From: Bart Schaefer <schaefer@brasslantern.com>
To: "S. Cowles" <scowles@ckhb.org>, zsh-users@zsh.org
Subject: Re: array element subsetting
Date: Fri, 26 Mar 2010 07:41:48 -0700 [thread overview]
Message-ID: <100326074148.ZM29047@torch.brasslantern.com> (raw)
In-Reply-To: <alpine.LN8.2.00.1003260202111.10812@ckhb06.ckhb.org>
On Mar 26, 2:24am, S. Cowles wrote:
}
} I am trying to figure out the correct syntax for constructing two
} one-liner subsetting operations on arrays. I have two objectives: 1)
} select nth character from each array element, and 2) select nth element
} within each array element.
}
} The array these methods operate upon is something simple such as:
} a=(
} "satu two trio"
} "sah funf seis"
} "boundarycase"
} "revert to pattern"
} )
(1) can be done with the (M) parameter flag and simple head/tail:
print ${(M)a#?}
To generalize to the Nth element, ${(M)${(M)a#?(#c$N)}%?} (requires
extendedglob, of course).
(2) is more difficult to do without looping, because zsh doesn't
support multidimensional arrays, so you have to force an eval step
via the (e) flag:
print ${(e):-'${${=:-'${^a}'}[2]}'}
However, this yields the second character of arrays that contain
only one word, because ${=...} reduces singular arrays to scalars.
A simple workaround is to insert an empty dummy element at the tail:
print ${(e):-'${${=:-'${^a}' ""}[2]}'}
In the event there are special characters in the strings in $a, an
extra level of quoting can be added and then removed:
print ${(e):-'${${=${(Q):-'${(q)^a}' ""}}[2]}'}
However, this removes again the empty element inserted by the double
quotes, i.e., it returns nothing for the short array rather than an
empty second element (use "print -l" in those examples to see the
difference more clearly). Remove the (e) if you want to see what's
going on with the ${(q)^a} business.
next prev parent reply other threads:[~2010-03-26 14:42 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-03-24 10:43 How much of it is zsh? zzapper
2010-03-24 11:04 ` Piotr Kalinowski
2010-03-24 12:03 ` Nadav Har'El
2010-03-24 19:49 ` Stephane Chazelas
2010-03-24 20:39 ` zzapper
2010-03-26 9:24 ` array element subsetting S. Cowles
2010-03-26 14:41 ` Bart Schaefer [this message]
2010-03-26 19:32 ` S. Cowles
2010-03-27 4:14 ` Bart Schaefer
2010-03-24 13:43 ` How much of it is zsh? Joke de Buhr
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