From: Oliver Kiddle <okiddle@yahoo.co.uk>
To: zsh-workers@zsh.org
Subject: Re: inf and nan in arithmetic expansions
Date: Tue, 27 Feb 2018 16:25:47 +0100 [thread overview]
Message-ID: <12828.1519745147@thecus.kiddle.eu> (raw)
In-Reply-To: <20180227130248.GA10630@cventin.lip.ens-lyon.fr>
Vincent Lefevre wrote:
> > This is actually system specific. We generate whatever printf(3)
> > generates. Try out Stephane's examples on Solaris and you get Inf and
> > NaN instead. I think I prefer those forms. We can make the printf code
> > detect them and hard code a consistent form so that we are consistent
> > across platforms.
>
> What do you mean by "We generate whatever printf(3) generates."?
Zsh calls printf(3) to do the work underneath. The following code:
#include <stdio.h>
int main() { printf("%g\n", 1e9999); }
Will output "Inf" on Solaris and "inf" on Linux (for glibc at least).
And the zsh printf builtin does likewise on each platform.
> On Debian/unstable:
>
> cventin% echo $((1e9999))
> inf.
That trailing . is unrelated. It is added to ensure floating point types
remain floating point which is not applicable to Inf and NaN.
> cventin% printf "%g\n" 1e9999
> cventin% /usr/bin/printf "%g\n" 1e9999
How 1e9999 is interpreted a different matter. Zsh first tries strtod()
then full zsh math evaluation. So printf "%g\n" 3+4 works in zsh but not
coreutils' printf.
I do intend to get the patch cleaned up and a follow-up submitted but it
has been a busy time.
Oliver
next prev parent reply other threads:[~2018-02-27 15:33 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-07 22:30 Stephane Chazelas
2018-02-07 23:25 ` Oliver Kiddle
2018-02-08 9:38 ` Peter Stephenson
2018-02-08 12:46 ` Daniel Shahaf
2018-02-08 14:22 ` Stephane Chazelas
2018-02-09 15:31 ` Daniel Shahaf
2018-02-09 21:09 ` Stephane Chazelas
2018-02-10 0:10 ` Bart Schaefer
2018-02-16 16:51 ` Oliver Kiddle
2018-02-17 0:38 ` Daniel Shahaf
2018-02-19 14:19 ` Stephane Chazelas
2018-02-27 13:02 ` Vincent Lefevre
2018-02-27 15:25 ` Oliver Kiddle [this message]
2018-02-27 16:56 ` Vincent Lefevre
2018-03-21 23:46 ` Oliver Kiddle
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