mapKeys -package:nonempty-containers

mapKeys f s is the map obtained by applying f to each key of s. The size of the result may be smaller if f maps two or more distinct keys to the same new key. In this case the value at the greatest of the original keys is retained.

mapKeys (+ 1) (fromList [(5,"a"), (3,"b")])                        == fromList [(4, "b"), (6, "a")]
mapKeys (\ _ -> 1) (fromList [(1,"b"), (2,"a"), (3,"d"), (4,"c")]) == singleton 1 "c"
mapKeys (\ _ -> 3) (fromList [(1,"b"), (2,"a"), (3,"d"), (4,"c")]) == singleton 3 "c"

mapKeys f s is the map obtained by applying f to each key of s. If f is monotonically non-decreasing, this function takes <math> time. The size of the result may be smaller if f maps two or more distinct keys to the same new key. In this case the value at the greatest of the original keys is retained.

mapKeys (+ 1) (fromList [(5,"a"), (3,"b")])                        == fromList [(4, "b"), (6, "a")]
mapKeys (\ _ -> 1) (fromList [(1,"b"), (2,"a"), (3,"d"), (4,"c")]) == singleton 1 "c"
mapKeys (\ _ -> 3) (fromList [(1,"b"), (2,"a"), (3,"d"), (4,"c")]) == singleton 3 "c"

mapKeys f s is the map obtained by applying f to each key of s. The size of the result may be smaller if f maps two or more distinct keys to the same new key. In this case there is no guarantee which of the associated values is chosen for the conflicting key.

>>> mapKeys (+ 1) (fromList [(5,"a"), (3,"b")])
fromList [(4,"b"),(6,"a")]

>>> mapKeys (\ _ -> 1) (fromList [(1,"b"), (2,"a"), (3,"d"), (4,"c")])
fromList [(1,"c")]

>>> mapKeys (\ _ -> 3) (fromList [(1,"b"), (2,"a"), (3,"d"), (4,"c")])
fromList [(3,"c")]

mapKeys f s is the map obtained by applying f to each key of s. The size of the result may be smaller if f maps two or more distinct keys to the same new key. In this case the value at the greatest of the original keys is retained.

mapKeys (+ 1) (fromList [(5,"a"), (3,"b")])                        == fromList [(4, "b"), (6, "a")]
mapKeys (\ _ -> 1) (fromList [(1,"b"), (2,"a"), (3,"d"), (4,"c")]) == singleton 1 "c"
mapKeys (\ _ -> 3) (fromList [(1,"b"), (2,"a"), (3,"d"), (4,"c")]) == singleton 3 "c"

O(n*log n). mapKeys f s is the map obtained by applying f to each key of s. The size of the result may be smaller if f maps two or more distinct keys to the same new key. In this case the value at the greatest of the original keys is retained.

mapKeys (+ 1) (fromList [(5,"a"), (3,"b")])                        == fromList [(4, "b"), (6, "a")]
mapKeys (\ _ -> 1) (fromList [(1,"b"), (2,"a"), (3,"d"), (4,"c")]) == singleton 1 "c"
mapKeys (\ _ -> 3) (fromList [(1,"b"), (2,"a"), (3,"d"), (4,"c")]) == singleton 3 "c"

Order preserving mapping of keys.

Map a function over all values in the queue.

mapKeys f q is the queue obtained by applying f to each key of q.

O(n). Map a function to each key of a map, if it will result in duplicated mappings, their values will be merged in unspecified order

mapKeys f s is the multimap obtained by applying f to each key of s.

O(n log n). mapKeys f s is the map obtained by applying f to each key of s. The size of the result may be smaller if f maps two or more distinct keys to the same new key. In this case the value at the smallest of these keys is retained.

Applies a function to all the keys of a MonoidMap that are associated with non-null values. If the resultant map would contain more than one value for the same key, values are combined together in ascending key order with the (<>) operator. Satisfies the following property for all possible keys k:

get k (mapKeys f m) ==
foldMap
(`get` m)
(filter ((==) k . f) (nonNullKeys m))

The index map must be an injection, that is, nodes must not collaps. Also the node and edge index maps must be consistent, i.e.

from (edgeMap e) == nodeMap (from e)
to   (edgeMap e) == nodeMap (to   e)

Strictly spoken, we would need the node map only for isolated nodes, but we use it for all nodes for simplicity.

Add the keys of map to keys. Since: 7.0.0

mapKeys f m applies f to each key of m and collects the results into a new map. For keys that were mapped to the same new key, the value is picked in an unspecified way.

mapKeys f m applies f to each key of m and collects the results into a new map. For keys that were mapped to the same new key, the value corresponding to the greatest of the original keys is retained.

mapKeys f m applies f to each key of m and collects the results into a new map. For keys that were mapped to the same new key, the value corresponding to the greatest of the original keys is retained.

mapKeysMonotonic f s == mapKeys f s, but works only when f is strictly monotonic. That is, for any values x and y, if x < y then f x < f y. Semi-formally, we have:

and [x < y ==> f x < f y | x <- ls, y <- ls]
==> mapKeysMonotonic f s == mapKeys f s
where ls = keys s

This means that f maps distinct original keys to distinct resulting keys. This function has slightly better performance than mapKeys. Warning: This function should be used only if f is monotonically strictly increasing. This precondition is not checked. Use mapKeys if the precondition may not hold.

mapKeysMonotonic (\ k -> k * 2) (fromList [(5,"a"), (3,"b")]) == fromList [(6, "b"), (10, "a")]

mapKeysWith c f s is the map obtained by applying f to each key of s. The size of the result may be smaller if f maps two or more distinct keys to the same new key. In this case the associated values will be combined using c.

mapKeysWith (++) (\ _ -> 1) (fromList [(1,"b"), (2,"a"), (3,"d"), (4,"c")]) == singleton 1 "cdab"
mapKeysWith (++) (\ _ -> 3) (fromList [(1,"b"), (2,"a"), (3,"d"), (4,"c")]) == singleton 3 "cdab"

Also see the performance note on fromListWith.