Data.Generics.Product.Positions

Derive positional product type getters and setters generically.

Lenses

class HasPosition i a s | s i -> a where

Records that have a field at a given position.

Minimal complete definition

position | setPosition, getPosition

Methods

position :: Lens' s a

A lens that focuses on a field at a given position. Compatible with the lens package's Lens type.

>>> human ^. position @1
"Tunyasz"
>>> human & position @2 .~ "Berlin"
Human {name = "Tunyasz", age = 50, address = "Berlin"}

getPosition :: s -> a

Get positional field

>>> getPosition @1 human
"Tunyasz"

setPosition :: a -> s -> s

Set positional field

>>> setPosition @2 (setField @1 "Tamas" human) 30
Human "Tamas" 30 "London"

Instances

(Generic s, ErrorUnless i s ((&&) ((<?) 0 i) ((<=?) i (Size (Rep s)))), GHasPosition 1 i (Rep s) a) => HasPosition i a s

Methods

position :: Lens' s a

getPosition :: s -> a

setPosition :: a -> s -> s