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 cl:constant_variables:pi [2019/12/05 02:00] cl:constant_variables:pi [2019/12/07 02:00] (current) Line 1: Line 1: + ====== Constant Variable PI ====== + + ====Value==== + an //​[[CL:​Glossary:​implementation-dependent]]//​ //​[[CL:​Glossary:​long float]]//. + + ====Description==== + The best //​[[CL:​Glossary:​long float]]// approximation to the mathematical constant ''​π''​. + + ====Examples==== + In each of the following computations,​ the precision depends on the //​[[CL:​Glossary:​implementation]]//​. Also, if //​[[CL:​Glossary:​long float]]// is treated by the //​[[CL:​Glossary:​implementation]]//​ as equivalent to some other //​[[CL:​Glossary:​float]]//​ format (e.g., //​[[CL:​Glossary:​double float]]//) the exponent marker might be the marker for that equivalent (e.g., ''​D''​ instead of ''​L''​). ​ + <​blockquote> ​ + pi <​r>​3.141592653589793L0 + ([[CL:​Functions:​cos]] pi) <​r>​-1.0L0​ + ([[CL:​Macros:​defun]] sin-of-degrees (degrees) ​ + ([[CL:​Special Operators:​let]] ((x ([[CL:​Special Operators:​if]] ([[CL:​Functions:​floatp]] degrees) ​ + ​degrees ​ + ​([[CL:​Functions:​float]] degrees pi)))) ​ + ([[CL:​Functions:​sin]] ([[CL:​Functions:​math-multiply*]] x ([[CL:​Functions:​math-divide|/​]] ([[CL:​Functions:​float]] pi x) 180))))) + [[CL:​Functions:​SIN-OF-DEGREES]] + ​ + + ====See Also==== + None. + + ====Notes==== + An approximation to ''​π''​ in some other precision can be obtained by writing ''​([[CL:​Functions:​float]] pi x)'',​ where ''​x''​ is a //​[[CL:​Glossary:​float]]//​ of the desired precision, or by writing ''​(coerce pi //​type//​)'',​ where //type// is the desired type, such as **[[CL:​Types:​short-float]]**.

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