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Re: reading NaNs
| 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.