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Is there a way to work around this issue without imposing additional constraints on map key and value types?

It doesn't appear doable in safe Rust, at least not with reasonable algorithmic complexity. (See Aiden4's answer for a solution that does it by re-building the whole map.)

But if you're allowed to use unsafe, and if you're determined enough that you want to delve into it, this code could do it:

Using getFirestore from lite library will not work with onSnapshot. You are importing getFirestore from lite version:

Here is a sample code to output what you need. I use the formula below to calculate pct change. percentage_change = 100*(new-old)/old

If old is 0 it is changed to 1 to avoid division by zero error.

Take a look at the recursive formula for combinations:

Suppose you have a combination space C(n,k). You can divide that space into two subspaces:

• C(n-1,k-1) all combinations, where the first element of the original set (of length n) is present
• C(n-1, k) where first element is not preset

If you have an index X that corresponds to a combination from C(n,k), you can identify whether the first element of your original set belongs to the subset (which corresponds to X), if you check whether X belongs to either subspace:

• X < C(n-1, k-1) : belongs
• X >= C(n-1, k-1): doesn't belong

Then you can recursively apply the same approach for C(n-1, ...) and so on, until you've found the answer for all n elements of the original set.

Python code to illustrate this approach:

I realize that the different behavior of equality (__eq__) can be actually a major concern, why such code snippet is probably not good.

However, you could maybe still do this:

The connection has to be a connection to the primary replica set and the user log in credentials are of a admin level user (needs to have a permission of cluster admin)

This is a somewhat confusing trick to save a small amount of time:

We are creating a defaultdict with a factory function that returns a bound append method of a new list instance with [].append. Then we can just do d[key(item)](item) instead of d[key(item)].append(item) like we would have if we create a defaultdict that contains lists. If we don't lookup append everytime, we gain a small amount of time.

But now the dict contains bound methods instead of the lists, so we have to get the original list instance back via __self__.

__self__ is an attribute described for instance methods that returns the original instance. You can verify that with this for example:

This is a bug. Have made an issue for it: https://github.com/rakudo/rakudo/issues/4403

I suggest using the workaround in the meantime.

You can do it already, the arguments of the constructor are mutable: