The specification is explicit for many list operations that nulls are considered equal for the purposes of list membership and duplicate detection. However, there are several operators where this exception is not called out (though it is implied by the core description of equality semantics for list operations).

The specification should be clarified to make this exception explicit in the following operators:

https://cql.hl7.org/09-b-cqlreference.html#contains-1

https://cql.hl7.org/09-b-cqlreference.html#in-1

https://cql.hl7.org/09-b-cqlreference.html#includes-1

https://cql.hl7.org/09-b-cqlreference.html#included-in-1

https://cql.hl7.org/09-b-cqlreference.html#indexof

https://cql.hl7.org/04-logicalspecification.html#contains

https://cql.hl7.org/04-logicalspecification.html#in

https://cql.hl7.org/04-logicalspecification.html#includes

https://cql.hl7.org/04-logicalspecification.html#included-in

https://cql.hl7.org/04-logicalspecification.html#proper-contains

https://cql.hl7.org/04-logicalspecification.html#proper-in

https://cql.hl7.org/04-logicalspecification.html#proper-includes

https://cql.hl7.org/04-logicalspecification.html#proper-included-in

https://cql.hl7.org/04-logicalspecification.html#indexof