Mapped List

Key Mapped List in Is Member Of refers to an optional 1D-array of values that correspond to those defined in Ref List
If ommitted, it is set to contain the same values as in Ref List
Its usefulness is the following:
When the predicate function is called with a given single input value x, if x is part of the reference list Ref List, the corresponding mapped value y is identified and can be retrieved and used as needed.
One such potential usage is as input ingredient to Row Filter Rules
Also, the function Mapped Value can be used to report the mapped value.