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From: Bart Schaefer <schaefer@brasslantern.com>
Message-Id: <150926152921.ZM17972@torch.brasslantern.com>
Date: Sat, 26 Sep 2015 15:29:21 -0700
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To: zsh-workers@zsh.org
Subject: Properties of special hashes in zsh/parameter module
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Some of the special parameters in zsh/parameter are referenced as read-only
hashes.  The normal properties of assocative arrays imply that if you refer
to all the values in one of these hashes, e.g. ${history[*]}, that they may
be returned in any order.

In practice these special hashes don't use a hash table implementation and
the order of values is guaranteed to be fixed, and in the case of $history
are guaranteed to be in the same order as $(history -rn 1).

Should we document this and make it a reliable condition for scripting?  Or
do we prefer to keep open the option of implementing atop an unordered hash
at some point in the future?