Allow `computed` computation function to access previous value about angular HOT 3 OPEN

Yep - this adds "hysteresis" to computeds, which drastically changes the mental model of state derivation. It could also be very confusing since computeds are not guaranteed to be re-evaluated for every state change, so code like this looks reasonable but doesn't work at all:

const sum = computed((prev) => prev + value());

I think we would like to understand what the use cases are where having access to the previous value makes something possible that was hard to do without it.

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I'd argue that this is one of the situations where you want to use a stream and not a signal. Imho this is exactly why signals don't replace rxjs and that's not a bad thing.

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This sounds a bit scary to me; it would mean that computeds are no longer a derivation of the state, but potentially about how the state was changed. To me, the beauty of signals is how all state "falls out" the recorded facts (WritableSignal)

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