Perl: Hash Table
In Perl, keyed-list is called hash table, or just hash. It is done like this:
Creating a hash table.
# -*- coding: utf-8 -*- # perl use Data::Dumper qw(Dumper); # load Data::Dumper, for printing array/hash $Data::Dumper::Indent = 0; # make it print in compact style # create a hash table %hh = ('a' =>3, 'b' => 4, 'c' => 5); print Dumper \%hh; # {'c' => 5,'a' => 3,'b' => 4};
Get value of a key:
# -*- coding: utf-8 -*- # perl use Data::Dumper qw(Dumper); %hh = ('john' =>3, 'mary' => 4, 'jane' => 5); # get value of a key print $hh{'mary'}; # 4
Delete a entry:
# -*- coding: utf-8 -*- # perl use Data::Dumper qw(Dumper); $Data::Dumper::Indent = 0; %hh = ('a' =>3, 'b' => 4, 'c' => 5); # delete a entry delete $hh{'b'}; print Dumper \%hh; # {'c' => 5,'a' => 3};
Get all keys:
# -*- coding: utf-8 -*- # perl use Data::Dumper qw(Dumper); $Data::Dumper::Indent = 0; %hh = ('a' =>3, 'b' => 4, 'c' => 5); # get all keys print Dumper [keys %hh]; # ['c','a','b']
Get all values:
# -*- coding: utf-8 -*- # perl use Data::Dumper qw(Dumper); $Data::Dumper::Indent = 0; %hh = ('a' =>3, 'b' => 4, 'c' => 5); # get all values print Dumper [values %hh]; # [5,3,4]
Check if a key exist:
# -*- coding: utf-8 -*- # perl use Data::Dumper qw(Dumper); $Data::Dumper::Indent = 0; %hh = ('a' =>3, 'b' => 4, 'c' => 5); # check if a key exists print exists $hh{'b'}; # 1 print exists $hh{'d'}; # (doesn't print anything)
If you are going to get values of a hash, you use $ in front of the hash variable. For example, $hash{'name'}.
The Dumper function's argument needs to be a “reference” to
the hash.
So, you can use it like this:
Dumper(\%hash)
or
Dumper([%hash]).
(parenthesis is usually optional)