Date: Tue, 04 Sep 2001 01:15:16 -0400
From: Benjamin Goldberg <goldbb2@earthlink.net>
Subject: Re: AoH - continued
Message-Id: <3B946364.43A1119F@earthlink.net>

TuNNe|ing wrote:
> 
> Yo,
> Ok. I was able to comprehend all the goodies from my previous post ,
> except for Godzilla's stuff...but that's ok, my lurking teaches me
> he/she just may be too smart for it's on good.
> 
> I am quite sure I need the mapping and sort functions to accomplish my
> goal, but I need references to a post or a document. I did a search in
> google.groups and walked away feeling spanked.
> 
> DATA is a _|_ delimited file with keys directly follwed by it's value.
> I would like to be able to use the first line of my DATA as a way to
> "sort " the rest of the data. So in this specific example the "print
> @goods;" statement should be equivalent to print @goods = ("music",
> "very good", "mp3" "video", "too long", "mpeg");
> 
[snip]

my @data = map {chomp;+{split, /\|/}} <DATA>;

# first line is category=>1, type=>3, info=>2.
# remove it and create 1=>category, 3=>type, 2=>info.
my %sortkeys = reverse %{shift @data};

# sort *numerically*, (1, 3, 2) to get (1, 2, 3).
# then use (1, 2, 3) to get (category, info, type)
my @sortkeys = @sortkeys{sort {$a <=> $b} keys %sortkeys};

# create the sortsub: sub { $a->{category} cmp $b->{category} || ... }
my $sortkeys = join " || ", map "\$a->{$_} cmp \$b->{$_}", @sortkeys;
my $sortsub = eval "sub { $sortkeys )";

my @sorted = sort $sortsub @data;

#my @goods = map values %$_, @sorted; # orig code does this
my @goods = map @$_{@sortkeys}, @sorted; # but what's wanted is this.

> __DATA__
> category|1|type|3|info|2
> category|music|type|mp3|info|very good
> category|video|info|too long|type|mpeg

Be *very careful* about creating $sortsub.  Since in your example, the
data is gotten from *DATA, I assume that it is free of malicious
content.  In particular, I assume all keys are things which are valid
barewords, and do not contain any spaces or other non-word characters.

If they might contain such things, the code becomes:
my $sortkeys = join " || ",
  map "\$a->{\$sortkeys[$_]} cmp \$b->{\$sortkeys[$_]}", 0..$#sortkeys;

If your data comes from outside your script, as it might in the real
world, then use a line like the one above.

If you're generating html, you might want to replace the assignment to
@goods with something like:
print "<TABLE>\n";
print "<TR>", map "<TH>$_", @sortkeys), "</TR>\n";
print "<TR>", map "<TD>", @$_{@sortkeys}, "</TR>\n" for @sorted;
print "</TABLE>\n";

-- 
"I think not," said Descartes, and promptly disappeared.