pi | Constant Variable |

**Value****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`

, where)*type*is the desired type, such as*type***short-float**.