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Within LTS Haskell 22.22 (ghc-9.6.5)

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1. ix :: Ixed m => Index m -> Traversal' m (IxValue m)

   lens	Control.Lens.At

   NB: Setting the value of this Traversal 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.

   >>> Seq.fromList [a,b,c,d] & ix 2 %~ f
   fromList [a,b,f c,d]
   

   >>> Seq.fromList [a,b,c,d] & ix 2 .~ e
   fromList [a,b,e,d]
   

   >>> Seq.fromList [a,b,c,d] ^? ix 2
   Just c
   

   >>> Seq.fromList [] ^? ix 2
   Nothing
   

2. ix :: (Ixed m, At m) => Index m -> Traversal' m (IxValue m)

   lens	Control.Lens.At

   NB: Setting the value of this Traversal 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.

   >>> Seq.fromList [a,b,c,d] & ix 2 %~ f
   fromList [a,b,f c,d]
   

   >>> Seq.fromList [a,b,c,d] & ix 2 .~ e
   fromList [a,b,e,d]
   

   >>> Seq.fromList [a,b,c,d] ^? ix 2
   Just c
   

   >>> Seq.fromList [] ^? ix 2
   Nothing
   

3. ix :: Ixed m => Index m -> Traversal' m (IxValue m)

   lens	Control.Lens.Combinators

   NB: Setting the value of this Traversal 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.

   >>> Seq.fromList [a,b,c,d] & ix 2 %~ f
   fromList [a,b,f c,d]
   

   >>> Seq.fromList [a,b,c,d] & ix 2 .~ e
   fromList [a,b,e,d]
   

   >>> Seq.fromList [a,b,c,d] ^? ix 2
   Just c
   

   >>> Seq.fromList [] ^? ix 2
   Nothing
   

4. ix :: (Ixed m, At m) => Index m -> Traversal' m (IxValue m)

   lens	Control.Lens.Combinators

   NB: Setting the value of this Traversal 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.

   >>> Seq.fromList [a,b,c,d] & ix 2 %~ f
   fromList [a,b,f c,d]
   

   >>> Seq.fromList [a,b,c,d] & ix 2 .~ e
   fromList [a,b,e,d]
   

   >>> Seq.fromList [a,b,c,d] ^? ix 2
   Just c
   

   >>> Seq.fromList [] ^? ix 2
   Nothing
   

5. ix :: Ixed m => Index m -> Traversal' m (IxValue m)

   microlens	Lens.Micro

   This traversal lets you access (and update) an arbitrary element in a list, array, Map, etc. (If you want to insert or delete elements as well, look at at.) An example for lists:

   >>> [0..5] & ix 3 .~ 10
   [0,1,2,10,4,5]
   

   You can use it for getting, too:

   >>> [0..5] ^? ix 3
   Just 3
   

   Of course, the element may not be present (which means that you can use ix as a safe variant of (!!)):

   >>> [0..5] ^? ix 10
   Nothing
   

   Another useful instance is the one for functions – it lets you modify their outputs for specific inputs. For instance, here's maximum that returns 0 when the list is empty (instead of throwing an exception):

   maximum0 = maximum & ix [] .~ 0
   

   The following instances are provided in this package:

   ix :: Int -> Traversal' [a] a
   
   ix :: Int -> Traversal' (NonEmpty a) a
   
   ix :: (Eq e) => e -> Traversal' (e -> a) a
   

   You can also use ix with types from array, bytestring, and containers by using microlens-ghc, or additionally with types from vector, text, and unordered-containers by using microlens-platform.

6. ix :: Ixed m => Index m -> Traversal' m (IxValue m)

   microlens	Lens.Micro.Internal

   This traversal lets you access (and update) an arbitrary element in a list, array, Map, etc. (If you want to insert or delete elements as well, look at at.) An example for lists:

   >>> [0..5] & ix 3 .~ 10
   [0,1,2,10,4,5]
   

   You can use it for getting, too:

   >>> [0..5] ^? ix 3
   Just 3
   

   Of course, the element may not be present (which means that you can use ix as a safe variant of (!!)):

   >>> [0..5] ^? ix 10
   Nothing
   

   Another useful instance is the one for functions – it lets you modify their outputs for specific inputs. For instance, here's maximum that returns 0 when the list is empty (instead of throwing an exception):

   maximum0 = maximum & ix [] .~ 0
   

   The following instances are provided in this package:

   ix :: Int -> Traversal' [a] a
   
   ix :: Int -> Traversal' (NonEmpty a) a
   
   ix :: (Eq e) => e -> Traversal' (e -> a) a
   

   You can also use ix with types from array, bytestring, and containers by using microlens-ghc, or additionally with types from vector, text, and unordered-containers by using microlens-platform.

7. ix :: Ixed m => Index m -> Traversal' m (IxValue m)

   rio	RIO.Lens

   This traversal lets you access (and update) an arbitrary element in a list, array, Map, etc. (If you want to insert or delete elements as well, look at at.) An example for lists:

   >>> [0..5] & ix 3 .~ 10
   [0,1,2,10,4,5]
   

   You can use it for getting, too:

   >>> [0..5] ^? ix 3
   Just 3
   

   Of course, the element may not be present (which means that you can use ix as a safe variant of (!!)):

   >>> [0..5] ^? ix 10
   Nothing
   

   Another useful instance is the one for functions – it lets you modify their outputs for specific inputs. For instance, here's maximum that returns 0 when the list is empty (instead of throwing an exception):

   maximum0 = maximum & ix [] .~ 0
   

   The following instances are provided in this package:

   ix :: Int -> Traversal' [a] a
   
   ix :: Int -> Traversal' (NonEmpty a) a
   
   ix :: (Eq e) => e -> Traversal' (e -> a) a
   

   You can also use ix with types from array, bytestring, and containers by using microlens-ghc, or additionally with types from vector, text, and unordered-containers by using microlens-platform.

8. ix :: Ixed m => Index m -> Optic' (IxKind m) NoIx m (IxValue m)

   optics-core	Optics.At.Core

   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
   

9. ix :: (Ixed m, At m, IxKind m ~ An_AffineTraversal) => Index m -> Optic' (IxKind m) NoIx m (IxValue m)

   optics-core	Optics.At.Core

   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
   

10. ix :: Ixed m => Index m -> Traversal' m (IxValue m)

    diagrams-lib	Diagrams.Prelude

    NB: Setting the value of this Traversal 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.

    >>> Seq.fromList [a,b,c,d] & ix 2 %~ f
    fromList [a,b,f c,d]
    

    >>> Seq.fromList [a,b,c,d] & ix 2 .~ e
    fromList [a,b,e,d]
    

    >>> Seq.fromList [a,b,c,d] ^? ix 2
    Just c
    

    >>> Seq.fromList [] ^? ix 2
    Nothing
    

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