#!/usr/bin/perl

use strict;
use warnings;

my @arr1 = (1, 2, 3, 4);
my @arr2 = (4 .. 7);

# from "perldoc perldata":
#
# If you evaluate an array in scalar context, it returns the length of
# the array.  (Note that this is not true of lists, which return the
# last value, like the C comma operator)

# note that an array slice is a list, not an array
# see perldoc -q "difference between a list and an array"

print "-" x 72, "\nbroken wrong way to do it:\n";

if (@arr1 == @arr2)
{
    print "\@arr1 same length as \@arr2\n";
}

if (@arr1[2,3] == @arr2[4,2,0])
{
    print "the two slice expressions each have the same number on the"
+,
        " end of the list\n";
}

if ((1,3,9) == (-10000,34,52,42,9))
{
    print "those two lists end with the same number\n";
}

my @arr3 = @arr1[2,3];
my @arr4 = @arr2[4,2,0];

if (@arr3 != @arr4)
{
    print "\@arr3 different length from \@arr4\n";
}

print "-" x 72, "\na correct way to see if arrays are equal:\n";

print "two arrays\n";
if (! arr_comp(\@arr1, \@arr2))
{
    print "\@arr1 is not equal to \@arr2\n";
}

# need to turn slices into arrays to compare them
# see "perldoc -f scalar"
print "two slices\n";
if (! arr_comp(\@{[ @arr1[2,3] ]}, \@{[ @arr2[3,2,0] ]}))
{
    print "the two slices are not equal\n";
}

print "two more slices\n";
if (arr_comp(\@{[ @arr3[0,1] ]}, \@{[ @arr1[2,3] ]}))
{
    print "these two slices are equal\n";
}

# compares two arrays, returns true if they are the same, false
# if they aren't
# pass in references to the arrays, please
sub arr_comp
{
    my $arr1 = shift;
    my $arr2 = shift;

    print "comparing @$arr1 and @$arr2\n";
    my $same = 0;
    if (@$arr1 != @$arr2)
    {
        # arrays have different length
        return $same;
    }

    $same = 1;
    for (my $i = 0; $i <= $#$arr1; $i++)
    {
        # using ne so it works for strings too
        if ($arr1->[$i] ne $arr2->[$i])
        {
            $same = 0;
            last;
        }
    }
    return $same;
}

__END__
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