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From: Bart Schaefer <schaefer@brasslantern.com>
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Date: Mon, 14 Sep 2015 14:46:54 -0700
In-Reply-To: <CABZhJg-AsuXy5AfpOHDhOGzKPaoO2j_uYrSsCtKiTd+oiyX0_g@mail.gmail.com>
Comments: In reply to Jesper Nygards <jesper.nygards@gmail.com>
        "Splitting into a one element array" (Sep 14, 10:06pm)
References: <CABZhJg-AsuXy5AfpOHDhOGzKPaoO2j_uYrSsCtKiTd+oiyX0_g@mail.gmail.com>
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To: Zsh Users <zsh-users@zsh.org>
Subject: Re: Splitting into a one element array
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On Sep 14, 10:06pm, Jesper Nygards wrote:
} Subject: Splitting into a one element array
} I am writing a function where I want to split the $LBUFFER on whitespace,
} and then handle the last element in the resulting array. My initial attempt
} looked like this:
} 
} local dir=${${(z)LBUFFER}[-1]}
} 
} This works if $LBUFFER contains more than one word, but fails if it is one
} word only.

Yes, this is a side-effect of nested expansion working "inside out"; if
if there's nothing for ${(z)...} to split, the result becomes a scalar
before the context one level up is even considered.

For the case of splitting on spaces you can fix this with a subscript
flag as in ${LBUFFER[(w)-1]}, but because (z) splits on syntax rather
than on spaces there's no simple corresponding flag for "subscript on
shell words".

So the most readable way is probably the local array that ZyX suggested,
but if you really want a single nested expansion:

    ${${(z)LBUFFER}[(wps:$'\0':)-1]}

This works because the subscript flag [(w)] is only active when applied
to a scalar, so (ps:$'\0':) only applies when (z) returns a single word,
which won't contain a $'\0' byte so is not split further.