hnix-0.10.1: Haskell implementation of the Nix language
Safe HaskellNone
LanguageHaskell2010

Nix.Frames

Synopsis

Documentation

data NixLevel Source #

Constructors

Fatal 
Error 
Warning 
Info 
Debug 

Instances

Instances details
Bounded NixLevel Source # 
Instance details

Defined in Nix.Frames

Enum NixLevel Source # 
Instance details

Defined in Nix.Frames

Eq NixLevel Source # 
Instance details

Defined in Nix.Frames

Ord NixLevel Source # 
Instance details

Defined in Nix.Frames

Show NixLevel Source # 
Instance details

Defined in Nix.Frames

type Framed e m = (MonadReader e m, Has e Frames, MonadThrow m) Source #

data NixFrame Source #

Constructors

NixFrame 

Instances

Instances details
Show NixFrame Source # 
Instance details

Defined in Nix.Frames

Has (Context m t) Frames Source # 
Instance details

Defined in Nix.Context

withFrame :: forall s e m a. (Framed e m, Exception s) => NixLevel -> s -> m a -> m a Source #

throwError :: forall s e m a. (Framed e m, Exception s, MonadThrow m) => s -> m a Source #

class Typeable (a :: k) #

The class Typeable allows a concrete representation of a type to be calculated.

Minimal complete definition

typeRep#

data TyCon #

Instances

Instances details
Eq TyCon 
Instance details

Defined in GHC.Classes

Methods

(==) :: TyCon -> TyCon -> Bool #

(/=) :: TyCon -> TyCon -> Bool #

Ord TyCon 
Instance details

Defined in GHC.Classes

Methods

compare :: TyCon -> TyCon -> Ordering #

(<) :: TyCon -> TyCon -> Bool #

(<=) :: TyCon -> TyCon -> Bool #

(>) :: TyCon -> TyCon -> Bool #

(>=) :: TyCon -> TyCon -> Bool #

max :: TyCon -> TyCon -> TyCon #

min :: TyCon -> TyCon -> TyCon #

Show TyCon

Since: base-2.1

Instance details

Defined in GHC.Show

Methods

showsPrec :: Int -> TyCon -> ShowS #

show :: TyCon -> String #

showList :: [TyCon] -> ShowS #

Binary TyCon

Since: binary-0.8.5.0

Instance details

Defined in Data.Binary.Class

Methods

put :: TyCon -> Put #

get :: Get TyCon #

putList :: [TyCon] -> Put #

NFData TyCon

NOTE: Prior to deepseq-1.4.4.0 this instance was only defined for base-4.8.0.0 and later.

Since: deepseq-1.4.0.0

Instance details

Defined in Control.DeepSeq

Methods

rnf :: TyCon -> () #

Serialise TyCon

Since: serialise-0.2.0.0

Instance details

Defined in Codec.Serialise.Class

typeOf7 :: Typeable t => t a b c d e f g -> TypeRep #

typeOf6 :: Typeable t => t a b c d e f -> TypeRep #

typeOf5 :: Typeable t => t a b c d e -> TypeRep #

typeOf4 :: Typeable t => t a b c d -> TypeRep #

typeOf3 :: Typeable t => t a b c -> TypeRep #

typeOf2 :: Typeable t => t a b -> TypeRep #

typeOf1 :: Typeable t => t a -> TypeRep #

rnfTypeRep :: TypeRep -> () #

Force a TypeRep to normal form.

typeRepFingerprint :: TypeRep -> Fingerprint #

Takes a value of type a and returns a concrete representation of that type.

Since: base-4.7.0.0

typeRepTyCon :: TypeRep -> TyCon #

Observe the type constructor of a quantified type representation.

typeRepArgs :: TypeRep -> [TypeRep] #

Observe the argument types of a type representation

splitTyConApp :: TypeRep -> (TyCon, [TypeRep]) #

Splits a type constructor application. Note that if the type constructor is polymorphic, this will not return the kinds that were used.

mkFunTy :: TypeRep -> TypeRep -> TypeRep #

Build a function type.

funResultTy :: TypeRep -> TypeRep -> Maybe TypeRep #

Applies a type to a function type. Returns: Just u if the first argument represents a function of type t -> u and the second argument represents a function of type t. Otherwise, returns Nothing.

gcast2 :: forall k1 k2 k3 c (t :: k2 -> k3 -> k1) (t' :: k2 -> k3 -> k1) (a :: k2) (b :: k3). (Typeable t, Typeable t') => c (t a b) -> Maybe (c (t' a b)) #

Cast over k1 -> k2 -> k3

gcast1 :: forall k1 k2 c (t :: k2 -> k1) (t' :: k2 -> k1) (a :: k2). (Typeable t, Typeable t') => c (t a) -> Maybe (c (t' a)) #

Cast over k1 -> k2

gcast :: forall k (a :: k) (b :: k) c. (Typeable a, Typeable b) => c a -> Maybe (c b) #

A flexible variation parameterised in a type constructor

eqT :: forall k (a :: k) (b :: k). (Typeable a, Typeable b) => Maybe (a :~: b) #

Extract a witness of equality of two types

Since: base-4.7.0.0

cast :: (Typeable a, Typeable b) => a -> Maybe b #

The type-safe cast operation

showsTypeRep :: TypeRep -> ShowS #

Show a type representation

typeRep :: forall k proxy (a :: k). Typeable a => proxy a -> TypeRep #

Takes a value of type a and returns a concrete representation of that type.

Since: base-4.7.0.0

type TypeRep = SomeTypeRep #

A quantified type representation.

rnfTyCon :: TyCon -> () #

data Proxy (t :: k) #

Proxy is a type that holds no data, but has a phantom parameter of arbitrary type (or even kind). Its use is to provide type information, even though there is no value available of that type (or it may be too costly to create one).

Historically, Proxy :: Proxy a is a safer alternative to the undefined :: a idiom.

>>> Proxy :: Proxy (Void, Int -> Int)
Proxy

Proxy can even hold types of higher kinds,

>>> Proxy :: Proxy Either
Proxy
>>> Proxy :: Proxy Functor
Proxy
>>> Proxy :: Proxy complicatedStructure
Proxy

Constructors

Proxy 

Instances

Instances details
Generic1 (Proxy :: k -> Type)

Since: base-4.6.0.0

Instance details

Defined in GHC.Generics

Associated Types

type Rep1 Proxy :: k -> Type #

Methods

from1 :: forall (a :: k0). Proxy a -> Rep1 Proxy a #

to1 :: forall (a :: k0). Rep1 Proxy a -> Proxy a #

Monad (Proxy :: Type -> Type)

Since: base-4.7.0.0

Instance details

Defined in Data.Proxy

Methods

(>>=) :: Proxy a -> (a -> Proxy b) -> Proxy b #

(>>) :: Proxy a -> Proxy b -> Proxy b #

return :: a -> Proxy a #

Functor (Proxy :: Type -> Type)

Since: base-4.7.0.0

Instance details

Defined in Data.Proxy

Methods

fmap :: (a -> b) -> Proxy a -> Proxy b #

(<$) :: a -> Proxy b -> Proxy a #

Applicative (Proxy :: Type -> Type)

Since: base-4.7.0.0

Instance details

Defined in Data.Proxy

Methods

pure :: a -> Proxy a #

(<*>) :: Proxy (a -> b) -> Proxy a -> Proxy b #

liftA2 :: (a -> b -> c) -> Proxy a -> Proxy b -> Proxy c #

(*>) :: Proxy a -> Proxy b -> Proxy b #

(<*) :: Proxy a -> Proxy b -> Proxy a #

Foldable (Proxy :: Type -> Type)

Since: base-4.7.0.0

Instance details

Defined in Data.Foldable

Methods

fold :: Monoid m => Proxy m -> m #

foldMap :: Monoid m => (a -> m) -> Proxy a -> m #

foldMap' :: Monoid m => (a -> m) -> Proxy a -> m #

foldr :: (a -> b -> b) -> b -> Proxy a -> b #

foldr' :: (a -> b -> b) -> b -> Proxy a -> b #

foldl :: (b -> a -> b) -> b -> Proxy a -> b #

foldl' :: (b -> a -> b) -> b -> Proxy a -> b #

foldr1 :: (a -> a -> a) -> Proxy a -> a #

foldl1 :: (a -> a -> a) -> Proxy a -> a #

toList :: Proxy a -> [a] #

null :: Proxy a -> Bool #

length :: Proxy a -> Int #

elem :: Eq a => a -> Proxy a -> Bool #

maximum :: Ord a => Proxy a -> a #

minimum :: Ord a => Proxy a -> a #

sum :: Num a => Proxy a -> a #

product :: Num a => Proxy a -> a #

Traversable (Proxy :: Type -> Type)

Since: base-4.7.0.0

Instance details

Defined in Data.Traversable

Methods

traverse :: Applicative f => (a -> f b) -> Proxy a -> f (Proxy b) #

sequenceA :: Applicative f => Proxy (f a) -> f (Proxy a) #

mapM :: Monad m => (a -> m b) -> Proxy a -> m (Proxy b) #

sequence :: Monad m => Proxy (m a) -> m (Proxy a) #

Representable (Proxy :: Type -> Type) 
Instance details

Defined in Data.Functor.Rep

Associated Types

type Rep Proxy #

Methods

tabulate :: (Rep Proxy -> a) -> Proxy a #

index :: Proxy a -> Rep Proxy -> a #

ToJSON1 (Proxy :: Type -> Type) 
Instance details

Defined in Data.Aeson.Types.ToJSON

Methods

liftToJSON :: (a -> Value) -> ([a] -> Value) -> Proxy a -> Value #

liftToJSONList :: (a -> Value) -> ([a] -> Value) -> [Proxy a] -> Value #

liftToEncoding :: (a -> Encoding) -> ([a] -> Encoding) -> Proxy a -> Encoding #

liftToEncodingList :: (a -> Encoding) -> ([a] -> Encoding) -> [Proxy a] -> Encoding #

FromJSON1 (Proxy :: Type -> Type) 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON :: (Value -> Parser a) -> (Value -> Parser [a]) -> Value -> Parser (Proxy a) #

liftParseJSONList :: (Value -> Parser a) -> (Value -> Parser [a]) -> Value -> Parser [Proxy a] #

Alternative (Proxy :: Type -> Type)

Since: base-4.9.0.0

Instance details

Defined in Data.Proxy

Methods

empty :: Proxy a #

(<|>) :: Proxy a -> Proxy a -> Proxy a #

some :: Proxy a -> Proxy [a] #

many :: Proxy a -> Proxy [a] #

MonadPlus (Proxy :: Type -> Type)

Since: base-4.9.0.0

Instance details

Defined in Data.Proxy

Methods

mzero :: Proxy a #

mplus :: Proxy a -> Proxy a -> Proxy a #

Eq1 (Proxy :: Type -> Type)

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Classes

Methods

liftEq :: (a -> b -> Bool) -> Proxy a -> Proxy b -> Bool #

Ord1 (Proxy :: Type -> Type)

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Classes

Methods

liftCompare :: (a -> b -> Ordering) -> Proxy a -> Proxy b -> Ordering #

Read1 (Proxy :: Type -> Type)

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Classes

Methods

liftReadsPrec :: (Int -> ReadS a) -> ReadS [a] -> Int -> ReadS (Proxy a) #

liftReadList :: (Int -> ReadS a) -> ReadS [a] -> ReadS [Proxy a] #

liftReadPrec :: ReadPrec a -> ReadPrec [a] -> ReadPrec (Proxy a) #

liftReadListPrec :: ReadPrec a -> ReadPrec [a] -> ReadPrec [Proxy a] #

Show1 (Proxy :: Type -> Type)

Since: base-4.9.0.0

Instance details

Defined in Data.Functor.Classes

Methods

liftShowsPrec :: (Int -> a -> ShowS) -> ([a] -> ShowS) -> Int -> Proxy a -> ShowS #

liftShowList :: (Int -> a -> ShowS) -> ([a] -> ShowS) -> [Proxy a] -> ShowS #

NFData1 (Proxy :: Type -> Type)

Since: deepseq-1.4.3.0

Instance details

Defined in Control.DeepSeq

Methods

liftRnf :: (a -> ()) -> Proxy a -> () #

Hashable1 (Proxy :: Type -> Type) 
Instance details

Defined in Data.Hashable.Class

Methods

liftHashWithSalt :: (Int -> a -> Int) -> Int -> Proxy a -> Int #

Semialign (Proxy :: Type -> Type) 
Instance details

Defined in Data.Semialign.Internal

Methods

align :: Proxy a -> Proxy b -> Proxy (These a b) #

alignWith :: (These a b -> c) -> Proxy a -> Proxy b -> Proxy c #

Align (Proxy :: Type -> Type) 
Instance details

Defined in Data.Semialign.Internal

Methods

nil :: Proxy a #

Unalign (Proxy :: Type -> Type) 
Instance details

Defined in Data.Semialign.Internal

Methods

unalign :: Proxy (These a b) -> (Proxy a, Proxy b) #

unalignWith :: (c -> These a b) -> Proxy c -> (Proxy a, Proxy b) #

Zip (Proxy :: Type -> Type) 
Instance details

Defined in Data.Semialign.Internal

Methods

zip :: Proxy a -> Proxy b -> Proxy (a, b) #

zipWith :: (a -> b -> c) -> Proxy a -> Proxy b -> Proxy c #

Repeat (Proxy :: Type -> Type) 
Instance details

Defined in Data.Semialign.Internal

Methods

repeat :: a -> Proxy a #

Unzip (Proxy :: Type -> Type) 
Instance details

Defined in Data.Semialign.Internal

Methods

unzipWith :: (c -> (a, b)) -> Proxy c -> (Proxy a, Proxy b) #

unzip :: Proxy (a, b) -> (Proxy a, Proxy b) #

Bounded (Proxy t)

Since: base-4.7.0.0

Instance details

Defined in Data.Proxy

Methods

minBound :: Proxy t #

maxBound :: Proxy t #

Enum (Proxy s)

Since: base-4.7.0.0

Instance details

Defined in Data.Proxy

Methods

succ :: Proxy s -> Proxy s #

pred :: Proxy s -> Proxy s #

toEnum :: Int -> Proxy s #

fromEnum :: Proxy s -> Int #

enumFrom :: Proxy s -> [Proxy s] #

enumFromThen :: Proxy s -> Proxy s -> [Proxy s] #

enumFromTo :: Proxy s -> Proxy s -> [Proxy s] #

enumFromThenTo :: Proxy s -> Proxy s -> Proxy s -> [Proxy s] #

Eq (Proxy s)

Since: base-4.7.0.0

Instance details

Defined in Data.Proxy

Methods

(==) :: Proxy s -> Proxy s -> Bool #

(/=) :: Proxy s -> Proxy s -> Bool #

Data t => Data (Proxy t)

Since: base-4.7.0.0

Instance details

Defined in Data.Data

Methods

gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> Proxy t -> c (Proxy t) #

gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (Proxy t) #

toConstr :: Proxy t -> Constr #

dataTypeOf :: Proxy t -> DataType #

dataCast1 :: Typeable t0 => (forall d. Data d => c (t0 d)) -> Maybe (c (Proxy t)) #

dataCast2 :: Typeable t0 => (forall d e. (Data d, Data e) => c (t0 d e)) -> Maybe (c (Proxy t)) #

gmapT :: (forall b. Data b => b -> b) -> Proxy t -> Proxy t #

gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Proxy t -> r #

gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Proxy t -> r #

gmapQ :: (forall d. Data d => d -> u) -> Proxy t -> [u] #

gmapQi :: Int -> (forall d. Data d => d -> u) -> Proxy t -> u #

gmapM :: Monad m => (forall d. Data d => d -> m d) -> Proxy t -> m (Proxy t) #

gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Proxy t -> m (Proxy t) #

gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Proxy t -> m (Proxy t) #

Ord (Proxy s)

Since: base-4.7.0.0

Instance details

Defined in Data.Proxy

Methods

compare :: Proxy s -> Proxy s -> Ordering #

(<) :: Proxy s -> Proxy s -> Bool #

(<=) :: Proxy s -> Proxy s -> Bool #

(>) :: Proxy s -> Proxy s -> Bool #

(>=) :: Proxy s -> Proxy s -> Bool #

max :: Proxy s -> Proxy s -> Proxy s #

min :: Proxy s -> Proxy s -> Proxy s #

Read (Proxy t)

Since: base-4.7.0.0

Instance details

Defined in Data.Proxy

Show (Proxy s)

Since: base-4.7.0.0

Instance details

Defined in Data.Proxy

Methods

showsPrec :: Int -> Proxy s -> ShowS #

show :: Proxy s -> String #

showList :: [Proxy s] -> ShowS #

Ix (Proxy s)

Since: base-4.7.0.0

Instance details

Defined in Data.Proxy

Methods

range :: (Proxy s, Proxy s) -> [Proxy s] #

index :: (Proxy s, Proxy s) -> Proxy s -> Int #

unsafeIndex :: (Proxy s, Proxy s) -> Proxy s -> Int #

inRange :: (Proxy s, Proxy s) -> Proxy s -> Bool #

rangeSize :: (Proxy s, Proxy s) -> Int #

unsafeRangeSize :: (Proxy s, Proxy s) -> Int #

Generic (Proxy t)

Since: base-4.6.0.0

Instance details

Defined in GHC.Generics

Associated Types

type Rep (Proxy t) :: Type -> Type #

Methods

from :: Proxy t -> Rep (Proxy t) x #

to :: Rep (Proxy t) x -> Proxy t #

Semigroup (Proxy s)

Since: base-4.9.0.0

Instance details

Defined in Data.Proxy

Methods

(<>) :: Proxy s -> Proxy s -> Proxy s #

sconcat :: NonEmpty (Proxy s) -> Proxy s #

stimes :: Integral b => b -> Proxy s -> Proxy s #

Monoid (Proxy s)

Since: base-4.7.0.0

Instance details

Defined in Data.Proxy

Methods

mempty :: Proxy s #

mappend :: Proxy s -> Proxy s -> Proxy s #

mconcat :: [Proxy s] -> Proxy s #

Hashable (Proxy a) 
Instance details

Defined in Data.Hashable.Class

Methods

hashWithSalt :: Int -> Proxy a -> Int #

hash :: Proxy a -> Int #

ToJSON (Proxy a) 
Instance details

Defined in Data.Aeson.Types.ToJSON

FromJSON (Proxy a) 
Instance details

Defined in Data.Aeson.Types.FromJSON

NFData (Proxy a)

Since: deepseq-1.4.0.0

Instance details

Defined in Control.DeepSeq

Methods

rnf :: Proxy a -> () #

Serialise (Proxy a)

Since: serialise-0.2.0.0

Instance details

Defined in Codec.Serialise.Class

type Rep1 (Proxy :: k -> Type) 
Instance details

Defined in GHC.Generics

type Rep1 (Proxy :: k -> Type) = D1 ('MetaData "Proxy" "Data.Proxy" "base" 'False) (C1 ('MetaCons "Proxy" 'PrefixI 'False) (U1 :: k -> Type))
type Rep (Proxy :: Type -> Type) 
Instance details

Defined in Data.Functor.Rep

type Rep (Proxy :: Type -> Type) = Void
type Rep (Proxy t) 
Instance details

Defined in GHC.Generics

type Rep (Proxy t) = D1 ('MetaData "Proxy" "Data.Proxy" "base" 'False) (C1 ('MetaCons "Proxy" 'PrefixI 'False) (U1 :: Type -> Type))

data (a :: k) :~: (b :: k) 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). a :~: a 

Instances

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

Since: base-4.7.0.0

Instance details

Defined in Data.Type.Coercion

Methods

testCoercion :: forall (a0 :: k0) (b :: k0). (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 :: forall (a0 :: k0) (b :: k0). (a :~: a0) -> (a :~: b) -> Maybe (a0 :~: b) #

GShow ((:~:) a :: k -> Type) 
Instance details

Defined in Data.GADT.Internal

Methods

gshowsPrec :: forall (a0 :: k0). Int -> (a :~: a0) -> ShowS #

GRead ((:~:) a :: k -> Type) 
Instance details

Defined in Data.GADT.Internal

Methods

greadsPrec :: Int -> GReadS ((:~:) a) #

GEq ((:~:) a :: k -> Type) 
Instance details

Defined in Data.GADT.Internal

Methods

geq :: forall (a0 :: k0) (b :: k0). (a :~: a0) -> (a :~: b) -> Maybe (a0 :~: b) #

GCompare ((:~:) a :: k -> Type) 
Instance details

Defined in Data.GADT.Internal

Methods

gcompare :: forall (a0 :: k0) (b :: k0). (a :~: a0) -> (a :~: b) -> GOrdering 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 :: forall r r'. (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) -> () #

data (a :: k1) :~~: (b :: k2) 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 (a :: k1). a :~~: a 

Instances

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

Since: base-4.10.0.0

Instance details

Defined in Data.Type.Coercion

Methods

testCoercion :: forall (a0 :: k0) (b :: k0). (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 :: forall (a0 :: k0) (b :: k0). (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 :: forall r r'. (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) -> () #

assert :: Bool -> a -> a #

If the first argument evaluates to True, then the result is the second argument. Otherwise an AssertionFailed exception is raised, containing a String with the source file and line number of the call to assert.

Assertions can normally be turned on or off with a compiler flag (for GHC, assertions are normally on unless optimisation is turned on with -O or the -fignore-asserts option is given). When assertions are turned off, the first argument to assert is ignored, and the second argument is returned as the result.

allowInterrupt :: IO () #

When invoked inside mask, this function allows a masked asynchronous exception to be raised, if one exists. It is equivalent to performing an interruptible operation (see #interruptible), but does not involve any actual blocking.

When called outside mask, or inside uninterruptibleMask, this function has no effect.

Since: base-4.4.0.0

catches :: IO a -> [Handler a] -> IO a #

Sometimes you want to catch two different sorts of exception. You could do something like

f = expr `catch` \ (ex :: ArithException) -> handleArith ex
         `catch` \ (ex :: IOException)    -> handleIO    ex

However, there are a couple of problems with this approach. The first is that having two exception handlers is inefficient. However, the more serious issue is that the second exception handler will catch exceptions in the first, e.g. in the example above, if handleArith throws an IOException then the second exception handler will catch it.

Instead, we provide a function catches, which would be used thus:

f = expr `catches` [Handler (\ (ex :: ArithException) -> handleArith ex),
                    Handler (\ (ex :: IOException)    -> handleIO    ex)]

data Handler a #

You need this when using catches.

Constructors

Exception e => Handler (e -> IO a) 

Instances

Instances details
Functor Handler

Since: base-4.6.0.0

Instance details

Defined in Control.Exception

Methods

fmap :: (a -> b) -> Handler a -> Handler b #

(<$) :: a -> Handler b -> Handler a #

bracketOnError #

Arguments

:: IO a

computation to run first ("acquire resource")

-> (a -> IO b)

computation to run last ("release resource")

-> (a -> IO c)

computation to run in-between

-> IO c 

Like bracket, but only performs the final action if there was an exception raised by the in-between computation.

bracket_ :: IO a -> IO b -> IO c -> IO c #

A variant of bracket where the return value from the first computation is not required.

finally #

Arguments

:: IO a

computation to run first

-> IO b

computation to run afterward (even if an exception was raised)

-> IO a 

A specialised variant of bracket with just a computation to run afterward.

bracket #

Arguments

:: IO a

computation to run first ("acquire resource")

-> (a -> IO b)

computation to run last ("release resource")

-> (a -> IO c)

computation to run in-between

-> IO c 

When you want to acquire a resource, do some work with it, and then release the resource, it is a good idea to use bracket, because bracket will install the necessary exception handler to release the resource in the event that an exception is raised during the computation. If an exception is raised, then bracket will re-raise the exception (after performing the release).

A common example is opening a file:

bracket
  (openFile "filename" ReadMode)
  (hClose)
  (\fileHandle -> do { ... })

The arguments to bracket are in this order so that we can partially apply it, e.g.:

withFile name mode = bracket (openFile name mode) hClose

onException :: IO a -> IO b -> IO a #

Like finally, but only performs the final action if there was an exception raised by the computation.

tryJust :: Exception e => (e -> Maybe b) -> IO a -> IO (Either b a) #

A variant of try that takes an exception predicate to select which exceptions are caught (c.f. catchJust). If the exception does not match the predicate, it is re-thrown.

try :: Exception e => IO a -> IO (Either e a) #

Similar to catch, but returns an Either result which is (Right a) if no exception of type e was raised, or (Left ex) if an exception of type e was raised and its value is ex. If any other type of exception is raised than it will be propogated up to the next enclosing exception handler.

 try a = catch (Right `liftM` a) (return . Left)

mapException :: (Exception e1, Exception e2) => (e1 -> e2) -> a -> a #

This function maps one exception into another as proposed in the paper "A semantics for imprecise exceptions".

handleJust :: Exception e => (e -> Maybe b) -> (b -> IO a) -> IO a -> IO a #

A version of catchJust with the arguments swapped around (see handle).

handle :: Exception e => (e -> IO a) -> IO a -> IO a #

A version of catch with the arguments swapped around; useful in situations where the code for the handler is shorter. For example:

  do handle (\NonTermination -> exitWith (ExitFailure 1)) $
     ...

catchJust #

Arguments

:: Exception e 
=> (e -> Maybe b)

Predicate to select exceptions

-> IO a

Computation to run

-> (b -> IO a)

Handler

-> IO a 

The function catchJust is like catch, but it takes an extra argument which is an exception predicate, a function which selects which type of exceptions we're interested in.

catchJust (\e -> if isDoesNotExistErrorType (ioeGetErrorType e) then Just () else Nothing)
          (readFile f)
          (\_ -> do hPutStrLn stderr ("No such file: " ++ show f)
                    return "")

Any other exceptions which are not matched by the predicate are re-raised, and may be caught by an enclosing catch, catchJust, etc.

newtype PatternMatchFail #

A pattern match failed. The String gives information about the source location of the pattern.

Constructors

PatternMatchFail String 

newtype RecSelError #

A record selector was applied to a constructor without the appropriate field. This can only happen with a datatype with multiple constructors, where some fields are in one constructor but not another. The String gives information about the source location of the record selector.

Constructors

RecSelError String 

Instances

Instances details
Show RecSelError

Since: base-4.0

Instance details

Defined in Control.Exception.Base

Exception RecSelError

Since: base-4.0

Instance details

Defined in Control.Exception.Base

Wrapped RecSelError 
Instance details

Defined in Control.Lens.Wrapped

Associated Types

type Unwrapped RecSelError #

t ~ RecSelError => Rewrapped RecSelError t 
Instance details

Defined in Control.Lens.Wrapped

type Unwrapped RecSelError 
Instance details

Defined in Control.Lens.Wrapped

newtype RecConError #

An uninitialised record field was used. The String gives information about the source location where the record was constructed.

Constructors

RecConError String 

Instances

Instances details
Show RecConError

Since: base-4.0

Instance details

Defined in Control.Exception.Base

Exception RecConError

Since: base-4.0

Instance details

Defined in Control.Exception.Base

Wrapped RecConError 
Instance details

Defined in Control.Lens.Wrapped

Associated Types

type Unwrapped RecConError #

t ~ RecConError => Rewrapped RecConError t 
Instance details

Defined in Control.Lens.Wrapped

type Unwrapped RecConError 
Instance details

Defined in Control.Lens.Wrapped

newtype RecUpdError #

A record update was performed on a constructor without the appropriate field. This can only happen with a datatype with multiple constructors, where some fields are in one constructor but not another. The String gives information about the source location of the record update.

Constructors

RecUpdError String 

Instances

Instances details
Show RecUpdError

Since: base-4.0

Instance details

Defined in Control.Exception.Base

Exception RecUpdError

Since: base-4.0

Instance details

Defined in Control.Exception.Base

Wrapped RecUpdError 
Instance details

Defined in Control.Lens.Wrapped

Associated Types

type Unwrapped RecUpdError #

t ~ RecUpdError => Rewrapped RecUpdError t 
Instance details

Defined in Control.Lens.Wrapped

type Unwrapped RecUpdError 
Instance details

Defined in Control.Lens.Wrapped

newtype NoMethodError #

A class method without a definition (neither a default definition, nor a definition in the appropriate instance) was called. The String gives information about which method it was.

Constructors

NoMethodError String 

Instances

Instances details
Show NoMethodError

Since: base-4.0

Instance details

Defined in Control.Exception.Base

Exception NoMethodError

Since: base-4.0

Instance details

Defined in Control.Exception.Base

Wrapped NoMethodError 
Instance details

Defined in Control.Lens.Wrapped

Associated Types

type Unwrapped NoMethodError #

t ~ NoMethodError => Rewrapped NoMethodError t 
Instance details

Defined in Control.Lens.Wrapped

type Unwrapped NoMethodError 
Instance details

Defined in Control.Lens.Wrapped

newtype TypeError #

An expression that didn't typecheck during compile time was called. This is only possible with -fdefer-type-errors. The String gives details about the failed type check.

Since: base-4.9.0.0

Constructors

TypeError String 

Instances

Instances details
Show TypeError

Since: base-4.9.0.0

Instance details

Defined in Control.Exception.Base

Exception TypeError

Since: base-4.9.0.0

Instance details

Defined in Control.Exception.Base

Wrapped TypeError 
Instance details

Defined in Control.Lens.Wrapped

Associated Types

type Unwrapped TypeError #

t ~ TypeError => Rewrapped TypeError t 
Instance details

Defined in Control.Lens.Wrapped

type Unwrapped TypeError 
Instance details

Defined in Control.Lens.Wrapped

data NonTermination #

Thrown when the runtime system detects that the computation is guaranteed not to terminate. Note that there is no guarantee that the runtime system will notice whether any given computation is guaranteed to terminate or not.

Constructors

NonTermination 

data NestedAtomically #

Thrown when the program attempts to call atomically, from the stm package, inside another call to atomically.

Constructors

NestedAtomically 

throwTo :: Exception e => ThreadId -> e -> IO () #

throwTo raises an arbitrary exception in the target thread (GHC only).

Exception delivery synchronizes between the source and target thread: throwTo does not return until the exception has been raised in the target thread. The calling thread can thus be certain that the target thread has received the exception. Exception delivery is also atomic with respect to other exceptions. Atomicity is a useful property to have when dealing with race conditions: e.g. if there are two threads that can kill each other, it is guaranteed that only one of the threads will get to kill the other.

Whatever work the target thread was doing when the exception was raised is not lost: the computation is suspended until required by another thread.

If the target thread is currently making a foreign call, then the exception will not be raised (and hence throwTo will not return) until the call has completed. This is the case regardless of whether the call is inside a mask or not. However, in GHC a foreign call can be annotated as interruptible, in which case a throwTo will cause the RTS to attempt to cause the call to return; see the GHC documentation for more details.

Important note: the behaviour of throwTo differs from that described in the paper "Asynchronous exceptions in Haskell" (http://research.microsoft.com/~simonpj/Papers/asynch-exns.htm). In the paper, throwTo is non-blocking; but the library implementation adopts a more synchronous design in which throwTo does not return until the exception is received by the target thread. The trade-off is discussed in Section 9 of the paper. Like any blocking operation, throwTo is therefore interruptible (see Section 5.3 of the paper). Unlike other interruptible operations, however, throwTo is always interruptible, even if it does not actually block.

There is no guarantee that the exception will be delivered promptly, although the runtime will endeavour to ensure that arbitrary delays don't occur. In GHC, an exception can only be raised when a thread reaches a safe point, where a safe point is where memory allocation occurs. Some loops do not perform any memory allocation inside the loop and therefore cannot be interrupted by a throwTo.

If the target of throwTo is the calling thread, then the behaviour is the same as throwIO, except that the exception is thrown as an asynchronous exception. This means that if there is an enclosing pure computation, which would be the case if the current IO operation is inside unsafePerformIO or unsafeInterleaveIO, that computation is not permanently replaced by the exception, but is suspended as if it had received an asynchronous exception.

Note that if throwTo is called with the current thread as the target, the exception will be thrown even if the thread is currently inside mask or uninterruptibleMask.

ioError :: IOError -> IO a #

Raise an IOError in the IO monad.

asyncExceptionToException :: Exception e => e -> SomeException #

Since: base-4.7.0.0

data BlockedIndefinitelyOnMVar #

The thread is blocked on an MVar, but there are no other references to the MVar so it can't ever continue.

data BlockedIndefinitelyOnSTM #

The thread is waiting to retry an STM transaction, but there are no other references to any TVars involved, so it can't ever continue.

data Deadlock #

There are no runnable threads, so the program is deadlocked. The Deadlock exception is raised in the main thread only.

Constructors

Deadlock 

Instances

Instances details
Show Deadlock

Since: base-4.1.0.0

Instance details

Defined in GHC.IO.Exception

Exception Deadlock

Since: base-4.1.0.0

Instance details

Defined in GHC.IO.Exception

data AllocationLimitExceeded #

This thread has exceeded its allocation limit. See setAllocationCounter and enableAllocationLimit.

Since: base-4.8.0.0

newtype CompactionFailed #

Compaction found an object that cannot be compacted. Functions cannot be compacted, nor can mutable objects or pinned objects. See compact.

Since: base-4.10.0.0

Constructors

CompactionFailed String 

newtype AssertionFailed #

assert was applied to False.

Constructors

AssertionFailed String 

data SomeAsyncException #

Superclass for asynchronous exceptions.

Since: base-4.7.0.0

Constructors

Exception e => SomeAsyncException e 

data AsyncException #

Asynchronous exceptions.

Constructors

StackOverflow

The current thread's stack exceeded its limit. Since an exception has been raised, the thread's stack will certainly be below its limit again, but the programmer should take remedial action immediately.

HeapOverflow

The program's heap is reaching its limit, and the program should take action to reduce the amount of live data it has. Notes:

  • It is undefined which thread receives this exception. GHC currently throws this to the same thread that receives UserInterrupt, but this may change in the future.
  • The GHC RTS currently can only recover from heap overflow if it detects that an explicit memory limit (set via RTS flags). has been exceeded. Currently, failure to allocate memory from the operating system results in immediate termination of the program.
ThreadKilled

This exception is raised by another thread calling killThread, or by the system if it needs to terminate the thread for some reason.

UserInterrupt

This exception is raised by default in the main thread of the program when the user requests to terminate the program via the usual mechanism(s) (e.g. Control-C in the console).

data ArrayException #

Exceptions generated by array operations

Constructors

IndexOutOfBounds String

An attempt was made to index an array outside its declared bounds.

UndefinedElement String

An attempt was made to evaluate an element of an array that had not been initialized.

uninterruptibleMask :: ((forall a. IO a -> IO a) -> IO b) -> IO b #

Like mask, but the masked computation is not interruptible (see Control.Exception). THIS SHOULD BE USED WITH GREAT CARE, because if a thread executing in uninterruptibleMask blocks for any reason, then the thread (and possibly the program, if this is the main thread) will be unresponsive and unkillable. This function should only be necessary if you need to mask exceptions around an interruptible operation, and you can guarantee that the interruptible operation will only block for a short period of time.

uninterruptibleMask_ :: IO a -> IO a #

Like uninterruptibleMask, but does not pass a restore action to the argument.

mask :: ((forall a. IO a -> IO a) -> IO b) -> IO b #

Executes an IO computation with asynchronous exceptions masked. That is, any thread which attempts to raise an exception in the current thread with throwTo will be blocked until asynchronous exceptions are unmasked again.

The argument passed to mask is a function that takes as its argument another function, which can be used to restore the prevailing masking state within the context of the masked computation. For example, a common way to use mask is to protect the acquisition of a resource:

mask $ \restore -> do
    x <- acquire
    restore (do_something_with x) `onException` release
    release

This code guarantees that acquire is paired with release, by masking asynchronous exceptions for the critical parts. (Rather than write this code yourself, it would be better to use bracket which abstracts the general pattern).

Note that the restore action passed to the argument to mask does not necessarily unmask asynchronous exceptions, it just restores the masking state to that of the enclosing context. Thus if asynchronous exceptions are already masked, mask cannot be used to unmask exceptions again. This is so that if you call a library function with exceptions masked, you can be sure that the library call will not be able to unmask exceptions again. If you are writing library code and need to use asynchronous exceptions, the only way is to create a new thread; see forkIOWithUnmask.

Asynchronous exceptions may still be received while in the masked state if the masked thread blocks in certain ways; see Control.Exception.

Threads created by forkIO inherit the MaskingState from the parent; that is, to start a thread in the MaskedInterruptible state, use mask_ $ forkIO .... This is particularly useful if you need to establish an exception handler in the forked thread before any asynchronous exceptions are received. To create a new thread in an unmasked state use forkIOWithUnmask.

mask_ :: IO a -> IO a #

Like mask, but does not pass a restore action to the argument.

getMaskingState :: IO MaskingState #

Returns the MaskingState for the current thread.

interruptible :: IO a -> IO a #

Allow asynchronous exceptions to be raised even inside mask, making the operation interruptible (see the discussion of "Interruptible operations" in Exception).

When called outside mask, or inside uninterruptibleMask, this function has no effect.

Since: base-4.9.0.0

throwIO :: Exception e => e -> IO a #

A variant of throw that can only be used within the IO monad.

Although throwIO has a type that is an instance of the type of throw, the two functions are subtly different:

throw e   `seq` x  ===> throw e
throwIO e `seq` x  ===> x

The first example will cause the exception e to be raised, whereas the second one won't. In fact, throwIO will only cause an exception to be raised when it is used within the IO monad. The throwIO variant should be used in preference to throw to raise an exception within the IO monad because it guarantees ordering with respect to other IO operations, whereas throw does not.

data MaskingState #

Describes the behaviour of a thread when an asynchronous exception is received.

Constructors

Unmasked

asynchronous exceptions are unmasked (the normal state)

MaskedInterruptible

the state during mask: asynchronous exceptions are masked, but blocking operations may still be interrupted

MaskedUninterruptible

the state during uninterruptibleMask: asynchronous exceptions are masked, and blocking operations may not be interrupted

Instances

Instances details
Eq MaskingState

Since: base-4.3.0.0

Instance details

Defined in GHC.IO

Show MaskingState

Since: base-4.3.0.0

Instance details

Defined in GHC.IO

NFData MaskingState

Since: deepseq-1.4.4.0

Instance details

Defined in Control.DeepSeq

Methods

rnf :: MaskingState -> () #

data IOException #

Exceptions that occur in the IO monad. An IOException records a more specific error type, a descriptive string and maybe the handle that was used when the error was flagged.

Instances

Instances details
Eq IOException

Since: base-4.1.0.0

Instance details

Defined in GHC.IO.Exception

Show IOException

Since: base-4.1.0.0

Instance details

Defined in GHC.IO.Exception

Exception IOException

Since: base-4.1.0.0

Instance details

Defined in GHC.IO.Exception

Error IOException 
Instance details

Defined in Control.Monad.Trans.Error

MonadError IOException IO 
Instance details

Defined in Control.Monad.Error.Class

Methods

throwError :: IOException -> IO a #

catchError :: IO a -> (IOException -> IO a) -> IO a #

throw :: forall (r :: RuntimeRep) (a :: TYPE r) e. Exception e => e -> a #

Throw an exception. Exceptions may be thrown from purely functional code, but may only be caught within the IO monad.

data ErrorCall #

This is thrown when the user calls error. The first String is the argument given to error, second String is the location.

Bundled Patterns

pattern ErrorCall :: String -> ErrorCall 

Instances

Instances details
Eq ErrorCall

Since: base-4.7.0.0

Instance details

Defined in GHC.Exception

Ord ErrorCall

Since: base-4.7.0.0

Instance details

Defined in GHC.Exception

Show ErrorCall

Since: base-4.0.0.0

Instance details

Defined in GHC.Exception

Exception ErrorCall

Since: base-4.0.0.0

Instance details

Defined in GHC.Exception

Wrapped ErrorCall 
Instance details

Defined in Control.Lens.Wrapped

Associated Types

type Unwrapped ErrorCall #

t ~ ErrorCall => Rewrapped ErrorCall t 
Instance details

Defined in Control.Lens.Wrapped

type Unwrapped ErrorCall 
Instance details

Defined in Control.Lens.Wrapped

class (Typeable e, Show e) => Exception e where #

Any type that you wish to throw or catch as an exception must be an instance of the Exception class. The simplest case is a new exception type directly below the root:

data MyException = ThisException | ThatException
    deriving Show

instance Exception MyException

The default method definitions in the Exception class do what we need in this case. You can now throw and catch ThisException and ThatException as exceptions:

*Main> throw ThisException `catch` \e -> putStrLn ("Caught " ++ show (e :: MyException))
Caught ThisException

In more complicated examples, you may wish to define a whole hierarchy of exceptions:

---------------------------------------------------------------------
-- Make the root exception type for all the exceptions in a compiler

data SomeCompilerException = forall e . Exception e => SomeCompilerException e

instance Show SomeCompilerException where
    show (SomeCompilerException e) = show e

instance Exception SomeCompilerException

compilerExceptionToException :: Exception e => e -> SomeException
compilerExceptionToException = toException . SomeCompilerException

compilerExceptionFromException :: Exception e => SomeException -> Maybe e
compilerExceptionFromException x = do
    SomeCompilerException a <- fromException x
    cast a

---------------------------------------------------------------------
-- Make a subhierarchy for exceptions in the frontend of the compiler

data SomeFrontendException = forall e . Exception e => SomeFrontendException e

instance Show SomeFrontendException where
    show (SomeFrontendException e) = show e

instance Exception SomeFrontendException where
    toException = compilerExceptionToException
    fromException = compilerExceptionFromException

frontendExceptionToException :: Exception e => e -> SomeException
frontendExceptionToException = toException . SomeFrontendException

frontendExceptionFromException :: Exception e => SomeException -> Maybe e
frontendExceptionFromException x = do
    SomeFrontendException a <- fromException x
    cast a

---------------------------------------------------------------------
-- Make an exception type for a particular frontend compiler exception

data MismatchedParentheses = MismatchedParentheses
    deriving Show

instance Exception MismatchedParentheses where
    toException   = frontendExceptionToException
    fromException = frontendExceptionFromException

We can now catch a MismatchedParentheses exception as MismatchedParentheses, SomeFrontendException or SomeCompilerException, but not other types, e.g. IOException:

*Main> throw MismatchedParentheses `catch` \e -> putStrLn ("Caught " ++ show (e :: MismatchedParentheses))
Caught MismatchedParentheses
*Main> throw MismatchedParentheses `catch` \e -> putStrLn ("Caught " ++ show (e :: SomeFrontendException))
Caught MismatchedParentheses
*Main> throw MismatchedParentheses `catch` \e -> putStrLn ("Caught " ++ show (e :: SomeCompilerException))
Caught MismatchedParentheses
*Main> throw MismatchedParentheses `catch` \e -> putStrLn ("Caught " ++ show (e :: IOException))
*** Exception: MismatchedParentheses

Minimal complete definition

Nothing

Methods

toException :: e -> SomeException #

fromException :: SomeException -> Maybe e #

displayException :: e -> String #

Render this exception value in a human-friendly manner.

Default implementation: show.

Since: base-4.8.0.0

Instances

Instances details
Exception Void

Since: base-4.8.0.0

Instance details

Defined in Data.Void

Exception PatternMatchFail

Since: base-4.0

Instance details

Defined in Control.Exception.Base

Exception RecSelError

Since: base-4.0

Instance details

Defined in Control.Exception.Base

Exception RecConError

Since: base-4.0

Instance details

Defined in Control.Exception.Base

Exception RecUpdError

Since: base-4.0

Instance details

Defined in Control.Exception.Base

Exception NoMethodError

Since: base-4.0

Instance details

Defined in Control.Exception.Base

Exception TypeError

Since: base-4.9.0.0

Instance details

Defined in Control.Exception.Base

Exception NonTermination

Since: base-4.0

Instance details

Defined in Control.Exception.Base

Exception NestedAtomically

Since: base-4.0

Instance details

Defined in Control.Exception.Base

Exception BlockedIndefinitelyOnMVar

Since: base-4.1.0.0

Instance details

Defined in GHC.IO.Exception

Exception BlockedIndefinitelyOnSTM

Since: base-4.1.0.0

Instance details

Defined in GHC.IO.Exception

Exception Deadlock

Since: base-4.1.0.0

Instance details

Defined in GHC.IO.Exception

Exception AllocationLimitExceeded

Since: base-4.8.0.0

Instance details

Defined in GHC.IO.Exception

Exception CompactionFailed

Since: base-4.10.0.0

Instance details

Defined in GHC.IO.Exception

Exception AssertionFailed

Since: base-4.1.0.0

Instance details

Defined in GHC.IO.Exception

Exception SomeAsyncException

Since: base-4.7.0.0

Instance details

Defined in GHC.IO.Exception

Exception AsyncException

Since: base-4.7.0.0

Instance details

Defined in GHC.IO.Exception

Exception ArrayException

Since: base-4.1.0.0

Instance details

Defined in GHC.IO.Exception

Exception FixIOException

Since: base-4.11.0.0

Instance details

Defined in GHC.IO.Exception

Exception ExitCode

Since: base-4.1.0.0

Instance details

Defined in GHC.IO.Exception

Exception IOException

Since: base-4.1.0.0

Instance details

Defined in GHC.IO.Exception

Exception ErrorCall

Since: base-4.0.0.0

Instance details

Defined in GHC.Exception

Exception ArithException

Since: base-4.0.0.0

Instance details

Defined in GHC.Exception.Type

Exception SomeException

Since: base-3.0

Instance details

Defined in GHC.Exception.Type

Exception ASCII7_Invalid 
Instance details

Defined in Basement.String.Encoding.ASCII7

Methods

toException :: ASCII7_Invalid -> SomeException #

fromException :: SomeException -> Maybe ASCII7_Invalid #

displayException :: ASCII7_Invalid -> String #

Exception ISO_8859_1_Invalid 
Instance details

Defined in Basement.String.Encoding.ISO_8859_1

Methods

toException :: ISO_8859_1_Invalid -> SomeException #

fromException :: SomeException -> Maybe ISO_8859_1_Invalid #

displayException :: ISO_8859_1_Invalid -> String #

Exception UTF16_Invalid 
Instance details

Defined in Basement.String.Encoding.UTF16

Methods

toException :: UTF16_Invalid -> SomeException #

fromException :: SomeException -> Maybe UTF16_Invalid #

displayException :: UTF16_Invalid -> String #

Exception UTF32_Invalid 
Instance details

Defined in Basement.String.Encoding.UTF32

Methods

toException :: UTF32_Invalid -> SomeException #

fromException :: SomeException -> Maybe UTF32_Invalid #

displayException :: UTF32_Invalid -> String #

Exception DeserialiseFailure 
Instance details

Defined in Codec.CBOR.Read

Exception CryptoError 
Instance details

Defined in Crypto.Error.Types

Exception HttpExceptionContentWrapper 
Instance details

Defined in Network.HTTP.Client.Types

Methods

toException :: HttpExceptionContentWrapper -> SomeException #

fromException :: SomeException -> Maybe HttpExceptionContentWrapper #

displayException :: HttpExceptionContentWrapper -> String #

Exception HttpException 
Instance details

Defined in Network.HTTP.Client.Types

Exception DigestAuthException 
Instance details

Defined in Network.HTTP.Client.TLS

Exception InvalidPosException 
Instance details

Defined in Text.Megaparsec.Pos

Exception ThunkLoop Source # 
Instance details

Defined in Nix.Thunk

Exception NixException Source # 
Instance details

Defined in Nix.Frames

Exception InferError Source # 
Instance details

Defined in Nix.Type.Infer

(Show s, Show (Token s), Show e, ShowErrorComponent e, Stream s, Typeable s, Typeable e) => Exception (ParseErrorBundle s e) 
Instance details

Defined in Text.Megaparsec.Error

(Show s, Show (Token s), Show e, ShowErrorComponent e, Stream s, Typeable s, Typeable e) => Exception (ParseError s e) 
Instance details

Defined in Text.Megaparsec.Error

(Typeable m, Typeable v) => Exception (SynHoleInfo m v) Source # 
Instance details

Defined in Nix.Eval

(Typeable m, Typeable v) => Exception (EvalFrame m v) Source # 
Instance details

Defined in Nix.Eval

MonadDataErrorContext t f m => Exception (ValueFrame t f m) Source # 
Instance details

Defined in Nix.Value

MonadDataErrorContext t f m => Exception (NormalLoop t f m) Source # 
Instance details

Defined in Nix.Normal

MonadDataErrorContext t f m => Exception (ExecFrame t f m) Source # 
Instance details

Defined in Nix.Exec

data SomeException #

The SomeException type is the root of the exception type hierarchy. When an exception of type e is thrown, behind the scenes it is encapsulated in a SomeException.

Constructors

Exception e => SomeException e 

Instances

Instances details
Show SomeException

Since: base-3.0

Instance details

Defined in GHC.Exception.Type

Exception SomeException

Since: base-3.0

Instance details

Defined in GHC.Exception.Type