Portability | non-portable |
---|---|
Stability | experimental |
Maintainer | Edward Kmett <ekmett@gmail.com> |
Safe Haskell | Trustworthy |
Control.Lens.At
Contents
Description
- class At m where
- type family IxValue m :: *
- class (Functor f, Contains (Accessor (IxValue m)) m) => Ixed f m where
- ix :: Index m -> IndexedLensLike' (Index m) f m (IxValue m)
- ixAt :: (Applicative f, At m) => Index m -> IndexedLensLike' (Index m) f m (IxValue m)
- ixEach :: (Applicative f, Eq (Index m), Each f m m (IxValue m) (IxValue m)) => Index m -> IndexedLensLike' (Index m) f m (IxValue m)
- class Functor f => Contains f m where
- contains :: Index m -> IndexedLensLike' (Index m) f m Bool
- containsIx :: (Gettable f, Ixed (Accessor Any) m) => Index m -> IndexedLensLike' (Index m) f m Bool
- containsAt :: (Gettable f, At m) => Index m -> IndexedLensLike' (Index m) f m Bool
- containsLength :: forall i s. (Ord i, Num i) => (s -> i) -> i -> IndexedGetter i s Bool
- containsN :: Int -> Int -> IndexedGetter Int s Bool
- containsTest :: forall i s. (i -> s -> Bool) -> i -> IndexedGetter i s Bool
- containsLookup :: forall i s a. (i -> s -> Maybe a) -> i -> IndexedGetter i s Bool
- _at :: Ixed f m => Index m -> IndexedLensLike' (Index m) f m (IxValue m)
- resultAt :: Ixed f m => Index m -> IndexedLensLike' (Index m) f m (IxValue m)
At
class At m where
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<.
traverse
Ixed
type family IxValue m :: *
class (Functor f, Contains (Accessor (IxValue m)) m) => Ixed f m where
This simple IndexedTraversal
lets you traverse
the value at a given
key in a Map
or element at an ordinal position in a list or Seq
.
Methods
ix :: Index m -> IndexedLensLike' (Index m) f m (IxValue m)
This simple IndexedTraversal
lets you traverse
the value at a given
key in a Map
or element at an ordinal position in a list or Seq
.
NB: Setting the value of this Traversal
will only set the value in the
Lens
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
Instances
Applicative f => Ixed f ByteString | |
Applicative f => Ixed f ByteString | |
Applicative f => Ixed f Text | |
Applicative f => Ixed f Text | |
Applicative f => Ixed f (Complex a) | |
(Applicative f, Unbox a) => Ixed f (Vector a) | |
(Applicative f, Storable a) => Ixed f (Vector a) | |
(Applicative f, Prim a) => Ixed f (Vector a) | |
Applicative f => Ixed f (Vector a) | |
Applicative f => Ixed f (IntMap a) | |
Applicative f => Ixed f (Seq a) | |
Applicative f => Ixed f (Tree a) | |
Functor f => Ixed f (Identity a) | |
Applicative f => Ixed f [a] | |
(Applicative f, ~ * a b) => Ixed f (a, b) | |
(Functor f, Eq k) => Ixed f (k -> a) | |
(Applicative f, IArray UArray e, Ix i) => Ixed f (UArray i e) | arr |
(Applicative f, Ix i) => Ixed f (Array i e) | arr |
(Applicative f, Eq k, Hashable k) => Ixed f (HashMap k a) | |
(Applicative f, Ord k) => Ixed f (Map k a) | |
(Applicative f, ~ * a b, ~ * b c) => Ixed f (a, b, c) | |
(Applicative f, ~ * a b, ~ * b c, ~ * c d) => Ixed f (a, b, c, d) | |
(Applicative f, ~ * a b, ~ * b c, ~ * c d, ~ * d e) => Ixed f (a, b, c, d, e) | |
(Applicative f, ~ * a b, ~ * b c, ~ * c d, ~ * d e, ~ * e f') => Ixed f (a, b, c, d, e, f') | |
(Applicative f, ~ * a b, ~ * b c, ~ * c d, ~ * d e, ~ * e f', ~ * f' g) => Ixed f (a, b, c, d, e, f', g) | |
(Applicative f, ~ * a b, ~ * b c, ~ * c d, ~ * d e, ~ * e f', ~ * f' g, ~ * g h) => Ixed f (a, b, c, d, e, f', g, h) | |
(Applicative f, ~ * a b, ~ * b c, ~ * c d, ~ * d e, ~ * e f', ~ * f' g, ~ * g h, ~ * h i) => Ixed f (a, b, c, d, e, f', g, h, i) |
ixAt :: (Applicative f, At m) => Index m -> IndexedLensLike' (Index m) f m (IxValue m)
ixEach :: (Applicative f, Eq (Index m), Each f m m (IxValue m) (IxValue m)) => Index m -> IndexedLensLike' (Index m) f m (IxValue m)
Contains
class Functor f => Contains f m where
This class provides a simple IndexedFold
(or IndexedTraversal
) that lets you view (and modify)
information about whether or not a container contains a given Index
.
Methods
contains :: Index m -> IndexedLensLike' (Index m) f m Bool
>>>
IntSet.fromList [1,2,3,4] ^. contains 3
True
>>>
IntSet.fromList [1,2,3,4] ^. contains 5
False
>>>
IntSet.fromList [1,2,3,4] & contains 3 .~ False
fromList [1,2,4]
Instances
containsIx :: (Gettable f, Ixed (Accessor Any) m) => Index m -> IndexedLensLike' (Index m) f m Bool
containsAt :: (Gettable f, At m) => Index m -> IndexedLensLike' (Index m) f m Bool
containsLength :: forall i s. (Ord i, Num i) => (s -> i) -> i -> IndexedGetter i s Bool
containsN :: Int -> Int -> IndexedGetter Int s Bool
Construct a contains
check for a fixed number of elements.
containsTest :: forall i s. (i -> s -> Bool) -> i -> IndexedGetter i s Bool
Construct a contains
check that uses an arbitrary test.
containsLookup :: forall i s a. (i -> s -> Maybe a) -> i -> IndexedGetter i s Bool