# [racket-dev] Adding pi.t

While adding racket/extflonum's exports to Typed Racket's base type
environment, I realized that we don't have an 80-bit pi constant. I
considered exporting this definition from "racket/extflonum.rkt":
(define pi.t (extfl* 4.0t0 (extflatan 1.0t0)))
(Multiplication by 4.0t0 is exact if it doesn't overflow, so this is
correctly rounded as long as `extflatan` is.) But what if the build
platform doesn't have extflonums? I've got this right now:
(define pi.t 3.1415926535897932385t0)
Conversion between 80-bit flonums and decimals round-trips nicely, at
least on my computer.
But does decimal conversion (besides 0.0t0 and other easy cases) also
require extflonums to be available? If so, is there a way to export an
80-bit pi approximation?
Neil ⊥