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| 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.