(setf values)

To assign the multiple return values of a function to multiple variables, you could use this:

(multiple-value-setq (whole partial) (truncate x 1024))

(setf values) is more general, and works on places:

(setf (values whole partial) (truncate x 1024))
(setf (values (aref v 0) (aref v 1)) (truncate x 1024))