From: Ray Andrews <rayandrews@eastlink.ca>
To: zsh-users@zsh.org
Subject: Re: grammar triviality with '&&'
Date: Sun, 01 Mar 2015 19:12:24 -0800 [thread overview]
Message-ID: <54F3D518.9030400@eastlink.ca> (raw)
In-Reply-To: <20150302022754.GA7449@xvii.vinc17.org>
On 03/01/2015 06:27 PM, Vincent Lefevre wrote:
> On 2015-03-01 13:49:38 -0500, Lawrence Velázquez wrote:
>> On Mar 1, 2015, at 12:01 PM, Ray Andrews <rayandrews@eastlink.ca> wrote:
>> [...] From zshmisc(1):
>>
>> A list is a sequence of zero or more sublists, in which each sublist
>> is terminated by `;', `&', `&|', `&!', or a newline.
>>
>> In your second example, `[ -e file1 ]` constitutes a list.
> However "&& [ -e file2 ]" could constitute a list too. There is
> currently a parse error, but zsh could have an extension to accept
> it as being equivalent to: "[[ $? -eq 0 ]] && [ -e file2 ]". Would
> there be anything wrong with such an extension?
>
> Similarly, "|| X" could be regarded as equivalent to
> "[[ $? -ne 0 ]] || X" by zsh.
>
I always thought of '&&' as logically equivalent to a keyword 'andif'
and '||' as 'orif' which is why I like to put them first on a line,
because we always put keywords first (mostly),
but it seems to me that even with Bart's definition of a 'hard'
syntax problem with the de-facto semicolon, if
[ -e file ]
... by itself on a line is legal, and if it returns success or failure
and if that success or failure is there for checking on the next
line, the '&&' could mean nothing else but 'check previous true/false',
so it should be unambiguous, so why wouldn't it be legal? It would be the
same as:
[ -e file ]; && ....
... which throws an error, but where is the ambiguity? What else could it
mean? Seems to me the semi doesn't/shouldn't change anything.
BTW, is there somewhere to read up on the 'list' idea, it's the first
I've ever heard of that concept.
next prev parent reply other threads:[~2015-03-02 3:12 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 [this message]
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
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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