R6RS introduced the concept of mantissa widths
as an alternative to the R5RS #s in numbers.
Do we want either or both of these?
Got citation? This is interesting...
No for WG1, this is a recommended topic for WG2.
Correction: WG1 Scheme will keep the R5RS situation (hash-sign digit yes, mantissa width no).
WG1 voted to eliminate # digits and not add mantissa widths.