From: Vincent Lefevre <vincent@vinc17.net>
To: zsh-users@zsh.org
Subject: Re: grammar triviality with '&&'
Date: Wed, 4 Mar 2015 09:55:12 +0100 [thread overview]
Message-ID: <20150304085512.GA3609@ypig.lip.ens-lyon.fr> (raw)
In-Reply-To: <150302084958.ZM17306@torch.brasslantern.com>
On 2015-03-02 08:49:58 -0800, Bart Schaefer wrote:
> On Mar 2, 11:31am, Vincent Lefevre wrote:
> } Subject: Re: grammar triviality with '&&'
> }
> } On 2015-03-02 00:54:40 -0800, Bart Schaefer wrote:
> } >
> } > If nothing else, the errexit option would fail. With errexit,
> }
> } I agree that's not equivalent, but this would not be a problem
> } in a "if ... then" construct (though I think it's a bad idea
> } to use such a feature here).
>
> Except that's exactly where Ray wants to use it!
The feature would be there. Then every programmer is free to do what
he likes.
>
> } > You also get strange crap like
> } >
> } > while && this; do || if && that; then || thus; fi; done
> } >
> } > which would mean what, exactly?
> }
> } while [[ $? -eq 0 ]] && this; do [[ $? -ne 0 ]] || if [[ $? -eq 0 ]] && that; then [[ $? -ne 0 ]] || thus; fi; done
>
> Yes obviously that's what you intend the literal interpretation to be,
> but in what way is it sensibly meaningful in an actual program?
A programmer is not forced to use this feature. Anyway even
while [[ $? -eq 0 ]] && this; do [[ $? -ne 0 ]] || if [[ $? -eq 0 ]] && that; then [[ $? -ne 0 ]] || thus; fi; done
is not really meaningful while this can already be done in zsh.
> } > Finally if it's OK to have nothing before && / ||, then it would also be
> } > syntactically OK to write
> } >
> } > && || && || && && ...
> }
> } I disagree. Only a && or || as the first word of a list would have
> } a special meaning.
>
> You can't escape the lunacy that easily:
>
> && { || { && { || { && { && ... } } } } }
Same as above. It would not be the first shell feature that could
be misused (see IFS and heredoc, for instance).
--
Vincent Lefèvre <vincent@vinc17.net> - Web: <https://www.vinc17.net/>
100% accessible validated (X)HTML - Blog: <https://www.vinc17.net/blog/>
Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)
next prev parent reply other threads:[~2015-03-04 9:05 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-03-01 16:07 Ray Andrews
2015-03-01 16:43 ` ZyX
2015-03-01 17:01 ` Ray Andrews
2015-03-01 18:48 ` Bart Schaefer
2015-03-01 19:00 ` ZyX
2015-03-01 19:16 ` Ray Andrews
2015-03-01 20:48 ` ZyX
2015-03-01 18:49 ` Lawrence Velázquez
2015-03-02 2:27 ` Vincent Lefevre
2015-03-02 3:12 ` Ray Andrews
2015-03-02 5:22 ` Lawrence Velázquez
2015-03-02 3:53 ` Kurtis Rader
2015-03-02 4:18 ` Ray Andrews
2015-03-02 5:22 ` Kurtis Rader
2015-03-02 16:17 ` Ray Andrews
2015-03-02 18:52 ` Kurtis Rader
2015-03-02 19:03 ` ZyX
2015-03-02 20:16 ` Kurtis Rader
2015-03-03 4:15 ` ZyX
2015-03-03 4:43 ` Kurtis Rader
2015-03-04 15:03 ` Vincent Lefevre
2015-03-04 19:07 ` ZyX
2015-03-02 19:25 ` Ray Andrews
2015-03-02 10:46 ` Vincent Lefevre
2015-03-02 11:06 ` Peter Stephenson
2015-03-02 19:19 ` Bart Schaefer
2015-03-04 14:47 ` Vincent Lefevre
2015-03-05 1:51 ` Bart Schaefer
2015-03-05 10:06 ` Peter Stephenson
2015-03-02 8:54 ` Bart Schaefer
2015-03-02 10:31 ` Vincent Lefevre
2015-03-02 16:31 ` Ray Andrews
2015-03-02 16:49 ` Bart Schaefer
2015-03-02 17:38 ` Ray Andrews
2015-03-02 18:51 ` Bart Schaefer
2015-03-04 8:55 ` Vincent Lefevre [this message]
2015-03-04 17:12 ` Ray Andrews
2015-03-06 4:59 ` Bart Schaefer
2015-03-06 16:10 ` Ray Andrews
2015-03-06 20:23 ` Lawrence Velázquez
2015-03-06 21:25 ` Ray Andrews
2015-03-06 16:32 ` Vincent Lefevre
2015-03-06 17:43 ` Bart Schaefer
2015-03-06 21:01 ` Ray Andrews
2015-03-09 11:26 ` Vincent Lefevre
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