Agreed with the polymophism efficiency concern. I was doing some farting around with heaps-the-data-structure earlier this year and changing my DEFUN to/from DE

Agreed with the polymophism efficiency concern. I was doing some farting around with heaps-the-data-structure earlier this year and changing my DEFUN to/from DEFMETHOD made a decent difference. `(defmethod insert ((heap heap)) ... )` is distinctly slower than `(defun insert-heap (heap) ... )` (even after as much tuning of SBCL as I could).