+ (when (rationalp number)
+ ;; This coercion to SINGLE-FLOAT seems as though it gratuitously
+ ;; loses precision (why not LONG-FLOAT?) but it's the default
+ ;; behavior in the ANSI spec, so in some sense it's the right
+ ;; thing, and at least the user shouldn't be surprised.
+ (setq number (coerce number 'single-float)))