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nth-value
n form ⇒ object
n—a non-negative integer; evaluated.
form—a form; evaluated as described below.
object—an object.
Evaluates n and then form, returning as its only value the nth value yielded by form, or nil if n is greater than or equal to the number of values returned by form. (The first returned value is numbered 0.)
(nth-value 0 (values 'a 'b)) ⇒ A (nth-value 1 (values 'a 'b)) ⇒ B (nth-value 2 (values 'a 'b)) ⇒ NIL (let* ((x 83927472397238947423879243432432432) (y 32423489732) (a (nth-value 1 (floor x y))) (b (mod x y))) (values a b (= a b))) ⇒ 3332987528, 3332987528, true
Operationally, the following relationship is true, although nth-value might be more efficient in some implementations because, for example, some consing might be avoided.
(nth-value n form) ≡ (nth n (multiple-value-list form))