From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <zsh-users-return-19423-mason-zsh=primenet.com.au@zsh.org>
Received: (qmail 8163 invoked by alias); 24 Nov 2014 11:12:08 -0000
Mailing-List: contact zsh-users-help@zsh.org; run by ezmlm
Precedence: bulk
X-No-Archive: yes
List-Id: Zsh Users List <zsh-users.zsh.org>
List-Post: <mailto:zsh-users@zsh.org>
List-Help: <mailto:zsh-users-help@zsh.org>
X-Seq: 19423
Received: (qmail 17057 invoked from network); 24 Nov 2014 11:12:06 -0000
X-Spam-Checker-Version: SpamAssassin 3.3.2 (2011-06-06) on f.primenet.com.au
X-Spam-Level: 
X-Spam-Status: No, score=-6.9 required=5.0 tests=BAYES_00,RCVD_IN_DNSWL_HI,
	SPF_HELO_PASS autolearn=ham version=3.3.2
X-AuditID: cbfec7f4-b7f126d000001e9a-17-54731282be25
Date: Mon, 24 Nov 2014 11:12:01 +0000
From: Peter Stephenson <p.stephenson@samsung.com>
To: Zsh hackers list <zsh-users@zsh.org>
Subject: Re: ${^var} and word splitting
Message-id: <20141124111201.161d8cf2@pwslap01u.europe.root.pri>
In-reply-to: <20141124095637.GA5716@chaz.gmail.com>
References: <20141124095637.GA5716@chaz.gmail.com>
Organization: Samsung Cambridge Solution Centre
X-Mailer: Claws Mail 3.7.9 (GTK+ 2.22.0; i386-redhat-linux-gnu)
MIME-version: 1.0
Content-type: text/plain; charset=US-ASCII
Content-transfer-encoding: 7bit
X-Brightmail-Tracker:
 H4sIAAAAAAAAA+NgFuphluLIzCtJLcpLzFFi42I5/e/4Vd0moeIQg83rRS12nFzJ6MDoserg
	B6YAxigum5TUnMyy1CJ9uwSujEPPvzIXbOCo6H7wl7WBcQ5bFyMnh4SAiUTjnRuMELaYxIV7
	68HiQgJLGSUaf8l3MXKB2EwSt5ueMYEkWARUJR6v6GcBsdkEDCWmbpoN1iwioCExZe9OMFtY
	QF2i7XkfK4jNK2Av8fDWfHYQm1PAWGLajT1MEAuMJM43fGMGsfkF9CWu/v3EBHGEvcTMK2cY
	IXoFJX5Mvge2i1lAS2LztiZWCFteYvOat8wTGAVmISmbhaRsFpKyBYzMqxhFU0uTC4qT0nMN
	9YoTc4tL89L1kvNzNzFCQvDLDsbFx6wOMQpwMCrx8P7oKQwRYk0sK67MPcQowcGsJMK7j7E4
	RIg3JbGyKrUoP76oNCe1+BAjEwenVAOj7/+7MWfP1XQ/UXKPVJhsM/n3y87gSU/NZzdsPfeV
	25+FR9L6VtTyfSHa6gVnri0QaSth5T+ueWRZcIPuVqdfMzWUGVvnxJ6NFDmYPY/5qGzMZPHM
	1xnv/y0XaNn7936xoM3T2o9hi1oNOGoqZK4oW0dmCh2tTK3sNGZQy3c0MuE59jt1YqcSS3FG
	oqEWc1FxIgDh1n4yHwIAAA==

On Mon, 24 Nov 2014 09:56:37 +0000
Stephane Chazelas <stephane.chazelas@gmail.com> wrote:
> $ a='  1 2   3  '
> $ print -l $=a
> 1
> 2
> 3
> $ print -l x$^=a
> x
> x1
> x2
> x3
> x
> $ print -l x${^${=a}}
> x1
> x2
> x3
> 
> 
> Why the extra "x" lines with x$^=a ?

In the case of $^=a, the steps are

- split a.  There's whitespace start and end so you get null elements
  corresponding to those.
- add the x's in front
- remove remaining null elements, but there aren't any.

With nested expansion, you get

- split a: same result
- remove null elements (before the x's get added).
- add the x's
- remove null elements for this level (but there aren't any more)

C.f.

$ print -l x${^"${(@)=a}"}
x
x1
x2
x3
x

which has been told explicitly to keep the null elements despite the nesting.

-- 
Peter Stephenson <p.stephenson@samsung.com>  Principal Software Engineer
Tel: +44 (0)1223 434724                Samsung Cambridge Solution Centre
St John's House, St John's Innovation Park, Cowley Road,
Cambridge, CB4 0DS, UK