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From: "Bart Schaefer" <schaefer@brasslantern.com>
Message-Id: <990201090246.ZM31742@candle.brasslantern.com>
Date: Mon, 1 Feb 1999 09:02:46 -0800
In-Reply-To: <199902011048.LAA07559@beta.informatik.hu-berlin.de>
Comments: In reply to Sven Wischnowsky <wischnow@informatik.hu-berlin.de>
        "Re: Example function" (Feb  1, 11:48am)
References: <199902011048.LAA07559@beta.informatik.hu-berlin.de>
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To: zsh-workers@sunsite.auc.dk
Subject: Associative array ordering and selective unset (Re: Example function)
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On Feb 1, 11:48am, Sven Wischnowsky wrote:
} Subject: Re: Example function
}
} I was thinking about this... we could make the code keep a counter in
} assoc arrays, increment it whenever a new key is added and store the
} current value in the structure for this new element. Then we can treat 
} the whole thing as being sorted by `time of addition'.
} 
} Hm, does this sound like the right thing?

Almost.  Something about it doesn't seem quite right to me, but I can't
put my finger on what different behavior I'd expect.

I don't like the idea that every parameter table hash would end up with
another integer of overhead in every entry, but maybe that's not so bad.

} P.S.: Is `foo=( ${(kv)foo[(I)^key]} )' the easiest way to remove a
}       key/value-pair from an associative array?

Probably, if you have extendedglob set.  If you don't have extendedglob,
that's a moderately hard way to remove -all- the key/value pairs.

We could go the ksh route and make `noglob unset foo[key]` work.  Like:

	function unset() {
	    emulate -R zsh
	    setopt localoptions extendedglob
	    local arg i
	    for i
	    do
		arg=( "${(@s:[:)i}" )
		if [[ $#arg > 1 &&
		    $(eval print '${(t)'${arg[1]}'}') == association ]]
		then
		    eval "$arg[1]=( \${(kv)$arg[1][(I)^${(j:[:)arg[2,-1]} )"
		else
		    builtin unset $i
		fi
	    done
	}

Can you think of a better idiom than $(eval print '${(t)'${arg[1]}'}') to
get the type of the variable whose name is the value of $arg[1] ?  I keep
thinking there ought to be a way with ${(e)...} but couldn't make it work.

-- 
Bart Schaefer                                 Brass Lantern Enterprises
http://www.well.com/user/barts              http://www.brasslantern.com