Re: Sort by value - new twist

First, the following allow you to switch the procedure being called:

$sorter = \&my_sorter;
foreach my $key (sort { &$sorter } keys %hash ) {
   # do something useful
}
[download]

Update:

Because %hash is not necessarily scoped in my_sorter

Option 1

$sorter = \&my_sorter;
foreach my $key (sort { &$sorter(\%hash) } keys %hash ) {
   # do something useful
}

sub my_sorter {
    my ($hashref) = @_;
    return $hashref->{$a} cmp $hashref->{$b};
}
[download]

Option 2

$sorter = \&my_sorter;
foreach my $key (
   map { $_->[0] }
   sort { &$sorter }
   map { [ $_, $hash{$_} ] }
   keys %hash
) {
   # do something useful
}

sub my_sorter {
    return $a->[1] cmp $b->[1];
}
[download]

Option 3

Use local %hash = %the_hash_to_process; before the foreach, and our %hash inside my_sorter.

There are more ways.

Comment on Re: Sort by value - new twist Select or Download Code

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Re^2: Sort by value - new twist by shemp (Deacon) on Sep 01, 2004 at 19:29 UTC
Option 1 does it exactly!!! Brilliant!	[reply]
Re^3: Sort by value - new twist by Limbic~Region (Chancellor) on Sep 01, 2004 at 22:07 UTC
shemp, This is also how Tie::Hash::Sorted is able to dynamically change the sort routine. It can even sort via lexicals that the package normally wouldn't even be able to see via closures. If you could deal with your hash being tied, Tie::Hash::Sorted gives you the ability to define your sort routine at runtime for free. Cheers - L~R	[reply]
Re^2: Sort by value - new twist by ihb (Deacon) on Sep 02, 2004 at 01:44 UTC
Regarding all options you propose: you need to handle that `$a` and `$b` is a package global if you want to have your sort routines elsewhere. IMHO, the easiest way to handle this is simply to pass them along in the function call. I.e. for option 1: `my $sorter = \&my_sorter; foreach my $key (sort { $sorter->(\%hash, $a, $b) } keys %hash) { # do something useful } sub my_sorter { my ($hashref, $a, $b) = @_; return $hashref->{$a} cmp $hashref->{$b}; }` [download] You can do it by using `caller` and symbolic links, but I don't see any real benefit by that. `ihb` Read argumentation in its context!	[reply] [d/l] [select]