this is important since different call-sites can have different number of parameters, and thus consult the memoization cache a different number of times, which would result in misalignment

however, sometimes you also want to track with the identity of the data or something. we introduced

Key

and

@Pivotal

to deal with this

so i can have a parameter be labeled as pivotal, which means that in addition the the source location integer being used, we will also check the parameter, and trigger moves/inserts/deletes based on that