If-then-else for bitps.
Function:
(defun b-ite$inline (test then else) (declare (xargs :guard (and (bitp test) (bitp then) (bitp else)))) (let ((__function__ 'b-ite)) (declare (ignorable __function__)) (if (zbp test) (bfix else) (bfix then))))
Theorem:
(defthm bitp-of-b-ite (b* ((bit (b-ite$inline test then else))) (bitp bit)) :rule-classes :type-prescription)