In Perl, is there a built in way to compare two arrays for equality?

user_102 0
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I have two arrays of strings that I would like to compare for equality:

my @array1 = ("part1", "part2", "part3", "part4");
my @array2 = ("part1", "PART2", "part3", "part4");

Is there a built-in way to compare arrays like there is for scalars? I tried:

if (@array1 == @array2) {...}

but it just evaluated each array in scalar context, and so compared the length of each array.

I can roll my own function to do it, but it seems like such a low-level operation that there should be a built-in way to do it. Is there?

Edit: sadly, I don't have access to 5.10+ or optional components.

match compare perl arrays
15 Answers

Data::Cmp is another recent option. The cmp_data() function operates similarly to the cmp operator (see perlop for cmp usage).

Example:

use 5.10;
use Data::Cmp qw/cmp_data/;

my @array1 = ("part1", "part2", "part3", "part4");
my @array2 = ("part1", "PART2", "part3", "part4");
my @array3 = ("part1", "PART2", "part3", "part4");

# sample usage 
say "1 & 2 are different" if cmp_data(\@array1, \@array2) ;
sat "2 & 3 are the same" unless cmp_data(\@array2, \@array3) ;

It's also possible to compare hashes and more complicated nested data structures (within reason). For a single module with no non-core dependencies, Data::Cmp is pretty "smart" ;-) ... errm I mean "useful".

user_20194150

My core-only solution with List::Util::all:

use List::Util qw(all);

if (@array1 == @array2 && all { $array1[$_] eq $array2[$_] } 0..$#array1) {
    print "matched\n";
}

As a subroutine:

# call me like string_array_equals([@array1], [@array2])
sub string_array_equals {
    my ($array1, $array2) = @_;

    @$array1 == @$array2 and
    all { $array1->[$_] eq $array2->[$_] } 0..$#$array1;
}

If you want a custom comparison:

# call me like array_equals { $a eq $b } [@array1], [@array2]
sub array_equals(&$$) {
    my ($compare, $array1, $array2) = @_;

    @$array1 == @$array2 and
    all {
        local $a = $array1->[$_];
        local $b = $array2->[$_];
        $compare->($a, $b);
    } 0..$#$array1;
}

At this point, all doesn't save much space and you could just do a for:

# call me like array_equals { $a eq $b } [@array1], [@array2]
sub array_equals(&$$) {
    my ($compare, $array1, $array2) = @_;

    @$array1 == @$array2 or return 0;
    for (0..$#$array1) {
        local $a = $array1->[$_];
        local $b = $array2->[$_];
        $compare->($a, $b) or return 0;
    }
    1;
}
user_1882560

if (join(",",sort @a) eq join(",",sort @b))

if performance concern can be ignored, as mentioned several times in the threads here

user_113672060
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