From: Yukihiro Matsumoto <matz@...>
Date: 2007-09-17T09:42:16+09:00
Subject: Re: Modifying a hash key

Hi,

In message "Re: Modifying a hash key"
    on Sun, 16 Sep 2007 17:10:05 +0900, Alex Shulgin <alex.shulgin@gmail.com> writes:

|This suggests me that the keys are actually stored in the hash by
|reference, not by value as I would expect from my prior experience
|with other languages.

Hash stores its values, as its name suggests, by hash values from
keys.  So, if you modifies the key, and subsequently the hash value of
the key, it screws up.  As a general rule, don't modify the keys, or
if you really need to modify the key for some unknown reason, call
rehash method on the hash.

FYI, as a special exception, string keys for hashes are copied for
practical reasons.

							matz.