Dep.Env

This module provides helpers for building dependency injection environments composed of records.

It's not necessary when defining the record components themselves, in that case Dep.Has should suffice.

>>> :{
type Logger :: (Type -> Type) -> Type
newtype Logger d = Logger {
    info :: String -> d ()
  }
--
data Repository d = Repository
  { findById :: Int -> d (Maybe String)
  , putById :: Int -> String -> d ()
  , insert :: String -> d Int
  }
--
data Controller d = Controller 
  { create :: d Int
  , append :: Int -> String -> d Bool 
  , inspect :: Int -> d (Maybe String)
  } 
--
type EnvHKD :: (Type -> Type) -> (Type -> Type) -> Type
data EnvHKD h m = EnvHKD
  { logger :: h (Logger m),
    repository :: h (Repository m),
    controller :: h (Controller m)
  } deriving stock Generic
    deriving anyclass (FieldsFindableByType, DemotableFieldNames, Phased)
deriving via Autowired (EnvHKD Identity m) instance Autowireable r_ m (EnvHKD Identity m) => Has r_ m (EnvHKD Identity m)
:}

The module also provides a monad transformer-less way of performing dependency injection, by means of fixEnv.

A general-purpose Has

class Has r_ (m :: Type -> Type) (env :: Type) | env -> m

A generic "Has" class. When partially applied to a parametrizable record-of-functions r_, produces a 2-place constraint saying that the environment e has the record r_ with effect monad m.

The constraint can be used on its own, or with Control.Monad.Dep.Class.

Instances

(FieldsFindableByType (env_ m), HasField (FindFieldByType (env_ m) (r_ m)) (env_ m) u, Coercible u (r_ m)) => Has r_ m (Autowired (env_ m))

Defined in Dep.Env

Methods

dep :: Autowired (env_ m) -> r_ m

(Dep r_, HasField (DefaultFieldName r_) (env_ m) u, Coercible u (r_ m)) => Has r_ m (TheDefaultFieldName (env_ m))

Defined in Dep.Env

Methods

dep :: TheDefaultFieldName (env_ m) -> r_ m

(HasField name (env_ m) u, Coercible u (r_ m)) => Has r_ m (TheFieldName name (env_ m))

Defined in Dep.Env

Methods

dep :: TheFieldName name (env_ m) -> r_ m

InductiveEnvFind r_ m rs => Has r_ m (InductiveEnv rs Identity m)

Works by searching on the list of types.

Defined in Dep.Env

Methods

dep :: InductiveEnv rs Identity m -> r_ m

Helpers for deriving Has

via the default field name

newtype TheDefaultFieldName (env :: Type)

Helper for DerivingVia HasField instances.

It expects the component to have as field name the default fieldname specified by Dep.

This is the same behavior as the DefaultSignatures implementation for Has, so maybe it doesn't make much sense to use it, except for explicitness.

Constructors

TheDefaultFieldName env

Instances

(Dep r_, HasField (DefaultFieldName r_) (env_ m) u, Coercible u (r_ m)) => Has r_ m (TheDefaultFieldName (env_ m))

Defined in Dep.Env

Methods

dep :: TheDefaultFieldName (env_ m) -> r_ m

via arbitrary field name

newtype TheFieldName (name :: Symbol) (env :: Type)

Helper for DerivingVia HasField instances.

The field name is specified as a Symbol.

Constructors

TheFieldName env

Instances

(HasField name (env_ m) u, Coercible u (r_ m)) => Has r_ m (TheFieldName name (env_ m))

Defined in Dep.Env

Methods

dep :: TheFieldName name (env_ m) -> r_ m

via autowiring

class FieldsFindableByType (env :: Type)

Class for getting the field name from the field's type.

The default implementation of FindFieldByType requires a Generic instance, but users can write their own implementations.

Associated Types

type FindFieldByType env (r :: Type) :: Symbol

type FindFieldByType env r = FindFieldByType_ env r

newtype Autowired (env :: Type)

Helper for DerivingVia HasField instances.

The fields are identified by their types.

It uses FindFieldByType under the hood.

BEWARE: for large records with many components, this technique might incur in long compilation times.

Constructors

Autowired env

Instances

(FieldsFindableByType (env_ m), HasField (FindFieldByType (env_ m) (r_ m)) (env_ m) u, Coercible u (r_ m)) => Has r_ m (Autowired (env_ m))

Defined in Dep.Env

Methods

dep :: Autowired (env_ m) -> r_ m

type Autowireable r_ (m :: Type -> Type) (env :: Type) = HasField (FindFieldByType env (r_ m)) env (Identity (r_ m))

Constraints required when DerivingVia all possible instances of Has in a single definition.

This only works for environments where all the fields come wrapped in Data.Functor.Identity.

Managing phases

class Phased (env_ :: (Type -> Type) -> (Type -> Type) -> Type) where

Class of 2-parameter environments for which the first parameter h wraps each field and corresponds to phases in the construction of the environment, and the second parameter m is the effect monad used by each component.

h will typically be a composition of applicative functors, each one representing a phase. We advance through the phases by "pulling out" the outermost phase and running it in some way, until we are are left with a Constructor phase, which we can remove using fixEnv.

Phased resembles FunctorT, TraversableT and ApplicativeT from the barbies library. Phased instances can be written in terms of them.

Minimal complete definition

Nothing

Methods

traverseH

Arguments

:: forall (h :: Type -> Type) (f :: Type -> Type) (g :: Type -> Type) (m :: Type -> Type). (Applicative f, Typeable f, Typeable g, Typeable h, Typeable m)

=> (forall x. h x -> f (g x))

-> env_ h m

-> f (env_ g m)

Used to implement pullPhase and mapPhase, typically you should use those functions instead.

default traverseH :: forall (h :: Type -> Type) (f :: Type -> Type) (g :: Type -> Type) (m :: Type -> Type). (Applicative f, Typeable f, Typeable g, Typeable h, Typeable m, Generic (env_ h m), Generic (env_ g m), GTraverseH h g (Rep (env_ h m)) (Rep (env_ g m))) => (forall x. h x -> f (g x)) -> env_ h m -> f (env_ g m)

liftA2H

Arguments

:: forall (a :: Type -> Type) (f :: Type -> Type) (f' :: Type -> Type) (m :: Type -> Type). (Typeable a, Typeable f, Typeable f', Typeable m)

=> (forall x. a x -> f x -> f' x)

-> env_ a m

-> env_ f m

-> env_ f' m

Used to implement liftA2Phase, typically you should use that function instead.

default liftA2H :: forall (a :: Type -> Type) (f :: Type -> Type) (f' :: Type -> Type) m. (Typeable a, Typeable f, Typeable f', Typeable m, Generic (env_ a m), Generic (env_ f m), Generic (env_ f' m), GLiftA2Phase a f f' (Rep (env_ a m)) (Rep (env_ f m)) (Rep (env_ f' m))) => (forall x. a x -> f x -> f' x) -> env_ a m -> env_ f m -> env_ f' m

Instances

Phased (InductiveEnv rs)

Defined in Dep.Env

Methods

traverseH :: forall h f g (m :: Type -> Type). (Applicative f, Typeable f, Typeable g, Typeable h, Typeable m) => (forall x. h x -> f (g x)) -> InductiveEnv rs h m -> f (InductiveEnv rs g m)

liftA2H :: forall a f f' (m :: Type -> Type). (Typeable a, Typeable f, Typeable f', Typeable m) => (forall x. a x -> f x -> f' x) -> InductiveEnv rs a m -> InductiveEnv rs f m -> InductiveEnv rs f' m

pullPhase

Arguments

:: forall (f :: Type -> Type) (g :: Type -> Type) (m :: Type -> Type) env_. (Phased env_, Applicative f, Typeable f, Typeable g, Typeable m)

=> env_ (Compose f g) m

-> f (env_ g m)

Take the outermost phase wrapping each component and "pull it outwards", aggregating the phase's applicative effects.

>>> :{
 newtype Foo d = Foo {foo :: String -> d ()} deriving Generic
 makeIOFoo :: MonadIO m => Foo m
 makeIOFoo = Foo (liftIO . putStrLn)
 env :: InductiveEnv '[Foo] (IO `Compose` Constructor (InductiveEnv '[Foo] Identity IO)) IO
 env = EmptyEnv 
     & AddDep @Foo (putStrLn "io phase" `bindPhase` \() -> constructor (\_ -> makeIOFoo))
 ioOutside :: IO (InductiveEnv '[Foo] (Constructor (InductiveEnv '[Foo] Identity IO)) IO)
 ioOutside = pullPhase env
:}

mapPhase

Arguments

:: forall (f :: Type -> Type) (f' :: Type -> Type) (g :: Type -> Type) (m :: Type -> Type) env_. (Phased env_, Typeable f, Typeable f', Typeable g, Typeable m)

=> (forall x. f x -> f' x)

-> env_ (Compose f g) m

-> env_ (Compose f' g) m

Modify the outermost phase wrapping each component.

>>> :{
 newtype Foo d = Foo {foo :: String -> d ()} deriving Generic
 makeIOFoo :: MonadIO m => Foo m
 makeIOFoo = Foo (liftIO . putStrLn)
 env :: InductiveEnv '[Foo] ((,) Int `Compose` Constructor String) IO
 env = EmptyEnv 
     & AddDep @Foo ((2,()) `bindPhase` \() -> constructor (\_ -> makeIOFoo))
 env' :: InductiveEnv '[Foo] ((,) String `Compose` Constructor String) IO
 env' = mapPhase (\(n,x) -> (show n,x)) env
:}

liftA2Phase

Arguments

:: forall (a :: Type -> Type) (f' :: Type -> Type) (f :: Type -> Type) (g :: Type -> Type) (m :: Type -> Type) env_. (Phased env_, Typeable a, Typeable f, Typeable f', Typeable g, Typeable m)

=> (forall x. a x -> f x -> f' x)

-> env_ (Compose a g) m

-> env_ (Compose f g) m

-> env_ (Compose f' g) m

Combine two environments with a function that works on their outermost phases.

Working with field names

class DemotableFieldNames env_ where

Class of 2-parameter environments for which it's possible to obtain the names of each field as values.

Minimal complete definition

Nothing

Methods

demoteFieldNamesH :: (forall x. String -> h String x) -> env_ (h String) m

default demoteFieldNamesH :: (Generic (env_ (h String) m), GDemotableFieldNamesH h (Rep (env_ (h String) m))) => (forall x. String -> h String x) -> env_ (h String) m

demoteFieldNames :: forall env_ m. DemotableFieldNames env_ => env_ (Constant String) m

Bring down the field names of the environment to the term level and store them in the accumulator of Data.Functor.Constant.

mapPhaseWithFieldNames

Arguments

:: forall (f :: Type -> Type) (f' :: Type -> Type) (g :: Type -> Type) (m :: Type -> Type) env_. (Phased env_, DemotableFieldNames env_, Typeable f, Typeable f', Typeable g, Typeable m)

=> (forall x. String -> f x -> f' x)

-> env_ (Compose f g) m

-> env_ (Compose f' g) m

Modify the outermost phase wrapping each component, while having access to the field name of the component.

A typical usage is modifying a "parsing the configuration" phase so that each component looks into a different section of the global configuration field.

Constructing phases

bindPhase and skipPhase are small convenience functions to help build nested compositions of functors.

bindPhase :: forall f g a b. Functor f => f a -> (a -> g b) -> Compose f g b

Use the result of the previous phase to build the next one.

Can be useful infix.

>>> :{
 type Phases = IO `Compose` IO `Compose` Identity
 phased :: Phases Int
 phased =
     pure 1 `bindPhase` \i1 -> 
     pure 2 `bindPhase` \i2 -> 
     Identity (i1 + i2)
:}

skipPhase :: forall f g a. Applicative f => g a -> Compose f g a

Don't do anything for the current phase, just wrap the next one.

>>> :{
 type Phases = IO `Compose` IO `Compose` Identity
 phased :: Phases Int
 phased =
     skipPhase $
     skipPhase $
     Identity 1
:}

fromBare and toBare are an alternative method to build nested compositions of functors, which relies on "coerce".

type family Bare x where ...

This type family clears newtypes like Compose, Identity and Constant from a composite type, leaving you with a newtypeless nested type as result.

The idea is that it might be easier to construct values of the "bare" version of a composite type, and later coerce them to the newtyped version using fromBare.

This is mainly intended for defining the nested Applicative "phases" of components that live in a Phased environment. It's an alternative to functions like bindPhase and skipPhase.

Equations

Bare (Compose outer inner x) = Bare (outer (Bare (inner x)))

Bare (Identity x) = Bare x

Bare (Const x k) = Bare x

Bare (Constant x k) = Bare x

Bare other = other

fromBare :: Coercible phases (Bare phases) => Bare phases -> phases

Convert a value from its bare version to the newtyped one, usually as a step towards inserting it into a Phased environment.

>>> :{
type Phases = IO `Compose` IO `Compose` IO
wrapped :: Phases Int = fromBare $ pure $ pure $ pure 3
:}

>>> :{
type Phases = Constructor Int
wrapped :: Phases Int
wrapped = fromBare $ succ
:}

>>> :{
type Phases = IO `Compose` Constructor Int
wrapped :: Phases Int
wrapped = fromBare $ pure $ succ
:}

toBare :: Coercible phases (Bare phases) => phases -> Bare phases

Convert from the newtyped value to the bare one. fromBare tends to be more useful.

Injecting dependencies by tying the knot

fixEnv

Arguments

:: (Phased env_, Typeable env_, Typeable m)

=> env_ (Constructor (env_ Identity m)) m

Environment where each field is wrapped in a Constructor

-> env_ Identity m

Fully constructed environment, ready for use.

This is a method of performing dependency injection that doesn't require Control.Monad.Dep.DepT at all. In fact, it doesn't require the use of any monad transformer!

If we have a environment whose fields are functions that construct each component by searching for its dependencies in a "fully built" version of the environment, we can "tie the knot" to obtain the "fully built" environment. This works as long as there aren't any circular dependencies between components.

Think of it as a version of fix that, instead of "tying" a single function, ties a whole record of them.

The env_ (Constructor (env_ Identity m)) m parameter might be the result of peeling away successive layers of applicative functor composition using pullPhase, until only the wiring phase remains.

>>> :{
newtype Foo d = Foo {foo :: String -> d ()} deriving Generic
newtype Bar d = Bar {bar :: String -> d ()} deriving Generic
makeIOFoo :: MonadIO m => Foo m
makeIOFoo = Foo (liftIO . putStrLn)
makeBar :: Has Foo m env => env -> Bar m
makeBar (asCall -> call) = Bar (call foo)
env :: InductiveEnv [Bar,Foo] (Constructor (InductiveEnv [Bar,Foo] Identity IO)) IO
env = EmptyEnv 
    & AddDep @Foo (constructor (\_ -> makeIOFoo))
    & AddDep @Bar (constructor makeBar) 
envReady :: InductiveEnv [Bar,Foo] Identity IO
envReady = fixEnv env
 :}

>>> :{
 bar (dep envReady) "this is bar"
:}
this is bar

type Constructor (env :: Type) = (->) env `Compose` Identity

A phase with the effect of "constructing each component by reading its dependencies from a completed environment".

The Constructor phase for an environment will typically be parameterized with the environment itself.

constructor :: forall r_ m env. (env -> r_ m) -> Constructor env (r_ m)

Turn an environment-consuming function into a Constructor that can be slotted into some field of a Phased environment.

Inductive environment with anonymous fields

data InductiveEnv (rs :: [(Type -> Type) -> Type]) (h :: Type -> Type) (m :: Type -> Type) where

An inductively constructed environment with anonymous fields.

Can be useful for simple tests. Also for converting Has-based components into functions that take their dependencies as separate positional parameters.

makeController :: (Monad m, Has Logger m env, Has Repository m env) => env -> Controller m
makeController = undefined
makeControllerPositional :: Monad m => Logger m -> Repository m -> Controller m
makeControllerPositional a b = makeController $ addDep @Logger a $ addDep @Repository b $ emptyEnv
makeController' :: (Monad m, Has Logger m env, Has Repository m env) => env -> Controller m
makeController' env = makeControllerPositional (dep env) (dep env)

Constructors

AddDep :: forall r_ m rs h. h (r_ m) -> InductiveEnv rs h m -> InductiveEnv (r_ ': rs) h m

EmptyEnv :: forall m h. InductiveEnv '[] h m

Instances

InductiveEnvFind r_ m rs => Has r_ m (InductiveEnv rs Identity m)

Works by searching on the list of types.

Defined in Dep.Env

Methods

dep :: InductiveEnv rs Identity m -> r_ m

Phased (InductiveEnv rs)

Defined in Dep.Env

Methods

traverseH :: forall h f g (m :: Type -> Type). (Applicative f, Typeable f, Typeable g, Typeable h, Typeable m) => (forall x. h x -> f (g x)) -> InductiveEnv rs h m -> f (InductiveEnv rs g m)

liftA2H :: forall a f f' (m :: Type -> Type). (Typeable a, Typeable f, Typeable f', Typeable m) => (forall x. a x -> f x -> f' x) -> InductiveEnv rs a m -> InductiveEnv rs f m -> InductiveEnv rs f' m

addDep :: forall r_ m rs. r_ m -> InductiveEnv rs Identity m -> InductiveEnv (r_ ': rs) Identity m

Unlike the AddDep constructor, this sets h to Identity.

emptyEnv :: forall m. InductiveEnv '[] Identity m

Unlike the EmptyEnv constructor, this sets h to Identity.

Re-exports

newtype Identity a

Identity functor and monad. (a non-strict monad)

Since: base-4.8.0.0

Constructors

Identity

Fields

• runIdentity :: a

Instances

Monad Identity

Since: base-4.8.0.0

Defined in Data.Functor.Identity

Methods

(>>=) :: Identity a -> (a -> Identity b) -> Identity b

(>>) :: Identity a -> Identity b -> Identity b

return :: a -> Identity a

Functor Identity

Since: base-4.8.0.0

Defined in Data.Functor.Identity

Methods

fmap :: (a -> b) -> Identity a -> Identity b

(<$) :: a -> Identity b -> Identity a

MonadFix Identity

Since: base-4.8.0.0

Defined in Data.Functor.Identity

Methods

mfix :: (a -> Identity a) -> Identity a

Applicative Identity

Since: base-4.8.0.0

Defined in Data.Functor.Identity

Methods

pure :: a -> Identity a

(<*>) :: Identity (a -> b) -> Identity a -> Identity b

liftA2 :: (a -> b -> c) -> Identity a -> Identity b -> Identity c

(*>) :: Identity a -> Identity b -> Identity b

(<*) :: Identity a -> Identity b -> Identity a

Foldable Identity

Since: base-4.8.0.0

Defined in Data.Functor.Identity

Methods

fold :: Monoid m => Identity m -> m

foldMap :: Monoid m => (a -> m) -> Identity a -> m

foldMap' :: Monoid m => (a -> m) -> Identity a -> m

foldr :: (a -> b -> b) -> b -> Identity a -> b

foldr' :: (a -> b -> b) -> b -> Identity a -> b

foldl :: (b -> a -> b) -> b -> Identity a -> b

foldl' :: (b -> a -> b) -> b -> Identity a -> b

foldr1 :: (a -> a -> a) -> Identity a -> a

foldl1 :: (a -> a -> a) -> Identity a -> a

toList :: Identity a -> [a]

null :: Identity a -> Bool

length :: Identity a -> Int

elem :: Eq a => a -> Identity a -> Bool

maximum :: Ord a => Identity a -> a

minimum :: Ord a => Identity a -> a

sum :: Num a => Identity a -> a

product :: Num a => Identity a -> a

Traversable Identity

Since: base-4.9.0.0

Defined in Data.Traversable

Methods

traverse :: Applicative f => (a -> f b) -> Identity a -> f (Identity b)

sequenceA :: Applicative f => Identity (f a) -> f (Identity a)

mapM :: Monad m => (a -> m b) -> Identity a -> m (Identity b)

sequence :: Monad m => Identity (m a) -> m (Identity a)

MonadZip Identity

Since: base-4.8.0.0

Defined in Control.Monad.Zip

Methods

mzip :: Identity a -> Identity b -> Identity (a, b)

mzipWith :: (a -> b -> c) -> Identity a -> Identity b -> Identity c

munzip :: Identity (a, b) -> (Identity a, Identity b)

InductiveEnvFind r_ m rs => Has r_ m (InductiveEnv rs Identity m)

Works by searching on the list of types.

Defined in Dep.Env

Methods

dep :: InductiveEnv rs Identity m -> r_ m

Bounded a => Bounded (Identity a)

Since: base-4.9.0.0

Defined in Data.Functor.Identity

Methods

minBound :: Identity a

maxBound :: Identity a

Enum a => Enum (Identity a)

Since: base-4.9.0.0

Defined in Data.Functor.Identity

Methods

succ :: Identity a -> Identity a

pred :: Identity a -> Identity a

toEnum :: Int -> Identity a

fromEnum :: Identity a -> Int

enumFrom :: Identity a -> [Identity a]

enumFromThen :: Identity a -> Identity a -> [Identity a]

enumFromTo :: Identity a -> Identity a -> [Identity a]

enumFromThenTo :: Identity a -> Identity a -> Identity a -> [Identity a]

Eq a => Eq (Identity a)

Since: base-4.8.0.0

Defined in Data.Functor.Identity

Methods

(==) :: Identity a -> Identity a -> Bool

(/=) :: Identity a -> Identity a -> Bool

Floating a => Floating (Identity a)

Since: base-4.9.0.0

Defined in Data.Functor.Identity

Methods

pi :: Identity a

exp :: Identity a -> Identity a

log :: Identity a -> Identity a

sqrt :: Identity a -> Identity a

(**) :: Identity a -> Identity a -> Identity a

logBase :: Identity a -> Identity a -> Identity a

sin :: Identity a -> Identity a

cos :: Identity a -> Identity a

tan :: Identity a -> Identity a

asin :: Identity a -> Identity a

acos :: Identity a -> Identity a

atan :: Identity a -> Identity a

sinh :: Identity a -> Identity a

cosh :: Identity a -> Identity a

tanh :: Identity a -> Identity a

asinh :: Identity a -> Identity a

acosh :: Identity a -> Identity a

atanh :: Identity a -> Identity a

log1p :: Identity a -> Identity a

expm1 :: Identity a -> Identity a

log1pexp :: Identity a -> Identity a

log1mexp :: Identity a -> Identity a

Fractional a => Fractional (Identity a)

Since: base-4.9.0.0

Defined in Data.Functor.Identity

Methods

(/) :: Identity a -> Identity a -> Identity a

recip :: Identity a -> Identity a

fromRational :: Rational -> Identity a

Integral a => Integral (Identity a)

Since: base-4.9.0.0

Defined in Data.Functor.Identity

Methods

quot :: Identity a -> Identity a -> Identity a

rem :: Identity a -> Identity a -> Identity a

div :: Identity a -> Identity a -> Identity a

mod :: Identity a -> Identity a -> Identity a

quotRem :: Identity a -> Identity a -> (Identity a, Identity a)

divMod :: Identity a -> Identity a -> (Identity a, Identity a)

toInteger :: Identity a -> Integer

Num a => Num (Identity a)

Since: base-4.9.0.0

Defined in Data.Functor.Identity

Methods

(+) :: Identity a -> Identity a -> Identity a

(-) :: Identity a -> Identity a -> Identity a

(*) :: Identity a -> Identity a -> Identity a

negate :: Identity a -> Identity a

abs :: Identity a -> Identity a

signum :: Identity a -> Identity a

fromInteger :: Integer -> Identity a

Ord a => Ord (Identity a)

Since: base-4.8.0.0

Defined in Data.Functor.Identity

Methods

compare :: Identity a -> Identity a -> Ordering

(<) :: Identity a -> Identity a -> Bool

(<=) :: Identity a -> Identity a -> Bool

(>) :: Identity a -> Identity a -> Bool

(>=) :: Identity a -> Identity a -> Bool

max :: Identity a -> Identity a -> Identity a

min :: Identity a -> Identity a -> Identity a

Read a => Read (Identity a)

This instance would be equivalent to the derived instances of the Identity newtype if the runIdentity field were removed

Since: base-4.8.0.0

Defined in Data.Functor.Identity

Methods

readsPrec :: Int -> ReadS (Identity a)

readList :: ReadS [Identity a]

readPrec :: ReadPrec (Identity a)

readListPrec :: ReadPrec [Identity a]

Real a => Real (Identity a)

Since: base-4.9.0.0

Defined in Data.Functor.Identity

Methods

toRational :: Identity a -> Rational

RealFloat a => RealFloat (Identity a)

Since: base-4.9.0.0

Defined in Data.Functor.Identity

Methods

floatRadix :: Identity a -> Integer

floatDigits :: Identity a -> Int

floatRange :: Identity a -> (Int, Int)

decodeFloat :: Identity a -> (Integer, Int)

encodeFloat :: Integer -> Int -> Identity a

exponent :: Identity a -> Int

significand :: Identity a -> Identity a

scaleFloat :: Int -> Identity a -> Identity a

isNaN :: Identity a -> Bool

isInfinite :: Identity a -> Bool

isDenormalized :: Identity a -> Bool

isNegativeZero :: Identity a -> Bool

isIEEE :: Identity a -> Bool

atan2 :: Identity a -> Identity a -> Identity a

RealFrac a => RealFrac (Identity a)

Since: base-4.9.0.0

Defined in Data.Functor.Identity

Methods

properFraction :: Integral b => Identity a -> (b, Identity a)

truncate :: Integral b => Identity a -> b

round :: Integral b => Identity a -> b

ceiling :: Integral b => Identity a -> b

floor :: Integral b => Identity a -> b

Show a => Show (Identity a)

This instance would be equivalent to the derived instances of the Identity newtype if the runIdentity field were removed

Since: base-4.8.0.0

Defined in Data.Functor.Identity

Methods

showsPrec :: Int -> Identity a -> ShowS

show :: Identity a -> String

showList :: [Identity a] -> ShowS

Ix a => Ix (Identity a)

Since: base-4.9.0.0

Defined in Data.Functor.Identity

Methods

range :: (Identity a, Identity a) -> [Identity a]

index :: (Identity a, Identity a) -> Identity a -> Int

unsafeIndex :: (Identity a, Identity a) -> Identity a -> Int

inRange :: (Identity a, Identity a) -> Identity a -> Bool

rangeSize :: (Identity a, Identity a) -> Int

unsafeRangeSize :: (Identity a, Identity a) -> Int

IsString a => IsString (Identity a)

Since: base-4.9.0.0

Defined in Data.String

Methods

fromString :: String -> Identity a

Generic (Identity a)

Since: base-4.8.0.0

Defined in Data.Functor.Identity

Associated Types

type Rep (Identity a) :: Type -> Type

Methods

from :: Identity a -> Rep (Identity a) x

to :: Rep (Identity a) x -> Identity a

Semigroup a => Semigroup (Identity a)

Since: base-4.9.0.0

Defined in Data.Functor.Identity

Methods

(<>) :: Identity a -> Identity a -> Identity a

sconcat :: NonEmpty (Identity a) -> Identity a

stimes :: Integral b => b -> Identity a -> Identity a

Monoid a => Monoid (Identity a)

Since: base-4.9.0.0

Defined in Data.Functor.Identity

Methods

mempty :: Identity a

mappend :: Identity a -> Identity a -> Identity a

mconcat :: [Identity a] -> Identity a

Storable a => Storable (Identity a)

Since: base-4.9.0.0

Defined in Data.Functor.Identity

Methods

sizeOf :: Identity a -> Int

alignment :: Identity a -> Int

peekElemOff :: Ptr (Identity a) -> Int -> IO (Identity a)

pokeElemOff :: Ptr (Identity a) -> Int -> Identity a -> IO ()

peekByteOff :: Ptr b -> Int -> IO (Identity a)

pokeByteOff :: Ptr b -> Int -> Identity a -> IO ()

peek :: Ptr (Identity a) -> IO (Identity a)

poke :: Ptr (Identity a) -> Identity a -> IO ()

Bits a => Bits (Identity a)

Since: base-4.9.0.0

Defined in Data.Functor.Identity

Methods

(.&.) :: Identity a -> Identity a -> Identity a

(.|.) :: Identity a -> Identity a -> Identity a

xor :: Identity a -> Identity a -> Identity a

complement :: Identity a -> Identity a

shift :: Identity a -> Int -> Identity a

rotate :: Identity a -> Int -> Identity a

zeroBits :: Identity a

bit :: Int -> Identity a

setBit :: Identity a -> Int -> Identity a

clearBit :: Identity a -> Int -> Identity a

complementBit :: Identity a -> Int -> Identity a

testBit :: Identity a -> Int -> Bool

bitSizeMaybe :: Identity a -> Maybe Int

bitSize :: Identity a -> Int

isSigned :: Identity a -> Bool

shiftL :: Identity a -> Int -> Identity a

unsafeShiftL :: Identity a -> Int -> Identity a

shiftR :: Identity a -> Int -> Identity a

unsafeShiftR :: Identity a -> Int -> Identity a

rotateL :: Identity a -> Int -> Identity a

rotateR :: Identity a -> Int -> Identity a

popCount :: Identity a -> Int

FiniteBits a => FiniteBits (Identity a)

Since: base-4.9.0.0

Defined in Data.Functor.Identity

Methods

finiteBitSize :: Identity a -> Int

countLeadingZeros :: Identity a -> Int

countTrailingZeros :: Identity a -> Int

Generic1 Identity

Since: base-4.8.0.0

Defined in Data.Functor.Identity

Associated Types

type Rep1 Identity :: k -> Type

Methods

from1 :: forall (a :: k). Identity a -> Rep1 Identity a

to1 :: forall (a :: k). Rep1 Identity a -> Identity a

type Rep (Identity a)

Defined in Data.Functor.Identity

type Rep (Identity a) = D1 ('MetaData "Identity" "Data.Functor.Identity" "base" 'True) (C1 ('MetaCons "Identity" 'PrefixI 'True) (S1 ('MetaSel ('Just "runIdentity") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 a)))

type Rep1 Identity

Defined in Data.Functor.Identity

type Rep1 Identity = D1 ('MetaData "Identity" "Data.Functor.Identity" "base" 'True) (C1 ('MetaCons "Identity" 'PrefixI 'True) (S1 ('MetaSel ('Just "runIdentity") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) Par1))

newtype Constant a (b :: k)

Constant functor.

Constructors

Constant

Fields

• getConstant :: a

Instances

Bitraversable (Constant :: Type -> Type -> Type)

Defined in Data.Functor.Constant

Methods

bitraverse :: Applicative f => (a -> f c) -> (b -> f d) -> Constant a b -> f (Constant c d)

Bifoldable (Constant :: Type -> Type -> Type)

Defined in Data.Functor.Constant

Methods

bifold :: Monoid m => Constant m m -> m

bifoldMap :: Monoid m => (a -> m) -> (b -> m) -> Constant a b -> m

bifoldr :: (a -> c -> c) -> (b -> c -> c) -> c -> Constant a b -> c

bifoldl :: (c -> a -> c) -> (c -> b -> c) -> c -> Constant a b -> c

Bifunctor (Constant :: Type -> Type -> Type)

Defined in Data.Functor.Constant

Methods

bimap :: (a -> b) -> (c -> d) -> Constant a c -> Constant b d

first :: (a -> b) -> Constant a c -> Constant b c

second :: (b -> c) -> Constant a b -> Constant a c

Eq2 (Constant :: Type -> Type -> Type)

Defined in Data.Functor.Constant

Methods

liftEq2 :: (a -> b -> Bool) -> (c -> d -> Bool) -> Constant a c -> Constant b d -> Bool

Ord2 (Constant :: Type -> Type -> Type)

Defined in Data.Functor.Constant

Methods

liftCompare2 :: (a -> b -> Ordering) -> (c -> d -> Ordering) -> Constant a c -> Constant b d -> Ordering

Read2 (Constant :: Type -> Type -> Type)

Defined in Data.Functor.Constant

Methods

liftReadsPrec2 :: (Int -> ReadS a) -> ReadS [a] -> (Int -> ReadS b) -> ReadS [b] -> Int -> ReadS (Constant a b)

liftReadList2 :: (Int -> ReadS a) -> ReadS [a] -> (Int -> ReadS b) -> ReadS [b] -> ReadS [Constant a b]

liftReadPrec2 :: ReadPrec a -> ReadPrec [a] -> ReadPrec b -> ReadPrec [b] -> ReadPrec (Constant a b)

liftReadListPrec2 :: ReadPrec a -> ReadPrec [a] -> ReadPrec b -> ReadPrec [b] -> ReadPrec [Constant a b]

Show2 (Constant :: Type -> Type -> Type)

Defined in Data.Functor.Constant

Methods

liftShowsPrec2 :: (Int -> a -> ShowS) -> ([a] -> ShowS) -> (Int -> b -> ShowS) -> ([b] -> ShowS) -> Int -> Constant a b -> ShowS

liftShowList2 :: (Int -> a -> ShowS) -> ([a] -> ShowS) -> (Int -> b -> ShowS) -> ([b] -> ShowS) -> [Constant a b] -> ShowS

Functor (Constant a :: Type -> Type)

Defined in Data.Functor.Constant

Methods

fmap :: (a0 -> b) -> Constant a a0 -> Constant a b

(<$) :: a0 -> Constant a b -> Constant a a0

Monoid a => Applicative (Constant a :: Type -> Type)

Defined in Data.Functor.Constant

Methods

pure :: a0 -> Constant a a0

(<*>) :: Constant a (a0 -> b) -> Constant a a0 -> Constant a b

liftA2 :: (a0 -> b -> c) -> Constant a a0 -> Constant a b -> Constant a c

(*>) :: Constant a a0 -> Constant a b -> Constant a b

(<*) :: Constant a a0 -> Constant a b -> Constant a a0

Foldable (Constant a :: Type -> Type)

Defined in Data.Functor.Constant

Methods

fold :: Monoid m => Constant a m -> m

foldMap :: Monoid m => (a0 -> m) -> Constant a a0 -> m

foldMap' :: Monoid m => (a0 -> m) -> Constant a a0 -> m

foldr :: (a0 -> b -> b) -> b -> Constant a a0 -> b

foldr' :: (a0 -> b -> b) -> b -> Constant a a0 -> b

foldl :: (b -> a0 -> b) -> b -> Constant a a0 -> b

foldl' :: (b -> a0 -> b) -> b -> Constant a a0 -> b

foldr1 :: (a0 -> a0 -> a0) -> Constant a a0 -> a0

foldl1 :: (a0 -> a0 -> a0) -> Constant a a0 -> a0

toList :: Constant a a0 -> [a0]

null :: Constant a a0 -> Bool

length :: Constant a a0 -> Int

elem :: Eq a0 => a0 -> Constant a a0 -> Bool

maximum :: Ord a0 => Constant a a0 -> a0

minimum :: Ord a0 => Constant a a0 -> a0

sum :: Num a0 => Constant a a0 -> a0

product :: Num a0 => Constant a a0 -> a0

Traversable (Constant a :: Type -> Type)

Defined in Data.Functor.Constant

Methods

traverse :: Applicative f => (a0 -> f b) -> Constant a a0 -> f (Constant a b)

sequenceA :: Applicative f => Constant a (f a0) -> f (Constant a a0)

mapM :: Monad m => (a0 -> m b) -> Constant a a0 -> m (Constant a b)

sequence :: Monad m => Constant a (m a0) -> m (Constant a a0)

Contravariant (Constant a :: Type -> Type)

Defined in Data.Functor.Constant

Methods

contramap :: (a0 -> b) -> Constant a b -> Constant a a0

(>$) :: b -> Constant a b -> Constant a a0

Eq a => Eq1 (Constant a :: Type -> Type)

Defined in Data.Functor.Constant

Methods

liftEq :: (a0 -> b -> Bool) -> Constant a a0 -> Constant a b -> Bool

Ord a => Ord1 (Constant a :: Type -> Type)

Defined in Data.Functor.Constant

Methods

liftCompare :: (a0 -> b -> Ordering) -> Constant a a0 -> Constant a b -> Ordering

Read a => Read1 (Constant a :: Type -> Type)

Defined in Data.Functor.Constant

Methods

liftReadsPrec :: (Int -> ReadS a0) -> ReadS [a0] -> Int -> ReadS (Constant a a0)

liftReadList :: (Int -> ReadS a0) -> ReadS [a0] -> ReadS [Constant a a0]

liftReadPrec :: ReadPrec a0 -> ReadPrec [a0] -> ReadPrec (Constant a a0)

liftReadListPrec :: ReadPrec a0 -> ReadPrec [a0] -> ReadPrec [Constant a a0]

Show a => Show1 (Constant a :: Type -> Type)

Defined in Data.Functor.Constant

Methods

liftShowsPrec :: (Int -> a0 -> ShowS) -> ([a0] -> ShowS) -> Int -> Constant a a0 -> ShowS

liftShowList :: (Int -> a0 -> ShowS) -> ([a0] -> ShowS) -> [Constant a a0] -> ShowS

Eq a => Eq (Constant a b)

Defined in Data.Functor.Constant

Methods

(==) :: Constant a b -> Constant a b -> Bool

(/=) :: Constant a b -> Constant a b -> Bool

Ord a => Ord (Constant a b)

Defined in Data.Functor.Constant

Methods

compare :: Constant a b -> Constant a b -> Ordering

(<) :: Constant a b -> Constant a b -> Bool

(<=) :: Constant a b -> Constant a b -> Bool

(>) :: Constant a b -> Constant a b -> Bool

(>=) :: Constant a b -> Constant a b -> Bool

max :: Constant a b -> Constant a b -> Constant a b

min :: Constant a b -> Constant a b -> Constant a b

Read a => Read (Constant a b)

Defined in Data.Functor.Constant

Methods

readsPrec :: Int -> ReadS (Constant a b)

readList :: ReadS [Constant a b]

readPrec :: ReadPrec (Constant a b)

readListPrec :: ReadPrec [Constant a b]

Show a => Show (Constant a b)

Defined in Data.Functor.Constant

Methods

showsPrec :: Int -> Constant a b -> ShowS

show :: Constant a b -> String

showList :: [Constant a b] -> ShowS

Semigroup a => Semigroup (Constant a b)

Defined in Data.Functor.Constant

Methods

(<>) :: Constant a b -> Constant a b -> Constant a b

sconcat :: NonEmpty (Constant a b) -> Constant a b

stimes :: Integral b0 => b0 -> Constant a b -> Constant a b

Monoid a => Monoid (Constant a b)

Defined in Data.Functor.Constant

Methods

mempty :: Constant a b

mappend :: Constant a b -> Constant a b -> Constant a b

mconcat :: [Constant a b] -> Constant a b

newtype Compose (f :: k -> Type) (g :: k1 -> k) (a :: k1) infixr 9

Right-to-left composition of functors. The composition of applicative functors is always applicative, but the composition of monads is not always a monad.

Constructors

Compose infixr 9

Fields

• getCompose :: f (g a)

Instances

Functor f => Generic1 (Compose f g :: k -> Type)

Since: base-4.9.0.0

Defined in Data.Functor.Compose

Associated Types

type Rep1 (Compose f g) :: k -> Type

Methods

from1 :: forall (a :: k0). Compose f g a -> Rep1 (Compose f g) a

to1 :: forall (a :: k0). Rep1 (Compose f g) a -> Compose f g a

TestEquality f => TestEquality (Compose f g :: k2 -> Type)

The deduction (via generativity) that if g x :~: g y then x :~: y.

Since: base-4.14.0.0

Defined in Data.Functor.Compose

Methods

testEquality :: forall (a :: k) (b :: k). Compose f g a -> Compose f g b -> Maybe (a :~: b)

(Functor f, Functor g) => Functor (Compose f g)

Since: base-4.9.0.0

Defined in Data.Functor.Compose

Methods

fmap :: (a -> b) -> Compose f g a -> Compose f g b

(<$) :: a -> Compose f g b -> Compose f g a

(Applicative f, Applicative g) => Applicative (Compose f g)

Since: base-4.9.0.0

Defined in Data.Functor.Compose

Methods

pure :: a -> Compose f g a

(<*>) :: Compose f g (a -> b) -> Compose f g a -> Compose f g b

liftA2 :: (a -> b -> c) -> Compose f g a -> Compose f g b -> Compose f g c

(*>) :: Compose f g a -> Compose f g b -> Compose f g b

(<*) :: Compose f g a -> Compose f g b -> Compose f g a

(Foldable f, Foldable g) => Foldable (Compose f g)

Since: base-4.9.0.0

Defined in Data.Functor.Compose

Methods

fold :: Monoid m => Compose f g m -> m

foldMap :: Monoid m => (a -> m) -> Compose f g a -> m

foldMap' :: Monoid m => (a -> m) -> Compose f g a -> m

foldr :: (a -> b -> b) -> b -> Compose f g a -> b

foldr' :: (a -> b -> b) -> b -> Compose f g a -> b

foldl :: (b -> a -> b) -> b -> Compose f g a -> b

foldl' :: (b -> a -> b) -> b -> Compose f g a -> b

foldr1 :: (a -> a -> a) -> Compose f g a -> a

foldl1 :: (a -> a -> a) -> Compose f g a -> a

toList :: Compose f g a -> [a]

null :: Compose f g a -> Bool

length :: Compose f g a -> Int

elem :: Eq a => a -> Compose f g a -> Bool

maximum :: Ord a => Compose f g a -> a

minimum :: Ord a => Compose f g a -> a

sum :: Num a => Compose f g a -> a

product :: Num a => Compose f g a -> a

(Traversable f, Traversable g) => Traversable (Compose f g)

Since: base-4.9.0.0

Defined in Data.Functor.Compose

Methods

traverse :: Applicative f0 => (a -> f0 b) -> Compose f g a -> f0 (Compose f g b)

sequenceA :: Applicative f0 => Compose f g (f0 a) -> f0 (Compose f g a)

mapM :: Monad m => (a -> m b) -> Compose f g a -> m (Compose f g b)

sequence :: Monad m => Compose f g (m a) -> m (Compose f g a)

(Eq1 f, Eq1 g) => Eq1 (Compose f g)

Since: base-4.9.0.0

Defined in Data.Functor.Compose

Methods

liftEq :: (a -> b -> Bool) -> Compose f g a -> Compose f g b -> Bool

(Ord1 f, Ord1 g) => Ord1 (Compose f g)

Since: base-4.9.0.0

Defined in Data.Functor.Compose

Methods

liftCompare :: (a -> b -> Ordering) -> Compose f g a -> Compose f g b -> Ordering

(Read1 f, Read1 g) => Read1 (Compose f g)

Since: base-4.9.0.0

Defined in Data.Functor.Compose

Methods

liftReadsPrec :: (Int -> ReadS a) -> ReadS [a] -> Int -> ReadS (Compose f g a)

liftReadList :: (Int -> ReadS a) -> ReadS [a] -> ReadS [Compose f g a]

liftReadPrec :: ReadPrec a -> ReadPrec [a] -> ReadPrec (Compose f g a)

liftReadListPrec :: ReadPrec a -> ReadPrec [a] -> ReadPrec [Compose f g a]

(Show1 f, Show1 g) => Show1 (Compose f g)

Since: base-4.9.0.0

Defined in Data.Functor.Compose

Methods

liftShowsPrec :: (Int -> a -> ShowS) -> ([a] -> ShowS) -> Int -> Compose f g a -> ShowS

liftShowList :: (Int -> a -> ShowS) -> ([a] -> ShowS) -> [Compose f g a] -> ShowS

(Alternative f, Applicative g) => Alternative (Compose f g)

Since: base-4.9.0.0

Defined in Data.Functor.Compose

Methods

empty :: Compose f g a

(<|>) :: Compose f g a -> Compose f g a -> Compose f g a

some :: Compose f g a -> Compose f g [a]

many :: Compose f g a -> Compose f g [a]

(Eq1 f, Eq1 g, Eq a) => Eq (Compose f g a)

Since: base-4.9.0.0

Defined in Data.Functor.Compose

Methods

(==) :: Compose f g a -> Compose f g a -> Bool

(/=) :: Compose f g a -> Compose f g a -> Bool

(Typeable a, Typeable f, Typeable g, Typeable k1, Typeable k2, Data (f (g a))) => Data (Compose f g a)

Since: base-4.9.0.0

Defined in Data.Functor.Compose

Methods

gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g0. g0 -> c g0) -> Compose f g a -> c (Compose f g a)

gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (Compose f g a)

toConstr :: Compose f g a -> Constr

dataTypeOf :: Compose f g a -> DataType

dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c (Compose f g a))

dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c (Compose f g a))

gmapT :: (forall b. Data b => b -> b) -> Compose f g a -> Compose f g a

gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Compose f g a -> r

gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Compose f g a -> r

gmapQ :: (forall d. Data d => d -> u) -> Compose f g a -> [u]

gmapQi :: Int -> (forall d. Data d => d -> u) -> Compose f g a -> u

gmapM :: Monad m => (forall d. Data d => d -> m d) -> Compose f g a -> m (Compose f g a)

gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Compose f g a -> m (Compose f g a)

gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Compose f g a -> m (Compose f g a)

(Ord1 f, Ord1 g, Ord a) => Ord (Compose f g a)

Since: base-4.9.0.0

Defined in Data.Functor.Compose

Methods

compare :: Compose f g a -> Compose f g a -> Ordering

(<) :: Compose f g a -> Compose f g a -> Bool

(<=) :: Compose f g a -> Compose f g a -> Bool

(>) :: Compose f g a -> Compose f g a -> Bool

(>=) :: Compose f g a -> Compose f g a -> Bool

max :: Compose f g a -> Compose f g a -> Compose f g a

min :: Compose f g a -> Compose f g a -> Compose f g a

(Read1 f, Read1 g, Read a) => Read (Compose f g a)

Since: base-4.9.0.0

Defined in Data.Functor.Compose

Methods

readsPrec :: Int -> ReadS (Compose f g a)

readList :: ReadS [Compose f g a]

readPrec :: ReadPrec (Compose f g a)

readListPrec :: ReadPrec [Compose f g a]

(Show1 f, Show1 g, Show a) => Show (Compose f g a)

Since: base-4.9.0.0

Defined in Data.Functor.Compose

Methods

showsPrec :: Int -> Compose f g a -> ShowS

show :: Compose f g a -> String

showList :: [Compose f g a] -> ShowS

Generic (Compose f g a)

Since: base-4.9.0.0

Defined in Data.Functor.Compose

Associated Types

type Rep (Compose f g a) :: Type -> Type

Methods

from :: Compose f g a -> Rep (Compose f g a) x

to :: Rep (Compose f g a) x -> Compose f g a

type Rep1 (Compose f g :: k -> Type)

Defined in Data.Functor.Compose

type Rep1 (Compose f g :: k -> Type) = D1 ('MetaData "Compose" "Data.Functor.Compose" "base" 'True) (C1 ('MetaCons "Compose" 'PrefixI 'True) (S1 ('MetaSel ('Just "getCompose") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (f :.: Rec1 g)))

type Rep (Compose f g a)

Defined in Data.Functor.Compose

type Rep (Compose f g a) = D1 ('MetaData "Compose" "Data.Functor.Compose" "base" 'True) (C1 ('MetaCons "Compose" 'PrefixI 'True) (S1 ('MetaSel ('Just "getCompose") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 (f (g a)))))