import { type Update } from "https://deno.land/x/rimbu@1.2.1/common/mod.ts";
A value of type T, or a function taking a value of type T and returning a new value of type T.
import { Update } from "https://deno.land/x/rimbu@1.2.1/common/mod.ts";
Returns the result of given update
parameter, where it can either directly give a new value,
or it is a function receiving the given value
, and returns a new value.