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| From: "Marcin 'Qrczak' Kowalczyk" <qrczak@xxxxxxxxxx> | Date: Tue, 25 Oct 2005 02:39:04 +0200 | | Aubrey Jaffer <agj@xxxxxxxxxxxx> writes: | | > | > 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? | | There are, there are useful too, but they must be explicitly turned | on. So the above description is good as long as "may" means that | the programmer chooses the behavior. | | > If the hardware returns a NaN, what the Scheme implementation | > does with the NaN is not within the scope of IEEE-754. | | I disagree. IEEE-754 specifies the language-independent interface, | as seem from the point of view of the programmer. According to IEEE-754: user. Any person, hardware, or program not itself specified by this standard, having access to and controlling those operations of the programming environment specified in this standard. A Scheme implementation is a program; thus it qualifies as a user. IEEE-754 does not constrain its behavior.