10.39.6 Null Foreign Terms

“NULL” foreign terms may be handled. The predicate

null_foreign_term(+Term, -Type)
null_foreign_term(-Term, +Type)

holds when Term is a foreign term of Type, but is NULL (the address is 0). At least one of Term and Type must be bound. This can be used to generate NULL foreign terms, or to check a foreign term to determine whether or not it is NULL.