But if your keys are just numbers, then the array index can be the number you need. Note that in my example, I used
undef as a place holder for array elements that did not have an entry. Unless your indices are not even remotely sequential or you have non-integer indices, an array will be faster, take less memory and will apply a useful constraint on your keys.
If there is a possibility that your arrays or hashes do not have equivalent keys, it is considered best practice to test prior to processing those values. Modifying the previously posted codes:
Hashes:
#!/usr/bin/perl
use strict;
use warnings;
use Data::Dumper;
my %hash1 = ("1", "20",
"2", "20",
"4", "19",
"5", "20",
"6", "18",
"7", "20");
my %hash2 = ("1", "19",
"2", "20",
"4", "16",
"5", "19",
"6", "20",
"8", "20");
my %differences;
for my $key ( sort {$a <=> $b} keys %hash1) {
unless (defined $hash2{$key}) {
print "$key is in \%hash1 but not \%hash2\n";
next;
}
$differences{$key} = $hash1{$key} - $hash2{$key};
print "$key ($hash1{$key} - $hash2{$key}) = $differences{$key}\n";
}
print "\n", Dumper \%differences;
__END__
1 (20 - 19) = 1
2 (20 - 20) = 0
4 (19 - 16) = 3
5 (20 - 19) = 1
6 (18 - 20) = -2
7 is in %hash1 but not %hash2
$VAR1 = {
'6' => -2,
'4' => 3,
'1' => 1,
'2' => 0,
'5' => 1
};
Arrays:
#!/usr/bin/perl
use strict;
use warnings;
use Data::Dumper;
my @array1 = (undef,20,20,19,20,undef,18,20);
my @array2 = (undef,19,20,16,19,undef,20,undef,20);
my @differences;
my $top = $#array1 > $#array2 ? $#array1 : $#array2;
for my $i (1 .. $top) {
if (defined $array1[$i] and not defined $array2[$i]) {
print "$i is in \@array1 but not \@array2\n";
}
if (not defined $array1[$i] and defined $array2[$i]) {
print "$i is in \@array2 but not \@array1\n";
}
next unless defined $array1[$i] and defined $array2[$i];
$differences[$i] = $array1[$i] - $array2[$i];
print "$i ($array1[$i] - $array2[$i]) = $differences[$i]\n";
}
print "\n", Dumper \@differences;
__END__
1 (20 - 19) = 1
2 (20 - 20) = 0
3 (19 - 16) = 3
4 (20 - 19) = 1
6 (18 - 20) = -2
7 is in @array1 but not @array2
8 is in @array2 but not @array1
$VAR1 = [
undef,
1,
0,
3,
1,
undef,
-2
];
Note that in the array case, I will not miss that the second set has a value that the first one is missing.
-
Are you posting in the right place? Check out Where do I post X? to know for sure.
-
Posts may use any of the Perl Monks Approved HTML tags. Currently these include the following:
<code> <a> <b> <big>
<blockquote> <br /> <dd>
<dl> <dt> <em> <font>
<h1> <h2> <h3> <h4>
<h5> <h6> <hr /> <i>
<li> <nbsp> <ol> <p>
<small> <strike> <strong>
<sub> <sup> <table>
<td> <th> <tr> <tt>
<u> <ul>
-
Snippets of code should be wrapped in
<code> tags not
<pre> tags. In fact, <pre>
tags should generally be avoided. If they must
be used, extreme care should be
taken to ensure that their contents do not
have long lines (<70 chars), in order to prevent
horizontal scrolling (and possible janitor
intervention).
-
Want more info? How to link
or How to display code and escape characters
are good places to start.