On Thursday, 28 August 2014 at 14:43:30 UTC, Don wrote:
No. Once you load an SNAN, it isn't an SNAN any more! It is a
QNAN.
By which definition? It is only if you consume the SNAN with an
fp-exception-free arithmetic op that it should be turned into a
QNAN. If you compute with an op that throws then it should throw
an exception.
MOV should not be viewed as a computation…
It also makes sense to save SNAN to file when converting
corrupted data-files. SNAN could then mean "corrupted" and QNAN
could mean "absent". You should not get an exception for loading
a file. You should get an exception if you start computing on the
SNAN in the file.
You cannot have an SNAN in a floating-point register (unless
you do a nasty hack to pass it in). It gets converted during
loading.
I don't understand this position. If you cannot load SNAN then
why does SSE handle SNAN in arithmetic ops and compares?
const float x = snan;
x = x;
// x is now a qnan.
I disagree (and why const?)
Assignment does nothing, it should not consume the SNAN.
Assignment is just "naming". It is not "computing".
