note
muba
<p>You can consider a hash to be much like an array, except instead of numerical indexes to access individual elements, you use strings as keys.</p>
<c>
# Define an array:
my @basket = qw(apple banana cherry);
# Get an element from the array:
# (remember that indexes are 0-based)
print "The second kind of fruit in the basket is $basket[1]\n";
# Change an element:
$basket[1] = "date";
print "Now it is $basket[1]\n";
</c>
<p>The above example shouldn't be unfamiliar. Now, instead of keeping a <c>@basket</c> that tells us what kinds of fruit we have in the basket, let's keep a <c>%basket</c> that can also tell us how much of that kind of fruit we have.</p>
<c>
# Define the hash:
my %basket = (
apple => 12,
banana => 6,
cherry => 32, # This final comma is optional,
); # but makes it easier to add more lines in the future.
# Get an element from the basket:
print "There are $basket{cherry} cherries in the basket.\n";
# Modify elements:
$basket{cherry}--;
print "Now there are $basket{cherry}.\n";
$basket{banana} *= 2;
print "Double Banana Bonus! $basket{banana} bananas in the basket!\n";
$basket{apple} = 10;
# Add an element:
$basket{date} = 16;
# Get all keys in the hash:
print "Fruits in my basket: ", join(", ", sort keys %basket), "\n";
# Using a variable as a key:
for my $fruit (sort keys %basket) {
print "You want a(n) $fruit? I have $basket{$fruit} in my basket.\n";
}
# The 'each' function:
while (my ($fruit, $amount) = each %basket) {
print "There are $amount ${fruit}s in my basket.\n";
}
# Getting rid of an element:
delete $basket{apple};
print "Fruits in my basket: ", join(", ", sort keys %basket), "\n";
</c>
<p>That pretty much covers the basics of hashes. Nothing to be afraid of, and quite a useful data type!</p>
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