update

update a value in a dict or list

(any xs, any key, function f) -> any

Given a dict or list of xs, returns the same type of collection with f(v) placed at key, where v is the original value at xs[key].

If xs is 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 key is nil.

Throws an error if f is nil.

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

Throws an error if xs is a dict and key cannot be cast to a string.

Parameters