It'd be great to have just a few basic list functions in the expression language:

Thinking

In: [If (In(x,list, valueIfTrue, valueIfFalse)] returns bool

Max: [Listmax(list) ] returns max element

Min: [Listmin(list)] returns min element

Would couple tremendously with lists as a native tag type (my other suggestion), or if it worked on datasets (optional argument: all rows or first row only).