Safe Haskell | None |
---|---|
Language | Haskell2010 |
Optics.At.Core
Contents
Description
This module provides optics for
Map
and
Set
-like containers, including an
AffineTraversal
to traverse a key in a map or an element of a sequence:
>>>
preview (ix 1) ['a','b','c']
Just 'b'
a
Lens
to get, set or delete a key in a map:
>>>
set (at 0) (Just 'b') (Map.fromList [(0, 'a')])
fromList [(0,'b')]
and a
Lens
to insert or remove an element of a set:
>>>
IntSet.fromList [1,2,3,4] & contains 3 .~ False
fromList [1,2,4]
The
Optics.At
module from
optics-extra
provides additional instances of
the classes defined here.
Synopsis
- type family Index (s :: Type ) :: Type
- type family IxValue (m :: Type ) :: Type
- class Ixed m where
- ixAt :: At m => Index m -> AffineTraversal' m ( IxValue m)
- class ( Ixed m, IxKind m ~ An_AffineTraversal ) => At m where
- at' :: At m => Index m -> Lens' m ( Maybe ( IxValue m))
- sans :: At m => Index m -> m -> m
- class Contains m where
Type families
type family Index (s :: Type ) :: Type Source #
Type family that takes a key-value container type and returns the type of
keys (indices) into the container, for example
.
This is shared by
Index
(
Map
k a) ~ k
Ixed
,
At
and
Contains
.
Instances
type Index IntSet Source # | |
Defined in Optics.At.Core |
|
type Index [a] Source # | |
Defined in Optics.At.Core |
|
type Index ( Maybe a) Source # | |
Defined in Optics.At.Core |
|
type Index ( Complex a) Source # | |
Defined in Optics.At.Core |
|
type Index ( Identity a) Source # | |
Defined in Optics.At.Core |
|
type Index ( NonEmpty a) Source # | |
Defined in Optics.At.Core |
|
type Index ( IntMap a) Source # | |
Defined in Optics.At.Core |
|
type Index ( Tree a) Source # | |
Defined in Optics.At.Core |
|
type Index ( Seq a) Source # | |
Defined in Optics.At.Core |
|
type Index ( Set a) Source # | |
Defined in Optics.At.Core |
|
type Index (e -> a) Source # | |
Defined in Optics.At.Core
type
Index
(e -> a) = e
|
|
type Index (a, b) Source # | |
Defined in Optics.At.Core |
|
type Index ( UArray i e) Source # | |
Defined in Optics.At.Core |
|
type Index ( Array i e) Source # | |
Defined in Optics.At.Core |
|
type Index ( Map k a) Source # | |
Defined in Optics.At.Core |
|
type Index (a, b, c) Source # | |
Defined in Optics.At.Core |
|
type Index (a, b, c, d) Source # | |
Defined in Optics.At.Core |
|
type Index (a, b, c, d, e) Source # | |
Defined in Optics.At.Core |
|
type Index (a, b, c, d, e, f) Source # | |
Defined in Optics.At.Core |
|
type Index (a, b, c, d, e, f, g) Source # | |
Defined in Optics.At.Core |
|
type Index (a, b, c, d, e, f, g, h) Source # | |
Defined in Optics.At.Core |
|
type Index (a, b, c, d, e, f, g, h, i) Source # | |
Defined in Optics.At.Core |
type family IxValue (m :: Type ) :: Type Source #
Type family that takes a key-value container type and returns the type of
values stored in the container, for example
. This
is shared by both
IxValue
(
Map
k a) ~ a
Ixed
and
At
.
Instances
type IxValue IntSet Source # | |
Defined in Optics.At.Core |
|
type IxValue [a] Source # | |
Defined in Optics.At.Core
type
IxValue
[a] = a
|
|
type IxValue ( Maybe a) Source # | |
Defined in Optics.At.Core |
|
type IxValue ( Identity a) Source # | |
Defined in Optics.At.Core |
|
type IxValue ( NonEmpty a) Source # | |
Defined in Optics.At.Core |
|
type IxValue ( IntMap a) Source # | |
Defined in Optics.At.Core |
|
type IxValue ( Tree a) Source # | |
Defined in Optics.At.Core |
|
type IxValue ( Seq a) Source # | |
Defined in Optics.At.Core |
|
type IxValue ( Set k) Source # | |
Defined in Optics.At.Core |
|
type IxValue (e -> a) Source # | |
Defined in Optics.At.Core
type
IxValue
(e -> a) = a
|
|
type IxValue (a0, a2) Source # |
|
Defined in Optics.At.Core
type
IxValue
(a0, a2) = a0
|
|
type IxValue ( UArray i e) Source # | |
Defined in Optics.At.Core |
|
type IxValue ( Array i e) Source # | |
Defined in Optics.At.Core |
|
type IxValue ( Map k a) Source # | |
Defined in Optics.At.Core |
|
type IxValue (a0, a1, a2) Source # |
|
Defined in Optics.At.Core
type
IxValue
(a0, a1, a2) = a0
|
|
type IxValue (a0, a1, a2, a3) Source # |
|
Defined in Optics.At.Core
type
IxValue
(a0, a1, a2, a3) = a0
|
|
type IxValue (a0, a1, a2, a3, a4) Source # |
|
Defined in Optics.At.Core
type
IxValue
(a0, a1, a2, a3, a4) = a0
|
|
type IxValue (a0, a1, a2, a3, a4, a5) Source # |
|
Defined in Optics.At.Core
type
IxValue
(a0, a1, a2, a3, a4, a5) = a0
|
|
type IxValue (a0, a1, a2, a3, a4, a5, a6) Source # |
|
Defined in Optics.At.Core
type
IxValue
(a0, a1, a2, a3, a4, a5, a6) = a0
|
|
type IxValue (a0, a1, a2, a3, a4, a5, a6, a7) Source # |
|
Defined in Optics.At.Core
type
IxValue
(a0, a1, a2, a3, a4, a5, a6, a7) = a0
|
|
type IxValue (a0, a1, a2, a3, a4, a5, a6, a7, a8) Source # |
|
Defined in Optics.At.Core
type
IxValue
(a0, a1, a2, a3, a4, a5, a6, a7, a8) = a0
|
Ixed
Provides a simple
AffineTraversal
lets you traverse the value at a given
key in a
Map
or element at an ordinal position in a list or
Seq
.
Minimal complete definition
Nothing
Associated Types
type IxKind (m :: Type ) :: OpticKind Source #
Type family that takes a key-value container type and returns the kind
of optic to index into it. For most containers, it's
An_AffineTraversal
,
Representable
(Naperian) containers it is
A_Lens
, and multi-maps would
have
A_Traversal
.
type IxKind m = An_AffineTraversal
Methods
ix :: Index m -> Optic' ( IxKind m) NoIx m ( IxValue m) Source #
NB:
Setting the value of this
AffineTraversal
will only set the value
in
at
if it is already present.
If you want to be able to insert
missing
values, you want
at
.
>>>
[1,2,3,4] & ix 2 %~ (*10)
[1,2,30,4]
>>>
"abcd" & ix 2 .~ 'e'
"abed"
>>>
"abcd" ^? ix 2
Just 'c'
>>>
[] ^? ix 2
Nothing
Instances
Ixed IntSet Source # | |
Ixed [a] Source # | |
Ixed ( Maybe a) Source # | |
Ixed ( Identity a) Source # | |
Ixed ( NonEmpty a) Source # | |
Ixed ( IntMap a) Source # | |
Ixed ( Tree a) Source # | |
Ixed ( Seq a) Source # | |
Ord k => Ixed ( Set k) Source # | |
Eq e => Ixed (e -> a) Source # | |
a0 ~ a1 => Ixed (a0, a1) Source # | |
( IArray UArray e, Ix i) => Ixed ( UArray i e) Source # |
arr |
Ix i => Ixed ( Array i e) Source # |
arr |
Ord k => Ixed ( Map k a) Source # | |
(a0 ~ a1, a0 ~ a2) => Ixed (a0, a1, a2) Source # | |
(a0 ~ a1, a0 ~ a2, a0 ~ a3) => Ixed (a0, a1, a2, a3) Source # | |
(a0 ~ a1, a0 ~ a2, a0 ~ a3, a0 ~ a4) => Ixed (a0, a1, a2, a3, a4) Source # | |
(a0 ~ a1, a0 ~ a2, a0 ~ a3, a0 ~ a4, a0 ~ a5) => Ixed (a0, a1, a2, a3, a4, a5) Source # | |
(a0 ~ a1, a0 ~ a2, a0 ~ a3, a0 ~ a4, a0 ~ a5, a0 ~ a6) => Ixed (a0, a1, a2, a3, a4, a5, a6) Source # | |
(a0 ~ a1, a0 ~ a2, a0 ~ a3, a0 ~ a4, a0 ~ a5, a0 ~ a6, a0 ~ a7) => Ixed (a0, a1, a2, a3, a4, a5, a6, a7) Source # | |
(a0 ~ a1, a0 ~ a2, a0 ~ a3, a0 ~ a4, a0 ~ a5, a0 ~ a6, a0 ~ a7, a0 ~ a8) => Ixed (a0, a1, a2, a3, a4, a5, a6, a7, a8) Source # | |
Defined in Optics.At.Core |
At
class ( Ixed m, IxKind m ~ An_AffineTraversal ) => At m where Source #
At
provides a
Lens
that can be used to read, write or delete the value
associated with a key in a
Map
-like container on an ad hoc basis.
An instance of
At
should satisfy:
ix
k ≡at
k%
_Just
Methods
at :: Index m -> Lens' m ( Maybe ( IxValue m)) Source #
>>>
Map.fromList [(1,"world")] ^. at 1
Just "world"
>>>
at 1 ?~ "hello" $ Map.empty
fromList [(1,"hello")]
Note:
Usage of this function might introduce space leaks if you're not
careful to make sure that values put inside the
Just
constructor are
evaluated. To force the values and avoid such leaks, use
at'
instead.
Note:
Map
-like containers form a reasonable instance, but not
Array
-like ones, where you cannot satisfy the
Lens
laws.
at' :: At m => Index m -> Lens' m ( Maybe ( IxValue m)) Source #
Version of
at
strict in the value inside the
Just
constructor.
Example:
>>>
(at () .~ Just (error "oops") $ Nothing) `seq` ()
()
>>>
(at' () .~ Just (error "oops") $ Nothing) `seq` ()
*** Exception: oops ...
>>>
view (at ()) (Just $ error "oops") `seq` ()
()
>>>
view (at' ()) (Just $ error "oops") `seq` ()
*** Exception: oops ...
It also works as expected for other data structures:
>>>
(at 1 .~ Just (error "oops") $ Map.empty) `seq` ()
()
>>>
(at' 1 .~ Just (error "oops") $ Map.empty) `seq` ()
*** Exception: oops ...
Contains
class Contains m where Source #
This class provides a simple
Lens
that lets you view (and modify)
information about whether or not a container contains a given
Index
.
Instances are provided for
Set
-like containers only.