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GHC 9.14.1 · lts/ghc-9.14.x · 45dd537 · 2026-10-11

Moduleeither-n-0.1.0.0Haskell2010

Data.Lens.Injection.Injection3

The third injection of a sum type, as a prism. The sum-type dual of Control.Lens.Field3.

1 class

Packageeither-n-0.1.0.0
Exports1
LanguageHaskell2010
LicenceBSD-3-Clause
SourceInjection3.hs

classclass Injection3 s t a b | s -> a, t -> b, s b -> t, t a -> s where

Access the third constructor of a sum type.

Where Control.Lens._3 is the third projection out of a product, _I3 is the third injection into a sum.

The default implementation is the prism to the third constructor of a Generic type, injection (Proxy :: Proxy 2).

Example3 expressions

>>> data T = C1 | C2 | C3 Int | C4 deriving (Show, Generic)>>> instance Injection3 T T Int Int>>> C3 1 ^? _I3Just 1

Example1 expression

>>> C4 ^? _I3Nothing

Example1 expression

>>> _I3 # 1 :: TC3 1

Methods

_I3 :: Prism s t a b

Instances3Injection3

Injection3 Ordering Ordering () ()Defined in either-n-0.1.0.0 · Data.Lens.Injection.Injection3
Example1 expression
```
>>> GT ^? _I3Just ()
```
Example1 expression
```
>>> LT ^? _I3Nothing
```
Example1 expression
```
>>> EQ ^? _I3Nothing
```
Example1 expression
```
>>> _I3 # () :: OrderingGT
```
Injection3 (Either3 a b c) (Either3 a b c') c c'Defined in either-n-0.1.0.0 · Data.Either3.Either3
Example1 expression
```
>>> (Third3 "x" :: Either3 Int Bool String) ^? _I3Just "x"
```
Example1 expression
```
>>> (First3 1 :: Either3 Int Bool String) ^? _I3Nothing
```
Injection3 (Either3T Identity a b c) (Either3T Identity a b c') c c'Defined in either-n-0.1.0.0 · Data.Either3.Either3T
Example1 expression
```
>>> e3 (Third3 1) ^? _I3Just 1
```
Example1 expression
```
>>> e3 (First3 "x") ^? _I3Nothing
```