5.6.2 Mutability and equivalence of records

The fields of a record type are designated mutable or immutable. Correspondingly, a record type with no mutable field is called immutable, and all records of that type are immutable objects. All other record types are mutable, and so are their records.

Each call to a record constructor returns a new record with a fresh location (scheme basic storage model). Consequently, for two records obj1 and obj2, the return value of (eqv? obj1 obj2), as well as the return value of (eq? obj1 obj2), adheres to the following criteria (baselib predicates):

• If obj1 and obj2 have different record types (i.e., their record–type descriptors are not eqv?), eqv? returns #f.
• If obj1 and obj2 are both records of the same record type, and are the results of two separate calls to record constructors, then eqv? returns #f.
• If obj1 and obj2 are both the result of a single call to a record constructor, then eqv? returns #t.
• If obj1 and obj2 are both records of the same record type, where applying an accessor to both yields results for which eqv? returns #f, then eqv? returns #f.