update in

update a value in nested data structure

(any xs, list keys, function f) -> any

Given a dict or list of xs, returns the same type of collection with f(v) placed at the end of navigating through the list of keys, where v is the value originally found.

If any intermediate structures have to be created, they will be, depending on key type. String keys create dicts. Long keys create lists.

If a value is placed in a list, any undefined indexes are filled with nil.

Returns nil if xs is nil.

Throws an error if xs is neither a dict nor a list.

Throws an error if xs is a dict or a list and keys is nil.

Throws an error if f is nil.

Throws an error if navigating into a list and the key cannot be cast to a long or the key is negative.

Throws an error if navigating into a dict and the key cannot be cast to a string.

Parameters