On Thu, May 03, 2001 at 06:28:31PM +0200, Detlef Lindenthal wrote:
> How can I test if two lists are equal?
>
> Examples:
> These two lists should be equal:
> @List1a = (1, 2, 3);
> @List1b = (1, 1+1, 1+1+1);
>
> No pair of these should be equal:
> @List2a = ("one", "two", "three");
> @List2b = ("two", "one", "three");
> @List2c = ("one", "two", "three", "four");
>
> Is there an elegant way?
> If not, I can write a sub for it.
>
perldoc -q arrays
...
How do I test whether two arrays or hashes are equal?
The following code works for single-level arrays. It uses a stringwise
comparison, and does not distinguish defined versus undefined empty
strings. Modify if you have other needs.
$are_equal = compare_arrays(\@frogs, \@toads);
sub compare_arrays {
my ($first, $second) = @_;
local $^W = 0; # silence spurious -w undef complaints
return 0 unless @$first == @$second;
for (my $i = 0; $i < @$first; $i++) {
return 0 if $first->[$i] ne $second->[$i];
}
return 1;
}
For multilevel structures, you may wish to use an approach more
like this one. It uses the CPAN module FreezeThaw:
use FreezeThaw qw(cmpStr);
@a = @b = ( "this", "that", [ "more", "stuff" ] );
printf "a and b contain %s arrays\n",
cmpStr(\@a, \@b) == 0
? "the same"
: "different";
This approach also works for comparing hashes. Here
we'll demonstrate two different answers:
use FreezeThaw qw(cmpStr cmpStrHard);
%a = %b = ( "this" => "that", "extra" => [ "more", "stuff" ] );
$a{EXTRA} = \%b;
$b{EXTRA} = \%a;
printf "a and b contain %s hashes\n",
cmpStr(\%a, \%b) == 0 ? "the same" : "different";
printf "a and b contain %s hashes\n",
cmpStrHard(\%a, \%b) == 0 ? "the same" : "different";
The first reports that both those the hashes contain the same data,
while the second reports that they do not. Which you prefer is left as
an exercise to the reader.
...
