Here's my attempt at an answer. Personally speaking, I love hashes. You just have to be aware of the limitations of which approach you take (array vs. hash).
I created a sub "isNull" as a homegrown replacement for "exists". The idea is to check your assumptions (and data) before you operate on that data.
#!/usr/bin/perl -w
use strict;
sub keyExists;
# Begin Main
my %hash1 = (); # Initialize empty hash. Perhaps unnecessary?
%hash1 = (
"1", "20",
"2", "20",
"4", "19",
"5", "20",
"10", "20",
"6", "18");
my %hash2 = (); # Initialize empty hash. Perhaps unnecessary?
%hash2 = (
"1", "19",
"2", "20",
"4", "16",
"5", "19",
"6", "20");
foreach my $thisKey (sort keys %hash1) {
# Check whether key from hash2 returns null to protect from undefi
+ned key for hash2
if (isNull(\%hash2, $thisKey)) {
print "hash2 contains null value for key: $thisKey", "\n";
}
else {
my $result = $hash1{$thisKey} - $hash2{$thisKey};
print "$thisKey $hash1{$thisKey} minus $hash2{$thisKey} equals
+ $result", "\n";
}
} # End foreach
exit 0; # End Main
sub isNull {
my $hashref = shift; # Reference to hash
my $key = shift; # key to check
my $rc = 0;
if ($hashref->{$key}) {
$rc = 0; # Hash returns non-null value
}
else {
$rc = 1; # Hash returns Null value
}
return $rc;
} # End sub isNull
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