op(box(x)) --> box, but is(op(box(x)) = box) --> false.



My boxp function returns false for all CRE inputs; Richard's is(op(box(x))=?mbox) should work correctly for
a CRE input. You could do 

  :lisp(setf (get 'mbox 'op) '$box)

Then is(op(box(x))='box) --> true and is(op(rat(box(x)))='box) --> true.

--Barton

-----maxima-bounces at math.utexas.edu wrote: -----

try is(op(box(x))=?mbox)

RJF