From: "Lawrence Velázquez" <larryv@macports.org>
To: Ray Andrews <rayandrews@eastlink.ca>
Cc: zsh-users@zsh.org
Subject: Re: surprise with echo
Date: Sat, 20 Dec 2014 00:08:07 -0500 [thread overview]
Message-ID: <B5AFD6F7-6A0F-4193-9732-CA3D0884B825@macports.org> (raw)
In-Reply-To: <5494F332.7000008@eastlink.ca>
On Dec 19, 2014, at 10:55 PM, Ray Andrews <rayandrews@eastlink.ca> wrote:
> My two cents would be (well, er, my 1/2 cent), that it should be the default, *but* that the little surprise should not be there
I believe Kurtis was saying that RC_QUOTES should be enabled by default, not RC_EXPAND_PARAM.
Having array substitution be distributive by default would be much more of a "little surprise" at this point.
> b) because it seems harsh to kill an entire string because one element in it is null.
You still don't understand what's going on. The expansion only results in a null result *if the array itself is empty*. Null *elements* do not produce the same behavior.
% emulate zsh && setopt RC_EXPAND_PARAM
% foo=()
% echo aaa${foo}bbb
% foo=('')
% echo aaa${foo}bbb
aaabbb
% foo=('' '' '')
% echo aaa${foo}bbb
aaabbb aaabbb aaabbb
%
> c) Because the doctrine of least surprise should be followed.
Agreed. That's why enabling RC_EXPAND_PARAM by default should never happen.
> OTOH Bart just showed how the surprise can be avoided so ....
It's only a surprise if you enable the option without understanding what it does first. I actually think that zsh's behavior is more consistent and sensible. Why does it make sense to treat an empty array in the same way as an array consisting of a single null element? Do you treat null sets that cavalierly?
Consider this contrived-ish example:
% include_dirs=(/opt/local/include /usr/include /usr/local/include)
% clang -I${include_dirs} test.c
The expansion here would be "clang -I/opt/local/include -I/usr/include -I/usr/local/include test.c". But:
% include_dirs=()
% clang -I${include_dirs} test.c
What would be the point of this expanding to "clang -I test.c"? It seems entirely reasonable to drop that word entirely and expand to "clang test.c", which is what actually happens.
vq
next prev parent reply other threads:[~2014-12-20 5:17 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-12-19 1:24 Ray Andrews
2014-12-19 3:06 ` Bart Schaefer
2014-12-19 3:20 ` Lawrence Velázquez
2014-12-19 6:09 ` Ray Andrews
2014-12-19 6:30 ` Kurtis Rader
2014-12-19 17:54 ` Ray Andrews
2014-12-19 4:14 ` Kurtis Rader
2014-12-19 4:39 ` Lawrence Velázquez
2014-12-19 5:19 ` Kurtis Rader
2014-12-19 6:00 ` Lawrence Velázquez
2014-12-19 5:57 ` Bart Schaefer
2014-12-19 6:08 ` Kurtis Rader
2014-12-19 6:58 ` Ray Andrews
2014-12-20 2:55 ` Bart Schaefer
2014-12-20 3:05 ` Kurtis Rader
2014-12-20 3:49 ` Ray Andrews
2014-12-20 4:40 ` Bart Schaefer
2014-12-20 5:50 ` Ray Andrews
2014-12-19 6:45 ` Ray Andrews
2014-12-19 11:21 ` Oliver Kiddle
2014-12-20 2:09 ` Bart Schaefer
2014-12-20 2:58 ` Kurtis Rader
2014-12-20 3:55 ` Ray Andrews
2014-12-20 5:08 ` Lawrence Velázquez [this message]
2014-12-20 5:37 ` Ray Andrews
2014-12-20 9:45 ` ZyX
2014-12-19 6:00 ` Ray Andrews
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