[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Storage model error?
Section 3.5 of R4RS says:
An object fetched from a location, by a variable reference or by a
procedure such as car, vector-ref, or string-ref, is equivalent in the
sense of EQV? to the object last stored in the location before the fetch.
Isn't this an error? Equivalence should be in the sense of EQ?,
otherwise the procedures EQ? (and ASSQ, MEMQ) are useless. For
example, the result of
(let ((x 5)) (eq? x x))
can be either #t or #f because any reference to a variable can return
a different (in the sense of EQ?) value (here, different 5's).
Now I understand why (eq? 5 5) should be unspecified but in the above
example there is only one source for the value x, so whatever that value
is I would like eq? to return true.