Feature Request: Add expression that returns the complement of 2 lists

[StacieClark-Elastic]

Add an expression that returns the values in the original list that are not seen in the second list
Example, given list1={1,2,3} and list2={3,4,5} the expression list1.diff(list2) would return {1,2}. (list1.complement(list2) works as well)

[efd6]

This has similar queries to #94; an efficient implementation of set operations is supported by the sets being in sort order. Can you detail the desired behaviours?

[StacieClark-Elastic]

Sorting is not part of the contract. Whether it is part of the implementation is another matter entirely.

[efd6]

I don't think we can do that. We need to state whether the returned list is sorted.

[StacieClark-Elastic]

Only if being sorted is a requirement. Lot's of implementations of specs for maps and sets say they don't guarantee sort order. Some implementations returned sorted and some don't. If you want to guarantee sort order then make it part of the requirement. I don't think sort order is a fundamental requirement for the behavior, but it can be added
However, adding sort as a requirement constrains your implementation, and possibly performance.