Excuse me, I wasn't being careful; my assume example didn't expose a
Maxima bug.
(C8) assume(p <= 0);
(D8) [p <= 0]
(C9) assume(p >= 0);
(D9) [p >= 0]
(C10) is(equal(p,0));
(D10) TRUE
(C11)
So yes, it's possible to give a variable a value by making assumptions on
it. If
the variable had been protected against assignment, that wouldn't be
very good.
Barton