Re: [HACKERS] NAN code

Bruce Momjian wrote:

>
> > Seems that only isnan() is defined as part of Posix. But not
> > a definition that can force a NAN. So we have to find a
> > portable way to define the value NaN for double and float.
> > Does anybody know of such a way?
>
> See my later postings. 0.0/0.0 seems to do it.

Seen them. Just that I'm a little in doubt if this construct
couldn't generate a SIGFPE on all of our supported
platform/compiler combos. Still think we should add autoconf
stuff to search for a NAN definition and only fallback to the
above if that fails.

While searching for the NAN definition I've noticed too that
our float4/float8 datatypes can output 'NaN', but do not
parse them back. They simply elog(ERROR, ...) if you try to
use 'NaN' as an input string for a floating point attribute.
Shouldn't all input functions be able to parse back any
possible result of the corresponding output function? As of
now, I cannot imagine a construct (except a user defined C
function), that could result in a float8-NaN value stored in
the database. But as soon as it happens, the database
wouldn't any longer be dump/reloadable!

Jan

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