Add optional not-found argument when invoking vectors or sets as functions

Description

Maps, keywords, and symbols when used as operators allow optional second arguments for 'default-not-found' values is if to 'get'.

However sets don't support this behavior (though they do with 'get') and vectors don't allow the optional default-not-found in their pseudo 'nth' semantics.

Environment

None

Assignee

Unassigned

Reporter

import

Labels

None

Approval

Triaged

Patch

Code and Test

Affects versions

Priority

Minor
Configure