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Re: arithmetic issues




On Oct 23, 2005, at 2:39 PM, Thomas Bushnell BSG wrote:

Aubrey Jaffer <agj@xxxxxxxxxxxx> writes:


 | From: Thomas Bushnell BSG <tb@xxxxxxxxxx>
 | Date: Sat, 22 Oct 2005 17:47:25 -0700
 |
 | Aubrey Jaffer <agj@xxxxxxxxxxxx> writes:
 | > ...
| > That still prevents an implementation from displaying information
 | > about what type of NaN was returned.  Such information could be
 | > helpful to find the call which generated the NaN.
 |
 | Huh?  How does it prevent such?  We *could* mandate a readable
| written representation for NaNs without manding that printing a NaN | should produce that representation, since it would still be allowed
 | to signal an error.  (And then, once it is signalled, it could
 | print *anything it wants*.)
 |
| Moreover, nothing prevents the mandated written representation from
 | optionally including implementation defined contents, if that
 | should be useful.

When different NaNs are returned depending on the circumstances
creating them, I would like my implementation to display them like
this:

  #<not-a-number expt>


Sure, that seems fine.  We could mandate that as the readable written
representation!

If "expt" means exponent, then you don't get any more information--- in IEEE arithmetic, the exponents of all NaNs of a given precision are the same.

Brad (who doesn't really want to get into this, ...)