Feature Request: Add a uniq() expression

[StacieClark-Elastic]

Add uniq() to operate on a list and return a list with the unique values from the original list.

Example list = {1,2,3,4,4,4,5,5}
llist.uniq() returns {1,2,3,4,5}

[efd6]

I think this needs additional specification; the example shows sorted values, which would allow an efficient unique value accumulator, but we don't have a sort (and can't implement an efficient — in place — sort), nor can we guarantee that any list is sorted. Should the order be preserved? Which duplicate element should be the one that is kept (first, last, ?)? What behaviours would be wanted here?

[StacieClark-Elastic]

I don't think uniq() requires sorting as a requirement. If a sorted outcome is desired by the user that is a different operation. Unique sets rarely have a sort order as part of the contract.
If we have found in operation that sorting a unique set is a common use case, then an additional expression may be required unless we can implement a sorted result with the same performance as an unsorted result.

[efd6]

The issue here is that their are two ways to get the set of members of a list; use a map to identify the unique elements of the list, or sort the list and compare adjacent elements, dropping repeats.

There is another issue here, what do we do about <list<dyn>>? Do we support that? Particularly when the underlying types in Go are not comparable (let's say list of lists for example)?

[StacieClark-Elastic]

The use case that we need for processing CEL inputs are numbers and text.