[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: external representations
On Jun 21, 2005, at 11:18 AM, William D Clinger wrote:
Aubrey Jaffer wrote:
SRFI-70 mandates no connection between IEEE-754 NaN and 0/0.
No one said it did. In the discussion of SRFI-70,
however, Bradley Lucier proposed having external
representations for NaNs. I was responding to
Lucier's proposal as much as to yours.
Re: Your idea of representing common Scheme values as NaNs.
I believe it is possible under IEEE 754 that the "hardware" could
return a different NaN for each execution of (/ 0. 0.) in the code (for
example). (Some proposals have suggested putting the address of the
code and/or a rough time stamp in the mantissa.) I'm a bit concerned
that a floating-point operation could return a value that would be
interpreted by your scheme as #\C (for example).