Safe Haskell | None |
---|---|

Language | Haskell2010 |

A

has the ability to lift a function of type
`Setter`

S T A B`A -> B`

`over`

a function of type `S -> T`

, applying the function
to update all the `A`

s contained in `S`

. This can be used to `set`

all the `A`

s to a single value (by lifting a constant function).

This can be seen as a generalisation of `fmap`

, where the type `S`

does not need to be a type constructor with `A`

as its last
parameter.

## Synopsis

- type Setter s t a b = Optic A_Setter NoIx s t a b
- type Setter' s a = Optic' A_Setter NoIx s a
- sets :: ((a -> b) -> s -> t) -> Setter s t a b
- over :: Is k A_Setter => Optic k is s t a b -> (a -> b) -> s -> t
- mapped :: Functor f => Setter (f a) (f b) a b
- set :: Is k A_Setter => Optic k is s t a b -> b -> s -> t
- set' :: Is k A_Setter => Optic k is s t a b -> b -> s -> t
- over' :: Is k A_Setter => Optic k is s t a b -> (a -> b) -> s -> t
- data A_Setter :: OpticKind

# Formation

# Introduction

sets :: ((a -> b) -> s -> t) -> Setter s t a b Source #

Build a setter from a function to modify the element(s), which must respect the well-formedness laws.

# Elimination

over :: Is k A_Setter => Optic k is s t a b -> (a -> b) -> s -> t Source #

Apply a setter as a modifier.

# Computation

# Well-formedness

# Additional introduction forms

# Additional elimination forms

set' :: Is k A_Setter => Optic k is s t a b -> b -> s -> t Source #

Apply a setter, strictly.

TODO DOC: what exactly is the strictness property?

over' :: Is k A_Setter => Optic k is s t a b -> (a -> b) -> s -> t Source #

Apply a setter as a modifier, strictly.

TODO DOC: what exactly is the strictness property?

Example:

f :: Int -> (Int, a) -> (Int, a) f k acc | k > 0 = f (k - 1) $`over'`

`_1`

(+1) acc | otherwise = acc

runs in constant space, but would result in a space leak if used with `over`

.

Note that replacing `$`

with `$!`

or `_1`

with
`_1'`

(which amount to the same thing) doesn't help when
`over`

is used, because the first coordinate of a pair is never forced.

# Subtyping

data A_Setter :: OpticKind Source #

Tag for a setter.