Or even better have the assertion offer a way to repair the problem: CL-USER 1 > (defun calculate-something (big small) (assert (>= big s

Or even better have the assertion offer a way to repair the problem: CL-USER 1 > (defun calculate-something (big small) (assert (>= big small) (big small) ; these can be reset "Big ~a must be bigger than small ~a" big small) (sqrt (- big small))) calculate-something The error handling will now offer me to repair it, if necessary: CL-USER 2 > (calculate-something 4 7) Error: Big 4 must be bigger than small 7 1 (continue) Retry assertion with new values for BIG, SMALL. 2 (abort) Return to debug level 0. 3 Restart top-level loop. Type :b for backtrace or :c <option number> to proceed. Type :bug-form "<subject>" for a bug report template or :? for other options. CL-USER 3 : 1 > :c 1 The old value of BIG is 4. Do you want to supply a new value? yes Enter a form to be evaluated: 17 The old value of SMALL is 7. Do you want to supply a new value? yes Enter a form to be evaluated: 5 3.4641016 The last number is the return value