Am So., 30. Aug. 2020 um 03:01 Uhr schrieb John Cowan <xxxxxx@ccil.org>:

> Correct, which means they will never be returned to the user and therefore won't confuse these procedures.  Ideally, nanboxing should only occupy the signaling NaN space and not the quiet NaN space, since 51 > 48 (the number of address bits in a 64-bit x86 or ARM architecture).

The rest of the bits outside the address bit range may be used for tagging,

All that's fine if the following implementation is also possible:

(define (nan-negative? nan) #f)
(define (nan-quiet? nan) #t)
(define (nan-payload nan) 0)
(define (nan=? nan1 nan2) #t)

Marc