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Allegro CL

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.

© Franz Inc. 1998-2012 - File last updated 02-24-2012