nth-value (Macro)

Syntax:

Arguments and Values:

n—a non-negative integer; evaluated.

form—a form; evaluated as described below.

object—an object.

Description:

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.)

Examples:

 (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

See Also:

multiple-value-list, nth

Notes:

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))