -> a :~~: b #

a ~~ b => Read (a :~~: b)

Since: base-4.10.0.0

Instance details

Defined in Data.Type.Equality

Methods

readsPrec :: Int -> ReadS (a :~~: b) #

readList :: ReadS [a :~~: b] #

readPrec :: ReadPrec (a :~~: b) #

readListPrec :: ReadPrec [a :~~: b] #

Show (a :~~: b)

Since: base-4.10.0.0

Instance details

Defined in Data.Type.Equality

Methods

showsPrec :: Int -> (a :~~: b) -> ShowS #

show :: (a :~~: b) -> String #

showList :: [a :~~: b] -> ShowS #

NFData (a :~~: b)

Since: deepseq-1.4.3.0

Instance details

Defined in Control.DeepSeq

Methods

rnf :: (a :~~: b) -> () #

HasDict (a ~~ b) (a :~~: b) Source # 
Instance details

Defined in Data.Constraint

Methods

evidence :: (a :~~: b) -> Dict (a ~~ b) Source #

data (a :: k) :~: (b :: k) :: forall k. k -> k -> Type where infix 4 #

Propositional equality. If a :~: b is inhabited by some terminating value, then the type a is the same as the type b. To use this equality in practice, pattern-match on the a :~: b to get out the Refl constructor; in the body of the pattern-match, the compiler knows that a ~ b.

Since: base-4.7.0.0

Constructors

Refl :: forall k (a :: k) (b :: k). a :~: a 
Instances
Category ((:~:) :: k -> k -> Type)

Since: base-4.7.0.0

Instance details

Defined in Control.Category

Methods

id :: a :~: a #

(.) :: (b :~: c) -> (a :~: b) -> a :~: c #

TestCoercion ((:~:) a :: k -> Type)

Since: base-4.7.0.0

Instance details

Defined in Data.Type.Coercion

Methods

testCoercion :: (a :~: a0) -> (a :~: b) -> Maybe (Coercion a0 b) #

TestEquality ((:~:) a :: k -> Type)

Since: base-4.7.0.0

Instance details

Defined in Data.Type.Equality

Methods

testEquality :: (a :~: a0) -> (a :~: b) -> Maybe (a0 :~: b) #

NFData2 ((:~:) :: Type -> Type -> Type)

Since: deepseq-1.4.3.0

Instance details

Defined in Control.DeepSeq

Methods

liftRnf2 :: (a -> ()) -> (b -> ()) -> (a :~: b) -> () #

NFData1 ((:~:) a)

Since: deepseq-1.4.3.0

Instance details

Defined in Control.DeepSeq

Methods

liftRnf :: (a0 -> ()) -> (a :~: a0) -> () #

a ~ b => Bounded (a :~: b)

Since: base-4.7.0.0

Instance details

Defined in Data.Type.Equality

Methods

minBound :: a :~: b #

maxBound :: a :~: b #

a ~ b => Enum (a :~: b)

Since: base-4.7.0.0

Instance details

Defined in Data.Type.Equality

Methods

succ :: (a :~: b) -> a :~: b #

pred :: (a :~: b) -> a :~: b #

toEnum :: Int -> a :~: b #

fromEnum :: (a :~: b) -> Int #

enumFrom :: (a :~: b) -> [a :~: b] #

enumFromThen :: (a :~: b) -> (a :~: b) -> [a :~: b] #

enumFromTo :: (a :~: b) -> (a :~: b) -> [a :~: b] #

enumFromThenTo :: (a :~: b) -> (a :~: b) -> (a :~: b) -> [a :~: b] #

Eq (a :~: b)

Since: base-4.7.0.0

Instance details

Defined in Data.Type.Equality

Methods

(==) :: (a :~: b) -> (a :~: b) -> Bool #

(/=) :: (a :~: b) -> (a :~: b) -> Bool #

(a ~ b, Data a) => Data (a :~: b)

Since: base-4.7.0.0

Instance details

Defined in Data.Data

Methods

gfoldl :: (forall d b0. Data d => c (d -> b0) -> d -> c b0) -> (forall g. g -> c g) -> (a :~: b) -> c (a :~: b) #

gunfold :: (forall b0 r. Data b0 => c (b0 -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (a :~: b) #

toConstr :: (a :~: b) -> Constr #

dataTypeOf :: (a :~: b) -> DataType #

dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c (a :~: b)) #

dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c (a :~: b)) #

gmapT :: (forall b0. Data b0 => b0 -> b0) -> (a :~: b) -> a :~: b #

gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> (a :~: b) -> r #

gmapQr :: (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> (a :~: b) -> r #

gmapQ :: (forall d. Data d => d -> u) -> (a :~: b) -> [u] #

gmapQi :: Int -> (forall d. Data d => d -> u) -> (a :~: b) -> u #

gmapM :: Monad m => (forall d. Data d => d -> m d) -> (a :~: b) -> m (a :~: b) #

gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> (a :~: b) -> m (a :~: b) #

gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> (a :~: b) -> m (a :~: b) #

Ord (a :~: b)

Since: base-4.7.0.0

Instance details

Defined in Data.Type.Equality

Methods

compare :: (a :~: b) -> (a :~: b) -> Ordering #

(<) :: (a :~: b) -> (a :~: b) -> Bool #

(<=) :: (a :~: b) -> (a :~: b) -> Bool #

(>) :: (a :~: b) -> (a :~: b) -> Bool #

(>=) :: (a :~: b) -> (a :~: b) -> Bool #

max :: (a :~: b) -> (a :~: b) -> a :~: b #

min :: (a :~: b) -> (a :~: b) -> a :~: b #

a ~ b => Read (a :~: b)

Since: base-4.7.0.0

Instance details

Defined in Data.Type.Equality

Methods

readsPrec :: Int -> ReadS (a :~: b) #

readList :: ReadS [a :~: b] #

readPrec :: ReadPrec (a :~: b) #

readListPrec :: ReadPrec [a :~: b] #

Show (a :~: b)

Since: base-4.7.0.0

Instance details

Defined in Data.Type.Equality

Methods

showsPrec :: Int -> (a :~: b) -> ShowS #

show :: (a :~: b) -> String #

showList :: [a :~: b] -> ShowS #

NFData (a :~: b)

Since: deepseq-1.4.3.0

Instance details

Defined in Control.DeepSeq

Methods

rnf :: (a :~: b) -> () #

HasDict (a ~ b) (a :~: b) Source # 
Instance details

Defined in Data.Constraint

Methods

evidence :: (a :~: b) -> Dict (a ~ b) Source #