The best long float approximation to the mathematical constant \pi.
;; In each of the following computations, the precision depends
;; on the implementation. Also, if `long float' is treated by
;; the implementation as equivalent to some other float format
;; (e.g., `double float') the exponent marker might be the marker
;; for that equivalent (e.g., `D' instead of `L').
pi ⇒ 3.141592653589793L0
(cos pi) ⇒ -1.0L0
(defun sin-of-degrees (degrees)
(let ((x (if (floatp degrees) degrees (float degrees pi))))
(sin (* x (/ (float pi x) 180)))))
An approximation to \pi in some other precision can be obtained
by writing (float pi x), where x is a float of the
desired precision, or by writing (coerce pi type),
where type is the desired type, such as short-float.