> On 2012-02-19, Raymond Wiker <firstname.lastname@example.org> wrote:
> > Helmut Eller <eller....@gmail.com> writes:
> >> I tried this code:
> >> (let ((a '(x y)))
> >> (loop for a in '((a b) (0 1))
> >> for b in a
> >> collect (list a b)))
> >> and expected that it evaluates to '(((a b) a) ((0 1) b)) but all the
> >> implementations I tried return nil.
> >> Can somebody give a pointer to the place in the spec that explains why
> >> this should/could return nil?
> >> Helmut
> > I think this happens because the two "for" clauses are executed in
> > parallel, and the initial value for "a" seen by the second clause is
> > nil.
> But there is no AND between the clauses to make them parallel. This is pretty
> fucked up.
Helmut is wrong. It is not "because the two "for" clauses are executed
in parallel." It's because the A in "for b in a" is evaluated after A
is bound but before it is assigned to '(a b).