The fact database sometimes holds unsimplified facts. One way to
see this is to insert a print into $sign:
(defmfun $sign (x)
(let ((x (specrepcheck x)) sign minus odds evens factored)
(print `(facts = ,($facts)))
...
Then, for example
(%i12) abs(sin(x)/x);
(FACTS = ((MLIST)))
(FACTS = ((MLIST) ((MNOT) (($EQUAL) $X 0))))
(FACTS = ((MLIST) ((MNOT) (($EQUAL) $X 0))))
(FACTS = ((MLIST) ((MNOT) (($EQUAL) $X 0))))
(FACTS = ((MLIST) ((MNOT) (($EQUAL) $X 0))))
(%o12) abs(sin(x))/abs(x)
The expression not equal(x,0) simplifies to notequal(x,0).
I don't know of any bugs that this causes (other than with the code I was playing with), but
it's really best to keep everything simplified. Circumventing simplifya to possibly speed things
up causes trouble.
--Barton