Safe Haskell | Safe-Inferred |
---|---|
Language | Haskell2010 |
IntMap
is an instance of At
and provides
at
as a lens on values at keys:
>>>
IntMap.fromList [(1, "world")] ^. at 1
Just "world"
>>>
IntMap.empty & at 1 .~ Just "world"
fromList [(1,"world")]
>>>
IntMap.empty & at 0 .~ Just "hello"
fromList [(0,"hello")]
We can traverse, fold over, and map over key-value pairs in an IntMap
,
thanks to indexed traversals, folds and setters.
>>>
iover imapped const $ IntMap.fromList [(1, "Venus")]
fromList [(1,1)]
>>>
ifoldMapOf ifolded (\i _ -> Sum i) $ IntMap.fromList [(2, "Earth"), (3, "Mars")]
Sum {getSum = 5}
>>>
itraverseOf_ ifolded (curry print) $ IntMap.fromList [(4, "Jupiter")]
(4,"Jupiter")
>>>
itoListOf ifolded $ IntMap.fromList [(5, "Saturn")]
[(5,"Saturn")]
A related class, Ixed
, allows us to use ix
to
traverse a value at a particular key.
>>>
IntMap.fromList [(2, "Earth")] & ix 2 %~ ("New " ++)
fromList [(2,"New Earth")]
>>>
preview (ix 8) IntMap.empty
Nothing
Documentation
toMapOf :: (Is k A_Fold, is `HasSingleIndex` Int) => Optic' k is s a -> s -> IntMap a Source #
Construct a map from an IxFold
.
The construction is left-biased (see union
), i.e. the first occurrences of
keys in the fold or traversal order are preferred.
>>>
toMapOf ifolded ["hello", "world"]
fromList [(0,"hello"),(1,"world")]
>>>
toMapOf (folded % ifolded) [(1,"alpha"),(2, "beta")]
fromList [(1,"alpha"),(2,"beta")]
>>>
toMapOf (icompose (\a b -> 10*a+b) $ ifolded % ifolded) ["foo", "bar"]
fromList [(0,'f'),(1,'o'),(2,'o'),(10,'b'),(11,'a'),(12,'r')]
>>>
toMapOf (folded % ifolded) [(1, "hello"), (2, "world"), (1, "dummy")]
fromList [(1,"hello"),(2,"world")]
lt :: Int -> IxAffineTraversal' Int (IntMap v) v Source #
Focus on the largest key smaller than the given one and its corresponding value.
>>>
IntMap.fromList [(1, "hi"), (2, "there")] & over (lt 2) (++ "!")
fromList [(1,"hi!"),(2,"there")]
>>>
ipreview (lt 1) $ IntMap.fromList [(1, 'x'), (2, 'y')]
Nothing
gt :: Int -> IxAffineTraversal' Int (IntMap v) v Source #
Focus on the smallest key greater than the given one and its corresponding value.
>>>
IntMap.fromList [(1, "hi"), (2, "there")] & over (gt 2) (++ "!")
fromList [(1,"hi"),(2,"there")]
>>>
ipreview (gt 1) $ IntMap.fromList [(1, 'x'), (2, 'y')]
Just (2,'y')
le :: Int -> IxAffineTraversal' Int (IntMap v) v Source #
Focus on the largest key smaller or equal than the given one and its corresponding value.
>>>
IntMap.fromList [(1, "hi"), (2, "there")] & over (le 2) (++ "!")
fromList [(1,"hi"),(2,"there!")]
>>>
ipreview (le 1) $ IntMap.fromList [(1, 'x'), (2, 'y')]
Just (1,'x')
ge :: Int -> IxAffineTraversal' Int (IntMap v) v Source #
Focus on the smallest key greater or equal than the given one and its corresponding value.
>>>
IntMap.fromList [(1, "hi"), (3, "there")] & over (ge 2) (++ "!")
fromList [(1,"hi"),(3,"there!")]
>>>
ipreview (ge 2) $ IntMap.fromList [(1, 'x'), (3, 'y')]
Just (3,'y')