Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!crdgw1!uunet!convex!newsadm
From: tchrist@convex.COM (Tom Christiansen)
Newsgroups: comp.lang.perl
Subject: Re: Sortin based on part of an associative array?
Message-ID: <1991Apr16.112826.10352@convex.com>
Date: 16 Apr 91 11:28:26 GMT
References: <17524@venera.isi.edu> <8310026@hpnmdla.hp.com>
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Reply-To: tchrist@convex.COM (Tom Christiansen)
Organization: CONVEX Software Development, Richardson, TX
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From the keyboard of chrise@hpnmdla.hp.com (Chris Eich):
    [quoting some faulty code of mine, deleted here]

:This doesn't seem to work; sort_by_len returns the lengths, not the keys
:of the original table.
:
:You seem to want sort_by_field to return the keys of the original table,
:so how about this:
:
:    sub sort_by_field {
:	local(*Table, $Field) = @_;
:	local(%Keys);
:
:	foreach (keys %Table) {
:	    $Keys{(split(/:/, $Table{$_}))[$Field]} = $_;
:	}
:	@Table{@Keys{sort by_num keys %Keys}};
:    }

After staring at it until it comes into focus, yes, this is much better,
as in I think it even works, unlike my original.  Mind you that I *did*
say "something like this (untested)".  I consider Chris's solution here
"something like this (tested)". :-)

I know, I know: untested code never runs.

This little gem is actually a pretty nice example of several things:  a
good time to use pass-by-name, inverting a table, and sorting with a
subroutine.  I also like the double @{} reference here, because I think to
understand it, you really need to get your $'s and @'s and %'s down cold.

--tom