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Re: reading NaNs

This page is part of the web mail archives of SRFI 77 from before July 7th, 2015. The new archives for SRFI 77 contain all messages, not just those from before July 7th, 2015.

 | From: "Marcin 'Qrczak' Kowalczyk" <qrczak@xxxxxxxxxx>
 | Date: Mon, 24 Oct 2005 20:17:43 +0200
 | Aubrey Jaffer <agj@xxxxxxxxxxxx> writes:
 | > We worked through this issue in SRFI-70.  I think SRFI-70's
 | > treatment is Schemely, compatible with IEEE-754, and doesn't
 | > unnecessarily constrain implementations:
 | >
 | >   The notation 0/0 is used within this report to designate a
 | >   numerical error-object.  A numerical function may return such
 | >   an object when no other number (including real infinities) is
 | >   the correct value.  An implementation may report a violation of
 | >   an implementation restriction in any calculation for which the
 | >   result would be 0/0.
 | It's not compatible with IEEE-754 because it doesn't guarantee that
 | by default operations like (/ 0.0 0.0) produce NaN.

Aren't there IEEE-754 modes which throw an exception rather than
returning NaN?

If the hardware returns a NaN, what the Scheme implementation does
with the NaN is not within the scope of IEEE-754.