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Date: Thu, 7 Mar 2013 14:08:42 -0500
From: Phil Pennock <zsh-workers+phil.pennock@spodhuis.org>
To: Christopher Browne <cbbrowne@gmail.com>
Cc: rahul <rahul2012@gmail.com>, Zsh Users <zsh-users@zsh.org>
Subject: Re: Higher order functions in zsh (article link)
Message-ID: <20130307190842.GA67680@redoubt.spodhuis.org>
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	rahul <rahul2012@gmail.com>, Zsh Users <zsh-users@zsh.org>
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 <CAFNqd5WwOHg3aed8OrbFdwfJ5cxemu6DzBOS5uxuDgGWH41HgQ@mail.gmail.com>
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On 2013-03-07 at 11:59 -0500, Christopher Browne wrote:
> cbbrowne@cbbrowne /tmp/maptest> function map {
>     local func_name=$1
>     shift
>     for elem in $@; print -- $(eval $func_name "${elem}")
> }
> 
> But somewhat curiously that doesn't help :-(.

Why does this code have an eval in there?  It's:
 (1) breaking the f3 example
 (2) introducing a security flaw

Hint:  touch 'f4 `mkdir snert`'

This works fine:
----------------------------8< cut here >8------------------------------
function map {
	local func_name=$1
	shift
	for elem in "$@"; print -- $($func_name "${elem}") 
}
----------------------------8< cut here >8------------------------------

With the eval in there, with { map echo * } f3 loses the quotes and f4
just shows "f4" and creates a new sub-directory, snert.

Lose the eval and things work, no new security hole.

Oh, and you need to quote the $@ to "$@" if you want to preserve empty
elements -- whether you do or not depends on what you're mapping across,
but I tend to think "present but empty" is distinct from "not present".

-Phil