David Abrahams wrote:
"Robert Ramey" <ramey@rrsd.com> writes:
BTW - as far as the serialization system is concerned I never had a problem with the idea of recovering the exact kind of "undefined" data. Its just that there's no way to do it with archives which might be ported from one machine to another as there is no guarentee that the reading machine has the same set of of undefined results as the source machine.
That doesn't mean there's no way to do it. I can think of any number of ways, including, for example, having a replaceable handler for translating unrepresentable values.
OK - let me rephrase. I looked into this sometime ago and could find no way to guarentee any given type of Nan. Also. Not all compilers support the same set of NaNs. So I could see no way that an archive created on one machine could be loaded on another and guarentee that the NaNs would be preserved. I asked for help on this list and no one else could do it figure out a way either. Too bad you didn't post to that discussion.
Its even worse, there is way to write portable code which will generate any specific one of the "undefined" types.
numeric_limits<float>::quiet_NaN()
Is "reasonably portable."
hmm - what's "reasonable portable" is hard to get a concensus on.
One might hack something together that would recover some undefined type but it wouldn't be guarenteed to the the same original type of undefined type.
Type of undefined type?
That was a joke - sorry. Robert Ramey