Data.Lens.Injection.Injection1 · either-n-0.1.0.0

classclass Injection1 s t a b | s -> a, t -> b, s b -> t, t a -> s where

Access the first constructor of a sum type.

Where Control.Lens._1 is the first projection out of a product, _I1 is the first injection into a sum.

The default implementation is the prism to the first constructor of a Generic type, injection (Proxy :: Proxy 0).

Example3 expressions

>>> data T = C1 Int | C2 deriving (Show, Generic)>>> instance Injection1 T T Int Int>>> C1 1 ^? _I1Just 1

Example1 expression

>>> C2 ^? _I1Nothing

Example1 expression

>>> _I1 # 1 :: TC1 1

Methods

_I1 :: Prism s t a b

Instances11Injection1, …

Injection1 Bool Bool () ()Defined in either-n-0.1.0.0 · Data.Lens.Injection.Injection1
Example1 expression
```
>>> False ^? _I1Just ()
```
Example1 expression
```
>>> True ^? _I1Nothing
```
Example1 expression
```
>>> _I1 # () :: BoolFalse
```
Injection1 Ordering Ordering () ()Defined in either-n-0.1.0.0 · Data.Lens.Injection.Injection1
Example1 expression
```
>>> LT ^? _I1Just ()
```
Example1 expression
```
>>> EQ ^? _I1Nothing
```
Example1 expression
```
>>> GT ^? _I1Nothing
```
Example1 expression
```
>>> _I1 # () :: OrderingLT
```
Injection1 () () () ()Defined in either-n-0.1.0.0 · Data.Lens.Injection.Injection1
A sum of one nullary constructor, so _I1 always matches.
Example1 expression
```
>>> () ^? _I1Just ()
```
Example1 expression
```
>>> _I1 # () :: ()()
```
Injection1 (Identity a) (Identity b) a bDefined in either-n-0.1.0.0 · Data.Lens.Injection.Injection1
A sum of one constructor, so _I1 always matches.
Example1 expression
```
>>> Identity 1 ^? _I1Just 1
```
Example1 expression
```
>>> _I1 # 1 :: Identity IntIdentity 1
```
Example1 expression
```
>>> over _I1 show (Identity 1)Identity "1"
```
Injection1 (Maybe a) (Maybe a) () ()Defined in either-n-0.1.0.0 · Data.Lens.Injection.Injection1
Example1 expression
```
>>> (Nothing :: Maybe Int) ^? _I1Just ()
```
Example1 expression
```
>>> Just 1 ^? _I1Nothing
```
Example1 expression
```
>>> _I1 # () :: Maybe IntNothing
```
Injection1 [a] [a] () ()Defined in either-n-0.1.0.0 · Data.Lens.Injection.Injection1
A list is the sum of the empty list and a cons cell.
Example1 expression
```
>>> ([] :: [Int]) ^? _I1Just ()
```
Example1 expression
```
>>> [1, 2, 3] ^? _I1Nothing
```
Example1 expression
```
>>> _I1 # () :: [Int][]
```

Injection1 (Either a c) (Either b c) a bDefined in either-n-0.1.0.0 · Data.Lens.Injection.Injection1

Example1 expression

>>> (Left 1 :: Either Int String) ^? _I1Just 1

Example1 expression

>>> (Right "x" :: Either Int String) ^? _I1Nothing

Example1 expression

>>> _I1 # 1 :: Either Int StringLeft 1

Example1 expression

>>> over _I1 show (Left 1 :: Either Int Bool)Left "1"

Injection1 (Either3 a b c) (Either3 a' b c) a a'Defined in either-n-0.1.0.0 · Data.Either3.Either3
Example1 expression
```
>>> (First3 1 :: Either3 Int Bool String) ^? _I1Just 1
```
Example1 expression
```
>>> over _I1 show (First3 1 :: Either3 Int Bool String)First3 "1"
```
Injection1 (Either3T Identity a b c) (Either3T Identity a' b c) a a'Defined in either-n-0.1.0.0 · Data.Either3.Either3T
Example1 expression
```
>>> e3 (First3 "x") ^? _I1Just "x"
```
Injection1 (Sum f g a) (Sum f' g a) (f a) (f' a)Defined in either-n-0.1.0.0 · Data.Lens.Injection.Injection1
Example1 expression
```
>>> (InL (Just 1) :: Sum Maybe [] Int) ^? _I1Just (Just 1)
```
Example1 expression
```
>>> (InR [1] :: Sum Maybe [] Int) ^? _I1Nothing
```
Example1 expression
```
>>> _I1 # Just 1 :: Sum Maybe [] IntInL (Just 1)
```
Injection1 ((:+:) f g p) ((:+:) f' g p) (f p) (f' p)Defined in either-n-0.1.0.0 · Data.Lens.Injection.Injection1
Example1 expression
```
>>> (L1 (Just 1) :: (Maybe :+: []) Int) ^? _I1Just (Just 1)
```
Example1 expression
```
>>> (R1 [1] :: (Maybe :+: []) Int) ^? _I1Nothing
```
Example1 expression
```
>>> _I1 # Just 1 :: (Maybe :+: []) IntL1 (Just 1)
```