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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