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From: Robert Ramey (ramey_at_[hidden])
Date: 2005-12-01 11:09:01

This will be helpful in serializiing non-number floats and doubles.

But there is even a bigger problem. That is, we haven't found
a portable way to create all the various flavors of these things.

For native binary archives this isn't problem as the orginal
bits are recovered. But I can't see how to handle these
kinds of floats in portable binary or text based arechives.

Robert Ramey

John Maddock wrote:
>> For a while now I've been meaning to clean up my floating-point
>> classification code to provide a more reliable way of testing for
>> Nan's and infinities.
>> The new TR1 complex number code could really use this to improved
>> it's reliability. I believe Robert Ramey was looking for this
>> functionality for serialisation, and frankly it's hard to write any
>> serious floating point
>> code without it.
>> So... attached is a first version of an fpclassify implementation
>> for Boost (if there's interest). As long as this one works (not a
>> given
>> unfortunately) then it's obviously trivial to sit isnan, isinfinity
>> etc on top of it.
>> So.... I'm looking for testers to run the attached program on as many
>> different platforms/compilers as possible, basically I want to see if
>> there's any mileage in this or if I'm on to a looser with this code!
>> Please build the test program with optimisations turned on: many
>> compilers make non-IEEE arithmetic assumptions once you tell them to
>> optimise the
>> code.
>> Tested so far:
>> Win32:
>> VC6: Can't detect signaling NaN's (_isnan is broken).
>> VC7, 7.1, 8: OK
>> Intel 7, 8, 9: OK provided you're not using the VC6 runtime.
>> GCC cygwin: OK.
>> Borland 5.6.4: So broken I don't know where to begin :-(
>> HP-UX:
>> gcc-3.4.2: OK.
>> aCC: OK (native fpclassify broken for long doubles, but portable
>> version works).
>> Tru64:
>> cxx : OK (but can't test infinities/NaN's as they're not supported?
>> Suse Linux:
>> gcc-3.3.3 : OK.
>> Many thanks, John.
>> _______________________________________________
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