- make-pair-comparatorprocedure
- type-test returns #t if argument is a pair, #f otherwise.
- equality predicate returns #t if cars are equal per car-comparator and cdrs are equal per cdr-comparator.
- ordering: cars are compared by car-comparator, if not equal, cdrs are compared and if not equal, ordering predicate is applied.
- hash function computes hash of car and cdr, and the hashes are hashed together.