multiple-value-bind discard first value

Question

In my code below , I only want r.

(let* ((frac  (multiple-value-bind (f r)  (floor amt  100) r)))
..use frac..)

I get compilation warnings saying unused variable f.

Is there an idiomatic way of writing this?

Answer 1

declare ignore is generally useful in this context, here:

(multiple-value-bind (_ frac)  (floor amt 100)
  (declare (ignore _))
  ; use frac)

Answer 2

NTH-VALUE allows you to choose one of a form's return values. This will behave like your snippet:

(let* ((frac (nth-value 1 (floor amt 100))))
  ...)