### pi (Constant Variable)

##### Value:

an *implementation-dependent* *long float*.

##### Description:

The best *long float* approximation to the mathematical constant π.

##### Examples:

;; 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)))))

##### Notes:

An approximation to π 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`

.