Christoph Zwerschke <[EMAIL PROTECTED]> wrote: ... > But I think the following rule is "natural" enough to consider it as THE > standard behavior of ordered dictionaries: > > "Insertion: If the key exists: Don't change the order. If it does not > exist: Append it to the sequence of keys. Deletion: Remove from the > sequence of keys." > > I think this is also the behavior of associative arrays in PHP or Perl
Perl hashes now keep track of 'order of keys'? That's new to me, they sure didn't back when I used Perl! It's been a while, but a little googling shows me, e.g at <http://www.openarchives.org/pipermail/oai-implementers/2002-September/0 00642.html>, assertions such as: """ Hashes don't maintain key order. To get them in sorted order try: foreach $i (sort keys(%afiliacao)) """ which fully match my memories. Could you produce a URL to support the hypothesis that Perl has changed its behavior? What about PHP? Thanks! > and could be considered as the "ONE unambiguous definition". "first insertion (since the last deletion if any)" is ONE unambiguous definition, but surely not "_the_ ONE" with emphasis on ``the''. I see nothing _ambiguous_ (nor _unnatural_) in being interested in the *last* insertion, for example; indeed if phrased as "upon insertion, put the key at the end of the sequence" (whether it was already elsewhere in the sequence of not), with no need for conditionals regarding previous existence, it might appear more "conceptually compact". Anyway -- subclassing dict to implement your definition is reasonably easy, and we could put the resulting package on the Cheese Shop. I hope python.org keeps good enough statistics to be able to tell us, a couple months later, how many people downloaded said package, vs how many people downloaded a complete Python distro; of course, that ratio is biased (in favour of the package) by the fact that many people already have a complete distro available, while initially nobody would have the package, but if we measure when things settle, after letting a month of two or 'transient' pass, that effect might be lessened. If we ran such an experiment, what fraction do you think would serve to convince Guido that a dict 'ordered' by your definition is necessary in Python 2.5's standard library (presumably in module 'collections')? Alex -- http://mail.python.org/mailman/listinfo/python-list
