From: Steven Penny <svnpenn@gmail.com>
To: cygwin@cygwin.com
Subject: Re: strtod ("nan") returns negative NaN
Date: Tue, 14 Aug 2018 19:24:00 -0000 [thread overview]
Message-ID: <5b730d82.1c69fb81.f063b.d706@mx.google.com> (raw)
In-Reply-To: <20180814132301.GX3747@calimero.vinschen.de>
On Tue, 14 Aug 2018 15:23:01, Corinna Vinschen wrote:
> I just wonder why returning -NaN when the input is "-nan" isn't the
> better approach. After all:
>
> printf ("nan (\"\") =3D %f\n", nan (""));
> printf ("-nan (\"\") =3D %f\n", -nan (""));
>
> =3D=3D>
>
> nan ("") =3D nan
> -nan ("") =3D -nan
>
> So, shouldn't the ideal outcome be this:
>
> strtod ("nan", NULL) =3D nan
> strtod ("-nan", NULL) =3D -nan
> strtold ("nan", NULL) =3D nan
> strtold ("-nan", NULL) =3D -nan
a number can be positive or negative. as "NaN" is by definition not a number,
it cannot be positive or negative, it is simply itself, something anathema to
a number.
The only case where "-nan" would be acceptable is the string case, but even in
that instance it is still not negative, it is merely a string that happens to
start with "hyphen-minus" U+002D, and has no bearing on a sign, just as a string
can have no sign.
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next prev parent reply other threads:[~2018-08-14 17:12 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-13 15:16 `std::stod ("nan")` " Masamichi Hosoda
2018-08-13 16:53 ` Stephen John Smoogen
2018-08-13 23:46 ` Duncan Roe
2018-08-14 0:46 ` Stephen John Smoogen
2018-08-14 1:10 ` Masamichi Hosoda
2018-08-14 2:31 ` strtod ("nan") returns negative NaN (was `std::stod ("nan")` returns negative NaN) Masamichi Hosoda
2018-08-14 3:25 ` strtod ("nan") returns negative NaN Steven Penny
2018-08-14 4:46 ` Masamichi Hosoda
2018-08-14 9:56 ` Corinna Vinschen
2018-08-14 10:39 ` Corinna Vinschen
2018-08-14 12:18 ` Masamichi Hosoda
2018-08-14 13:23 ` Corinna Vinschen
2018-08-14 13:41 ` Stephen John Smoogen
2018-08-14 15:25 ` Heavenly Avenger
2018-08-14 15:54 ` Corinna Vinschen
2018-08-14 17:08 ` Heavenly Avenger
2018-08-14 16:05 ` Masamichi Hosoda
2018-08-14 19:24 ` Steven Penny [this message]
2018-08-14 21:45 ` Andy Moreton
2018-08-14 22:23 ` Stephen John Smoogen
2018-08-15 0:02 ` Eric Blake
2018-08-15 7:36 ` Steven Penny
2018-08-21 3:18 ` Brian Inglis
2018-08-14 19:44 ` Achim Gratz
2018-08-21 13:28 ` Brian Inglis
2018-08-14 15:05 ` Masamichi Hosoda
2018-08-14 15:21 ` Masamichi Hosoda
2018-08-14 15:35 ` Heavenly Avenger
2018-08-14 20:05 ` Joseph Myers
2018-08-14 20:19 ` Joseph Myers
2018-08-15 8:51 ` Masamichi Hosoda
2018-08-15 12:55 ` Masamichi Hosoda
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