RE: [boost] Math Functions

From: Paul A. Bristow (boost_at_[hidden])
Date: 2001-09-09 15:48:35

This useful summary table gives for C++ double

7FF8000000000000
to
7FFFFFFFFFFFFFFF

as the range of quiet NaNs, so any number with
the top 7FF8 bits all set is indeed a NaN and
indeterminate - which is what I am trying to check for.

MSVC std::numeric_limits<double>::quite_NaN gives

double quiet NaN -1.#IND ==  fff8 0000 0000 0000.

Is testing for the FFF8 part portable?

Thanks

Paul

> -----Original Message-----
> From: Swatosh, Joe R NWP [mailto:joe.r.swatosh_at_[hidden]]
> Sent: Thursday, September 06, 2001 4:54 PM
> To: 'boost_at_[hidden]'
> Subject: RE: [boost] Math Functions
>
>
>
> > -----Original Message-----
> >
> > Or an I doing something silly?
> >
> > HOwever, I can compare in hex (double quiet NaN -1.#IND ==
> > fff8 0000 0000
> > 0000) using a union
> >
>
> When we were struggling with some of these issues in MSVC I found
> this page
> http://babbage.cs.qc.edu/courses/cs341/IEEE-754references.html.
>
> According to the table at the bottom, fff8 0000 0000 0000 is not
> a NaN, but
> "Indeterminate."
>
> Hope that helps.
>
> Joe Swatosh                | mailto:Joe.R.Swatosh_at_[hidden]
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