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From: Daniel Shahaf <d.s@daniel.shahaf.name>
To: zsh-workers@zsh.org
Subject: Re: sh emulation POSIX non-conformances ("inf"/"Inf" in arithmetic expressions)
Date: Thu, 22 Apr 2021 20:45:31 +0000
Message-ID: <20210422204531.GB13421@tarpaulin.shahaf.local2> (raw)
In-Reply-To: <CAH+w=7a2XgrCqYAuDD4QYm7DBnNsshZQN6MazEVL0L-wngLTZg@mail.gmail.com>

Bart Schaefer wrote on Thu, Apr 22, 2021 at 11:55:25 -0700:
> On Thu, Apr 22, 2021 at 8:31 AM Vincent Lefevre <vincent@vinc17.net> wrote:
> >
> > On 2021-04-13 08:17:42 +0100, Stephane Chazelas wrote:
> > > I think it would be worth documenting that nan and inf are
> > > recognised in arithmetic expressions (and warn against using
> > > variables with the same name).
> >
> > IMHO, zsh should also output a warning when such variables are used.
> 
> Exactly how would that work?
> 
> Warning anytime the names "inf" or "nan" (and case variants) get
> values assigned to them seems like overkill.
> 

Warn only when the variable is created, e.g., upon «typeset -F inf» or
«(( nan = 3.14 ))», but not subsequent assignments?

> If they appear as $inf or $nan then there's no conflict.  Still warn?

No, I guess?  No one expects «$42» and «42» to mean the same thing, nor
«$0.0» and «0.0».

> If "inf" and "nan" appear in math context as the bare strings they're
> currently taken as constants.  Always make a (usually
> wasted/fruitless) check to see whether there happens to be a variable
> of the same name and emit a "watch out, not used" message?

No; optimize for the common case that $inf and $nan don't exist.
Warning upon creation of those suffices.

>

Predefine $inf and $nan as readonly float variables initialized to the
respective values?  (Not saying this is a good idea; just mentioning it
for completeness)

Cheers,

Daniel


  reply	other threads:[~2021-04-22 20:45 UTC|newest]

Thread overview: 60+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-10 23:31 [PATCH] Document imperfections in POSIX/sh compatibility dana
2021-04-10 23:50 ` Bart Schaefer
2021-04-11  0:19   ` dana
2021-04-11 16:54     ` Bart Schaefer
2021-04-11 17:57       ` sh emulation POSIX non-conformances (Was: [PATCH] Document imperfections in POSIX/sh compatibility) Stephane Chazelas
2021-04-11 18:13         ` Bart Schaefer
2021-04-11 19:18         ` sh emulation POSIX non-conformances (no word splitting upon arithmetic expansion) Stephane Chazelas
2021-04-22 15:03           ` Vincent Lefevre
2021-04-22 18:27             ` Bart Schaefer
2021-04-11 19:31         ` sh emulation POSIX non-conformances ("inf"/"Inf" in arithmetic expressions) Stephane Chazelas
2021-04-12 20:41           ` Bart Schaefer
2021-04-13  7:17             ` Stephane Chazelas
2021-04-22 15:31               ` Vincent Lefevre
2021-04-22 18:55                 ` Bart Schaefer
2021-04-22 20:45                   ` Daniel Shahaf [this message]
2021-04-22 21:25                     ` Bart Schaefer
2021-04-23 16:45                   ` Vincent Lefevre
2021-04-23 20:31                     ` Bart Schaefer
2021-04-23 22:46                       ` Oliver Kiddle
2021-04-23 23:34                         ` Bart Schaefer
2021-04-24  2:10                           ` Daniel Shahaf
2021-04-24  3:42                             ` Bart Schaefer
2021-04-24  7:33                               ` Stephane Chazelas
2021-04-24 16:04                                 ` Bart Schaefer
2021-04-24 23:02                         ` Vincent Lefevre
2021-04-25  2:18                           ` Bart Schaefer
2021-04-25 20:17                             ` Vincent Lefevre
2021-04-25 21:58                               ` Bart Schaefer
2021-04-26 10:28                                 ` Vincent Lefevre
2021-04-25 22:00                               ` Bart Schaefer
2021-04-26 10:34                                 ` Vincent Lefevre
2021-04-26 23:25                                   ` Vincent Lefevre
2021-04-11 19:33         ` sh emulation POSIX non-conformances (some of zsh's special variables) Stephane Chazelas
2021-04-11 19:42         ` sh emulation POSIX non-conformances (printf %10s and bytes vs character) Stephane Chazelas
2021-04-13 15:57           ` Daniel Shahaf
2021-04-13 18:03             ` Stephane Chazelas
2021-04-13 21:09               ` Bart Schaefer
2021-04-22 13:59           ` Vincent Lefevre
2021-04-22 14:28             ` Vincent Lefevre
2021-04-22 19:22             ` Bart Schaefer
2021-04-23 16:53               ` Vincent Lefevre
2021-04-23 23:01                 ` Oliver Kiddle
2021-04-24 21:41                   ` Vincent Lefevre
2021-04-24 21:46                   ` Vincent Lefevre
2021-04-24  7:09                 ` Stephane Chazelas
2021-04-24 21:52                   ` Vincent Lefevre
2021-04-24 22:28                     ` Bart Schaefer
2021-04-24 23:18                       ` Vincent Lefevre
2021-04-25  2:20                         ` Bart Schaefer
2021-04-25 11:07                           ` Vincent Lefevre
2021-04-11 23:04       ` [PATCH] Document imperfections in POSIX/sh compatibility dana
2021-04-13 16:01 ` Daniel Shahaf
2021-04-13 16:12   ` Peter Stephenson
2021-04-13 20:28   ` Oliver Kiddle
2021-04-13 21:40     ` dana
2021-04-13 22:02       ` Bart Schaefer
2021-04-14 12:38       ` Daniel Shahaf
2021-04-18  4:50         ` dana
2021-04-20 21:26           ` Daniel Shahaf
2021-05-03 23:42             ` dana

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