Modify the
In the execution this is an array write, but the logical definition is just a thin wrapper for update-nth:
Function:
(defun update-nats$ai (stobjs::i stobjs::v natarr$a) (declare (xargs :guard (and (natarr$ap natarr$a) (integerp stobjs::i) (<= 0 stobjs::i) (< stobjs::i (nats$a-length natarr$a)) (natp stobjs::v) (stobjs::typep$ stobjs::v (integer 0 *))))) (ec-call (update-nth stobjs::i (nfix stobjs::v) natarr$a)))