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| ANSI Common Lisp 12 Numbers 12.2 Dictionary of Numbers
12.2.22 pi | Constant Variable
  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)))))
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. Allegro CL Implementation Details: None.

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