On Wed, 1 Aug 2018, 06:45 Paul Eggert, <eggert@cs.ucla.edu> wrote:

>
> These should be fine on a 64-bit platform. file-system-info invariably
> yields floating-point numbers with the bottom three bits zero, due to
> how modern file systems are built (their sizes are multiples of powers
> of two). file-attributes returns an exact value unless your file is
> larger than 2**61 bytes (2 EiB), and once we get to the rare files
> larger than that we should be using bignums anyway. (The same could be
> said for file-system-info, of course.)
>

Sorry for butting in, but in reading this discussion I'm wondering why you
don't use the high order bits of the exponent instead of the low order bits
of the mantissa?

Sure, you'd need some bit fiddling (rotation and masking) to make it into a
proper floating point number, but now you'll find yourself in a situation
where almost 100% of floating point numbers will fit in a word with tags.

Regards,
Elias

>