**Value:**

an *implementation-dependent* *long float*.

**Description:**

The best *long float* approximation to the mathematical constant <PI>.

**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)))))

**See Also:** None.

**Notes:**

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**.