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Re: external representations

This page is part of the web mail archives of SRFI 70 from before July 7th, 2015. The new archives for SRFI 70 contain all messages, not just those from before July 7th, 2015.

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).