Re: external representations

[Bradley Lucier <lucier@xxxxxxxxxxxxxxx>]

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).

Brad