(* 2 pi) as a double-float.
(* 2 pi)
double-float
graphics-ports
The constant 2pi is the result of (* 2 cl:pi). It is a cl:double-float.
2pi
(* 2 cl:pi)
cl:double-float
fpi pi-by-2
CAPI User Guide and Reference Manual (Unix version) - 3 Aug 2017