An integer in the inclusive range [0,7].
A designator for a function of one argument, the object.
function should take one argument, the object. It can allocate, but if it allocates heavily the sweeping becomes unreliable. Small amounts of allocation will normally happen only in generation 0, and so will not affect sweeping of other generations.
Note: sweep-gen-num-objects is not implemented in 32-bit LispWorks, where you can use sweep-all-objects instead.